Full report

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r, NASA Technical Memorandum 104594, Vol. 3 MODIS Technical Report Series Volume 3, MODIS Airborne Simulator Level 1B Data User's Guide Liam E. Gumley, Paul A. Hubanks, and Edward J. Masuoka April 1994 (NASA-TM-I04594) REPORT SERIES. MODIS TECHNICAL N94-29385 VOLUME 3: MO01S AIRBORNE SIMULATOR LEVEL 1B DATA (NASA. GodGard Space Unclas USER'S GUIDE Flight Center) 413 p G3/31 0003832

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NASA Technical Memorandum 104594, Vol. 3 MODIS Technical Report Series Volume 3, MODIS Airborne Simulator Level 1B Data User's Guide Liam E. Gumley Applied Research Corporation Landover, Maryland Paul A. Hubanks Research and Data Systems Corporation Greenbelt, Maryland Edward J. Masuoka Goddard Space Flight Center Greenbelt, Maryland National Aeronautics and Space Administration Scientific and Technical Information Program 1994

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Table of Contents Page ...................................................................................... ,........... 1 ° Introduction ..................................... ................................. 2 2. MAS Instrument Summary ............................................................................ 2 2.1 MAS Specifications 2.2 MAS Channel Configuration ........................................................... 3 2.3 MAS Experiment Acronyms 2.4 Glossary Summary ...................................... 2 4 ................................................................................. 5 ° MAS Data Calibration Calibration ....................................... 5 3.1 Visible/Near-Infrared Band Visible/Near-Infrared Bands ........ 5 3.2 Temperature Correction of ................................................................. 6 3.3 Infrared Band Calibration . MAS Data Geolocation ................................................................................ ................................................................ 10 5. Obtaining MAS LEVEL-1B Data 8 5.1 Distribution Contact Points .............................................................. 10 5.2 SDST Distribution Tape Format o How to decode MAS LEVEL-1B Data ..................................................... 10 ....................................................... 12 6.1 Introduction to HDF .......................................................................... 12 ................................................................... 13 6.2 Obtaining HDF Libraries 6.3 Decoding and Extracting MAS Level-lB Data .............................. 14 ° Structure and Contents of MAS LEVEL-1B Data ................................... 16 .................................................................. 16 7.1 Data Structure Summary 7.2 Data Structure Term Definitions .................................................... 18 ° Obtaining Summary and Browse Information ..................................... 27 9. MAS Contact List .......................................................................................... 31 10. References ...................................................................................................... 32 ........................................................... 33 Appendix A. MAS Spectral Bands iii PRmBEIDalI_i PACJE IKANK NOT F!K.I_ED

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List Of Tables Table Title Page 1. MODIS Airborne Simulator Specifications ......................................... 2 2. MODIS Airborne Simulator Channel Configuration ....................... 3 3. Platforms on which HDF 3.3 Release 3 has been tested by NCSA .. 34 V

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1. Introduction The MODIS Airborne Simulator (MAS) is a modified Daedalus Wildfire scanning spectrometer which flies on a NASA ER-2 and provides spectral information similar to that which will be provided by the Moderate Resolution Imaging Spectroradiometer (MODIS), scheduled to be launched on the EOS-AM platform in 1998 (King et al. 1992). The principal investigators for the MAS are Dr. Michael King (NASA/GSFC, Greenbelt MD), and Dr. Paul Menzel (NOAA/NESDIS, Madison WI). The Wildfire Spectrometer was delivered April 1991. A single visible channel was the infrared port were altered to configure experiment. In January 1992 the modified to NASA Ames Research Center in added and several spectral channels in the instrument for the FIRE Cirrus-II Wildfire was then further modified to become MAS. Beginning in June of 1992, the MAS has been flown in a series of experiments that lasted on average 2 to 4 weeks and were held approximately every 6 months. The MAS spectrometer acquires high spatial resolution imagery in the wavelength range 0.55 to 14.3 microns. in this range, and currently the digitizer A total of 50 spectral bands are available is configured before each mission to record any 12 of these bands during flight. For all pre-1994 MAS missions the 12channel digitizer was configured with four 10-bit channels and seven 8-bit channels. The MAS spectrometer is mated to a scanner sub-assembly which collects image data with an IFOV of 2.5 mrad, giving a ground resolution of 50 meters from 20000 meters altitude, and a cross track scan width of 85.92 degrees. More details on the MAS sensor and scanner characteristics are shown in Section 2. A 50-channel digitizer which will resolution is currently under development mid 1994. record all 50 spectral bands at 12 bit and is expected to be completed in In support of the MODIS program, a MAS LEVEL-1B processing system was designed and implemented by the MODIS Science Data Support Team (SDST) at NASA Goddard Space Flight Center in 1991. The purpose of the processing system is to ingest MAS LEVEL-0 aircraft sensor, engineering and navigation data, and produce calibrated, geolocated radiances (LEVEL-1B) in a portable format (HDF). The system was designed by Liam Gumley, and is currently maintained by Paul Hubanks of Research and Data Systems, Corporation. The purpose of this document is to describe the characteristics of MAS LEVEL-1B data, the calibration and geolocation methods used in processing, the structure and format of the LEVEL-1B data files, and methods for accessing the data. Questions about MAS LEVEL-1B data should be directed to: Paul A. Hubanks, MODIS Science Data Support Team, Research and Data Systems Corporation, (301) 982-3724, phubanks@ltpsun.gsfc.nasa.gov.

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1. MAS Instrument Summary 2.1 MAS Specifications The MAS spectrometer is mated to a scanning system of the type described by Jedlovec et al. (1989). Table 1 summarizes platform, and scanning system. Table 1. MODIS Airborne Platform NASA ER-2 aircraft Altitude 20 kilometers that characteristics of the MAS sensor, Simulator Specifications (nominal) Ground speed 206 meters per second (nominal) Total field of view 85.92 degrees Swath width 37.25 kilometers Field of view 2.5 milliradians (at 20 kilometers altitude) (instantaneous) Pixel spatial resolution 50 meters (at 20 kilometers altitude) Pixels per scan line 716 (roll corrected) Scan rate 6.25 scan lines Spectral bands 50 Spectral range 0.55 - 14.3 btm _er second Data channels * 12 (selected from 50 spectral bands) Bits per channel 8 (4 channels Data rate 246 Megabytes/hour @ 10 bits, 7 channels @ 8 bits) Visible calibration Integrating sphere on the ground - none onboard Infrared calibration Two temperature * Note: MAS data system to be reconfigured 2.2 MAS Channel Configuration controlled black bodies onboard to fifty 12-bit channels in mid 1994. Summary In November/December 1991, the modified Wildfire instrument was flown in the FIRE Cirrus-II experiment onboard a NASA ER-2 in coordination with other aircraft and satellites over the Coffeyville coast. In January 1992, the modified KS field site as well as the TX/LA Gulf Wildfire was converted to MAS configuration. In June 1992 the MAS was flown over portions of the Atlantic Ocean in the region of the Azores during the ASTEX experiment. During early 1993 the MAS was flown in the southwestern Pacific Ocean during the TOGA/COARE and CEPEX experiments. the northeastern United States during In July 1993 the MAS was flown over the SCAR-A experiment. During 1994, two missions are planned: a Navy ship-tracks experiment (MAST) and a fire experiment over California (SCAR-C). Although the MAS instrument is a 50 band spectrometer, the data system used until mid 1994 has had the capability resolution). The tables that follow show data system for missions flown through to record only 12 channels (at 8 bit the channel configuration of the MAS July 1993. The recording of particular

