BOREAS Level-2 MAS Surface Reflectance and Temperature Images in BSQ Format Summary: The BOREAS Staff Science Aircraft Data Acquisition Program focused on providing the research teams with the remotely sensed aircraft data products they needed to compare and spatially extend point results. The MAS images, along with other remotely sensed data, were collected to provide spatially extensive information over the primary study areas. This information includes biophysical parameter maps such as surface reflectance and temperature. Collection of the MAS images occurred over the study areas during the 1994 field campaigns. The level-2 MAS data cover the dates of 21-Jul-1994, 24-Jul-1994, 04-Aug-1994 and 08-Aug-1994. The data are not geographically/geometrically corrected; however, files of relative X and Y coordinates for each image pixel were derived by using the C130 navigation data in a MAS scan model. The data are provided in binary image format files. Note that due to storage space limitations, only the level-2 MAS images collected on 21-Jul-1994 are included on the BOREAS CD-ROM series. Users interested in images from other dates should refer to the inventory listing provided on the CD-ROMs and Section 15 to determine how to obtain the data of interest. Some of the image data files on the BOREAS CD-ROMs have been compressed using the Gzip program. See section 8.2 for details. Table of Contents * 1 Data Set Overview * 2 Investigator(s) * 3 Theory of Measurements * 4 Equipment * 5 Data Acquisition Methods * 6 Observations * 7 Data Description * 8 Data Organization * 9 Data Manipulations * 10 Errors * 11 Notes * 12 Application of the Data Set * 13 Future Modifications and Plans * 14 Software * 15 Data Access * 16 Output Products and Availability * 17 References * 18 Glossary of Terms * 19 List of Acronyms * 20 Document Information 1. Data Set Overview 1.1 Data Set Identification BOREAS Level-2 MAS Surface Reflectance and Temperature Images in BSQ Format 1.2 Data Set Introduction The BOREAS Staff Science effort covered those activities which were BOREAS community level activities, or required uniform data collection procedures across sites and time. These activities included the acquisition of the relevant aircraft image data. Data from the Moderate Resolution Imaging Spectroradiometer (MODIS) Airborne Simulator (MAS) onboard the National Aeronautics and Space Administration (NASA) C130 aircraft were acquired by staff of the Medium Altitude Aircraft Branch at NASA Ames Research Center (ARC) and provided for use by BOREAS researchers. BOREAS Information System (BORIS) personnel worked with MAS personnel at NASA Goddard Space Flight Center (GSFC) in processing the MAS and related C130 navigation data to derive and archive the 12 band Level-1b MAS imagery. The Level-1b MAS imagery were atmospherically corrected by personnel at NASA Ames Research Center to generate the 12 band Level-2 MAS imagery. 1.3 Objective/Purpose For BOREAS, the MAS data, along with the other remotely sensed images, were collected to provide spatially-extensive information over the primary study areas. This information includes detailed land cover and biophysical parameter maps such as fPAR (fraction of Photosynthetically Active Radiation), and LAI (Leaf Area Index). The MAS data were also to serve as test data sets for the MODIS Land Group (MODLAND) in exercising their parameter derivation algorithms. 1.4 Summary of Parameters Level-2 MAS data in the BORIS contain the following parameters: Descriptive information as American Standard Code for Information Interchange (ASCII) text records, reflectance values for image bands 1 to 12, relative X and Y pixel coordinates, and per pixel view zenith and azimuth angles. 1.5 Discussion BORIS personnel at NASA GSFC created the level-1b MAS imagery by: Extracting aircraft location and attitude information from BOREAS Level-0 C130 Navigation Data, Combining MAS image and C130 navigation data to make a Hierarchical Data Format (HDF) file, Extracting image and ancillary information from the HDF file and reformatting it into a band sequential (BSQ) format 8mm tape product for distribution, and creating a descriptive inventory of the MAS data product in the BORIS database. ARC personnel created the Level-2 MAS imagery by: obtaining the Level-1b MAS imagery from BORIS, obtaining radiosonde data from BORIS, modeling the path transmittance and path radiative emission (thermal channels) using a Moderate Resolution Model of LOWTRAN7 (MODTRAN), modeling the path water vapor column concentration and downwelling irradiance using the Second Simulation of the Satellite Signal in the Solar Spectrum (6S), and processing the imagery using NASA Ames' Image Atmospheric Correction (Imagecor) program. 1.6 Related Data Sets BORIS Level-1b MAS Imagery: At-sensor Radiance in Band Sequential Format BOREAS RSS-12 Airborne Tracking Sunphotometer Measurements BOREAS RSS-12 Automated Ground Sunphotometer Measurements in the SSA 2. Investigator(s) 2.1 Investigator(s) Name and Title Robert C. Wrigley (retired) Principal Investigator Co-Investigators: Michael A. Spanner NASA Ames Research Center Robert E. Slye NASA Ames Research Center 2.2 Title of Investigation BOREAS Staff Science Aircraft Data Acquisition Program 2.3 Contact Information Contact 1 ------------ Brad Lobitz Johnson Controls World Services NASA Ames Research Center Moffett Field, CA (650) 604-3223 blobitz@gaia.arc.nasa.gov Contact 2 ------------ Jeffrey A. Newcomer Raytheon STX Corporation GSFC Greenbelt, MD (301) 286-7858 (301) 286-0239 (fax) Jeffrey.Newcomer@gsfc.nasa.gov 3. Theory of Measurements The MODIS was developed as part of the Earth Observing System (EOS) to meet the scientific needs for global remote sensing of clouds, aerosols, water vapor, land, and ocean properties from space. MODIS is scheduled to be launched in 1999 on the EOS AM-1 platform (King et al. 1995). In support of MODIS remote sensing algorithm development, the MAS was developed by Daedalus Enterprises, Inc. for NASA's high-altitude ER-2 research aircraft, and is an outgrowth of the development of the Wildfire infrared imaging spectrometer. In a cooperative effort between the High Altitude Missions Branch at NASA Ames Research Center and the MODIS science team, Wildfire was converted to the MAS and upgraded over a series of several experiments, starting with the First ISCCP Regional Experiment cirrus campaign (FIRE II) in November 1991. The locations of the MAS spectral channels were chosen to enable a wide variety of Earth science applications. Of the 50 MAS channels, 19 have corresponding channels on MODIS. The remaining MAS channels fill in the spectral region around MODIS locations and some provide unique coverage. One application of the MAS solar channels is the study of cloud properties at high spatial resolution. The majority of the molecular absorption in the shortwave region of the solar spectrum is due to water vapor, with some ozone absorption in the broad