7# f@^^^4^(apa~dLdLdLdL"dneee xdLe ee*f^eeeef,eeeeee Earth Observations by the Astronauts in Support of the Shuttle Imaging Radar (SIR-C/X-SAR) The Students: Alicyn Campbell* Freedom Dean* Timothy Garrett* Hillary Hartley* Aaron Moshiashwil* Jonathan Woodring* Eric Cooper Eric Mortenson David Ouellette Robert Parrott Marta Rives * 1992 and 1993 * 1993 1992 The Science Investigators: JoBea Way Benjamin Holt Jet Propulsion Laboratory Supported by: The Johns Hopkins University Center for Talented Youth and the Durfee Foundation 1993 Challenge Awards Student Project October 1, 1993 Jet Propulsion Laboratory California Institute of Technology This document was assembled to train the astronauts for Earth observations on the SIR-C/X-SAR mission. Excerpts from the document are included below. The shuttle photographs which you find throughout this education CD are excellent examples of the kinds of documentation the astronauts can make from their unique perspective. Preface In 1992 and 1993, the Durfee Foundation funded a graduate version of the Student Challenge Awards Program. The Challenge Awards are designed to provide a unique perspective to students gifted in the arts and humanities from which to understand scientific endeavor by giving students an opportunity to participate in an ongoing research project. In this advanced program, seven students who had participated in previous Challenge Awards programs were selected to help develop the tools for Earth observations for the astronauts on the Shuttle Imaging Radar missions. The program was coordinated by Earthwatch in 1992 and The Johns Hopkins University Center for Talented Youth (CTY) in 1993. The 1993 program, as opposed to all previous Earthwatch programs, was for six weeks instead of two weeks in order to provide an extended opportunity for the students to work on their tasks. The 1993 program also was unique in that the students were given a scholarship award at the end the project. The goal of the 1993 program was to prepare a training manual for the astronauts on the Shuttle Imaging Radar missions. This manual was started in the 1992 program in which the students collected radar imagery and shuttle photographs of the shuttle imaging radar sites. The Shuttle Imaging Radar, or SIR-C/X-SAR, will fly several times during different seasons and will image selected regions of the Earth in order to develop an understanding of the information which might be extracted from a radar image. Although imaging radars can operate day and night and in any season or through any cloud cover, the meteorological state of the Earth affects the image return by changing the electrical properties of the soil and vegetation. Documentation by the astronauts will be used in the interpretation of the radar images, particularly for regions outside of the areas where the SIR-C/X-SAR investigators collect data during the mission. For the ocean, documentation of the ocean surface and atmosphere state will help considerably in describing the large scale feature across which the smaller radar data passes have been collected. For the first part of the project, the students collected information to describe the expected state of the entire Earth for the planned launch times of SIR-C/X-SAR. This information consists of hand-made maps of vegetation greenness, soil type, and rainfall, for example, as well as electronic image files collected from CDs. This information will help to focus the astronauts' observations on particular environmental events, and will provide background information such that potential targets of opportunity, such as hurricanes and monsoons, are well known, and such that the multi-seasonal aspects of the experiment are realized. The second part of the project consisted of collecting information about the specific SIR-C/X-SAR sites including a map to locate the site, photographs of the site collected on previous shuttle missions, and radar images collected on previous spaceborne and airborne radar flights. Photographs and images were selected to emphasize aspects of each site which should be documented by the crew. The state of the Earth maps were also used to describe the multi-seasonal aspects expected for each site. The final phase of the project is yet to come: a few of the students will be brought to the missions when they occur. As time and mission anomalies permit, the students will be brought into the Payload Operations Control Center to discuss the observations of the sites with the astronauts. The preparation and hypotheses developed during the student project will permit the students to have intelligent and interesting discussions with the crew about the effect of the weather and season on the radar imagery, and how these data may help in solving some of our environmental problems. Acknowledgements We would like to acknowledge a number of people who helped make this project possible: William G. Durden; The Johns Hopkins University Center for Talented Youth Elizabeth Jones Stork; The Johns Hopkins University Center for Talented Youth Scott Milroy; The Johns Hopkins University Center for Talented Youth Robert Macfarlane; Durfee Foundation Russell Avery; Durfee Foundation Judith Newkirk; Durfee Foundation Michael Newkirk; Durfee Foundation Megan Godfrey; Earthwatch Cathy Weitz; Jet Propulsion Laboratory Marguerite Schier; Jet Propulsion Laboratory Mike Kobrick; Jet Propulsion Laboratory Tony Freeman; Jet Propulsion Laboratory Ellen O'Leary; Jet Propulsion Laboratory Annie Richardson; Jet Propulsion Laboratory Don Harrison; Jet Propulsion Laboratory Mike Sander; Jet Propulsion Laboratory Peter Mouginis-Mark; University of Hawaii Scott Rowland; University of Hawaii Randy Koster; Goddard Space Flight Center Dorothy Hall; Goddard Space Flight Center John Naunheimer; Canada Centre for Remote Sensing Linda Godwin; Johnson Space Center Tom Jones; Johnson Space Center Sally Ride; California Space Institute Vickie Conners; Langley Research Center Nancy Robertson; Lunar and Planetary Institute Mary Ann Hager; Lunar and Planetary Institute David Pitts; Johnson Space Center Dave Amsbury; Johnson Space Center Richard Monson; NASA Headquarters Miriam Baltuck; NASA Headquarters Jason McGuire; The Johns Hopkins University Center for Talented Youth Section I Introduction In the spring of 1994, the first in a series of shuttle-based multi-seasonal Earth observation missions will occur. These missions are called the Space Radar Laboratory (SRL); the payload includes the third Shuttle Imaging Radar (SIR-C/X-SAR) and the Mapping of Air Pollution from Space (MAPS) instruments. SIR-C is the NASA contribution to the imaging radar system and includes a two-frequency (L-and C-band) polarimetric radar system. The X-SAR radar is contributed by Germany and Italy and is an X-band radar. Together these radars will provide the first multi-frequency polarimetric radar images ever acquired from space. MAPS is designed to measure carbon monoxide (CO) in the troposphere. The radar acquires images of the Earth's surface at microwave frequencies. These data are used to map land and ocean features and estimate properties such as soil moisture, ocean wavelength and direction, and vegetation type which are related to the water content and geometry of the surface constituents. Our experience with airborne imaging radar systems is that the seasonal state and meteorological conditions or oceanic state change the backscatter signatures measured by the radars significantly. In one case, seasonal and meteorological differences resulted in up to a 10 dB change in backscatter in a forested region. It is these differences that inspired NASA to fly the SRL instruments at least two times in different seasons. One of the primary challenges to the many scientists working on the SIR-C/X-SAR project is to measure and document the seasonal state at the time data are acquired. This is easy in point locations where the scientists are working at the time of mission, but difficult to do on a regional basis (30-50 km) or along transects across continents and oceans. Observations made by the shuttle astronauts will help determine the regional environmental state. The combination of the scientists' observations from the ground and the shuttle crew's observations from space should result in an understanding of the state of the surface at the time of data acquisition. This scenario has been used very successfully on aircraft experiments. In this project, radar images were obtained from the Jet Propulsion Laboratory (JPL) and include data from Seasat, SIR-A, SIR-B, ERS-1, JERS-1 and AIRSAR. Shuttle photographs were primarily obtained from a laser disk assembled by the Johnson Space Center called "Earth Observation Images STS-1 through STS-44. Section II Background This section provides some background information on the SRL instruments, crew observations and the shuttle perspective. A. The SRL Instruments SIR-C/X-SAR acquires images of the surface of the Earth at long radar wavelengths. The SIR-C/X-SAR instrument consists of three synthetic aperture radars (SARs) which transmit pulses of microwave energy towards the surface of the Earth and then collect the backscattered energy. Each radar operates at a different frequency. This returned signal is processed into an image. The motion of the shuttle is used to synthesize an aperture of a much longer length than the physical antenna, and this increased size allows images of much higher resolution to be generated. The SAR is sensitive to surface roughness on the scale of the radar wavelength, to the geometric structures, and to the surface electrical properties, or dielectric constant, which can be a function of water content and state. The SAR provides its own illumination and thus produces reliable repeat data independent of weather conditions or the availability of sunlight, through all seasons and at any latitude. Radar waves easily penetrate clouds and, under certain conditions, vegetation and thin layers of dry sand, making it possible to explore regions of the Earth's surface that are not accessible using other remote sensing techniques. The images are 30 to 100 km in width and thousands of kilometers in length. The resolution is 30 to 50 m. The geometric and hydrologic state of the Earth's surface is captured in these images and the data are used to understand oceanographic, ecological, hydrological and geophysical phenomena. The three flights of SRL will differ from earlier missions of the SIR-A and SIR-B in that SRL will be the primary payload, the three-mission experiment will provide a unique look at temporal change in the radar signatures as a function of seasonal state, and there will be round-the-clock observations of the Earth by the shuttle crew. The crew onboard the SRL flight will have an opportunity to help explore the relationships between the radar data and the meteorological state of the Earth beyond what is possible by the investigators on the ground. B. Crew Observations Science observations by the shuttle crew include two aspects: photographic documentation of the sites on a routine basis, and visual observations of features of interest which are recorded as notes, voiced down to the operations center during the mission, and discussed with the science investigators after the mission. These observations may or may not be backed up with photographic documentation. The observations are to describe interactions of the atmosphere, oceans and land surface, and to identify unpredicted or transient phenomena for potential future imaging or, if the feature is recorded in the SIR-C/X-SAR data swath, for priority processing during or after the mission. The primary camera used for Earth observations is a Hasselblad 70 mm camera. Accompanying equipment includes four lenses (40, 50, 100, and 250 mm), a data back to record time, filters, film magazines and various types of film. The 100 mm lens offers spatial resolution similar to the Landsat Multi-Spectral Scanner (MSS) (80 m) and the 250 mm lens offers Landsat TM resolution (30 m). With the 250 mm lens, the Hasselblad is capable of obtaining photographs at the same resolution as the SAR images but with a much larger field of view. A Linhof Aero Technika camera is also available. The Linhof uses 5 inch film and is useful for photographing large areas with resolutions similar to the Hasselblad. Lenses include a 90 and a 250 mm. The shuttle provides a number of unique optical perspectives. The non-polar shuttle orbit provides an opportunity to obtain variable sun-angle photography over the duration of the mission. The current polar orbiting platforms (SPOT, Landsat, AVHRR, etc.) are all in sun-synchronous orbits therefore preventing acquisition of variable sun angle data. From the shuttle's lower inclination orbits, the complete range of sun angles from terminator to terminator are available; all are useful for observations, although low sun angles are particularly useful for highlighting subtle topographic or roughness features. Sun glint photography is also available and is described below in the Ocean section. Section III Dynamic Surface Phenomena Although the radar can penetrate clouds and "see" the Earth's surface day or night and in all seasons, the radar is very sensitive to the seasonal and meteorological state of the surface at the time of imaging. Changes in the seasonal state of the surface can change the radar backscatter by up to 10 dB. In addition, clouds will not only affect the state of the surface as viewed by the radar, but may attenuate the radar beam by several dB, especially at the shorter X- and C-band wavelengths. Observations of cloud