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bands in specified channels is arbitrary by the principal investigators (scientists) the wavelength at 100% response, and 50% response of the MAS band recorded and is determined before each experiment for each mission. The ;k column shows the Ak column shows the bandwidth at in each data channel. Note that channel 1 is currently used as a "bit bucket" to store the two 'extra' bits for channels 9-12. In cases where laboratory measurements of the spectral response for a band were not available, Gaussian curves were fit to the predicted central and 50% response points. Plots of MAS spectral responses Table 2(a,b). MODIS Airborne for each experiment are in Appendix A. Simulator Channel Configuration (a) Channel FIRE (10/91) ASTEX (6/92) TOGA/COARE Number _, (tim) AX _, (btm) 1 2 0.681 0.009 0.664 3 1.617 0.056 0.875 4 1.933 0.048 0.945 5 2.088 0.047 1.621 6 2.139 0.047 2.142 7 3.748 0.144 3.725 8 4.695 0.144 13.952 9 4.539 0.144 8.563 10 8.800 0.339 11.002 11 10.950 0.500 13.186 12 11.950 0.500 12.032 Channel CEPEX (3/93) , (p_m) AX ..... 2 0.664 0.055 3 0.875 0.041 4 1.623 0.057 5 1.880 0.050 6 2.142 0.047 7 3.725 0.151 8 13.952 0.517 9 8.563 0.396 10 11.002 0.448 11 13.186 0.352 12 12.032 0.447 2.3 MAS Experiment Acronyms FIRE First ISCCP Radiation (1/93) of bits A, X (_tm) AX 0.053 0.664 0.053 8 0.041 0.875 0.041 8 0.043 1.621 0.057 8 0.057 1.830 0.050 8 0.047 2.142 0.047 8 0.151 3.725 0.151 8 0.517 13.952 0.517 8 0.395 8.563 0.395 10 0.448 11.002 0.448 10 0.351 13.186 0.351 10 0.446 12.032 0.446 10 ¢o) SCAR-A (7/93) Number of bits _, (btm) AX 0.547 0.043 8 0.664 0.055 8 0.875 0.041 8 0.945 0.043 8 1.880 0.050 8 2.142 0.047 8 3.725 0.151 8 8.563 0.395 10 11.002 0.448 10 13.186 0.352 10 12.032 0.447 10 Experiment (10/91 - 12/91)

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ASTEX Atlantic Stratocumulus Transition Experiment (5/92 - 6/92) TOGA/COARE Tropical Ocean Global Atmosphere/Coupled Ocean-Atmosphere Response Experiment (1/93 - 3/93) CEPEX Central Equatorial Pacific Experiment (3/93 - 4/93) SCAR-A Sulfates, Clouds and 2.4 Glossary Ames NASA Ames Research Radiation - America (7/93) Center Band One detector/filter assembly Blackbody Radiation source, emittance=absorptance=l, reflectance=0 Browse Uncalibrated reduced resolution image product Calibration Conversion from sensor digital counts to physical units Channel Area in LEVEL-0 format reserved for data from 1 band Data system MAS digital flight data digitizer/recorder onboard ER-2 ER-2 NASA high altitude research version of U-2 spy plane Exabyte 8 mm tape drive for digital data storage Exabyte format Storage format for ER-2 Exabyte data system Flight track (line) Portion of aircraft track where heading is constant FTP File Transfer Protocol (Internet) Geolocation Computation of earth coordinates of a sensor measurement GIF Graphics Interchange HDF format Hierarchical Data Format IFOV Instantaneous Field INS Inertial Navigation Intermediate (format): Data format IR Infrared: Wavelengths ISCCP International Satellite Format Of View System onboard ER-2 created by unpacking LEVEL-0 data of 3.7 microns and longer Cloud Climatology Project LEVEL-0 Unformatted, raw, packed, unprocessed sensor data LEVEL-1A Unpacked and reformatted sensor data LEVEL-1B Calibrated and geolocated sensor data MAS MODIS Airborne Simulator Metadata Descriptive information pertaining to a dataset MODIS Moderate Resolution Imaging Spectroradiometer Navigation data Record of the position and orientation of a sensor platform NIR Near-Infrared: Wavelengths from 0.7 to 3.7 microns PCM Tape drive used for old ER-2 data system Scanner MAS scan mirror and blackbody target assembly SGI Silicon Graphics Workstation Spectrometer MAS optics and detector assembly VIS Visible: Wavelengths from 0.4 to 0.7 microns 4

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1. MAS Data Calibration 3.1 Visible/Near-Infrared Band Calibration Calibration coefficients for the MAS visible (x < 0.7 btm) and near-infrared (0.7 _tm < _, < 3.7 btm) bands are derived from integrating spheres used pre and post launch. The transformation from digital • CBBavg ) ) • Slope (1) Radiance = ( Count - ( Gain where Radiance = computed radiance, Count = recorded count, Gain = channel gain, count to radiance is defined by CBBavg = running average of 30 previous cold black body counts, Slope = slope coefficient, determined for each band. The radiance units are Watts per square meter per steradian per micron (W m -2 sr -1 _tm-1). Integrating sphere calibrations may be carried out several times during a MAS flight experiment. There each applied to data from a discrete time more details, see Arnold et al. (1994a, 1994b). 3.2 Temperature Correction of MAS testing in a cold chamber at NASA some MAS VIS/NIR bands are subject may be several sets of calibration slopes, period, during a single experiment. For Visible/Near-Infrared Bands Ames Research Center has shown that to sensitivity changes as a function of temperature. This is important, since at cruise altitude (20000 meters) the MAS instrument environmental temperature is typically around -35°C. The cold chamber data is used to develop equations which predict the sensitivity of the VIS/NIR channels at given temperatures. Temperature sensors mounted on the MAS in-flight are then used as a reference for computing the sensitivity correction. For example in ASTEX data it was found that only channels 5 and 6 were sensitive to this phenomenon. For these two channels Count=Ceff, for all other VIS/NIR channels Count=Cre c. The form of the equation for Cef f during ASTEX was: Count = Cef f = Gain. Ccb b + (Cre c- (Gain. Ccb b )) / (al-Tma s + b I ) (2) where Ceff = temperature corrected effective digital count, Gain = channel gain, Ccbb = recorded in-flight digital count for cold black body,