Chappuis band (~0.6 um) continuum. The reflectance measurements in the 1.61, 2.13, and 3.74 um windows provide useful information on the cloud droplet size. Reflectance measurements in the visible wavelength region, in contrast, show little variation with droplet size and can thus be used to retrieve cloud optical thickness (cf. Twomey and Cocks 1989, Nakajima and King 1990). The reflectance at 0.94 um is attenuated by atmospheric water vapor; these measurements, in conjunction with spectrally close atmospheric window reflectances, can provide an estimate of the total precipitable water in cloud-free regions (Kaufman and Gao 1992). Cloud properties can also be estimated from the thermal bands. In the 3.7 um window, both solar reflected and thermal emitted radiation are significant, though the use of the reflectance for cloud droplet size retrieval is seen to be much more sensitive than the thermal component. CO2 absorption is important around 4.3 um and at wavelengths greater than about 13 um. The MAS bands in these spectral regions can indicate vertical changes of temperature. The 4.82-5.28 um channels are useful for investigating both horizontal and vertical distributions of moisture. Low level moisture information is available in the split window measurements at 11.02 and 11.96 um, and correction for moisture attenuation in the infrared windows at 3.90, 11.02, and 11.96 um enables estimation of sea surface skin temperature (Smith et al. 1995). The MAS infrared spectral bands enable the study of cloud properties at high spatial resolution. Products include cloud thermodynamic phase (ice vs water, clouds vs snow), cloud top properties, and cloud fraction. The cloud top properties (height, temperature, and effective emissivity) can be investigated using the CO2 slicing algorithm (Wylie et al. 1994) that corrects for cloud semi-transparency with the MAS infrared CO2 bands at 11.02, 13.23, and 13.72 um. Cloud phase can be obtained using MAS 8.60, 11.02, and 11.96 um brightness temperature differencing (Strabala et al. 1994) as well as by using visible reflection function techniques (King et al. 1992) utilizing ratios of the MAS 1.61 and 0.66 um bands. In addition to the remote sensing of cloud radiative and microphysical properties, the MAS is of value for the remote sensing of land and water properties under channel clear-sky conditions. MAS visible and near-infrared channels have been used to estimate suspended sediment concentration in near- shore waters and to identify water types (Moeller et al. 1993, Huh et al. 1995). Land vegetation properties can also be studied. In a cooperative effort between Dr. M. King (Code 900, NASA GSFC), BOREAS scientists, and the NASA ARC C130 missions staff, the MAS was installed into the NASA C130 aircraft for use during the 1994 summer field campaign of BOREAS. 4. Equipment 4.1 Sensor/Instrument Description In support of MODIS remote sensing algorithm development, the MAS was developed by Daedalus Enterprises, Inc. for NASA's high-altitude ER-2 research aircraft. Over the past several years, upgrades included new detector arrays, grating modifications, an improved broadband lens for the infrared channels, new dewars, and various electronics improvements, all of which resulted in improved in- flight radiometric performance. The overall goal was to modify the spectral coverage and gains of the MAS to emulate as many of the MODIS spectral channels as possible. With its much higher spatial resolution (50 m vs 250-1000 m for MODIS), MAS is able to provide unique information on the small-scale distribution of various geophysical parameters. Originally, and for the BOREAS deployment, MAS used a 12 channel, 8 bit data system that somewhat constrained the full benefit of having a 50 channel scanning spectrometer. Beginning in January 1995, a 50 channel, 16-bit digitizer was used, which greatly enhanced the capability of MAS to simulate MODIS data over a wide range of environmental conditions. The 12 data channels configured for the BOREAS IFC-2 C130 flights were: Data MAS Spectral Center Spectral Channel Channel Wavelength (um) Feature ------- ------------ ------------------ -------------------- 01 01 0.547 green peak 02 02 0.664 chlorophyll 03 04 0.745 NIR plateau 04 05 0.786 NIR plateau 05 06 0.834 NIR plateau 06 07 0.875 aerosols 07 09 0.945 water vapor 08 10 1.623 pollutants 09 20 2.142 mid-IR water 10 32 3.900 11 45 11.002 surface temperature 12 46 12.032 surface temperature A total of 716 Earth-viewing pixels are acquired per scan at a scan rate of 6.25 Hz. Information provided by the aircraft inertial navigation system is used to adjust the timing of the digitizer, providing up to 3.5 degrees of roll compensation, in 0.03 degree increments. 4.1.1 Collection Environment As part of the BOREAS staff science data collection effort, the Ames Research Center Medium Altitude Aircraft Branch collected the 12-band MAS multispectral scanner data. The MAS was flown on NASA's C-130 aircraft during BOREAS (see the BOREAS Experiment Plan for flight pattern details and objectives). The MAS was flown at medium altitudes aboard NASA's C-130 aircraft based at the NASA ARC and provided 20 meter spatial resolution at nadir at an altitude of 7,500 meters. 4.1.2 Source/Platform For the BOREAS missions in 1994, the MAS was mounted in the NASA C130 aircraft operated by the NASA ARC. 4.1.3 Source/Platform Mission Objectives The C130 mission objectives for BOREAS were to acquire high resolution digital imagery with a variety of sensors during optimally clear days of the BOREAS field effort in 1994. 4.1.4 Key Variables Emitted radiation, reflected radiation, and temperature. 4.1.5 Principles of Operation The optical system of the MAS is composed of a configuration of dichroic beam splitters, collimating mirrors, folding mirrors, diffraction gratings, filters, lenses, and detector arrays. Both the spectrometer and fore optics portions are mounted to an aluminum optical baseplate assembly, which are pinned and mated. A full face scan mirror canted 45 degrees to the along track direction directs light into an afocal Gregorian telescope followed by a fold mirror that directs light back through a field stop aperture. A 2.5 cm Pfund assembly paraboloid forms a collimated image of the aperture, which strikes a fold mirror that directs the incoming radiation upward into the aft optics spectrometer unit Thermal and dark visible references are viewed on the backscan rotation of the scan mirror. The thermal reference sources are two blackened copper plate temperature-controllable blackbodies. One blackbody is viewed prior to the Earth-viewing (active scan) portion of the scan, while the other is viewed following the active scan. The telescope alignment is maintained under the low temperature environment using Invar steel and aluminum structural components. The spectrally broadband energy transmitted and reflected by the dichroics is dispersed onto the detector arrays from blazed