location and type are readily made from space. For the quantitative, multi-temporal experiments which make up the SIR-C/X-SAR investigations, knowledge of the state of the surface and the atmosphere are essential to the interpretation of the radar data. In addition, the interpretation of the radar data must be done in the broad spatial and temporal context of the state of the surface of the Earth at the time of imaging. The following sections describe some of the dynamic surface and atmospheric processes which will affect the interpretation of the radar data. A. Oceans The ocean is a very dynamic system and is strongly influenced by the atmosphere. In turn, the surface temperature of the ocean, also has a significant effect on clouds, particularly in frontal regions. The radar is sensitive to the manifestations of this dynamic air-sea system, specifically to capillary and small-scale gravity waves. Ocean features, especially waves and currents, modulate the distribution and character of the wind-induced small-scale waves. This results in generally characteristic manifestations or signatures of the various features in the radar return. The principle ocean features seen in SAR imagery are ocean swell, internal waves, mesoscale and sub-mesoscale (spiral) eddies, current boundaries, sub-surface bathymetric features (and tides), thermal fronts, and various forms of atmospheric phenomena including rain cells, windrows and lee waves. In addition, the SAR return is sensitive to oil slicks, both from natural surfactants and anthroprogenic sources, and ship wakes. The SAR provides a unique two-dimensional view of the ocean surface, due to resolution and its sensitivity to the small scale wave field, which is not captured by any other remote sensing instrument. The SIR-C/X-SAR mission and instrument present a unique opportunity for oceanography investigations for several reasons. In terms of the mission plan, the near one-day repeat is well suited to the dynamics of many ocean phenomenon, including surface waves, and to the detection of many types of features which are more transient. Other satellite SAR platforms have had 3-day orbital repeats or longer. The relatively low orbital altitude reduces the risks of ocean surface wave nonlinearities which are problematic in higher-altitude SAR platforms. Within the constraints of the orbital inclination, more ocean regions are accessible, because of on-board data recording, that are difficult to view with other satellite SAR platforms which require direct recording within a ground receiving station mask. The multiple frequency and polarization design of the instrument will be extremely useful for examining scattering characteristics and wave-current interactions. Our current understanding of the geophysical information contained in radar imagery of the ocean's surface is often limited due to the lack of other data describing the state of the ocean at the time of data collection. Documentation of ocean state in parallel with SIR-C/X-SAR may provide key information needed to evaluate the radar ocean imagery. In addition, photography of the ocean experiment sites will indicate the location of investigators' ships involved relative to the radar swath and ocean features. Observations and photography of regional ocean systems and clouds will provide the context within which the radar swath is located. Photography of sun glint regions provides the most valuable information on the ocean state and ocean features that can be provided from the shuttle. In fact, sun glint photography obtained simultaneously to a SAR acquisition would provide a powerful companion data set for reasons described below. Sun glint is the reflection from the surface of the ocean from the sun; it represents scattering in the forward direction and is a function of the sun angle and the amount of small-scale surface roughness. Wind stress, waves, and currents control the ocean patterns that may be observed in sun glint. In radar, the ocean return is also due to the small-scale surface roughness and modulations due to longer waves and currents. When the ocean is calm, the sun glint is bright and the area of bright ocean is small. When the ocean is rougher, the scattered light is more diffuse and the bright area is enlarged by wave facets that produce reflections from many different directions. Thus the sun glint can be related to physical phenomena that roughen and calm the ocean's surface such as wind stress, wave-current interactions, and biochemical properties of the surface of the ocean which can create surface slicks. In a similar fashion, radar energy is scattered off the surface of the ocean, but in this case in the backscattered direction. The rougher the ocean the greater the radar return. The contrasting returns could be used together to further understand the ocean physical state and interactions. Radar imagery is also particularly useful for imaging sea ice. Ice extends to near or below the 57 orbit inclination in either the northern or southern hemisphere during about 8 months of the year. The ice margins are very dynamic due to the often intense air-sea-ice interactions. Often waves and eddies will be visible within the ice cover due to ice being swept along by the current motion. Ice concentration and motion and the location of ice bergs will change from day-to-day throughout the mission. Documentation of the presence of ice, ice bergs, and ocean features within or near the ice will be quite useful in aiding in the analysis of corresponding SAR imagery. An example is Carsey et al. (1986) where coincident photography was useful for resolving the identification of sea ice and ocean, which had undergone a reversal in contrast between image sets. B. Ecosystems The Earth's vegetated surface as viewed by SAR varies significantly with surface cover and meteorology (Figure III-B-1). Recent results of experiments to understand the day-night variations in the radar backscatter of forests indicate there is a strong diurnal signature related to the dielectric constant which in turn is related to plant water status. When clouds pass over vegetation and cut off solar energy, the photosynthetic process slows down or stops, water potential rises and the dielectric constant changes.  Figure III-B-1. Tree under sunny summer conditions and under variable meteorological conditions. On a longer term basis, changes in the forest meteorological and phenologic state over the duration of the shuttle mission and from mission to mission will produce significant changes in the radar backscatter. Specific phenomena which may be documented through visual observations include snow existence and extent, flood existence and extent (through sun glint photography), leaf on/off and/or leaf color (green or yellow/red), deforestation extent and vegetation vigor or greenness which is related to water status. In addition, acquisition of radar imagery of forests during and after forest fires would provide a valuable "target of opportunity" data set. Depending on the season, the probability of fire occurrence in particular regions will determine specific areas to monitor intensively. An example of an observation of clouds which affected the image interpretation of an AIRSAR image is by Way et al. 1993. C. Hydrology The hydrologic state of the surface will vary significantly over the duration of the mission and from mission to mission due to precipitation (including snow) and the ensuing dry-down. Although it is not possible to observe either rain or soil moisture visually from the shuttle, it is possible to observe clouds which could potentially be raining by identifying cloud type, and lightning, which is directly correlated to rain. This knowledge is important for rain and snow experiments. It is also important to other experimenters requiring either absolutely or relatively calibrated radar data as the existence of snow and/or rain within the experimental area will strongly influence the radar backscatter. D. Geology Although the geologic state of the surface is unlikely to change during the SRL mission or even from mission to mission, the meteorological state of the surface in terms of vegetation and snow cover will change and these will strongly influence the interpretation of the radar imagery for geologic purposes. In addition to monitoring meteorological conditions, shuttle-based photographs for geology experiments with SIR-C/X-SAR will provide information on the geologic setting and regional context of the radar imagery. Low sun angle photography not available through SPOT or Landsat will provide a unique opportunity for viewing subtle surface features to which the radar is sensitive; these photographs will be particularly valuable in understanding the mechanisms of subsurface imaging of ancient river systems in northeastern Africa as they will highlight surface roughness patterns which may be confused for subsurface radar signatures. Stereo photography will provide a three-dimensional perspective of a region. Monitoring of active volcanoes during the mission may provide an opportunity to obtain radar imagery of erupting volcanoes and/or fresh lava flows. The likelihood of finding an active volcano during the SRL flight is very high. Active volcanoes are observed on approximately 50% of all shuttle flights. E. Rain and Clouds Throughout the history of radar, one of the main selling points has been its ability to "see through clouds". Recently, however, clouds have become an important factor in the analysis of SIR-C/X-SAR data due to three factors: (1) At X-band (3 cm) and possibly at C-band (5 cm), clouds and associated rain may attenuate or scatter radar signals significantly. In addition, rain occurring at the time of data acquisition will change the dielectric properties of the surface soil and vegetation, thus affecting the backscatter. (2) Clouds indicate wind direction, thermal boundaries and storm systems associated with ocean surface state. In particular, cloud patterns in the southern ocean can be used to predict the position of convective storms thus providing a means of focusing data collection for the southern ocean wave experiments. (3) Clouds limit incident radiation on the Earth's surface and therefore change the water status of the surface vegetation. In particular, clouds decrease or stop transpiration which in turn changes plant water potential, dielectric constant and radar backscatter. In addition, there are two experiments with the SIR-C/X-SAR to image rain. These investigations require imaging of rain systems and therefore real time decisions on whether or not to take data will have to be made. Characterization of cloud type will help determine the effect of the cloud (and associated potential rain) on the radar data. Clouds are first classified by form into two groups: heaped or cumulus clouds which form from unstable rising air, and layered or stratus which form from stable air. Clouds are then further classified according to their height above the ground (high or cirrus, middle or alto, low or strato) and by their ability to produce precipitation (nimbus). 1. Cumulus (Heaped) Clouds Heaped clouds form from rising unstable air currents. They are flat-based with a cauliflower dome. Cumulus clouds are formed by convection and the base forms at the condensation level of the rising warm current. If the upward current continues, the dome will develop turrets, and then the cloud is called a cumulus congestus, or "towering cumulus" and may produce light showers. If the convective process continues energetically, a large cumulonimbus may result, with the possibility of a thundershower or thunderstorm, including heavy rain, hail, and lightening. As long as the convection continues, the cumulonimbus will develop actively in size and intensity for about 30 minutes to an hour. 2. (Stratus) Layered Clouds Stratus clouds result from stable air. Stratus clouds appear as wide sheets with minimal vertical and extended horizontal dimensions. Sometimes they cover the entire sky to the horizon and beyond. There is little or no convection present. They are created when layers of air of different temperatures come into close contact with each other. This can be caused by the lifting of the air layer in a cyclonic storm system, or by the rising terrain, which reduces the temperature of the air to its condensation level. 