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Crec = recorded original in-flight digital count, al, b I = coefficients determined for each band, Tma s = temperature of cold black body (degrees Celsius). The coefficients aI and b I are determined for each temperature sensitive channel in each MAS experiment. This correction is applied before the linear transformation to radiance units. For more details on the corrections used in various field experiments, see Arnold et al. (1994a, 1994b). 3.3 Infrared Band Calibration Calibration data for the MAS infrared (IR) bands (X > 3.7 btm) are obtained during flight from two blackbody sources which The first (cool) blackbody is usually although it can be temperature controlled. maintained at a higher temperature temperature level is set depending on are viewed during every mirror scan. left to float at ambient temperature, The second (warm) blackbody is than the cool blackbody, and the the desired scene temperature range. Thermistors measure the temperature of the blackbodies during flight. The equivalent Planck radiances for the blackbodies (assuming unit emissivity) are computed using a sensor weighted integral R(X,T) = _ B(X,T) S(X) dx J"S(X) dx over the wavelength range of the spectral of the Planck function of the form: (3) band where R(X,T) = sensor weighted equivalent Planck radiance, B(X,T) = Planck radiance at wavelength and blackbody temperature T, S(X) = sensor spectral response. The Planck radiance in Watts per square sr -1 btm -1) is computed by the equation B(X,T) = 10-6. C1 k5.(exp(C2/(X.T)) where C 1 = 2. h. c 2 = 1.1910439.10 meter per steradian per micron (W m -2 (4) - 1) -16 W m -2, C 2 = ( h. c ) / k = 1.4387686.10 -2 m K, x = wavelength in meters, T = temperature in degrees Once the equivalent Planck radiances Kelvin. known, the for the blackbodies are calibration slope and intercept are computed by the relationships 6

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Slope = R(X,T)BB2 - R(X,T)BB1 (5) CountBB 2 - CountBB Intercept = ( R(X,T)BB1 CountBB CountBB where R(MT)BB1 and R(X,T)BB2 are the and warm blackbodies respectively, CountBB 1 and CountBB 2 are the warm blackbodies respectively. 1 2 ) - ( R(X,T)BB2 • CountBB1 ) (6) 2 - CountBB 1 equivalent Planck radiances for the cool digital radiance counts for the cool and The calibration from digital counts to radiance is then a linear transformation of the form Radiance = Slope-Count + Intercept (7) The radiance units are Watts per square sr -1 btm-1). This procedure is performed No averaging of MAS blackbody data is done. Conversion from IR radiance to Planck temperature' may be done by inverting equation is of the form T(X,B) = C 2 meter per steradian per micron (W m -2 for every IR channel on every scanline. equivalent temperature or 'brightness the Planck equation. The reverse (8) X.log e(C 1/(X 5.B(X,T).106) + 1) where T(X,B) = brightness temperature in degrees Kelvin, C 2 = ( h. c ) / k = 1.4387686.10 -2 m K, C 1 = 2. h. c 2 = 1.1910439.10 X = wavelength in meters, -16 W m -2, B(X,T) = Planck radiance in W m -2 sr -1 btm -1. 7

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1. MAS Data Geolocation Navigation data onboard the ER-2 is recorded by an Inertial Navigation System (INS). This system has a dedicated tape MAS tape recorder. Before February 1992, recorder, which is separate from the INS data was obtained from the INS recorder itself. This data was unpacked and formatted by staff at Ames Research Center, and distributed as a separate file along with the MAS data. Since February 1992, the new MAS Exabyte data recorder has had the capability to record data from the INS system at the same time as it records MAS data, thus giving one integrated dataset which contains both MAS and navigation information. In the old INS recording system, aircraft position and attitude were updated every 5 seconds. In the new recording system, the update interval is 1 second. The geolocation algorithm is only applied to those portions of a flight where the aircraft flew straight, level, and on a constant heading. Data recorded during ascent, turns, and descent is not processed to LEVEL-lB. Ascent data is not processed since the scanner is not looking at nadir, and thus the imagery is distorted. During turns, the scanner roll correction system cannot compensate for high roll angles, and the imagery is distorted so that black bands appear on either side of the flight track. During descent, the scan mirror optics become covered with condensation, and the image The straight line flight track start and end program which analyzes altitude, heading, information is lost_ times are identified by an automated pitch, and roll. Once the start and end times for all flight tracks are determined, linear regressions for aircraft latitude, longitude, heading and altitude versus time are computed. This is the simplest way to represent the INS data set when it is referenced to the MAS data set, which is sampled at a higher rate (6.25 scanlines/second). To geolocate a given MAS flight track, the MAS start beginning of the flight track are determined. time and scanline number at the These are used as a reference for the rest of the flight track, since the time code recorded by the MAS is stored as integer seconds. The scanline number and scan rate are used to determine the time at subsequent scanlines in the flight track by t = t o + (S-S 0)/r where (9) t o = time of the first scan line in a flight track, S = scan line number of a data line in the flight track, S O = scan line number of the first data line in the flight track, r = scan rate (6.25 scans/second). Once time for a given scanline is computed, the linear regression relationships are used to compute aircraft latitude, longitude, heading and altitude at that time. The scan angle is determined from 8 the pixel number by the relationship

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DD = K . ( E - E n ) where DD = scan angle (displacement (10) from aircraft nadir point, degrees), K = angular distance between IFOVs ( 85.92 degrees / 715 steps ), E = pixel number, = pixel number at nadir The distance from the aircraft nadir point D = Z. tan ( DD ) where Z = aircraft altitude. (358.5). to the pixel is then given by (11) Once the distance and azimuth from nadir to the pixel are known (azimuth is computed from the heading), trigonometric transformations are used to compute the latitude and longitude for every 10th pixel on a scanline (pixels 1, 10, 20, 30, .... ,690, 700, 710, 716). The reason for geolocating every 10th pixel on a scan line is to save space in the output data set. Solar zenith and azimuth angles and sensor zenith and azimuth angles More details on the MAS geolocation (1989). are also computed for every 10th pixel. algorithm are given in Jedlovec et al. 9