diffraction gratings. The bandpass of a channel is determined by the geometry of the detector monolithic array and its location with respect to the grating. The radiation transmitted by the first dichroic (D1) is reflected by a mirror and diffracted by grating G1 onto a filter and lens assembly that focuses the radiation onto a silicon photovoltaic array with channel response in the wavelength range from 0.55 to 0.95 um (channels 1-9). Part of the radiation reflected by D1 reflects off the second dichroic (D2) and is redirected by two fold mirrors, diffracted by grating G2, passed through a cold blocking filter, and focused onto an indium-antimonide (InSb) focal plane array assembly containing channels 10-25 (1.61 to 2.38 um). From D2 the remainder of the spectrally separated energy strikes the third dichroic D3, part of which is reflected and enters port 3, where it is redirected by two fold mirrors, diffracted by grating G3, and focused onto another InSb detector array that defines band-pass characteristics for channels 26-41 (2.96 to 5.28 um). The remainder of the energy from the scanner is transmitted through dichroic D3 into port 4, where it encounters a fold mirror, diffraction grating G4, and lens that focuses the thermal radiation onto three separate mercury-cadmium- telluride (HgCdTe) detector arrays, each with its own cold-filter to improve the signal-to-noise ratio in its respective wavelength range. Port 4 senses radiation in the wavelength range from 8.60 to 14.17 um (channels 42-50). The InSb and HgCdTe detectors are cryogenically cooled by liquid nitrogen to 77 K in pressurized dewars. The following table shows the spectral and radiometric characteristics of each MAS channel in the complete 50 channel system. Spectral resolution, defined as the full-width at half-maximum bandwidth of the channel, ranges from around 40 nm in the visible and infrared to about 450 nm in the thermal infrared. Central Spectral Scene Saturation MAS MODIS Wavelength Res. Equiv Temp Level Signal-to channel channel (um) (um) Noise* (K)** + noise ratio** ------- ------- ---------- -------- ------ ----- ---------- ---------- 1 4 0.547 0.044 0.335 867 45.2 - 1052 2 1 0.657 0.053 0.157 1035 44.6 - 1948 3 0.704 0.042 0.178 1323. 28.7 - 1586 4 15 0.745 0.041 0.180 1412 21.5 - 1406 5 0.786 0.041 0.254 1638 12.4 - 912 6 0.827 0.042 0.237 1890 10.7 - 923 7 2 0.869 0.042 0.281 1935 8.1 - 728 8 7 0.909 0.033 0.150 314 14.9 - 1232 9 19 0.947 0.046 0.226 1600 5.5 - 720 10 6 1.609 0.052 0.039 892 4.5 - 397 11 1.663 0.052 0.029 272 5.8 - 570 12 1.723 0.050 0.026 252 5.1 - 659 13 1.775 0.049 0.026 244 2.8 - 624 14 1.825 0.046 0.025 246 1.3 - 503 15 1.879 0.045 0.029 232 1.1 - 289 16 1.932 0.045 0.014 58 1.4 - 257 17 1.979 0.048 0.019 193 1.7 - 93 18 2.030 0.048 0.022 195 2.0 - 88 19 2.080 0.047 0.012 53 3.8 - 221 20 7 2.129 0.047 0.003 55 1.0 - 1309 21 2.178 0.047 0.023 211 2.3 - 255 22 2.227 0.047 0.026 240 2.0 - 245 23 2.276 0.046 0.027 263 1.6 - 198 24 2.327 0.047 0.026 268 1.5 - 140 25 2.375 0.047 0.033 329 1.0 - 83 26 2.960 0.160 9.780 291 TBD 1.7 27 3.110 0.160 7.050 284 TBD 2.4 28 3.280 0.160 3.090 284 TBD 5.9 29 3.420 0.170 1.280 291 TBD 15.7 30 3.590 0.160 0.720 293 TBD 29.7 31 20 3.740 0.150 0.470 293 TBD 47.5 32 21 3.900 0.170 0.370 292 TBD 62.4 33 23 4.050 0.160 0.300 289 TBD 78.2 34 4.210 0.160 0.810 257 TBD 23.8 35 4.360 0.150 1.740 234 TBD 9.5 36 25 4.520 0.160 0.280 272 TBD 83.2 37 4.670 0.160 0.140 289 TBD 192.9 38 4.820 0.160 0.130 286 TBD 210.2 39 4.970 0.150 0.120 286 TBD 234.9 40 5.120 0.160 0.140 280 TBD 199.7 g 41 5.280 0.160 0.180 275 TBD 153.7 42 29 8.600 0.440 0.140 292 TBD 363.2 43 30 9.790 0.620 0.120 287 TBD 465.0 44 10.55 0.490 0.090 294 TBD 697.7 45 31 11.02 0.540 0.100 294 TBD 654.7 46 32 11.96 0.450 0.190 294 TBD 370.9 47 12.88 0.460 0.460 291 TBD 161.2 48 33 13.23 0.470 0.490 283 TBD 147.0 49 35 13.72 0.600 1.320 256 TBD 46.7 50 36 14.17 0.420 2.000 229 TBD 25.5 * Noise equivalent DI (W m -2 mm -1 sr -1 ) for channels 1-25; noise equivalent temperature difference NEDT (K) for channels 26-50. All noise measurements are based on in-flight measurements over the Gulf of Mexico on 16 January 1995. ** The thermal data (channels 26-50) are based on in-flight measurements over the Gulf of Mexico on 16 January 1995. The shortwave data (channels 1-25) are based on in-flight measurements over the Gulf of Mexico for the clear-sky scene (low signal level, where the reflectance is often less than 1%) and clouds on the north slope of Alaska on 7 June 1995 for the cloudy scene (high signal level). The range of signal-to-noise values for the shortwave channels reflects this range of scene radiance values. + Units of Watts/(meter^2 * steradian * micrometer) For a more detailed description, the reader is directed to King, M. D., W. P. Menzel, et. Al, 1995 for a more through description of the MAS system. 4.1.6 Sensor/Instrument Measurement Geometry BOREAS IFC-2 MAS Instrument/Platform Specifications Platform: NASA/AMES C130 Altitude: 8000 meters (nominal) Ground Speed: 200 knots Pixel Spatial Resolution: 20 meters (at 8000 meters altitude) Pixels per Scan Line: 716 (roll corrected) Scan Rate: 6.25 scans/second Swath width: ~14 km at 7.5 km altitude Total Field of View: 85.92 degrees Instantaneous Field of View: 2.5 milliradians Roll Correction: Plus or minus 3.5 degrees (approx) Bits per Channel: 12 Data Rate: 246 Megabytes/hour Visible Calibration: Integrating sphere on the ground Infrared Calibration: Two onboard temperature controlled blackbodies 4.1.7 Manufacturer of Sensor/Instrument Daedalus Enterprises, Inc. 4.2 Calibration Radiometric calibration of the shortwave (<2.5 mm) channels is obtained by observing laboratory standard integrating sphere sources on the ground before and after flight missions, while calibration of the infrared channels is performed in flight by viewing two onboard blackbody sources once every scan. The blackbody sources are located on either side of the scan aperture in the scanner subassembly. Shortwave calibration Two radiometric sources are used for shortwave laboratory calibration during MAS development, a 76.2 cm diameter integrating sphere maintained at NASA ARC, and a 121.9 cm diameter integrating hemisphere maintained at NASA GSFC. Both sources are coated with BaSO4 paint and internally illuminated by 12 quartz- halogen lamps. The 76.2 cm sphere is used at Ames for MAS calibrations just prior to the aircraft departure for field deployments as well as immediately following its return. This source is used to monitor long-term stability of the absolute calibration of the MAS. The 121.9 cm hemisphere has often been shipped to deployment sites and employed for MAS calibrations during the deployment. More recently, a 50.8 cm diameter integrating hemisphere was purchased by NASA ARC to ship with the MAS on all deployments. The 50.8 cm integrating hemisphere is coated with Duraflect by Labsphere, North Sutton, NH, and is internally illuminated by 10 lamps. Recent