3. Cumulus and Stratus Clouds Cumulus and stratus clouds sometimes coexist. Low-level stratiform clouds often develop small convective cells, which produce alternately thick and thin areas in the cloud sheet. The resulting clouds are called stratocumulus, and their tops are often arranged in rows across the sky. At middle altitudes, these are called altocumulus. At much higher altitudes, above the freezing level, the same pattern can form in a cloud composed of supercooled water and ice crystals, creating a cirrocumulus cloud. The individual convective cells in cirrocumulus and altocumulus clouds appear to be much smaller than those of stratocumulus because of their distance from the observer. Section IV The State of the Earth Some of the maps referenced here are included in the Climates folder on this CD. A. Vegetation Greenness Vegetation greenness has been estimated using NDVI maps generated using AVHRR data for April, July, October and December. Seasonally, deciduous high latitude boreal forests change in greenness and leaf biomass. In April, the greenness and leaf biomass is minimal in the northern hemisphere. This is because it is spring, and the trees are just beginning to become active again and photosynthesize. As the photosynthetic activity increases as the season progresses, so will the greenness. This increasing activity is clearly visible if you view the greenness in the forests for the month of July. July is the peak month to investigate radar's ability to estimate green leaf biomass. In October, the activity of the deciduous trees in the boreal region is winding down as the leaves turn yellow and fall from the trees. In December, the northern latitude greenness is extremely minimal because the trees are generally inactive. There will be no leaves on deciduous trees and snow on the ground at the higher latitudes. B. Topical Wet/Dry Season Tropical forests are affected by the varying wet and dry seasons. For example, during the time of the potential shuttle radar flights, three different seasonal states will be observed. These consist of the wet season, the short dry season, and the long dry season. In April, most of the tropical forests near the equator are experiencing a wet season, while a very small extent, generally located around 15 south latitude, are in the midst of a long dry season. The SIR-C/X-SAR sites near the equator are experiencing the wet season; while sites to the south of the Amazon basin are in the long dry season. In the month of July, all three wet and dry seasons will be present at different latitudes. From around the equator southward, the tropical forests are experiencing the long dry season. The tropical forests located around the equator are in the midst of a wet season, and the region about 3 north is in the midst of the short dry season. Also in July, the SIR-C/X-SAR sites near the equator are experiencing the long dry season; while Sena Madureira is in the wet season. In the month of October, the condition of the tropical forests is generally the same. Almost all the forests are in the wet season, with the exception the forests at the northernmost latitude of fifteen degrees. They are beginning the long dry season. All of the SIR-C/X-SAR sites are beginning or continuing with the wet season. Additionally, in the month of December, a fair amount of forest is participating in each of the three seasons. The tropical forest at about 20+ degrees south is in the wet season, still. From about 10 to 20 degrees south, the forest is in the short dry season, and from about ten to zero degrees south the forest is again in the wet season. Finally, from about zero degrees to twenty degrees north, the forest is in transition into the long dry season. A variety of different conditions are visible in all the sites during December. Sena Madureira and Bebedouro are experiencing the long dry season; Manaus is in the midst of the short dry season, and Pantanal is still in the wet season. Thus, different forest activity will be visible from space depending upon the season, the forest type, and the forest location. C. Rain Annual rainfall amounts vary globally and seasonally. Precipitation effects radar data by varying the wetness of the Earth's surface. The extremes of rain in the oceans are hurricanes and tropical storms. D. Flooding In regions and seasons of heavy rains as well as during snow melt, flooding can occur along rivers. In the Amazon, flooding occurs seasonally along the Rio Negro and Amazon. The annual maximum, mean and minimum fluctuation of the Rio Negro at Manaus for 1969-78 and the length of inundation period of the igapo and varzea forest sites (1 = minimum, 2 = mean and 3 = maximum) vary throughout the year. A cross section of the river floodplain and a cross section of the canopy in the floodplain show no flooding, partial flooding and complete flooding. Flooding in vegetated regions can be observed from space as a sun glint pattern. Such patterns should not be confused with hot spot patterns in which is light reflected (or backscattered) from the vegetation leaves directly back to the shuttle along its incident path. E. Snow Snow cover in the northern hemisphere is quite different for April, July, October and December. The snow cover extent is expected to vary significantly from mission to mission which will in turn effect the snow sites as well as other sites where backscatter may be confused by snow. F. Soil Moisture Soil moisture, or soil wetness, is different in January, April, July and October. The soil wetness is equivalent to the degree of saturation and varies from 0 to 1. High soil moisture in January and April probably reflect the model's parameterization of snowmelt. When snow melts, is is allowed to infiltrate the top soil layer before it runs off. G. Seasonal Freeze/Thaw Seasonally, the Earth freezes and thaws to various degrees. Regions of discontinuous permafrost, seasonal freeze/thaw, and short duration freeze/thaw can be identified as a function of latitude, elevation and season. H. Burning In October, burning is high in the Amazon and South America. In April, burning is highest in the northeast US, mid-west Africa, and China inland from Japan. These levels are seasonally constant at the southern latitudes but change seasonally in the northern latitudes. Burning is also indicated by atmospheric CO levels. CO levels are highest in April and lowest in October. In October, the background CO is the same at all latitudes. In April, CO levels are much higher in the northern latitudes. I. Dust Storms Dust storms may change the geometry and/or roughness of the surface from day to day. The deserts of the Earth and the major directions and distances of dust transport are vary seasonally and globally. J. Ice Edge The Arctic and Antarctic ice edge extent changes seasonally. April will be the best month to image the Arctic ice edge and also the worst for the Antarctic ice edge. In the north, the ice will extend down around the Newfoundland coast in the Atlantic and possible down to the northern island of Japan in the Pacific, following the coastlines in both cases. K. Volcanoes and Earthquakes A major earthquake of volcanic event would produce a unique target of opportunity. The following summarizes several volcanoes of particular interest as part of both his SIR-C/X-SAR project: Region Volcano Ethiopia Erta Ale Indian Ocean Karthala Piton de la Fournaise Hawaii Kilauea Mauna Loa Galapagos Fernadina Wolf Darwin Sierra Negra Azul Mediterranean Etna Papua New Guinea Ulawun Java Merapi Philippines Mayon Taal Mexico Colima Kamchatka Plosky-Tolbalchik Bezmianny Kliuchevskoi Section V Supersites and Backup Supersites This section includes more detailed descriptions of the supersites for the SIR-C/X-SAR mission. Included for each site are a map locating the test site, a description of the site and its expected seasonal variability and recommended crew observations. A. Oceanography Sites For the oceans, it is often difficult to find existing shuttle photographs or radar images of the selected SIR-C/X-SAR sites to demonstrate the various kinds of ocean features which should be observed by the crew. Therefore, in this section, we start with an overview of the main features of interest for many of the ocean sites, which includes shuttle photography and SAR imagery that is not located necessarily within a specific site. This is followed by a description of the specific sites, which includes site-specific photographs or radar images if they exist. 1. Overview of Ocean Features and Documentation This section provides a brief description of the key ocean features of interest for SAR imaging and documentation which is applicable to many of the ocean experiment sites. For SAR imaging of the ocean, the best look angles are between 20 and 30 degrees. These angles provide sufficient radar backscatter from the ocean for good signal-to-noise in the imagery. Most of the examples of SAR imagery were obtained by Seasat and SIR-B. In general, ocean features are detectable at wind speeds between 2-8 m/s. Winds less than 2 m/s generally do not produce small-scale waves with sufficient distribution to result in detectable backscatter. Winds higher than about 8 m/s have been found to often obliterate surface signatures of many features, including internal waves and current and eddie boundaries. Because of the uncertainty in detection of many features due to variations in wind speed, the mission plan generally incorporates as many repetitive acquisitions as possible over the site areas in order to increase probability of feature detection. In general, most of the ocean features detected in radar imagery are not frequency-dependent. However, multiple frequencies are useful because each frequency responds to a different range of Bragg scattering from the short surface waves. The varying ranges of resonant scatters may or may not be present, thus providing information on the wind conditions as well as being useful for testing ocean scattering modelling. The key type of feature which is more frequency-dependent are those involving atmospheric interactions, such as rain cells and low level boundary interactions such as lee waves and convergence zones. The shorter two frequencies are more likely to be affected by atmospheric conditions. From recent ERS-1 C-band SAR data, there are numerous examples of lower boundary layer atmospheric features that are detectable. Imagery from L-band SAR from Seasat and SIR-B have few such examples. Also rain and ice particles in the atmosphere are more likely to generate scattering on the shorter two frequencies. Thus it is in important to document both larger-scale as well as smaller-scale atmospheric conditions over ocean sites in order to aid in interpretation of the multi-frequency SAR data. The size of the sites and the in situ activities affect the requested documentation. However, in general, for all sites both the regional context and identification and photography of features is of primary importance, as opposed to identification of the site center or deployed ship location. Several of the ocean sites (Southern Ocean and Equatorial Pacific) cover wide areas, where repeated radar mapping is important but not generally of the same exact location, so the radar will operate at uniform look angles. Many of the sites will have ships and aircraft deployed to obtain in situ ocean measurements. Some of the secondary sites, such as the Strait of Gibraltar and the East Australian current, smaller areas are being imaged and photos of those same regions are important. Concerning visual sightings in hand-held photography to document radar data takes, the optimum ocean photography is taken in the sun glint regions, where surface waves, currents, internal waves and eddies are best seen. The sun glint pattern is affected by the wind, where the size of the glint region is largest when winds are lowest. This works in an opposite sense to radar scattering from the ocean, as discussed in section III. The most useful ocean photography will be that taken as nearly coincidentally as opposed with the SAR data. Sun glint of the specific areas will be hard to come by, but visual data of an overcast/cloudy day is also very important. Clouds can inform oceanographers about the location of current and/or temperature fronts, since storm fronts and cloud patterns often follow current boundaries and temperature fronts. Repeated ocean documentation is important since the ocean is dynamic and constantly changing. Some general trends in human eye documentation are: water features tend to show subtle variances in color; features in the sun glint pattern have a high contrast, but since they are transient and confined to a narrow viewing range and sun angles, they can often only effectively be seen after the film has been processed. Within some sites, if certain features are seen, locational information may be used to redirect the SAR imaging geometry to obtain coverage of the feature on a subsequent day. Lastly, it is important to emphasize that documentation by photography and observations from the shuttle is at a scale that is at least similar to or better than other ocean satellite sensors that are likely to be operating during the mission. These ocean sensors include visible/IR sensors, altimeter, and microwave radiometers. Thorough documentation of oceanography sites will be extremely valuable to the analysis of the SAR imagery.   