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1. Obtaining MAS LEVEL-1B Data 5.1 Distribution Contact Points MAS LEVEL-1B data are currently distributed by the MODIS Science Data Support Team (SDST). However it is expected that by the end of 1994 the NASA Langley and Goddard DAAC's (Distributed Active Archive Center) will be the distribution points for MAS data. At that time users will need to contact the appropriate DAAC for specific media and data from the FIRE II Cirrus and ASTEX format information. MAS LEVEL-1B missions will be distributed by the Langley DAAC. MAS LEVEL-1B TOGA/COARE data will be distributed by the Goddard DAAC. Distribution points for other experiments have yet to be determined. MODIS Science Data Support Team Paul A. Hubanks Research and Data Systems Corporation 7855 Walker Drive, Suite 460 Greenbelt MD 20770 Phone: (301) 982-3724 Internet: hubanks@ltpsun.gsfc.nasa.gov. Langley DAAC User and Data Services Mail Stop 157-B NASA Langley Research Center Hampton VA 23681 Phone: (804) 864-8656 Internet: userserv@eosdis.larc.nasa.gov Goddard DAAC DAAC User Support Office Global Change Data Center Code 902.2 NASA Goddard Space Flight Center Greenbelt MD 20771 Phone: (301) 286-3209 Internet: daacuso@daac.gsfc.nasa.gov 5.2 SDST Distribution Tape Format MAS LEVEL-1B data distributed by the MODIS SDST are stored on Exabyte 8500 8mm tape. The tapes are formatted as simply as possible, so they may be read on any other system without the problems files, block lengths, and formatting. Each imposed by system dependent header tape contains all the flight lines for one MAS flight (one day). The number of flight lines per flight varies, but is generally between 10 and 20. The volume gigabytes per flight. 10 of data varies, but is generally 1 to 3

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The archive tapes are created by writing each output data file (1 straight-line flight track) to tape in fixed-length blocks of 16384 bytes, in time ascending order. One end-of-file (EOF) mark is written at the end of the data blocks for each file, and an extra EOF is written at the end of the data on the tape. The last block of each file has good data at the start of the block and unused bytes (filled with null characters) at the end. Information on the length of the file is encoded in the header when the file is created. No file name, protection, or ownership information is written onto the archive tape. All information necessary to identify the file is stored in the file itself. To read the data files from tape, system utilities should be used. For example on a UNIX system, the following command could be used to read the first file on the tape: % dd if=/dev/mt/tpsOd3nrnsv.8500 of=outfileOl.hdf ibs=16384 Note that "/dev/mt/tps0d3nrnsv. 8500" is the tape device driver. This is system dependent. However, the user should ensure that the device driver is for an Exabyte 8500 (not 8200) drive, and handles fixed length blocks which are 16384 bytes long. The output file name is a sample only: the user could specify any output file name. To read the first straight-line flight track file on a DEC VAX/VMS system, the following commands could be used (note that any VMS utility which reads tapes with fixed-length blocks is suitable): $ allocate mual: tape $ mount/foreign/over=own/blocksize=16384/recordsize=16384 tape $ set magtape/rewind tape $ copy tape: outfileOl.hdf $ dismount tape $ dealloc tape Tape Format Summary: Fixed length blocks, 16384 bytes per block, one EOF after each file, two EOFS at end of tape. Each file represents one flight line. 11

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1. How to decode MAS Level-lB Data 6.1 Introduction to HDF MAS LEVEL-1B data are stored in Hierarchical Data Format (HDF). The data are organized into individual straight-line flight tracks. Each MAS LEVEL-1B HDF file contains one straight-line flight track, general there are 10 to 20 flights (or flight 20 flight tracks in a given flight. HDF is developed and maintained by the Applications (NCSA), and has been selected and defines a granule of data. In days) in a given experiment and 10 to National Center for Supercomputing as the standard data format for all Earth Observing System (EOS) data products. HDF is a multi-object file format for the transfer of graphical and numerical the user to create, access, and share scientific and network-transparent. "Self-describing" information defining the data it contains. data between machines, and allows data in a form that is self-describing means that a file includes "Network-transparent" means that a file is represented in a form that can be accessed by computers with different ways of storing integers, characters, and floating-point numbers. HDF files also allow direct access, so that a small subset of a large dataset may be accessed efficiently, without first reading through all the preceding data. It should be noted that HDF files should only be accessed through the HDF library of subroutine and function calls (from FORTRAN or C). HDF is not a data by knowing word locations, byte ordering format which can be unpacked easily and so on. With HDF, the user is insulated from these details, so that differences in system specific storage details are transparent. MAS LEVEL-1B data are stored in a subset of HDF known as HDF/netCDF. Initial versions of the MAS LEVEL-1B data were written in netCDF (Network Common Data Form) format, developed Atmospheric Research (UCAR). In HDF integrated with the HDF software library. by the University Corporation for Version 3.3, the netCDF interface was All MAS LEVEL-1B data is now written in HDF/netCDF to comply with the EOS data format standard. From the user's perspective, this means HDF/netCDF, the data may be extracted either FORTRAN or C. This is the preferred LEVEL-1B data files. While it is possible method is not described in this document. Data Format Summary: MAS data is stored using netCDF-like calls to the HDF library. 12 that while the data is stored in using netCDF-like software calls, from means of extracting data from MAS to use HDF software calls alone, this in HDF/netCDF, and may be extracted

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6.2 Obtaining HDF libraries In order to extract data from MAS LEVEL-1B data files, the HDF software library must be compiled and installed. The source code is available from NCSA by anonymous FTP on Internet. The following commands may be used on a Unix system to retrieve the source code: % ftp ftp.ncsa.uiuc.edu Name: anonymous Password: guest ftp> cd HDF/HDF3.3r3/tar ftp> binary ftp> get HDF3.3r3.tar. Z ftp> quit % uncompress HDF3.3r3.tar. Z % tar xvf HDF3.3r3.tar. Z The instructions provided in the README files should then be followed to compile the source code and construct the library. If problems are encountered, please contact HDF user support by electronic mail at hdfhelp@ncsa.uiuc.edu. Table 3. Platforms on which HDF 3.3 Release 3 has been tested by NCSA Platform HDF Convex/ConvexOS Cray Y-MP/UNICOS DEC Alpha/OSF DecStation / MIPSEL Fujitsu VP/UXPM HP/UX 9.01 IBM PC - MSDOS IBM PC - Windows 3.1 IBM PC - Windows NT IBM/RS6000 Intel i860 Mac/MacOS NeXT/NeXTSTEP SGI/IRIX4 Sun4/Solaris Sun4/SunOs VAX/VMS X Successfully tested. The netCDF interface works but addition, the FORTRAN interface finished. base library HDF/netCDF X X X X X X X X X X X X X X X ** X X X X X X X X X X old netCDF XDR files cannot be read. In and ncdump utility have yet to be There is no FORTRAN support for either PC version of HDF 3.3r3. The netCDF part of the HDF/netCDF merger is not working correctly. 13