intercomparisons in the 76.2 and 121.9 cm integrating sources suggest that this smaller, more portable, source is suitable for MAS field calibration purposes. This source is set up beneath the MAS prior to each flight to monitor day-to-day fluctuations in the MAS shortwave calibration. Calibration of the spherical integrating sources, both at Ames and during field deployments, is performed by NASA GSFC personnel using a monochromator to transfer calibration to the integrating sources at spectral intervals of 10 nm. Thus, for each MAS shortwave channel, the radiance is related to digital count by Ib = Sb (Cb - Ob ) / mb , where Ib is the radiance measured in each shortwave spectral band b, Cb is the count value representing the detector response to the integrating source, Sb is the slope, Ob is the offset (digital counts when observing 'zero' radiance level), and mb is the reflectance of the 45 degree mirror (not used since 1993). Details of the shortwave calibration and temperature correction procedure are given by Arnold et al. (1994a, b). b. Longwave calibration The calibration of wavelengths greater than 2.96 mm is obtained from in-flight observations of two onboard blackbody sources, one operated at the ambient temperature and the other at an elevated temperature (typically 30 degree C). The two blackbodies are coated with Krylon interior/exterior ultra flat black paint. The calibration slope and intercept for the thermal channels are determined from this two point measurement. The blackbody sources are viewed during every scan of the mirror. The amount of energy received by the detector is related to the digitized count value by Ib = Sb*Cb + ib , where Ib is the radiance measured in each infrared spectral band b, Cb is the count value representing the detector voltage response to the scene radiance, Sb is the slope, and ib is the intercept. We assume a linear response, as laboratory determinations indicate fractional nonlinearity parameters of less than 0.0001. The slope and intercept, and hence the calibration of counts to radiance, are calculated for each scan line using the count values recorded when viewing two on-board blackbody sources. Using w to indicate the warm blackbody, a to indicate the ambient blackbody, m to indicate the MAS instrument, and taking into account blackbody emissivity e, then Sb = eb (Iwb - Iab ) / (Cwb - Cab ), ib = Iab + (Im - Iab ) (1 - eb ) - Sb*Cab. Blackbody count values are derived as the average of twelve FOVs across each blackbody surface during each scan, with the temperature of the blackbodies monitored by embedded thermistors. The emissivity of the blackbodies was obtained by viewing a well characterized source in the laboratory, from which the emissivity was determined to be 0.94 and 0.98 for the longwave and short- wave infrared bands, respectively. For typical ocean scene temperatures, corrections for instrument radiation (IM) reflected by the MAS blackbodies are approximately 1.25 C for the longwave and 0.25 C for the shortwave bands, respectively. Equivalent Planck radiances from the blackbodies are calculated for each spectral band using a spectral response weighted integral of the form Ib (T) = Integral[B(h, T) F (h)dh] / Integral[F(h) dh], where B(h, T) is the Planck function, F(h) is the spectral response for a given band, h is wavelength, and T is the blackbody temperature. This can be fitted to an adjusted Planck function for the range of Earth emitted temperatures by introducing coefficients a0 and a1 such that Ib (T) = B(hb , a1*T + a0), where hb is the central wavelength or wavenumber of band b. 4.2.1 Specifications The wavelength range (in micrometers) of the MAS bands selected for the BOREAS/IFC-2 (Boreal Ecosystem-Atmosphere Study/Field Campaign 2) are: DATA CHANNEL MAS BAND Central Wavelength 50%Bandwidth ------------ -------- ------------------ ------------ 01 01 0.547 0.043 02 02 0.664 0.055 03 04 0.745 0.040 04 05 0.786 0.040 05 06 0.834 0.042 06 07 0.875 0.041 07 09 0.945 0.043 08 10 1.623 0.057 09 20 2.142 0.047 10 32 3.900 0.150 11 45 11.002 0.448 12 46 12.032 0.447 4.2.1.1 Tolerance Details of the short-wave calibration and temperature correction procedure are given by Arnold et al. (1994a, b). 4.2.2 Frequency of Calibration See section 4.2 4.2.3 Other Calibration Information For a more detailed calibration description, the reader is directed to King, M. D., W. P. Menzel, et. Al, 1995. 5. Data Acquisition Methods As part of the BOREAS staff science data collection effort, the NASA ARC personnel collected and provided the 12-band MAS data to BOREAS for use in science investigations. The MAS was flown on NASA's C-130 aircraft during BOREAS (see the BOREAS Experiment Plan for flight pattern details and objectives). Maintenance and operation of the instrument are the responsibility of NASA ARC. 6. Observations 6.1 Data Notes Flight summary reports and verbal records on video tapes are available for the BOREAS MAS data. 6.2 Field Notes None. 7. Data Description 7.1 Spatial Characteristics Each of the ten MAS flight lines cover a portion of the BOREAS Southern Study Area (SSA). Together, the ten lines cover a majority of the SSA. 7.1.1 Spatial Coverage The North American Datum 1983 (NAD83) corner coordinates of the SSA are: Latitude Longitude -------- --------- Northwest 54.321 N 106.228 W Northeast 54.225 N 104.237 W Southwest 53.515 N 106.321 W Southeast 53.420 N 104.368 W The NAD83 corner coordinates of the NSA are: Latitude Longitude -------- --------- Northwest 56.249 N 98.825 W Northeast 56.083 N 97.234 W Southwest 55.542 N 99.045 W Southeast 55.379 N 97.489 W 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution At the nominal C130 operating altitude of 8000 m, the MAS provided pixel resolutions of 20 m at nadir to 28 m at the scanning extremes. 7.1.4 Projection The geographic orientation of each scene depends on the direction of the aircraft line of flight. Pixels and lines progress left to right, and top to bottom so pixel n, line n is in the lower right-hand corner of each scene. The flight lines SSA stored in their raw spatial form with pixel resolutions varying from 20 m at nadir to 28 m at the scanning extremes. The provided files of relative X and Y coordinate indicate the relative positions of the pixels from the arbitrary origin. These relative X and Y coordinates were derived from the C130 navigation data (see section 9.3). 7.1.5 Grid Description The provided files of relative X and Y coordinate indicate the relative positions of the pixels. These relative X and Y coordinates were derived from the C130 navigation data (see section 9.3). 