a. Surface Waves Surface waves are the waves with which we all are familiar. These are more difficult to see in hand-held photos (HHPs) than some of the other ocean features, but are picked up by SAR quite well. The SIR-C/X-SAR platform is an excellent platform for wave imaging due to principally to its low and rapid repeating orbit. With specific interests for each supersite, documentation of surface waves is important to resolve potential nonlinearities in SAR wave imagery. It is most important to attempt to determine the correct viewing orientation for photography of surface waves since that will maximize the value for analysis of the SAR imagery. Some of the most interesting radar wave data is imaged during different types of atmospheric interactions, i.e. storms. Surface waves are imaged by three main mechanisms: (1) The sea-surface tilt of long waves causes periodic variation in the local incidence angle, thus yielding modulation in the scattering cross section of short waves that backscatter the radio waves (the "tilting effect"). This is the dominant imaging mechanism for waves that are traveling perpendicular or in range to the orbital flight track. (2) The alteration of the surface velocity caused by long waves produces modulations in the height of short waves (the "straining effect"). This mechanism also affects range-traveling waves. (3) The radial component of the orbital motion of long waves creates a periodic azimuthal target displacement (the "velocity bunching effect"). This is the dominant imaging mechanism for waves that are traveling parallel or in the azimuth direction to the orbital flight track. Azimuth-traveling waves are those most subject to non-linear imaging, especially prevalent during high sea states. Several of the mission's ocean experiments are focused on examining surface waves. These involve examining wave-current interaction (Gulf Stream and Equatorial Pacific), evaluating wave imaging theories relating to the imaging mechanisms described above (East North Atlantic, North Sea, Labrador Sea, and Japan), and the generation and evolution of waves during storms (Southern Ocean, including the use of the wave processor built by the Applied Physics Laboratory and carried on the SRL pallet). Most of these sites require documentation of the regional conditions over the sites in a mapping sense rather than specifically over the exact location of a ship or buoy. b. Internal Waves Internal waves appear on the ocean as alternating bands of rough and smooth water which are prevalent in coastal and shelf waters under low winds. These near-surface internal waves are generated primarily by the interaction of tidal currents and abrupt topographic features including seamounts. Internal waves have been well documented near coastal regions where sharp, shallow thermoclines are present, especially during spring and summer months. Internal waves are believed to be seen by camera and radar by two mechanisms: (1) the surface currents of the internal waves sweep together oils and materials in the surface water, resulting in severe damping of short waves to form visible slicks (dark on radar and bright in sunglint); (2) the interaction of short waves and the surface current field induced by the internal waves results in a periodic modulation of the short waves, thus producing rough and slick zones associated with convergent and divergent near-surface currents. The wavelength of internal waves range between 1 and 6 km and are commonly organized into groups of 4 to 8 waves. The water column, however, must be stratified for internal waves to be formed. Thus, at high latitudes they will only be found from mid-spring to late autumn. In the lower-latitudes internal waves can be found at all times of the year. There are several other characteristics of internal waves systems that can be summarized as follows: (1) Most are found in coastal areas with wave crests parallel to the bottom topography. (2) These waves generally propagate onto the shores in separate groups or packets with the distance between groups commonly between 10 and 60 kilometers, a distance usually related to the intertidal period. (3) The wavelength within each group decreases from the leading wave to the trailing wave. (4) The wave crests range in length from 10 to 100 km. (5) The wave crests are characterized by narrow bright lines in a dark background or by wider dark lines in a bright background. This indicates that internal waves can be detected at a very wide range of wind speeds, although higher winds tend to obscure the crests. For the mission ocean sites, internal waves are likely to be seen in the near the Gulf Stream along the Atlantic continental shelf, the East North Atlantic, Gulf of Mexico, Juan de Fuca Strait, Japan, Australia and especially in the Straits of Gibraltar. Other regions where internal waves are likely to be present include the Gulf of California and the eastern North Pacific coasts, the Andaman Sea, the Straits of Messina and Hormuz, and the Sulu Sea. Documentation of internal waves and their location are especially important for the mission sites because they are very difficult to visually observe from a ship and they are often difficult to measure with ocean instruments. The presence of these waves is indicative of upper ocean stratification and dynamic processes. c. Currents The relatively wide swath of a spaceborne SAR has the potential to monitor the location and mesoscale variability of large-scale current systems in the ocean. Larger currents like the Gulf Stream and Kuroshio are seen through several mechanisms in radar imagery. First, a change in surface wind stress that generates short gravity waves usually occurs across a current boundary as a result of the difference in water temperature on the two sides of the current, with reduced wind stress occurring on the colder side where the boundary layer is more stable. Second, due to wave-current interactions, the short gravity waves are altered across a current boundary, resulting in either an increased or decreased backscatter, depending on the orientation of the wave field relative to the current. Third, under a uniform wind field, the velocity of the air relative to the water surface is different within a current than outside a current, thus resulting in a variable surface wind stress. Fourth, the line-of-sight component of a current produces an azimuthal displacement of its image, thus making the current detectable on SAR imagery. Lastly, waves passing through a current may be refracted, which is detectable by SAR. Measurements of the refraction can be inverted with wave-current models to produce estimates of current velocity. Current boundaries are often obscured by high winds. Several of the mission's ocean experiments will be studying aspects of major current systems and wave-current interactions, including the Gulf Stream, Equatorial Pacific, Labrador Sea, and the Southern Ocean. Documentation of these sites for the presence of currents is critical to the analysis of the SAR imagery. The current boundaries are most likely to appear as isolated curvilinear features, possibly associated with cloud streaks but they may also be associated with eddies, waves, and even with chaotic surface mixing with surrounding coastal waters. The current boundaries often are clearly seen in sea surface temperature maps from AVHRR, but are affected by cloud cover. Also the temperature contrast in and outside the current may not be present in the warmer summer months which may preclude current detection with SST. Photography is clearly important to reveal the location and often dynamic surrounding conditions. d. Eddies and Fronts An eddy is a circular movement of water and embodies a concentration of energy in a relatively small three-dimensional space. Eddies redistribute energy from areas of high kinetic energy where they are formed to surrounding waters where they dissipate. Eddies also redistribute water masses since the water contained in them is different from the surrounding water. Often eddies will form in a current downstream of a barrier to the flow, such as an island or headland along the coast which causes the current to deflect or meander. In the open ocean, eddies form in areas of large horizontal shear in the water circulation pattern. Eddies have a wide range of scales, from those which are pinched off during Gulf Stream meanders (150 km) to those formed by shear or mixing (10-20 km), often referred to as sub-mesoscale or spiral eddies. The larger eddies are called warm- or cold-water eddies, depending on the temperature of the water within the eddy compared to the surrounding water. In general, most eddies are long-lived, often surviving up to 6 months or more and may travel far from their origins. Eddies have been referred to as being the weather of the ocean. Fronts refer to temperature and salinity fronts. Fronts are associated with large current systems but are also prevalent near upwelling regions and at boundaries of different water masses including river mouths. Fronts are often present along the Pacific Coast of the U. S. Eddies and fronts are detected on SAR in basically the same ways that currents are detected, as discussed above, except for the smaller eddies. Large eddies and fronts are reliably detected for surface winds up to at least 7 m/s. These features generally have strong thermal signatures on SST maps, although the thermal boundaries may not always coincide with SAR-observed boundaries. Sub-mesoscale eddy fields have been seen in satellite SAR imagery principally over coastal shelves. These smaller eddies often contain circular streaks of calm (dark) water. Eddies and fronts are of particular interest for the Juan de Fuca Strait and Gulf of Mexico experiments. Eddies will likely be present during several ocean experiments including the Gulf Stream, Labrador Sea, and Australia sites. Other areas when extensive fields of sub-mesoscale eddies have been observed previously include the Mediterranean, mid-Atlantic Bight, Caribbean, and at ice margins. Documentation of eddies and fronts is very important to determine the location, estimate the surface mixing, and the extent of especially the sub-mesoscale eddies. The small eddies are very difficult to identify using ocean instruments and to detect on AVHRR data. e. Atmospheric Interactions There are several forms of air-sea interactions that are detectable on SAR imagery. Hurricanes are detected by the variable winds at the eye and the outer edge in addition to generated wave field. Tropical storms, squall lines, and rain cells can also be imaged by similar means. Windrows or roll vortices, which are indicative of high winds, lee waves, and boundary layer convection cells have also been detected. These features are seen because of the relation of radar backscatter with wind speed and the spatial variations of surface winds resulting from various atmospheric phenomena. Heavy rainfalls also have strong effects on radar backscatter by attenuating small-scale roughness on the surface. The atmospheric supersite is located in the Western and Eastern Pacific, regions of heavy rainfall. Other ocean sites that may subject to smaller-scale interactions, as opposed to large storms, include the Gulf of Mexico and the Equatorial Pacific. As mentioned previously, documentation of both large-scale storms as well as smaller-scale rain cells, convection cells, and the location of atmospheric fronts are important over all sites. Many of these smaller-scale phenomena may be frequency-dependent, especially those related to rainfall, where the higher two frequencies are likely to most affected. It is also important to document the atmospheric conditions because several types of features, such as temperature fronts, eddies, and storm lines have often similar appearances on radar imagery and it is critical to be able to clearly distinguish the various phenomena. f. Sea Ice Sea ice has an important role in the global climate through its contribution to the Earth's heat budget, and in such coastal operations as oil exploration, fishing and ship routing. Due its day/night capabilities and high resolution, radar imagery is an excellent remote sensing instrument to observe many of the key parameters of sea ice. Also, the SAR is sensitive to the surface roughness and dielectric constant of sea ice, thus enabling the detection of ice type, surface features, extent, and motion plus seasonal changes. Including the imaging of both first-year and multi-year ice, these two major categories of ice are imaged quite differently depending on frequency. At C- and X-bands, during winter conditions, the SAR penetrates through the upper surface of multiyear ice and scatters from air bubbles. When combined with surface scattering, this additional volume scattering from multiyear ice results in a brighter return than from first-year ice, where the salt content prevents penetration and the surface is relatively smooth which results in low returns. At L-band, the radar frequency is not sensitive to air bubbles, which results in similar relatively low returns from both multi-year and first-year ice. However, the imaging of young ice and first-year ice is quite similar at these same 3 frequencies. The orbital inclination precludes almost entirely precludes the imaging of multi-year, the only slight possibility being the presence of limited quantities of older ice in the Weddell Sea which possibly could extend equatorward in the months of September and October which are the months of the largest ice extent in the Southern Ocean. For an April flight, sea ice will be present in the Labrador Sea down to Newfoundland. The experiment at that site is intended to examine the characteristics of waves propagating into the ice cover. Also, sea ice will be present in the Sea of Okhotsk and the upper reaches of the Japan Sea. For the August flight, sea ice will extend northward in the Weddell and Ross Seas, often above 60S. This will affect particularly the Southern Ocean experiment, reducing somewhat the coverage of open ocean waves. Documentation of sea ice includes determining the extent and form of the ice as well as the presence of ocean features including waves and eddies that may be detectable within or near the ice margin. 