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6.3 Decoding and Extracting MAS To make it easier to get started using the Silicon Graphics (SGI) platform is Level-lB Data HDF library, a compiled version for a available via anonymous FTP at ltpiris2.gsfc.nasa.gov. In the future, compiled libraries for several different platforms will be available. The user should log in with username anonymous and password guest. The files are stored in the directory pub/MAS/hdf_netcdf / SGI_IRIX4.0 5. The following files are provided (A = ASCII mode, B = binary mode in FTP): libdf.a compiled HDF software object libnetcdf.a compiled HDF/netCDF software library (B) object library (B) ncdump executable utility program to dump HDF files as formatted text (B) netcdf.h C header file needed to call the HDF/netCDF library (A) netcdf.inc FORTRAN include file needed to call the HDF/netCDF library (A) simple executable utility program toread MAS LEVEL-1B HDF files (B) simple.f FORTRAN program to read MAS LEVEL-1B HDF data (A) simple.sh script to compile the FORTRAN program simple.f (A) These files provide the tools to begin extracting data from the MAS LEVEL-1B HDF data files using the FORTRAN or C netCDF interface. For further information on programming using the consult the netCDF User's Guide, available from UCAR as shown: % ftp unidata.ucar.edu Name: anonymous Password: guest ftp> cd pub/netcdf ftp> binary ftp> get guide.ps.Z ftp> quit % uncompress guide.ps.Z Note that if you downloaded the HDF3.3r3 copy of the netCDF User's Guide is included netCDF FORTRAN or C interface in PostScript form via anonymous FTP source code as previously described, a in the distribution. The following FORTRAN program (simple.f described above) gives a simple demonstration of how to extract MAS radiance data from a LEVEL-1B HDF file using the netCDF interface. While it does not exercise many of the features of the netCDF interface, it does demonstrate the basic functions of opening the file, defining the variables to be read, and extracting a portion of the selected data. Please note that the netCDF User's Guide is indispensable when developing code to read and/or write HDF/netCDF files. 14

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a simple program to demonstrate Liam Gumley, RDC, 03-SEP-1992 include the netcdf definitions include 'netcdf.inc' how to read a MAS HDF file set up necessary data types for netCDF (note that you should leave these as the default type for your compiler) integer cdfid, rcode, dataid, start( 3 ), count( 3 ) c set up types for variables and attributes integer2 value real4 scale( 12 ) character string72 character name72 c set netCDF error options call ncpopt( NCVERBOS + NCFATAL ) c open the netcdf file write(,'('' Enter HDF file name : ''$)') read(, ' (a72) ') name cdfid = ncopn( name , NCNOWRIT, rcode ) c get the variable id for the desired variable dataid = ncvid( cdfid, 'CalibratedData', rcode ) c get the scale factor values (from attribute scale_factor) call ncagt( cdfid, dataid, 'scale_factor', scale, rcode ) c get the units text description call ncagtc( cdfid, dataid, (from attribute units) 'units', string, 72, rcode ) set the pixel, channel and record counters count( 1 ) = 1 count( 2 ) = 1 count( 3 ) = 1 c get the start record, channel and pixel coordinates 20 write(,) 'enter record, channel, pixel' read(,) start( 3 ), start( 2 ), start( 1 ) get the hyperslab of data (one value in this case) call ncvgt( cdfid, dataid, start, count, value, rcode ) write the resulting radiance, after rescaling to a real number write(*,40) real( value ) * scale( start( 2 ) ), string( 1 :29 ) 40 format( ' Radiance = ', f12.3, ix, a29 ) go to 20 end 15

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1. Structure and Contents of MAS 7.1 Data Structure Summary LEVEL-1B Data Each individual MAS LEVEL-1B file contains calibrated, geolocated radiances for all MAS channels for one straight line various ancillary data such as instrument flight track. Each file also contains configuration, and time and date codes. When the MAS LEVEL-1B data structure was designed, a major concern was that all LEVEL-0 engineering and ancillary input data be maintained in the output data set. For this purpose, all LEVEL-0 parameters (except the raw digital image counts) are retained in the LEVEL-1B structure. In this way, the health and performance of the sensor may be monitored, and the data may be reversed to LEVEL-0 if necessary. The MAS LEVEL-1B data structure was designed to be easy to understand and to reflect the physical characteristics of the data. All variables, dimensions, attributes, and data are named descriptively to aid interpretation. The following listing was created from an actual MAS LEVEL-1B HDF file using NCDUMP (see Section 7.2). Due to size constraints only attributes are listed here. The data portion netcdf 92169-08 { dimensions: Time = UNLIMITED ; // (5367 currently) NumberOfChannels = 12 i Number©fPixels = 716 HeaderLength = 6160 ; AnchorIndexSize = 73 variables: the dimensions, variables, and global is not shown. float Left50%ResponseWavelength(NumberOfChannels) ; Left50%ResponseWavelength:units = "microns" ; float Centrall00%ResponseWavelength(NumberOfChannels) ; Centrall00%ResponseWavelength:units = "microns" ; float Right50%ResponseWavelength(NumberOfChannels) ; Right50%ResponseWavelength:units float SolarSpectralIrradiance(NumberOfChannels) SolarSpectralIrradiance:units SolarSpectralIrradiance:title Corrected Solar Spectral Irradiance" ; short AnchorPointIndex(AnchorIndexSize) char DataSetHeader(HeaderLength) short DataFrameStatus(Time) ; short RunNumber(Time) ; long ScanLineCounter(Time) ; 10ng ThumbWheelSwitches(Time) short ScanRate(Time) ; ScanRate:units = "hertz" ScanRate:scale_factor long GreenwichMeanTime(Time) ; long MasTime(Time) ; long InsTime(Time) ; short S-BendIndicator(Time ; 16 = "microns" ; ; = "watts/meter2/micron" ; = "Sensor Weighted and Orbit ; ; ; ; = 0.1f ;