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Currently the level-2 MAS data set contains data collected on the following dates: 10 flight lines collected on July 21, 1994 over the BOREAS SSA. 15 flight lines over towers collected on July 21, 1994 over the BOREAS SSA 6 flight lines over towers collected on July 24, 1994 over the BOREAS SSA 6 flight lines over towers collected on August 4, 1994 over the BOREAS NSA 7 flight lines collected on August 8, 1994 over the BOREAS NSA. 7.2.2 Temporal Coverage Map The following table shows the dates and times when the areas were imaged: Start End Number of Site Date Time Time Flight Lines ------- --------- -------- -------- ------------ SSA 21-JUL-94 15:46:07 17:35:35 10 SSA-90A 21-JUL-94 17:46:19 18:22:03 3 SSA-OBS 21-JUL-94 18:46:32 19:16:16 3 SSA-OJP 21-JUL-94 19:24:26 19:53:21 3 SSA-YJP 21-JUL-94 20:00:06 20:26:54 3 SSA-FEN 21-JUL-94 20:35:48 21:15:30 3 SSA-9YA 24-JUL-94 17:09:44 17:38:34 3 24-JUL-94 15:58:03 16:28:30 3 NSA-YJP 04-AUG-94 16:47:17 17:23:00 3 NSA-OBS 04-AUG-94 16:23:44 16:18:02 3 NSA 08-AUG-94 14:31:58 15:43:08 7 7.2.3 Temporal Resolution The entire NSA and SSA were only imaged once in 1994. The individual tower site coverage is shown in section 7.2.2. 7.3 Data Characteristics 7.3.1 Parameter/Variable The main parameters contained in the image data files are: Scaled Reflectance Scaled Surface Temperature Relative X coordinate Relative Y coordinate Scaled View zenith Scaled View Azimuth 7.3.2 Variable Description/Definition For the image data files: Scaled Reflectance The ratio of derived radiant energy incident on the sensor aperture and incident radiant solar energy at the time of data collection in the specific MAS wavelength regions. Scaled Surface Temperature The derived surface temperature at the time of data collection in the specific MAS thermal infrared wavelength regions. Relative X coordinate The X coordinate of the center of the image pixel in relation to the arbitrarily selected origin. The trend of the X coordinates of the pixels is dependent on the direction of flight of the aircraft. The X, Y coordinate system, starts with the nadir pixel location of image line 1 for all flight lines positioned near the origin (0,0) and progresses based on the direction of flight. The flight direction refers to the angle of the flight path relative to magnetic North with North as 0 or 360 degrees, East as 90, South as 180, and West as 270 degrees. For example, the X coordinates for an idealized flight line in the direction of 180 degrees (South) would be increasingly positive to the left of the flight line and increasingly negative to the right of the flight line with the X coordinate for the nadir pixel being approximately 0 (zero). Relative Y coordinate The Y coordinate of the center of the image pixel in relation to the arbitrarily selected origin. The trend of the Y coordinates of the pixels is dependent on the direction of flight of the aircraft. The X, Y coordinate system, starts with the nadir pixel location of image line 1 for all flight lines positioned near the origin (0,0) and progresses based on the direction of flight. The flight direction refers to the angle of the flight path relative to magnetic North with North as 0 or 360 degrees, East as 90, South as 180, and West as 270 degrees. For example, the Y coordinates for an idealized flight line in the direction of 90 degrees (East) would be increasingly positive to the left of the flight line and increasingly negative to the right of the flight line with the Y coordinate for the nadir pixel being approximately 0 (zero). Scaled View zenith The scaled value of the target-centered view zenith angle (complement of elevation angle). The view zenith indicates the zenith angle at which the radiant energy was traveling when detected by the sensor. The view zenith angle increases from 0 (straight up) to 90 degrees at the horizon. Scaled View Azimuth The scaled value of the target-centered view azimuth angle. The view azimuth angle indicates the direction in which the radiant energy was traveling when detected by the sensor. The view azimuth angle increases from 0 to 360 degrees with North as 0 or 360 degrees, East as 90, South as 180, and West as 270 degrees. 7.3.3 Unit of Measurement For the image data files: Scaled Reflectance - Fraction. Look near the end of the ASCII header file for scaling factors. Scaled Surface Temperature - Temperature in degrees Celsius. Look near the end of the ASCII header file for scaling factors. Relative X coordinate - Tenths of meters Relative Y coordinate - Tenths of meters Scaled View zenith - Tenths of degrees Scaled View Azimuth - Tenths of degrees 7.3.4 Data Source The values stored in the listed parameters were extracted from the level-1b MAS HDF files provided to BOREAS by MAS processing personnel and processed to reflectance or surface temperature. The reflectance and surface temperature values are derived from the Level-1b at-sensor radiance. The scaled at-sensor radiance and view angle values are the result of calibration and processing of the raw MAS data by MAS personnel. The relative X and Y coordinates were derived in a joint effort between BORIS and MAS personnel. 7.3.5 Data Range Scaled Reflectance Dependent on the particular MAS band of interest due to the wavelength region covered and the scaling factor listed near the end of the ASCII header file. Surface Temperature Dependent on the particular MAS band of interest due to the wavelength region covered and the scaling factor listed near the end of the ASCII header file. Relative X coordinate Dependent on the direction of flight with an absolute minimum of -2,147,483,648 and absolute maximum of 2,147,483,647. Relative Y coordinate Dependent on the direction of flight with an absolute minimum of -2,147,483,648 and absolute maximum of 2,147,483,647. Scaled View zenith Minimum - 0 Maximum - 900 Scaled View Azimuth Minimum - 0 Maximum - 3599 7.4 Sample Data Record Sample data records are not applicable to the image data itself. 8. Data Organization 8.1 Data Granularity The smallest unit of data for the Level-2 MAS images is a single acquisition containing 17 sequential files. 8.2 Data Format(s) 8.2.1 Uncompressed Data Files One Level-2 MAS image product consists of 17 files in the following order: File 1: An ASCII header file containing information relating to the mission, location, acquisition time, sensor parameters, aircraft location and attitude, and radiometric calibration parameters. Files 2 - 10: Bands 1 to 9 stored as 16-bit (2-byte) (low order byte first) binary scaled reflectance values. Scaling factors are provided at the end of the end of the ASCII header file. File 11 - 13: Bands 10 - 12 stored as 16-bit (2-byte) (low order byte first) binary scaled temperature values (degrees Celsius). The scaling factor is provided at the end of the end of the ASCII header file. File 14: Relative X coordinates stored as 32-bit binary values in tenths of meters (low order byte first). File 15: Relative Y coordinates stored as 32-bit binary values in tenths of meters (low order byte first). File 16: Scaled view azimuth values stored as 16-bit binary values in tenths of degrees (low order byte first). File 17: Scaled view zenith values stored as 16-bit binary values in tenths of degrees (low order byte first). The geographic orientation of each scene depends on the direction of the aircraft line of flight. Pixels and lines progress left to right, and top to bottom so pixel n, line n is in the lower right-hand corner of each scene. All scene files contain a variable number of fixed length records. The ASCII header files contain records that are 80 bytes in length. All binary files associated together for a given flight contain the same number of records. The number of binary records in a flight varies depending on the length of that flight line. Each binary data record in all flights represents 716 image pixels. Therefore, the image and view angle file records contain 716*2 = 1432 bytes and the relative X and Y coordinate files contain 716*4 = 2864 bytes. 