2. The Sites a. Southern Ocean The Southern ocean is composed of the ocean waters surrounding Antarctica. This includes the southernmost regions of the Pacific, Atlantic, and Indian Oceans. Its poleward boundary is the Antarctic Continent, while its northernmost boundary is the 50 south latitude mark. The supersite is specifically located between 30 south, and 57 south. The objectives of this experiment are to construct a spatially continuous daily estimate of the directional wave energy transport across the only pure-ocean circumpolar route on the planet, a route that is just to the south of the maximum wind zone; and determine the relative contributions from proposed mechanisms for the imaging of ocean surface waves by SARs. This experiment will use both the APL wave processor carried on the pallet which receives signal data and generates wave spectra which are downlinked to the ground as well as data recorded on-board for later processing. The investigators are particularly interested in imaging waves generated within storm regions and will be doing daily replanning to record onboard data near storm regions. Crew Observations: Document weather and storm activity and ocean conditions including waves, currents and ice extent. The Hasselblad should be used to photograph any waves and storms; low angle sun glint photographs are desired. Also, document transient ocean phenomena within the sun glint pattern. b. Equatorial Pacific This study will examine the small-scale velocity structure of the front separating cold Pacific equatorial water from warmer tropical water to the north. This front develops as instability waves in the autumn during non-El Nio years when the North Equatorial Current is most intense. The waves have lengths of about 1200 km and propagate westward at about 0.5 m/s. As these waves are major contributors to heat and momentum fluxes in these regions, it is important to understand the mechanisms responsible for their growth and their effects on thermohaline structure on the equatorial current systems. In addition, it is important to study the processes that mix the narrow cold filaments with the surrounding warm tropical water; these are at present largely unknown. SIR-C/X-SAR images will be used to map the interaction of swell and current shear, convergence zones, and small-scale variability in surface wind stress and to use AVHRR images of sea surface temperature to locate thermal boundaries. Real-time AVHRR images will be collected at the University of Hawaii receiving station. SAR images using multiple frequencies are needed to locate and assess the wave structure at the current shear zones. Ocean-measurements are planned during the SIR-C/X-SAR flights and include temperature, salinity, density, and velocity. The latitudes of the fronts can vary between 1N and 7N within 130W and 180W longitude. The eastern portion of this region is adjacent to the Eastern Pacific rain site, which results in one set of orbital data which are shared. Frequent SAR sampling, both spatially and temporally, is needed to determine front locations, frontal wavelengths, and wave propagation velocity, and to compensate for high and low wind periods which may preclude detection of the wave/current interaction. Crew Observations: Document the location of current and frontal boundaries and photograph surface waves in sun glint patterns. Other ocean features that may be present include small-scale eddies and atmospheric features. It is also important to photograph cloud conditions, so as to resolve whether the radar is detecting current boundaries or atmospheric interactions. c. Western and Eastern Pacific Two rain experiments will be conducted at the Western and Eastern Pacific supersites. The first will determine the effect of precipitation on SIR-C and X-SAR measurements. These radar data will be analyzed using radiative transfer models to provide profiles of the attenuation coefficient (a) and the vertical profile of the rain rate (R). Dual-frequency radar data provided by SIR-C/X-SAR will overcome beam-filling problems and provide information on the spatial distribution of ice and liquid water in the clouds. The second experiment involves several proof-of-concept experiments for remote sensing of precipitation by the SIR-C/X-SAR. These experiments will significantly increase the understanding of the ability of spaceborne synthetic aperture radar to conduct global measurement and monitor precipitation. SIR-C/X-SAR's two experiments involving rain offer a unique challenge to the operation of the radar during the flight. Whereas all other experiments can be reasonably tied to a specific area on the surface of the Earth, the rain experiments only require that a reasonably deep rainstorm be in progress. The requirement is a difficult one because weather targets are transitory in both space and time and cannot be scheduled. The elusiveness of their character can make documentation a challenge. The probability of observing a good target depends on the correlation time of the weather event, the average frequency of events, and the number of independent looks at the target. Since the planning process for the Shuttle flight requires a fixed location, the rain experiments have been chosen to concentrate on an area where longer correlation times may exist. Such areas associated with monsoons and tropical convective systems near the Intertropical Convergence Zone and mid-latitude mesoscale convective complexes, which naturally leads one to either the western or eastern Pacific. The Eastern Pacific orbital track is adjacent to the Equatorial Pacific site. Crew Observations: Document storm areas and locate areas of intensive storms within the storm region. Identify potential storm activity for future potential data takes. The Hasselblad will be used to photograph the ocean surface and any storm activity near or within the site region. d. East North Atlantic This supersite is defined by coordinates 45 to 54 N and 10 to 20W, lying west of the British Isles and the Bay of Biscay. The SIR-C/X-SAR experiments in the East North Atlantic involve the imaging of surface and internal waves. This region has been shown to have a high probability of significant wave heights in excess of two meters. The 1984 SIR-B mission documented a similar area of the East North Atlantic. The SIR-B image enclosed was taken on October 11, 1984 and shows examples of surface waves and variable patterns of internal waves. Ships and ocean instrumentation will be deployed at specific point locations throughout the mission. These points are positioned at crossing orbits and are selected so that both pairs of orbits have similar incidence angles and the ships can travel daily from point to point. If weather conditions are good, photographs of the surface wave field and other oceanic features should be obtained to compare with the radar data. Conditions for photography may be poor, since cold rain cells and overcast/cloudy skies are prevalent in this area. Photos of clouds, weather systems and other atmospheric phenomenon as well as ocean conditions should be obtained to help in interpreting what the radar "saw" under the clouds, whether it be the effects of wind, rain cells, etc. Seasonal change will be negligible as the sea-surface temperature remains fairly constant. The wind speed varies slightly, only two to three meters per second. Possibly the only variation will be with the prevalence of internal waves, which occur primarily in the spring and summer. Crew Observations: Photographs of surface and internal waves near the site and also near western coasts of the British Isles. Also of interest will be atmospheric conditions near the site and in the coastal areas. Photographs of ocean surface features near the coastal waters and in the English Channel will be useful for secondary experiments in those regions. e. Gulf Stream The Gulf Stream supersite is located within corners (42N, 75W), (36N, 65W), (30N, 73W), with nominal center at 36N, 73W. The "Gulf Stream System" begins in the Caribbean Sea, and flows through the Gulf of Mexico and along the east coast of the U.S. until reaching Cape Hatteras, where it begins to flow eastward and gradually loses its identity in the eastern North Atlantic after it passes the Grand Banks south of Newfoundland. The SIR-C/X-SAR experimental area is along the east coast of the U.S. It is the goal of this experiment to gain further information on radar imaging of current and oceanic features; and to have corresponding visible conditions documented as well. Numerous previous shuttle missions such as STS51B, 51F, 41G, and STS 40 have taken many very useful pictures of this area. The hand held photos selected for this manual were taken on missions STS039 and STS 40. They were selected because they successfully show many features of the Gulf Stream area, such as current boundaries, fronts, waves, eddies, and the "mushroom" shaped eddies that can occur near current systems. This is one of the most well documented areas of the ocean by radar data as well. The Seasat mission of 1978 captured many good images of the Gulf Stream. The Seasat image taken on September 3, 1978 reveals the western boundary of the Gulf Stream near Cape Hatteras, the temperature front between adjacent shelf waters and the current water, and surface waves propagating shoreward. The waves are being refracted within the current and around the coastal area. Additional SAR imagery of the Gulf Stream was included in the overview section on currents. Internal waves are generated on the continental shelf regions most commonly in the summer months. Large eddies are spun off both to the north and south of the Gulf Stream. Submesoscale eddies have also been imaged in the shelf areas. Tropical storms and hurricanes are a possibility for the months of August, September and October. Crew Observations: Observe oceanic features including the current boundaries, warm and cold rings, eddies, internal waves, and fronts. Atmospheric conditions associated with rain cells, hurricanes, and other types of cloud patterns and weather systems should be documented. Clouds will often follow current or temperature boundaries. The Hasselblad should be used to photograph storms and waves. f. Gulf of Mexico The Gulf of Mexico site, centered at 26 45' N, 87 30' W, is also one of the most documented ocean areas for radar data. The main features of interest will be similar to those of the Gulf Stream on the U.S. East Coast: current activity and boundaries, eddies, atmospheric conditions and waves. The Loop current passes northward between Yucatan and Cuba towards Louisiana and Texas, then bends eastward toward the Florida Straits. Occasionally the Loop Current sheds a large eddy which may drift westward. The area is quite dynamic as indicated by current mixing, small eddies, and frontal structures. Extensive surface slicks, related to either natural biological surfactants or oil seepage, are often present. Small tropical rain cells may also be present, especially in the warmer months. For the August flight, the temperature contrast of the surface waters in the Gulf are greatly reduced, making sea surface temperature maps unreliable. The combination of photography and SAR can provide valuable information on the location of eddies and currents. Crew Observations: Observe oceanic features including fronts, large and small scale eddies, surface and internal waves, and the Loop Current Effect. Atmospheric phenomena, both large- and small-scale (including rain cells), should also be documented. g. North Sea The North Sea is nestled between the British Isles, the Netherlands, Denmark and the Scandinavian Peninsula, and is centered roughly at 55N and 7E. The main focus of this supersite involves understanding the imaging properties of surface waves on SAR imagery. Related experiments will also involve the effects of oil on damping the ocean surface and mapping sea bottom topography. Waves in this area are relatively unique because the limited fetch generates relatively short but steep waves. Near the Netherlands and within the English Channel, the shallow sand bars interact with surface currents, modulating the surface sufficiently to enable detection on SAR imagery, which can be used to map the location of the sand bars and estimate water depth. Crew Observations: Document surface waves in sun glint areas, internal waves propagating from the coastal regions, and clouds and storm systems, possibly along fronts. Document and photograph internal waves and storm activity. Both the Hasselblad and Linhof cameras should be used. h. Labrador Sea The Labrador Sea lies off the northeastern coast of the island of Newfoundland and the southwestern coast of Greenland, with nominal center located at 48 33.8' N and 63 45' W. The experiments linked with this backup supersite will focus on the interaction of waves as they pass through sea ice. The ice edge should extend down the coast of Newfoundland in April, rapidly disappearing in late April with warming. Along with sea ice, eddies are also likely to be present adjacent to or within the ice margin. Ice bergs may also be present in this area. Radar imagery of sea ice shows considerable details. In this region, new and young ice as well as thicker first-year ice will be present. New ice often appears as extensive slicks since the slush-like crystals damp out short waves. Surface waves can propagate through ice, but will eventually be attenuated by the ice itself at a rate that depends on the waves' characteristics and the structure of the ice. Waves affect the ice cover by breaking up floes and increasing deformation. Waves are detectable in the ice cover on SAR imagery. Crew Observations: Document and photograph the location and extent of sea ice and ice bergs, as well as surface waves and eddies within the ice margin. Atmospheric conditions over the ice regions should be noted. i. Straits of Gibraltar (Internal Waves and Coastal Phenomena The Strait of Gibraltar is the outlet of the Mediterranean Sea into the Atlantic Ocean, located between Spain and Morocco. This site is well known for being a source region for internal waves. The internal wave packets are triggered by inflowing Atlantic water accelerated by its passage through the narrow Strait and across the sill at the entrance to the Strait. At the interference between fresher, lighter Atlantic water and more saline, dense Mediterranean