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short AircraftRollCount(Time) long YearMonthDay(Time) ; float ScanlineTime(Time) ; ; ScanlineTime:units = "hours" ; short BlackBodylTemperature(Time, BlackBodylTemperature:units NumberOfChannels) ; = "degree_Celsius" ; BlackBodylTemperature:scale_factor = 0.0099999998f ; short BlackBody2Temperature(Time, BlackBody2Temperature:units NumberOfChannels) ; = "degree_Celsius" ; BlackBody2Temperature:scale_factor = 0.0099999998f ; short AmplifierGain(Time, NumberOfChannels) ; AmplifierGain:scale_factor = 0.001f ; short BlackBodylCounts(Time, NumberOfChannels) ; short BlackBody2Counts(Time, NumberOfChannels) ; float CalibrationSlope(Time, NumberOfChannels) ; CalibrationSlope:units float CalibrationIntercept(Time, CalibrationIntercept:units "watts/meter2/steradian/micron" ; = "watts/meter2/steradian/micron" ; NumberOfChannels) ; = float PixelLatitude(Time, AnchorIndexSize) ; PixelLatitude:units = "degree_north" ; float PixelLongitude(Time, AnchorIndexSize) ; PixelLongitude:units = "degree_east" ; float SensorZenithAngle(Time, SensorZenithAngle:units float SensorAzimuthAngle(Time, SensorAzimuthAngle:units AnchorIndexSize) ; = "degree" ; AnchorIndexSize) ; = "degree" ; float SolarZenithAngle(Time, AnchorIndexSize) ; SolarZenithAngle:units float SolarAzimuthAngle(Time, SolarAzimuthAngle:units float AircraftLatitude(Time) AircraftLatitude:units float AircraftLongitude(Time) AircraftLongitude:units float AircraftHeading(Time) ; AircraftHeading:units float AircraftAltitude(Time) AircraftAltitude:units float AircraftPitch(Time) ; = "degree" ; AnchorIndexSize) ; = "degree" ; ; = "degree_north" ; ; = "degree_east" ; = "degree_true" ; ; = "meters" ; AircraftPitch:units = "degree" ; short CalibratedData(Time, NumberOfChannels, NumberOfPixels) ; CalibratedData:units CalibratedData:scale_factor = "watts/meter2/steradian/micron" ; = 0.f, 0.1f, 0.1f, 0.0099999998f, 0.0099999998f, 0.0099999998f, 0.001f, 0.0099999998f, 0.0099999998f, 0.0099999998f, 0.0099999998f, 0.0099999998f ; // global attributes: :title = "MODIS Airborne :CreationDate = "27-Jan-94 :ExperimentName = "ASTEX Simulator (MAS) Level-iB Data" ; 10:39:54" ; " ; :FlightDate = "17 June 1992 " ; :FlightNumber = ,92-107 :ClockUsedToProcess = "INS :FlightLineNumber : 8 ; :TotalFlightLines = 13 ; " ; Clock " ; Gumley/design Paul Hubanks/modify MODIS :Credits = "Liam SDST)" ; ]7

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:MASDataUsersGuideSource = "Paul Hubanks (MODIS SDST) 301-982- 3724 or hubanks@itp.gsfc.nasa.gov" ; :ClockProblemDescription = "The MAS and INS (navigation) clocks often displayed different times. For offset was computed and and stored in MAS)Hours. The clock used in the FIRE stored in the array GreenwichMeanTime. the FIRE experiment a single clock the variable FIREClockOffset(INSexperiment was the MAS Clock, and is For all post-FIRE experiments, either the MAS or INS clock may have been used. To determine this check the entry ClockUsedToProcess. This may be set to either MAS_Clock or INS_Clock. During a flight, for both FIRE and post-FIRE flights, time is computed from the recorded start time of each flight track, incrementing .16 seconds per scanline. This time is stored in ScanlineTime. Finally, for all post-FIRE experiements the entire string of INS and MAS clocktimes are stored in the arrays InsTime and MasTime" ; :FIREClockOffset(INS-MAS)Hours :VIS/NIRCountSensitivityAd3ustment :SoftwareVersion = "Version :CalibrationVersion = "ASTEX :data_set = " MAS ASTEX :data product = "straight-line :geog_flag = "c" ; :day_night_flag = "d" ; :granule_version = 3 ; :metadata_version = " 3a" "Version 3.0 ASTEX King 1.0 ,, ; :producer_granule_id = :data_quality = "Fair: some :granule_size = 1.0884502e+08f = -99.f ; = "Yes (See DataSetHeader) " 3.0 " ; King 1.0 " ; flight tracks " ; ; noise in IR channels " ; :begin_date = "19920617 122120" ; :end_date = "19920617 123544" ; :lat_LL = 36.782097f ; :lon_LL = -24.800873f ; :lat_UL = 35.914349f ; :lon_UL = -23.128139f ; :lat_UR = 35.639751f ; :lon_UR = -23.356495f ; :lat_LR = 36.501247f ; :lon_LR = -25.026567f ; 7.2 Data Structure Term Definitions Dimensions: This section defines the dimensions dimension contained in the data set. and gives a brief description of each Dimensions are named integers which specify the shape of one or more multi-dimensional variables in the HDF file. Time = UNLIMITED ;//(5367 currently) The 'length' dimension of the data set. This dimension corresponds to elapsed time, and also corresponds with the incrementing of the scan line counter. NumberOfChannels = 12 ; The number of data channels. 18

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NumberOfPixels = 716 ; The number of pixels (IFOVs) across a MAS scan. HeaderLength = 6160 ; The length of the ASCII data set header. characters, which contain no carriage separators. The header contains a copy that was used in processing. AnchorIndexSize = 73 ; The number of geolocation anchor points The header is composed of blocks of 80 return, line feed or similar record of the MAS instrument configuration file per scan line. Each MAS scan line has geolocation data for every 10th pixel (to save space). The geolocation data is defined for pixel numbers 1, 10, 20, 30, 40, ...... 680, 690, 700, 710 and 716 which makes a total of 73 geolocation anchor points. It should be noted that pixels 1 to 358 are on the starboard (right) side of the aircraft, while pixels 359 to 716 are on the port (left) side of the aircraft. Variables: This section defines the type and size description of each, in the output data dimensional array of values of the same of the variables, along with a brief set. A variable represents a multitype. The type definitions are from the C language, however the equivalent FORTRAN types are byte: BYTE 8 bit data char: CHARACTER synonymous with byte short: INTEGER2 16 bit integers long: INTEGER4 32 bit integers float: REAL*4 32 bit IEEE floating point double: DOUBLE PRECISION 64 bit IEEE floating point Note that the listing of variable names which follows show the dimensions in C order. In FORTRAN, the order of dimensions is reversed. For example, the variable declared as CalibratedData(Time, NumberOfChannels, NumberOfPixels) in C would be declared as CalibratedData(NumberOfPixels, NumberOfChannels, Time) in FORTRAN. float Left50% ResponseWavelength(NumberOfChannels) ; Left50%ResponseWavelength:units = "microns" ; The wavelength corresponding to the spectral response function for each channel. left hand 50% response point of the float Central100% ResponseWavelength(NumberOfChannels) ; Central100% ResponseWavelength:units = "microns" ; The wavelength corresponding to the central 100% response point of the spectral response function for each channel. float Right50%ResponseWavelength(NumberOfChannels) ; 19