8.2.2 Compressed CD-ROM Files On the BOREAS CD-ROMs, the ASCII header file (file 1) for each image is stored as ASCII text; however, files 2 to 17 have been compressed with the Gzip compression program (file name *.gz). These data have been compressed using gzip version 1.2.4 and the high compression (-9) option (Copyright (C) 1992-1993 Jean-loup Gailly). Gzip (GNU zip) uses the Lempel-Ziv algorithm (Welch, 1994) used in the zip and PKZIP programs. The compressed files may be uncompressed using gzip (-d option) or gunzip. Gzip is available from many websites (for example, ftp site prep.ai.mit.edu/pub/gnu/gzip-*.*) for a variety of operating systems in both executable and source code form. Versions of the decompression software for various systems are included on the CD-ROMs. 9. Data Manipulations 9.1 Formulae The atmospheric correction algorithm, Imagecor, applied to the MAS Level-1b data is fully documented in Wrigley et al. (1992), which has been since been modified to include water vapor, and to remove path thermal emission for thermal channels. Imagecor was developed by Robert Wrigley and Robert Slye for the atmospheric correction of data from the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE) and uses a simple atmospheric model with a modified single-scattering approximation, which permits full image scenes to be processed relatively quickly. 9.1.1 Derivation Techniques and Algorithms Derivation of the relative X and Y coordinates starts with determining the relative positions of the nadir pixel in each image line. The nadir pixel coordinates are defined to proceed relative to an arbitrary starting X,Y location. Nadir X,Y coordinates are derived as a function of the following parameters: - Instantaneous Velocities X, Y, and Z from the C130 Navigation data. - Tracking (Actual direction aircraft is pointing) values derived as a function of true heading and drift. To arrive upon nadir pixel tracking, the 1 Hz drift values and 30 Hz true heading values are interpolated to nadir pixel values. Nadir pixel drift is added to the nadir true heading values to obtain nadir pixel tracking values. Note that drift may be a positive or negative value. The calculations used to derive relative X and Y coordinates of the nadir pixels are: X0 = First (earlier) nadir X location. X1 = Succeeding nadir X location Y0 = First (earlier) nadir Y location. Y1 = Succeeding nadir Y location. DTime = Time1 - Time0 [Delta time stamps between succeeding nadir pixels] TH0, TH1 = True Heading at succeeding nadir pixels. Dr0, Dr1 = Drift values at succeeding nadir pixels. Tr0, Tr1 = Tracking at succeeding nadir pixels. VX,VY,VZ = GPS velocities in an X, Y and Z GPS reference system. Sp0, Sp1 = Ground Speed [square root ((VX*VX) + (VY*VY) + (VZ*VZ))] V0x = SP0 * cos(TH0 + Dr0) [X Velocity at Time0] V1x = SP1 * cos(TH1 + Dr1) [X Velocity at Time1] V0y = SP1 * sin(TH0 + Dr0) [Y Velocity at Time0] V1y = SP1 * sin(TH1 + Dr1) [Y Velocity at Time1] AVEV01X = (V0x + V1x) / 2.0 [Average X velocity between Time0 and Time1] AVEV01Y = (V0y + V1y) / 2.0 [Average Y velocity between Time0 and Time1] X = X0 + (AVE01X * DTime) [Succeeding nadir X coordinate] Y = Y0 + (AVE01Y * Dtime) [Succeeding nadir Y coordinate] The atmospheric correction algorithm, Imagecor, applied to the MAS Level-1b data is fully documented in Wrigley et al. (1992). Changes implemented since then were the inclusion of water vapor corrections and the ability to process thermal data. Water vapor corrections are based on modeled water vapor transmittance output by 6S combined with water vapor transmittance derived from 940nm channel sunphotometer data. This transmittance and the spectral response function of the sunphotometer channel was used to determine the equivalent water vapor column content. Imagecor then uses this content to estimate the transmittance across the scene. The thermal channels were corrected by using MODTRAN to model path emission and transmittance at twelve equally spaced angles across the scene and interpolating the path emission between these points. 9.2 Data Processing Sequence 9.2.1 Processing Steps BORIS creates Level-1B MAS image products from Hierarchical Data Format (HDF) files. The input HDF file is created by combining MAS image data with aircraft navigation data in an iterative procedure as follows: 1) BORIS staff extracts start and end flight line times from the Level-0 C130 aircraft navigation data associated with the flight. 2) The start and end times for the flight line are used by BORIS staff toextract the relevant aircraft navigation data to determine nadir pixel times. 3) BORIS staff process/linearly interpolate the extracted navigation parameters such as roll, pitch, heading, drift and acceleration for the nadir pixel time. 4) The nadir location parameters (Roll, Pitch, Radar Altitude, X and Y grid coordinates) are plotted to perform visual review of the data for anomalous values. 5) Nadir pixel navigation parameter values are then combined with MAS spectral data by MAS processing staff to create an HDF image product consisting of MAS spectral data and ancillary information for each flight line run. 6) All HDF files are written to 8mm tape and logged in the BORIS database. 7) Each MAS HDF file is converted to the BORIS band sequential 8mm tape product. 8) The 17 files, as described above, for each unique flight, are written to tape, in BORIS Level-1B BSQ format, for distribution. 9) The BORIS format MAS tapes are then logged into the BORIS database. The flight lines were then sent to NASA Ames for atmospheric correction processing. This processing was as follows: 1) Upload the data tape and export the image data to files with native byte order. 2) Download the 21-Jul-1994 radiosonde data from BORIS. 3) Model the path transmittance and path radiative emission for the thermal channels using a MODTRAN. Model the path water vapor column concentration and downwelling irradiance using the 6S for visible and near- and mid-infrared channels. 4) Process the image data to reflectance or surface temperature using Imagecor. 5) Generate a header file for each of the MAS flight lines. 