water, more internal wave sets are generated. Each soliton develops independently as the tidally driven, eastward flowing water is compressed and upwelling results. To the east of the Strait, currents and fronts are often also present along the coastlines. Crew Observations: Observations of internal waves and fronts and eddies should be documented near and to the east of the Strait. B. Ecology Recent work using AIRSAR has demonstrated a strong relationship between the atmosphere and the land surface which is manifested in a changing dielectric constant distribution and is thus potentially observable by the radar. SIR-C/X-SAR has a potential to demonstrate SAR's utility in monitoring the dynamic biogeochemical and hydrologic processes that are essential to understanding global change. The onboard observations of meteorological conditions will be a key to this success. In general, observations for ecosystem studies will involve test sites which are well studied, well measured and monitored intensively during the shuttle flights by the investigators. If SIR-C/X-SAR had flown several years ago and the investigators had not had AIRSAR data, this might be the extent of the experiments. However, with the advances which have been made with AIRSAR data, most of the ecosystem investigators are expanding their areas of research to include ecosystems which extend many hundreds of kilometers along track and, in some cases, across track using scanSAR and mosaicking capabilities. The ability to obtain ground truth in these large sites, however, is impossible even given great quantities of money. The strategy then is to use other means of obtaining the "ground truth" than the classical means of measuring it in the field. SIR-C/X-SAR provides a unique opportunity to expand beyond the classical test site to large regions. The first step in this process is to test the models which have been developed at the test site in regions outside the test site. These regions are usually documented to some degree with respect to "static" canopy properties (species, height, DBH, number density), however, usually do not contain in-situ weather stations from which environmental properties can be obtained. Local weather stations in airports and global weather maps can provide some information, however, it is next to impossible to determine the exact environmental state at the time of overflight. Observations from the shuttle can provide some of this information. 1. Boreal Forest Until now, the full impact of temporally different radar data of the same sites of the world hasn't been fully assessed or its importance realized. With the SIR-C/X-SAR shuttle flights currently scheduled for April and December (and possibly July or August and October), we should be able to see changes take place over time (day-to-day throughout the mission) and season. The photosynthetic activity of the boreal forests, overall greenness, leaf biomass, and soil moisture will all change over the year. As the shuttle flies over the radar sites, it is very important to document the seasonal state using photographs and notes. On previous shuttle radar missions, no coincident photographs or notes have been taken to correlate the data with what is temporally occurring, and because the world is a dynamic, ever-changing place, it is impossible to always classify a radar image without such supplemental data. In April at mid to high northern latitudes, the greenness and leaf biomass of the deciduous forests are low and the photosynthetic activity in the trees and interchange of carbon is just starting up. Radar may have a low backscatter return because there isn't as much water in the tree and the foliage biomass is low. In July, the photosynthetic activity of the trees is at its peak and there is a much larger amount of leaf biomass and greenness found in the forests. This may cause a greater backscatter from the radar. When the year starts winding down in October, the activity of the trees returns to a more dormant state. Finally, in December, the forests are at the lowest activity of the year, with no biomass in the foliage of deciduous trees and very little water transport; this will likely result in the least amount of radar backscatter. Conifers are green throughout the year, but the freeze/thaw cycle of passing seasons effects their growing season cycles and their backscatter as water in the trees and soil changes phase from solid to liquid. The documentation of the seasonal state of the site goes beyond observing expected seasonal changes. Other events may occur during the shuttle mission that will change the image backscatter. Rain, fires, floods, deforestation, and other such phenomena, man made or natural, all effect the radar return drastically. Documentation of what is happening during each data acquisition will allow scientists to interpret the image data beyond the small region which is documented in the field. a. Raco, Michigan (46.4N, 84.9W) The Raco supersite is in an ecosystem transitional zone; it is located at the ecotone between the boreal forests and the northern temperate forests of North America. Such transitions are expected to be ecologically sensitive to anticipated global changes. The supersite is located at the eastern end of Michigan's Upper Peninsula. The site contains most of the boreal forest species as well as many of the temperate species. Thus, studies here link studies performed to the north and south. The primary objective for the Raco supersite is to use polarimetric radar observations to determine forest state for input to ecosystem models. Specific parameters include total biomass, water status and seasonal leaf biomass. The Raco supersite is located on the borderline between seasonal freeze-thaw and discontinuous permafrost. In April, on a scale of 1 to 0, the greenness factor is 0, or there is no greenness. In July, the greenness increases to .8 to 1. Finally, in October, the greenness decreases, approaching 0 again. Crew Observations: Observations should focus on cloud cover and cloud type, and the extent of the photosynthetic activity or greenness (including fall colors) and should be made all along track, especially into the boreal regions of Canada. Sunglint indicating flooding on land is also important to document. Finally, note the snow cover extent and existence of fires or recent burns. b. Prince Albert and Nelson House, Canada (53.8N, 106.2W and 53N, 106W) The two Canadian boreal forest sites, Prince Albert, Saskatchewan and Nelson House, Manitoba, represent two extremes of a thousand by thousand kilometer test region. The northern site is controlled primarily by temperature and the southern site by water availability. These sites are a part of a much larger NASA project called BOREAS. BOREAS is a four-year, regional-scale experiment to study the forested interior of Canada. The objective of BOREAS is to improve our understanding of the interaction between the Earth's climate system and the boreal forest in order to understand the role of boreal forests in global change. BOREAS will focus on the biological and physical interactions between the boreal ecosystem and the land-atmosphere interchange of energy, water, carbon and greenhouse gases. In the BOREAS sites, there is discontinuous permafrost throughout the year. From May 1 to October 31, the average rainfall for is approximately 5 to 10 inches for the half year for the Prince Albert site. From November 1 to April 30, the rainfall decreases to the point where there is less than 5 inches. At the Nelson House site, the rainfall is approximately 10 to 20 inches from May 1 to October 31, while from November 1 to April 30, it decreases to 5 to 10 inches. In April, there is no greenness at either BOREAS site. In July, the greenness for both sites ranges from .6 to .8. Moving into October, there is again no greenness. Crew Observations: Observations should focus on cloud cover and cloud types greenness (including leaf color change), sunglint on land indicating inundation, snow cover, and indicators of lake freeze/thaw state. 2. Tropical Forests a. Manaus, Brazil (2.7S, 60.8W; 3.3S, 61.0W; 2.4S, 59.8W) Manaus is the major Amazon ecology site of the SIR-C/X-SAR mission. It is situated at the convergence of the Solimoes and Negro Rivers, which then combine to form the Amazon. The Solimoes river is important because it is rich in dissolved nutrients, suspended sediments, and contains vast fertile floodplains. Conversely, the Negro River is nutrient deficient and contains large concentrations of dissolved organic carbon, thus yielding a black water color. These variances make for interesting comparisons. The Manaus site is divided into three different site targets, each located a degree or two apart along different points of rivers and their intersection. One site is a floodplain of geomorphologic and hydrologic significance located at about 150 km west of Manaus. It is the Cabaliana floodplain, named after a prominent nearby lake. Since the land surrounding the site is so nutrient rich, it is a prime target for clear cutting. A second floodplain site is Anavilhas. The third site is the Critical Size Area Project (CSAP) where extensive biodiversity and deforestation projects are on-going. Crew Observations: Document the state of forest and agricultural areas and note any burning activities or smoke near the site. Document the flood extent with high resolution nadir looking photographs. Describe cloud cover, cloud types, and the presence of any rain clouds. Document the clear-cut extent along swath. Note sunglint under the forest as evidence for inundation. b. Pantanal, Brazil (18.8S, 57.0W) Pantanal is another Amazon site. Both Amazon sites, Manaus and Pantanal, though located at differing latitudes, have similar goals. They are tropical floodplain study sites. They consist of wetlands, which are a key element in understanding global, hydrologic and biochemical cycles. Floodwater residence times are located on the extensive floodplains of major river systems (Amazon) and are closely related to rates of evapotranspiration, groundwater recharge, primary production, trace gas generation, river flood waters, etc. Crew Observations: The Pantanal area has been extensively clear-cut and developed in the past. Documentation of any developmental changes or trends would be helpful. c. Sena Madureira, Brazil (9.0S, 68.4W) Sena Madureira is another important Amazon site. Its latitude varies from Pantanal, yet still has been the victim of extensive clear cutting. Crew Observations: Photographic documentation of the site and surrounding development would be extremely beneficial in interpreting current trends. 3. Mid Latitude Forests a. Duke Forest, North Carolina (36.0N, 79.0W) The Duke Forest is located immediately west-southwest of Durham, North Carolina. There are 3400 ha within the Duke Forest, 800 of which are old-field loblolly pine stands. The ages of these pine stands range from one to greater than 100 years, and represent the successional stages of southern pine species. Numerous ecological studies have been performed on test stands within the Duke Forest, the earliest being in the 1930s. The need to develop remote sensing techniques to study temperate forest ecosystems is especially compelling: such forests occupy approximately 36 percent of the Earth's forested land surface. These forests produce over 75 percent of the forest products (timber and fiber) used by human society. In addition, temperate forests are especially important in studies of trace gas fluxes from the Earth's surface. Most temperate forests have been disturbed to a lesser or greater extent over the past two centuries, and are in various stages of succession. This fact greatly affects their carbon source-sink relationships, and may contribute greatly to fluxes in carbon dioxide. Recent studies indicate that an understanding of the carbon dynamics of temperate region forests may be crucial. Crew Observations: Describe the weather conditions at the site. b. Howland, Maine (45.2N, 68.8W) Howland has been the focus of intensive studies over the past several years. On or near the site, there are a variety of different-aged clearings, small plantations, and larger expanses of natural forest cover. The natural forest is transitional boreal with major forest types of mixed hardwoods (aspen, birch), spruce-hemlock, and hemlock-mixed hardwoods. Because of the glacial history of the area, soil drainage classes vary from well drained to very poorly drained over a limited distance producing a complex mosaic of forest communities. In addition, significant areas of bogs and wetlands occur throughout the area. Crew Observations: Documentation of cloud extent and type; weather systems, and vegetation greenness (including leaf color changes). Notation of recent burns or ongoing fires should be made. Snow extent and evidence of inundation through sun glint should be documented. In support of the experiment to study turbulent exchange with the forest canopy, documentation of upwind source areas is important. c. Altona, Canada (49.1N, 97.6W) Altona, Canada is an agricultural site, extremely close to the US/Canada border near North Dakota. Its main focus revolves around crop discrimination and assessment. Some goals are to determine The Leaf Area Index (LAI) for crop yield models, and the watershed soil moisture runoff for hydrologic cycle models. Snowpack and watershed snowmelt are associated important model inputs. Crew Observations: Documentation of cloud extent and type; weather systems, and vegetation greenness. Snow extent and evidence of inundation through sun glint should be documented. Document seasonal burning. 