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Right50% ResponseWavelength:units = "microns" ; The wavelength corresponding to the right hand 50% response point of the spectral response function for each channel. float SolarSpectralIrradiance(NumberOfChannels) ; SolarSpectralIrradiance:units = "watts/meter2/micron" ; SolarSpectralIrradiance:title = "Sensor Spectral Irradiance" ; Weighted and Orbit Corrected Solar The sensor weighted and orbit corrected solar spectral irradiance at the top of the atmosphere for each channel. This is computed using the LOWTRAN7 database of solar spectral irradiance and the spectral Sw(X) = J S(X). R(X) dX R(X) dx where response function for each channel by (12) Sw(X ) = sensor weighted orbit corrected exoatmospheric solar spectral irradiance, S(X) = orbit corrected exoatmospheric R(X) = sensor spectral response. short AnchorPointIndex(AnchorIndexSize) solar spectral irradiance, ; The pixel numbers for which geolocation information is defined. The geolocation data is defined for pixel numbers 1, 10, 20, 30, 40, ...... 680, 690, 700, 710 and 716 which makes a total of 73 geolocation anchor points. char DataSetHeader(HeaderLength) ; The data set header text. The header is composed of blocks of 80 characters, which contain no carriage return, line feed or similar record separators. The header contains a copy of the MAS instrument configuration file that was used in processing. This indicates, among other things, which spectral bands were enabled, which channels had 8 or 10 bit data, which channels were calibrated using the MAS blackbodies (IR channels), and slopes/intercepts for the visible/near-IR channels. short DataFrameStatus(Time) ; (LEVEL-0 MAS engineering data) Data Frame Status. Zero indicates good data. Bits are set to 1 to indicate errors as follows: Bit Position Meaning 1 Bad digit in scanline count 2 Bad digit in time code 4 Bad digit in thumbwheel data 8 Bad digit in reference temperature 16 Incorrect channel 64 Bad sync word 128 No match for end-of-frame 20 code (last word)

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sign Set to 1 if any other bit set short RunNumber(Time) ; (LEVEL-0 MAS engineering data) Not used. Was intended for operator to encode flight line number during flight. long ScanLineCounter(Time) ; (LEVEL-0 MAS engineering data) Scan line count, increments by 1 for each long ThumbWheelSwitches(Time) ; (LEVEL-0 MAS engineering data) Data system thumbwheel switch settings financial year, FFF is flight number, DDD short ScanRate(Time) ; ScanRate:units = "hertz" ; ScanRate:scale_factor = 0.1f ; (LEVEL-0 MAS engineering data) Scan rate in scans per second (x 10, nearest long GreenwichMeanTime(Time) ; (LEVEL-0 MAS/INS engineering data) consecutive scan line. formatted as YYFFFDDD, where YY is is day of year. integer). Greenwich Mean Time is either the MAS or INS time, selected at the time of processing. It is used to determine the time at the start of the straight line flight tracks and is formatted as HHMMSSS, where HH is hours, MM is minutes, SSS is seconds and tenths of a second. The recorded, therefore it is always zero. long MasTime(Time) ; (LEVEL-0 MAS engineering data) tenths of a second field is not currently Time recorded by the MAS clock and is formatted as HHMMSSS, where HH is hours, MM is minutes, SSS is seconds and tenths of a second. The tenths of a second field is not currently recorded, therefore it is always zero. long InsTime(Time) ; (LEVEL-0 INS engineering data) Time recorded by the INS clock formatted as HHMMSSS, where HH is hours, MM is minutes, SSS is seconds and tenths of a second. The tenths of a second field is not currently recorded, therefore short S-BendIndicator(Time) ; (LEVEL-0 MAS engineering data) it is always zero. S-bend indicator where 0 = no S-bend, 1 = S-bend. Not used. Was intended to indicate whether hardware geometric correction was enabled. short AircraftRollCount(Time) ; (LEVEL-0 MAS engineering data) 21

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Aircraft roll count. Signed integer where long YearMonthDay(Time) ; positive is right, 0.03 degrees per count. Date formatted as YYYYMMDD where YYYY is year, MM is month, DD is day. float ScanlineTime(Time) ; ScanlineTime:units = "hours" ; Time of the current scanline in fractional hours, computed from the scanline number and scan rate (as described in the Section 5). ScanlineTime is accurate to the nearest scanline (0.16 seconds) whereas GreenwichMeanTime is accurate only to the nearest whole second. short BlackBodylTemperature(Time, NumberOfChannels) ; BlackBodylTemperature:units = "degree_Celsius" ; BlackBodylTemperature:scale_factor (LEVEL-0 MAS engineering data) = 0.0099999998f ; Black Body 1 (cool) thermal reference temperature (degrees C x 100). short BlackBody2Temperature(Time, NumberOfChannels) ; BlackBody2Temperature:units = "degree_Celsius" ; BlackBody2Temperature:scale_factor (LEVEL-0 MAS engineering data) = 0.0099999998f ; Black Body 2 (warm) thermal reference temperature (degrees C x 100). short AmplifierGain(Time, NumberOfChannels) ; AmplifierGain:scale_factor = 0.001f Gain setting for each channel (x 1000). ; short BlackBodylCounts(Time, NumberOfChannels) ; (LEVEL-0 MAS engineering data) Black Body 1 (cool) radiance digital counts. short BlackBody2Counts(Time, NumberOfChannels) ; (LEVEL-0 MAS engineering data) Black Body 2 (warm) radiance digital counts. float CalibrationSlope(Time, NumberOfChannels) ; CalibrationSlope:units = "watts/meter2/steradian/micron" ; Linear calibration slope for each channel for digital scene count to radiance conversion. float CalibrationIntercept(Time, NumberOfChannels) ; CalibrationIntercept:units = "watts/meter2/steradian/micron" ; Linear calibration intercept for each channel for digital scene count to radiance conversion. float PixelLatitude(Time, AnchorIndexSize) PixelLatitude:units = "degree_north" 22 ; ;