6) For each flight line, write to tape each header file and Level-2 image data. 7) Send the level-2 data tape to BORIS. When the level-2 images are returned, BORIS personnel: 1) Extract and verify information from the data products for logging into the relational data base inventory, and 2) Compress the data for distribution on CD-ROM. 9.2.2 Processing Changes None. 9.3 Calculations 9.3.1 Special Corrections/Adjustments See section 9.1.1. 9.3.2 Calculated Variables See section 9.1.1. 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error Errors could arise in the acquired imagery due to location accuracy, distortion of lengths, anisomorphism, instrument's local coherence, and multispectral registration. Other errors could arise from inherent radiometric imperfections of the sensors. Whatever the processing level, the geometric quality of the image depends on the accuracy of the viewing geometry. Spectral errors could arise due image wide signal-to-noise ratio, saturation, cross-talk, spikes, response normalization due to change in gain. In addition to these errors, the Level-2 errors are dependent on the accuracy of the aerosol optical depth measurements used in the atmospheric correction processing. Errors due to using a single-scattering approximation should be minimal because the BOREAS optical depths low (met the single-scattering requirement). 10.2 Quality Assessment 10.2.1 Data Validation by Source MAS Level-2 pixel data agreed well with RSS-03 helicopter acquired Barnes Modular Multispectral Radiometer (MMR, BOREAS PI: Charles Walthall) data for the BOREAS primary study sites. With similar geometric and site condition inputs, both 6S and MODTRAN modeled reflectances also were in close agreement to the Imagecor results. 10.2.2 Confidence Level/Accuracy Judgment One set of calibration coefficients were used throughout the Boreas project rather than recalculated for each flight. Errors are usually +/- 5% when recalculated for each flight. 10.2.3 Measurement Error for Parameters None given. 10.2.4 Additional Quality Assessments None given. 10.2.5 Data Verification by Data Center 11. Notes 11.1 Limitations of the Data None. 11.2 Known Problems with the Data None. 11.3 Usage Guidance Before uncompressing the Gzip files on CD-ROM, be sure that you have enough disk space to hold the uncompressed data files. Then use the appropriate decompression program provided on the CD-ROM for your specific system. 11.4 Other Relevant Information None. 12. Application of the Data Set These data would be useful for creating a reflectance mosaic of the study sites and in investigating the bidirectional reflectance properties at the tower flux sites. 13. Future Modifications and Plans None. 14. Software 14.1 Software Description BORIS personnel developed software and command procedures to: 1) Unpack and subset the level-0 C130 navigation data, 2) Perform linear interpolation of the level-0 C130 navigation parameters, 3) Convert the HDF data files received from MAS personnel to the BORIS band sequential 8mm tape product. 4) Write the 17 files for each unique flight to tape for distribution. 5) Extract header information from level-1b BSQ images on tape, 6) Log the BSQ format MAS tapes into the BORIS database. The software is written in the C language and is operational on VAX 6410 and MicroVAX 3100 systems at GSFC. The primary dependencies in the software are the tape I/O library and the Oracle data base utility routines. The details of the software used by MAS personnel to derive the HDF level-1b products is currently unknown. The atmospheric correction software, Imagecor, was written in the C language and is operation on Sun Microsystems Solaris systems and has few hardware dependencies. Gzip (GNU zip) uses the Lempel-Ziv algorithm (Welch, 1994) used in the zip and PKZIP commands. 14.2 Software Access All of the described BORIS software is available upon request. BORIS staff would appreciate knowing of any problems discovered with the software, but cannot promise to fix them. Gzip is available from many websites across the net (for example) ftp site prep.ai.mit.edu/pub/gnu/gzip-*.*) for a variety of operating systems in both executable and source code form. Versions of the decompression software for various systems are included on the CD-ROMs. 15. Data Access 15.1 Contact for Data Center/Data Access Information These BOREAS data are available from the Earth Observing System Data and Information System (EOS-DIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The BOREAS contact at ORNL is: ORNL DAAC User Services Oak Ridge National Laboratory (865) 241-3952 ornldaac@ornl.gov ornl@eos.nasa.gov 15.2 Procedures for Obtaining Data BOREAS data may be obtained through the ORNL DAAC World Wide Web site at http://www-eosdis.ornl.gov/ or users may place requests for data by telephone, electronic mail, or fax. 15.3 Output Products and Availability Requested data can be provided electronically on the ORNL DAAC's anonymous FTP site or on various media including, CD-ROMs, 8-MM tapes, or diskettes. The complete set of BOREAS data CD-ROMs, entitled "Collected Data of the Boreal Ecosystem-Atmosphere Study", edited by Newcomer, J., et al., NASA, 1999, are also available. 16. Output Products and Availability 16.1 Tape Products The BOREAS Level-2 MAS data can be made available on 8 mm, DAT, or 9-track tapes at 6250 or 1600 BPI. 16.2 Film Products Color aerial photographs and video records were made during data collection. The video record includes aircraft crew cabin intercom conversations and an audible tone that was initiated each time the sensor was triggered. The BOREAS data base contains an inventory of available BOREAS aircraft flight documentation, such as flight logs, video tapes, and photographs. 16.3 Other Products Note that due to storage space limitations, only the level-2 MAS images collected on 21-Jul-1994 are included on the BOREAS CD-ROM series. Users interested in images from other dates should refer to the inventory listing provided on the CD-ROMs and Section 15 to determine how to obtain the data of interest. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation Arnold, G. T., M. Fitzgerald, P. S. Grant and M. D. King, 1994a: MODIS Airborne Simulator Visible and Near-Infrared Calibration - 1992 ASTEX Field Experiment: Calibration Version - ASTEX King 1.0. NASA Technical Memorandum 104599, 19 pp. Arnold, G. T., M. Fitzgerald, P. S. Grant and M. D. King, 1994b: MODIS Airborne Simulator Visible and Near-Infrared Calibration - 1991 FIRE-Cirrus Field Experiment: Calibration Version - FIRE King 1.1. NASA Technical Memorandum 104600, 23 pp. Gumley, L. E., P. A. Hubanks and E. J. Masuoka, 1994: MODIS Airborne Simulator Level 1B data user's guide. NASA Technical Memorandum 104594 Vol. 3, NASA Goddard Space Flight Center, Greenbelt MD. Welch, T.A. 1984, A Technique for High Performance Data Compression, IEEE Computer, Vol. 17, No. 6, pp. 8 - 19. 