4. Sahel Transition A number of data takes have been planned which cross the Sahel transition in Africa. A series of AVHRR images are shown indicating changes in vegetation greenness with season across this transition zone. Also shown is a Seasat scatterometer "image" of Africa. This image is essentially a 4 km resolution K-band radar image of Africa; the Sahel transition is clearly shown. Crew Observations: Observations of cloud extent and type, existence of fires and recently burned areas, vegetation greenness and indications of flood extent are important all along the Sahel transition data takes as well as along the data takes for the north African deserts which cross the Sahel. C. Hydrology In general, crew observations of all hydrology sites should include at least one pass with continuous photography to capture the seasonal state of the site at the time of the mission. This would best be done when the shuttle flies directly overhead which is a pass when no radar data would be acquired. Weather predictions should, however, be taken into account as it may be forecast to be clear early in the mission and cloudy later therefore implying the carpeting photographs should be taken early in the mission even if the look angle is high. For supersites and backup supersites, it is desirable to obtain carpet coverage for all data takes to document temporal changes in the hydrologic state of the surface from day to day. Snow cover, water extent and weather should be documented along each hydrology data pass. 1. Snow a. Mammoth, California (37.5N, 119.0W) The instrumented site at Mammoth Mountain ski area is on the eastern slope of the south-central Sierra Nevada at an elevation of 2930 m, approximately 50 km northwest of Bishop, California. A snow study plot has been maintained there since 1978. The site is an open, high altitude area characterized by high winds and dry snow, and is typical of the Sierra Nevadas alpine region. Wind speeds of 30 meters per second are not uncommon. Vegetation is sparse with only a few large trees 50 to 200 meters away. Mean winter air temperature is approximately -5C, and mean annual maximum snow water equivalent is about 0.8 m. Snowfall usually begins in early November, and the snowpack often persists well into May. The site is instrumented with complete automatic meteorological capabilities, radiometers, a snow pillow, and snow lysimeters. At this site, it is possible to carry out a complete energy budget from the beginning of the accumulation season until the end of the snow melt season. The major goal of the proposed work is to model the spatial distribution of snow surface energy exchange, snow metamorphism, and snow melt in alpine drainage basins. For hydrologic and land surface climate investigations in alpine areas, seasonal snow cover and alpine glaciers are important parameters. Over major portions of the middle and high latitudes, and at high elevations in the tropical latitudes, snow and alpine glaciers are the largest contributors to runoff in rivers and to ground water recharge. Snow and ice also play important interactive roles in the regional climates because snow has a higher albedo than any other natural surface. Understanding processes in the seasonal snow cover is also important for studies of the chemical balance of alpine drainage basins because of translocation of anions and cations within the snowpack and possible concentrated release in the first phases of the melt season. Crew Observations: Observations should focus on careful documentation of the extent of the snow along the Sierra Nevada Range and on meteorological conditions at the time of each data pass. b. tztal, Austria (46.8N, 10.8E) The tztal test site is located in the Central Alps of Tyrol, Austria, north of the main east-west ridge of the divide between the rivers Inn and Danube, which drain to the Black Sea, and the river Etsch, which drains to the Mediterranean Sea. The mountains of upper tztal are composed of paragneisses with subordinate amphibolites and orthogneiss. The summits of the main peaks reach elevations of 3500 to 3768 meters above sea level. About 25% of the test site is covered by glaciers; the largest glacier is Gepatschferner which covers 17 km2. The firn areas of the large glaciers are located on plateaus above 2900 meters. These relatively level areas are considered to be relic landforms from the Miocene Epoch. The tongues of the large glaciers descend from the firn fields down into narrow valleys which formed during the last ice age. Cirques below mountains ridges are frequently occupied by small cirque glaciers. The test site's core area is the glacier region of the Venter Tal, which is one of the most intensively studied areas for glacier research in the world. Research in the Venter Tal includes studies of glacier dynamics, glacier-climate relations, and snow and glacier hydrology. After dangerous outbreaks of glacier-dammed lakes, the first scientific glacier observations were reported in 1772. Continuous glacier surveys were initiated in the Vent Valley in the 1890s, resulting in a valuable record of glacier-climate interactions. In addition to scientific research on glaciers and snow cover, these phenomena are also important to water management, water power production, and flood and avalanche protection. Permanent equipment for snow and glacier research includes two research stations at high altitudes, runoff gauges, and meteorological stations. Crew Observations: Document the snow extent at the site. 2. Soil Moisture a. Chickasha, Oklahoma (34.9N, 98.0W) The Little Washita River Watershed covers 235.6 square miles and is a tributary of the Washita River in southwest Oklahoma. The watershed is in the southern part of the Great Plains of the United States. The climate is classified as moist and subhumid; the average annual rainfall was 29.42 inches. Summers are typically long, hot, and relatively dry, and winters are typically short, temperate, and dry but are usually very cold for a few weeks. Much of the annual precipitation and most of the large floods occur in the spring and fall. The Little Washita River Watershed in southwest Oklahoma is unique in that over a period of several years it has had an unusually large amount of soil and water conservation treatment and research. In 1961, the USDA's Agricultural Research Service began collecting hydrologic data on the Little Washita River Watershed and other watersheds in the vicinity to determine the downstream hydrologic impacts of the floodwater-retarding reservoirs. This data collection process involved an intensive rain gauge network and a stream gauging station near the watershed outlet that provided data on continuous flow, suspended sediment transport, and, for a few years, water quality. Data on groundwater levels and channel geometry were also collected to determine possible effects of the treatment program. Crew Observations: Observations should focus on describing the weather, cloud cover and the vegetation greenness. Emphasis should be on the entire basin as opposed to the small test site. Regional hydrologic events such as storms, snow, flooding and leaf color are important to document. Low sun angle photography is important to help understand terrain effects on the local incidence angle of the radar. b. Bebedouro, Brazil (9.1S, 40.2W) Bebedouro is a hydrology site located in the northern Rio Sao Francisco Valley, northeast Brazil. It is centered around the Bebedouro irrigation project. The irrigated area is 1750 ha, the size of individual fields varies between 5 and 12 ha. The regional climate is classified after Kppen as Bsh'w-type, with a minimum air temperature of 14C and a maximum temperature of 39C, and an average annual precipitation of 391.5 mm; the relative humidity varies from 56.7 to 67.1% and the annual evaporation is 2106 mm. Agriculture plays an important economic and social role in Brazil. One of the major problems related to Brazilian agriculture is estimating planting areas and productivity. Optical remote sensing techniques have been useful for performing this work. Summer crops (December/April) account for more than 90% of the agricultural production. Due to the coincidence of the summer growing season and the rainy season (precipitation above 1200 mm at the crop-producing region in southern and southeastern Brazil), it is difficult to obtain useful remote sensing data at the visible and infrared wavelengths on a regular basis. Spaceborne microwave remote sensing techniques are considered a potential alternative to solving this problem. Flood plains of major Brazilian rivers have high potential for the expansion of Brazilian agriculture. This is especially true in semi-arid regions in northeastern Brazil where long drought periods cause many social and economic problems. There are approximately 800,000 ha of floodplains suitable for irrigation at the Rio So Francisco Valley (a Brazilian south-north flowing river system). Of these, approximately 90,000 ha are operational and 75,000 ha are being implemented. The Bebedouro test site includes an experimental irrigation project. A major hydrologic problem related to these floodplains is salinization due to improper irrigation practices. Within this context, irrigation techniques that would integrate hydrological data are of great relevance. Microwave remote sensing techniques are of special interest to estimate surficial soil moisture, one of the fundamental components of the hydrological cycle. Crew Observations: Document weather, floodplain conditions, extent of inundation, and the condition of the vegetation canopy. The investigators are particularly interested in the floodplain. D. Geology Crew observations for geologic application should focus on obtaining high resolution photographs of the sites with attention also to any temporal changes in snow cover or storm cloud conditions from day to day which might be confused with incidence angle effects. Low sun angle photographs are particularly useful for emphasizing subtle topographic and/or roughness features. The mission timeline in terms of sun angle over the sites should be assessed to determine the optimum passes for low sun angle photography. The best high resolution photographs might acquired when the shuttle is directly over the sites when no radar data are being acquired. Stereo pairs are also useful. Photographs should be primarily focused on the target site with less emphasis on carpeting the entire pass. 1. Geology-Climate Interaction a. Andes The Andes Mountains of South America provide an ideal laboratory to study the effects of both modern and Quaternary climate changes. Their vast stretch of 60 degrees across numerous climate zones, and the traces left by centuries of glaciers and ice sheets make them perfect for tracing and reconstructing the Earth's changing climate. Previous glaciations produced a series of extensive moraines, the earliest of which is at least 700,000 years old. The sparse vegetation and slow weathering rates, resulting from the semi-arid climate, allow the use of SIR-C/X-SAR to estimate moraine chronology from space. This information can then be used as a "calibration" for the Andes enabling this SAR dating technique to be extended to other moraines imaged by future SAR missions. Due to remoteness and cloud cover, the two Patagonian ice caps adjacent to the supersite are among the least studied of the Earth's major alpine snow and ice fields. SIR-C/X-SAR images across the Patagonian Lake District will provide a powerful means to determine the present-day glacier and snow extents, and to estimate equilibrium line altitudes on glaciers. The specific Andes sites are: Puerto Aisen, Andes (46.0S, 73.0W) Cerro Cumbrera, Andes (47.5S, 73.0W) Cerro Laukara, Andes (49.0S, 73.0W) Crew Observations: The biggest indicator for site location will be the distinctive river system. If major rivers are located and identified, it will be easy to locate the supersites. The northern-most supersite is Puerto Aisen, bordered directly to the south by the second Andean supersite, Cerro Cumbrera. The third and southern-most of the supersites is Cerro Laukaru. Crew observations should focus on monitoring dust storms and determining the extent of the snow line and locations of glaciers. Observations of weather related phenomena including clouds, snow extent, dust storms and major weather systems are important. Documentation of lake and glacier extent and location using high resolution photography is also important. Where possible, stereo photography should be acquired. 2. Volcanoes (Much of the following text was taken from a document titled "Space Shuttle Observations of Basaltic Volcanoes: An Astronaut's Guide for the SIR-C/X-SAR Mission" by Scott Rowland and Peter Mouginis-Mark.) All the volcanoes that will be imaged during the SIR-C/X-SAR mission are basaltic shields, characterized by mostly gradual slopes, hundreds of lava flows, and calderas at their summits. The radar data will be used mostly for mapping the distribution of surface units (the lava flow and possibly ash deposits), so observations of associated features will be extremely important. These include vent structures (i.e. spatter ramparts, cinder cones), fissures, and faults. Unusual vegetation patterns can also be used to interpret both the spatial and temporal distribution of eruptive products. a. Galapagos Islands (0.2S, 91.3W) Not much is known about the volcanoes of the western Galapagos Islands. The seven shield volcanoes in this area (Fernandina, Ecuador, Wolf, Darwin, Alcedo, Sierra Negra, and Azul) collectively have erupted more than sixty times in this century alone. Due to their inaccessibility and delicate ecology, these volcanoes are rarely studied. In addition, the rugged terrain, lack of water and field support make these volcanoes difficult to map and study in the field. Volcanoes in the Galapagos are spaced 10-25 km apart. The identification of proto-rift zones may indicate that the inside of the volcano has preferred lines of weakness that permit easy eruption of lava. These lines of weakness may be influenced by the regional structure of the islands rather than the shape of the individual volcano. The derived radar maps may help decide between these two models. The northern flanks of Wolf Volcano, and most of the flanks of Alcedo Volcano, are either covered with vegetation that is approximately 50 cm high or ash deposits that measure less than a meter in thickness. In Landsat and SPOT data, however, these areas are bland. In addition, evidence is seen for changes in the locations of rift zones on Wolf and, from field work, buried lava flows have been identified on Alcedo and may be visible in radar images. Identification of changes in the location of the rift zone would permit the long-term evolution of the volcanoes to be determined for the first time. The flanks of all the volcanoes, but particularly Fernandina, Wolf, and Darwin, are in very steep elevations. Many lava flows descend the slopes of these volcanoes and will possibly show wide variations in lava texture. Such textures are usually used to indicate flow rheology and mass eruption rate. The calderas of Fernandina, Wolf, Darwin, and Azul experience multiple collapse events and produce kilometer-deep summit craters. Crew Observations: Historically, Darwin Volcano has been less active than Fernandina, but its surface is still dominated by young flows. Darwin differs from Fernandina in that its caldera is presently in a state of infilling. High-magnification photos of the near-caldera region are needed to help determine whether this relative fullness of the caldera has had an effect on the number and orientation of fractures. Of equal interest are the two large tuff cones on the west southwest coastline. Ash from these eruptions appears to make up a large part of the volcanic flank in this area and photographs of this area would be useful. Fernandina, the westernmost island in the Galapagos archipelago, has been studied extensively using remote sensing. High magnification photos of the summit plateau and caldera interior would be useful since this is the most active part of the volcano. Also, any use of side-lighting techniques to accentuate textural differences should make mapping these areas easier. The attached photo and overlay give a detailed map of Fernandina. b. Hawaii (19.35N, 155.3W) The Hawaiian test site extends from the summit of Kilauea Volcano along the Southwest Rift Zone towards the ocean and centers on the Ka'u desert. Bordered by Mauna Loa Volcano to the northwest and the Koae Fault system to the southeast, the Ka'u desert contains many lava morphologies and ash deposits that are expected on other volcanoes. Rift zone eruptions in Hawaii differ from the summit activity in both lava flow morphology and rate of surface eruption. Some structural features associated with the rift zones of Mauna Loa appear to reflect the interaction between magma injection into the upper parts of the volcano, gravitational slumping of the edifice, and the buttressing of the flanks by adjacent volcanoes. Evidence from the SIR-C/X-SAR data may prove changes in eruption style may be related to dike propagation and the internal structure of the volcanoes. Crew Observations: Kilauea, on the south coast of Hawaii, is the most active of the volcanoes being imaged on the SIR-C/X-SAR mission, and stands a good chance of being in eruption during the shuttle flight. Since the radar will be used to detect changes in the active flow field during the flight, any observations of where the activity is occurring at a particular time (especially at night) would be most helpful. The east rift zone curves first southeast then northeast away from the caldera. Two prominent compound flow fields along this rift are those of Mauna Ulu (1969-1974) and Puu Oo/Kupaianaha (1983-present). Of special interest is the accentuation of different units within these flow fields by use of sun glint, therefore, observations and photographs of Kilauea at slanting angles would be useful. The attached photo and overlay should make identification of target areas much easier. Focus on possible eruptions as indicated by plumes in the day and glow from the eruptions at night. 3. Buried Rivers a. Sahara (20.0N, 0E - 30E) The Sahara Desert is riddled with river channels that dried up long ago. These channels have been degraded by time. Sand piles up in them, burying a link to the past. When you look at shuttle photographs of the desert, you can hardly see the river channels. You can only notice slight topographic features that may be related to the location of the river channels. Huge dust storms also often obscure the rivers in shuttle photographs. The camera cannot see through sand that is blowing in the wind. This makes the photo slightly blurry. SIR-C/X-SAR radar penetrates the sand in the air and on the ground and is able to detect the river channels that lay beneath. When these rivers were flowing, there is a high possibility that there was life in what is now the biggest desert in the world. People probably lived near these water sources. Global climate change caused these rivers to dry up, making human life in the Sahara virtually impossible. Humans moved on to the present Nile, but they left behind clues that will help us figure out what life was like in their time. The location of these river channels would be a valuable resource in the fields of archaeology and anthropology. If people lived near these water sources, the channels would be full of artifacts that tell about the past. Locating the channels may also help locate groundwater and mineral sources that would benefit the people struggling to survive there today. When you look at the desert sites from space there are many different features to notice about the desert. When the sand has ridges that look fairly straight and are going in the same direction, they are wind streaks, or lines made in the sand by the wind. The features that look like ocean waves in the sand are probably sand dunes. They are formed by the wind blowing sand into piles that keep building up as the wind continues to blow in that direction. Crew Observations: Observations should focus on documenting dust storms and sketching drainage patterns and sand dunes along the radar swaths. Low sun angle photographs are particularly useful. b. Safsaf, Egypt (22.18N, 29.79E) The Safsaf site extends from southcentral Egypt to northwestern Sudan. It is a flat plain that is also known as the Selima Sand Sheet. Safsaf has many geological features that are covered by sand and dust. These features were discovered by pits that were dug during field experiments in 1982, 1983 and 1984. It was discovered that there is a wide range of sediments, including bedrock, limestone, and sandstone, that were preserved there. This site is used to test the SIR-C/X-SAR radar responses to different rock types and determine the depth of radar penetration. Sensors will be placed at different depths in the sand to determine how the signal penetrates the sand. The photos of Safsaf show no indication of a river system. Low sun angle photos of the desert need to be studied to differentiate surface from sub-surface backscatter returns. There are many photos taken of the Nile River and other recognizable sites, however, we need photos that look west of the Nile, into the Sahara. It may just look like sand, but the slightest topographical features can help to locate buried features. Crew Observations: Document dust storms and weather conditions at the site. Sketch subtle regional topographic control of relic drainage patterns and aeolian sand transport pathways. c. Saudi Arabia (19.1N - 28.9N, 39.9E - 57.0E) Saudi Arabia is a desert country, but it has many valuable resources buried beneath the sand. Using SIR-C/X-SAR to map the surface may help locate these resources. The Saudi Arabia sites are spread over central Saudi Arabia, however, there is a high concentration of sites in the southcentral part of the country. The SIR-C/X-SAR radar will be used to map surface roughness of Saudi Arabia. The radar can see through shallow sand or soil to determine the surface roughness of the rocks. The surface roughness of the rocks will indicate the rock type which in turn may help determine prospective areas for oil, gas, and water reserves. Crew Observations: Low sun angle photos of Saudi Arabia should be acquired to highlight subtle surface features in shadow, allowing the surface to be studied in more detail. Crew observations should also focus on documenting dust storms and wind streaks in the sand. Color and IR photographs of the region should be obtained in a carpeting mode. 4. Geomorphology and Weathering a. Stovepipe Wells, California (36.6N, 117.1W) Death Valley is located in central eastern California near the Nevada border. Stovepipe Wells is the specific region of interest within Death Valley. It is in the southern part of the Great Basin. It has a wide range of elevations from 70 m below sea level to 3300 m above sea level at Telescope Peak. The main area of interest at this site is the valley floor and the formation of alluvial fans. Interest also lies in documenting how the fans have weathered through climatic change. Death Valley, California is a fragile environment that has great variety in it's surface features. There are differences in the rock and soil types throughout the valley. There are many different sedimentary, igneous, and metamorphic rocks that have been exposed to different types of environments in the valley. Using SIR-C/X-SAR, lithic maps can be made of Death Valley. It is a good site to test lithologic mapping techniques because of the variety in the rock types. These maps can be used in long term studies with the goal of understanding past climatic changes. By understanding the changes in the rocks prompted by the environment, we can better understand how future climatic changes will effect the Earth by erosion. Crew Observations: Observations should focus on aeolian activity (especially sand or dust storms) and weather. High resolution photographs focusing on the alluvial fans and dune orientation are important. Color IR photography is desired. b. Hotien, China (36.8N, 80.8E) SIR-C/X-SAR data from the Hotien East, China test site will be used to determine the history of Quaternary climate change for a portion of northwestern China. This history will be included in global paleoclimate models and reconstructions of the tectonic history of the area. This work will test the hypotheses that: 1) Chronologies developed at a few widely separated sites in northwestern China may be used to correlate surfaces and make surface-age maps using remote sensing data; 2) These maps contain information about the temporal and spatial distribution of climate changes that can be related to other global climate records; and 3) The surface-age maps can be used to date fault movements over a large area of northwestern China. The specific objectives are to: 1) Determine the extended spectral signatures of desert piedmont surfaces and landforms of different ages using laboratory, field, and remote sensing data in a few widely separated test sites in northwestern China where chronological control is available or can be developed; 2) Use the spectral signatures to map the distribution and correlate the ages of surfaces and landforms related to past climate changes; 3) Determine the history of Quaternary climate change for the region based on the maps and ages; 4) Determine the ages of Quaternary movements on some of the large, active faults in northwestern China; and 5) Compare the types, rates, and magnitudes of surficial modification processes that have operated in northwestern China to those in the southwest U.S. which are also being studied. Crew Observations: Observations should focus on monitoring snow extent and weather conditions. Stereo photographs of the test site and full resolution photographic series along the swath on a clear day are desired.  The Johns Hopkins University Center for Talented Youth (CTY) is dedicated to identifying young people with exceptional academic abilities and offering them accelerated academic programs specially suited to their own individual rates of learning.  Way, J.B., K. McDonald and J. Bachman, 1993. Diurnal change in SAR backscatter and scattering mechanism as observed with AIRSAR at the Duke University Experimental Forest. IEEE Trans. on Geosci. and Rem. Sens., in preparation.  The Changing Carbon Cycle: A Global Analysis, 1982. Trabalka, Reichle, eds. Springer-Verlag, New York, p236.  Zimmermann's notes.  Earth Science Mapping, 1989. Joseph McCall and Brian Marks, eds., Sterling House, London, England, p169.  Vickie Conners, Langley Research Center  Campbell, William J., et al., 1987. Arctic Sea Ice, 1973-1976: Satellite Passive Microwave Observations. NASA SP-489, Scientific and Technical Information Branch, NASA, Washington D.C. Campbell, William J., et al., 1983. Antarctic Sea Ice, 173-1976: Satellite Passive Microwave Observations. NASA SP-459, Scientific and Technical Information Branch, NASA, Washington D.C.  Justice, C. O., 19xx. 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