17.2 Journal Articles and Study Reports Ardanuy, P. E., D. Han and V. V. Salomonson, 1991: The Moderate Resolution Imaging Spectrometer (MODIS) science and data system requirements. IEEE Trans. Geosci. Remote Sens., 29, 75-88. Anderson, G. P., and J. H. Chetwynd, 1992: FASCOD3P User's Guide, Phillips Laboratory, Hanscom AFB. Bromba, M. U. A., and H. Ziegler, 1981: Digital filter for computationally efficient smoothing of noisy spectra. Anal. Chem., 53, 1299-1302. Clough, S. A., F. X. Kneizys, L. S. Rothman, and W. O. Gallery, 1981: Atmospheric spectral transmittance and radiance: FASCOD1B. SPIE, 277, 152-166. Gao, B. C., A. F. H. Goetz and W. J. Wiscombe, 1993: Cirrus cloud detection from airborne imaging spectrometer data using the 1.38 mm water vapor band. Geophys. Res. Lett., 20, 301-304. Gordon, H. R., D. K. Clark, J. W. Brown, O. B. Brown, R. H. Evans, and W. W. Broenkow. 1983: Phytoplankton pigment concentrations in the Middle Atlantic Bight: Comparison of ship determinations and CZCS estimates. Appl. Opt., 22, 20-36. Gumley, L. E., and M. D. King, 1995: Remote sensing of flooding in the US upper midwest during the summer of 1993. Bull. Amer. Meteor. Soc., 76, 933- 943. Huh, O. K., C. C. Moeller, W. P. Menzel, L. J. Rouse, Jr. and H. H. Roberts, 1995: Remote sensing of turbid coastal and estuarine water: A method of multis- pectral water-type analysis. Submitted to J. Coastal Res. Jedlovec, G. J., K. B. Batson, R. J. Atkinson, C. C. Moeller, W. P. Menzel and M. W. James, 1989: Improved Capabilities of the Multispectral Atmospheric Kaufman, Y. J., and B. C. Gao, 1992: Remote sensing of water vapor in the near IR from EOS/MODIS. IEEE Trans. Geosci. Remote Sens., 30, 871-884. King, M. D., W. P. Menzel, P. S. Grant, J. S. Meyers, G. T. Arnold, S. E. King, M. D., D. D. Herring and D. J. Diner, 1995: The Earth Observing System (EOS): A space-based program for assessing mankind's impact on the global environment. Opt. Photon. News, 6, 34-39. King, M. D., Y. J. Kaufman, W. P. Menzel and D. Tanr_, 1992: Remote sensing of cloud, aerosol, and water vapor properties from the Moderate Resolution Imaging Spectrometer (MODIS). IEEE Trans. Geosci. Remote Sens., 30, 2-27. Mapping Sensor (MAMS). NASA Technical Memorandum 100352, Marshall Space Flight Center, Huntsville, AL, 71 pp. Moeller, C. C., O. K. Huh, H. H. Roberts, L. E. Gumley, and W. P. Menzel, 1993: Response of Louisiana coastal environments to a cold front passage. J. Coastal Res. 9, 434-447. Nakajima, T., and M. D. King, 1990: Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. Part I: Theory. J. Atmos. Sci., 47, 1878-1893. Platnick, L. E. Gumley, S. Tsay, C. C. Moeller, M. Fitzgerald, K. S. Brown, and F. G. Osterwisch, 1995: Airborne Scanning Spectrometer for Remote Sensing of Cloud, Aerosol, Water Vapor and Surface Properties, Journal of Atmospheric and Oceanic Technology. Revercomb, H. E., H. Buijs, H. B. Howell, D. D. LaPorte, W. L. Smith and L. A. Sromovsky, 1988: Radiometric calibration of IR Fourier transform spectrometers: Solution to a problem with the High-spectral resolution Interferometer Sounder. Appl. Opt., 27, 3210-3218. Running, S. W., C. O. Justice, V. Salomonson, D. Hall, J. Barker, Y. J. Kaufman, A.H. Strahler, A. R. Huete, J. P. Muller, V. Vanderbilt, Z. M. Wan, P. Teillet and D. Carneggie, 1994: Terrestrial remote sensing science and algorithms planned for EOS/MODIS. Int. J. Remote Sens., 15, 3587-3620. Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J. Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E. Wickland. 1995. The boreal ecosystem-atmosphere study (BOREAS): an overview and early results from the 1994 field year. Bulletin of the American Meteorological Society. 76(9):1549-1577. Sellers, P. and F. Hall, K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). Sellers, P.and F. Hall, K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96). Sellers, P.J., F.G. Hall, R.D. Kelly, A. Black, D. Baldocchi, J. Berry, M. Ryan, K.J. Ranson, P.M. Crill, D.P. Lettenmaier, H. Margolis, J. Cihlar, J. Newcomer, D. Fitzjarrald, P.G. Jarvis, S.T. Gower, D. Halliwell, D. Williams, B. Goodison, D.E. Wickland, and F.E. Guertin. (1997). "BOREAS in 1997: Experiment Overview, Scientific Results and Future Directions", Journal of Geophysical Research (JGR), BOREAS Special Issue, 102(D24), Dec. 1997, pp. 28731-28770. Smith, W. L., R. O. Knuteson, H. E. Revercomb, W. Feltz, H. B. Howell, W. P. Menzel, N. Nalli, O. Brown, J. Brown, P. Minnett, and W. McKeown, 1995: Observations of the infrared radiative properties of the ocean - Implications for the measurement of sea surface temperature via satellite remote sensing. Submitted to Bull. Amer. Meteor. Soc. Strabala, K. I., S. A. Ackerman and W. P. Menzel, 1994: Cloud properties inferred from 8-12 mm data. J. Appl. Meteor., 33, 212-229. Tsay, S. C., K. Stamnes and K. Jayaweera, 1989: Radiative energy balance in the cloudy and hazy Arctic. J. Atmos. Sci., 46, 1002-1018. Tsay, S. C., K. Stamnes and K. Jayaweera, 1990: Radiative transfer in planetary atmospheres: Development and verification of a unified model. J. Quant. Spectrosc. Radiat. Transfer, 43, 133-148. Twomey, S., and T. Cocks, 1982: Spectral reflectance of clouds in the near- infrared: Comparison of measurements and calculations. J. Meteor. Soc. Japan, 60, 583-592. Wrigley, R. C., M. A. Spanner, R. E. Slye, R. F. Puseschel, and H. R. Aggarwal. 1992. Atmospheric Correction of Remotely Sensed Image Data by a Simplified Model. Journal of Geophysical Research 97(D17):18797-18814. Wylie, D. P., W. P. Menzel, H. M. Woolf and K. I. Strabala, 1994: Four years of global cirrus cloud statistics using HIRS. J. Clim., 7, 1972-1986. 17.3 Archive/DBMS Usage Documentation 18. Glossary of Terms None. 19. List of Acronyms 6S - Second Simulation of the Satellite Signal in the Solar Spectrum ARC - Ames Research Center ASCII - American Standard Code for Information Interchange BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System BPI - Byte per inch CCT - Computer Compatible Tape CD-ROM - Compact Disk-Read-Only Memory DAAC - Distributed Active Archive Center DAT - Digital Archive Tape EOS - Earth Observing System EOSDIS - EOS Data and Information System GSFC - Goddard Space Flight Center HDF - Hierarchical Data Format IFOV - Instantaneous Field-of-View LOWTRAN - Low Resolution Atmospheric Transmission Code MAS - MODIS Airborne Simulator MODIS - MODerate Imaging Spectroradiometer MODLAND - MODIS Land Group MODTRAN - MODerate Resolution Atmospheric Transmission Code NASA - National Aeronautics and Space Administration ORNL - Oak Ridge National Laboratory URL - Uniform Resource Locator 20. Document Information 20.1 Document Revision Date Written: 27-Jan-1997 Last Updated: 27-Jul-1999 20.2 Document Review Date(s) BORIS Review: 08-Sep-1998 Science Review: 20.3 Document ID 20.4 Citation The Level-2 MAS images were processed at the NASA/Ames Research Center under BOREAS investigation RSS-12, with Robert Wrigley as Principal Investigator. If appropriate, the references cited in Section 17 may be used. 20.5 Document Curator 20.6 Document URL Surface reflectance Surface temperature MAS_L2.doc 08/21/99