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Latitudes for pixels at geolocation anchor points. Latitude ranges from -90 degrees at the South Pole to +90 degrees float PixelLongitude(Time, AnchorIndexSize) PixelLongitude:units = "degree_east" at theNorth Pole. ; ; Longitudes for pixels at geolocation anchor points. Longitude is zero at the Greenwich Meridian, and ranges from -180 degrees (West) to +180 degrees (East). float SensorZenithAngle(Time, AnchorIndexSize) ; SensorZenithAngle:units = "degree" ; Sensor zenith angle for pixels at geolocation anchor points. Defined as the zenith angle (degrees) of a vector from zenith angle = 0). the sensor to the pixel (nadir sensor float SensorAzimuthAngle(Time, AnchorIndexSize) ; SensorAzimuthAngle:units = "degree" ; Sensor azimuth angle for pixels at geolocation anchor points. Defined as the azimuth angle (degrees) clockwise from sensor. North of a vector from the pixel to the float SolarZenithAngle(Time, AnchorIndexSize) ; SolarZenithAngle:units = "degree" Solar zenith angle for pixels at geolocation angle (degrees) of a vector from the pixel ; anchor points. Defined as the zenith to the Sun. float SolarAzimuthAngle(Time, AnchorIndexSize) ; SolarAzimuthAngle:units = "degree" ; Solar azimuth angle for pixels at geolocation anchor points. Defined as the azimuth angle (degrees) clockwise from Sun. float AircraftLatitude(Time) ; North of a vector from the pixel to the AircraftLatitude:units = "degree_north" ; Aircraft subpoint latitude (degrees, derived from linear regression of INS data in the flight track). float AircraftLongitude(Time) ; AircraftLongitude:units = "degree_east" ; Aircraft subpoint longitude (degrees, derived from linear regression of INS data in the flight track). float AircraftHeading(Time) ; AircraftHeading:units = "degree_true" Aircraft heading (degrees, derived from track). float AircraftAltitude(Time) ; AircraftAltitude:units = "meters" 23 ; linear regression of INS data in the flight ;

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Aircraft altitude (meters, derived from linear regression of INS data in the flight track). float AircraftPitch(Time) ; AircraftPitch:units = "degree" ; Aircraft pitch angle (degrees, derived from linear regression of INS data in the flight track). short CalibratedData(Time, NumberOfChannels, NumberOfPixels) ; CalibratedData:units = "watts/meter2/steradian/micron" ; CalibratedData:scale_factor = 0.f, 0.1f, 0.1f, 0.0099999998f, 0.0099999998f, 0.0099999998f, 0.001f, 0.0099999998f, 0.0099999998f, 0.0099999998f, 0.0099999998f, 0.0099999998f ; Calibrated radiances for all pixels in all channels. 32 bit floating point radiance values are scaled to 16 bit integers to save space. Variable scaling factors are used for each channel. To retrieve real radiances, multiply the integer radiance value by the appropriate scaling factor for that channel. Global Attributes: This section describes the global attributes of the output data set. Global attributes contain descriptive information pertaining to the entire data set. : title = "MODIS Airborne Simulator (MAS) Level-lB Data" ; : CreationDate = "27-Jan-94 10:39:54" ; Date that this file was created (processed). : ExperimentName = "ASTEX Name of the MAS mission. ,l . : FlightDate = "17 June 1992 Date of the MAS flight. : FlightNumber = "92-107" ; Flight number assigned. : ClockUsedToProcess = "INS Clock "," Clock used to determine the start time of the straight line flight tracks. : FlightLineNumber = 8 ; Flight line number. :TotalFlightLines = 13 ; Total number of flight lines (straight-line flight tracks) during this day (flight). :Credits = "Liam Gumley/design Paul Hubanks/modify (MODIS SDST)" ; 24

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: MASDataUsersGuideSource = "Paul Hubanks (MODIS SDST) 301-982-3724 or hubanks@ltp.gsfc.nasa.gov" ; : ClockProblemDescription = (Description 2) ; : FIREClockOffset (INS-MAS) Hours = -99 .f; of time keeping problems onboard ER- Offset between INS and MAS clocks for pre-Exabyte recording system LEVEL-0 data only. Before the Exabyte recording system was brought into use in February 1992 the MAS and INS data streams were internal clock. During the FIRE mission• recorded separately• each using it's own the INS clock was found to be leading the MAS clock by anywhere from 30 to 90 seconds. This offset had to be corrected to ensure accurate geolocation• so the INS clock time was adjusted in postprocessing to match the MAS clock time. This variable records the time subtracted from the INS clock time. After February 1992 the Exabyte LEVEL-0 recording system encoded the MAS and INS in one synchronous data stream, so this problem was eliminated. : VIS/NIRCountSensitivityAdjustment = "Yes (See Data Set Header) "; Flag to indicate form of adjustment (if any) to VIS/NIR digital counts to compensate for instrument temperature dependent changes in sensitivity. See the section on calibration for details. NONE indicates no adjustment. If used, the form of the adjustment is listed in the instrument configuration file which is stored in DataSetHeader. : SoftwareVersion = "Version 3.0 " • Version of the software used to create granule). : CalibrationVersion = "ASTEX King 1.0 this HDF file (MAS LEVEL-1B data ",- Version of the calibration used in the processing of this particular HDF file (MAS LEVEL-1B data granule). : data set = "MAS ASTEX " • Data set name (DAAC required metadata). : data_product = "straight-line flight tracks "; Data product name (DAAC required metadata). : geog_flag = "c" ; geographic flag (DAAC required metadata) : day_night_flag = "d" ; Day/Night flag (DAAC required metadata). : granule_version = 3 ; c=constrained. Version of the granule. Shows the number of time of times this data has been processed in the past (DAAC required metadata). 25

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: metadata version = " 3a" ; Version of the metadata included in this particular HDF file (MAS LEVEL-1B data granule). Allows indication of an update to the metadata when no update is done to the calibrated radiances. : producer_granule_id = "Version 3.0 ASTEX King 1.0 " ; A unique ID assigned by the data producer (DAAC required metadata). : data_quality = "Fair: some noise in IR channels " ; Data quality assessment (DAAC required : granule_size = 1.0884502e+08f ; Approximate size of the granule in bytes : begin_date = "19920617 122120" ; metadata). (DAAC required metadata). Date and time of the start of the flight track (granule) (DAAC required metadata). : end_date = "19920617 123544" ; Date and time of the start of the flight track (granule) (DAAC required metadata). :lat_LL = 36.782097f ; :lon_LL = -24.800873f ; :lat_UL = 35.914349f ; :lon_UL = -23.128139f ; :lat_UR = 35.639751f ; :lon_UR = -23.356495f ; :lat_LR = 36.501247f ; :lon_LR = -25.026567f ; Latitude and longitude of the corner metadata). 26 points of the granule (DAAC required

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1. Obtaining Summary and Browse Information MAS flight summary information and browse data are available via anonymous FTP at ltpiris2.gsfc.nasa.gov in directory pub/MAS/data This site may be accessed as shown: % ftp itpiris2.gsfc.nasa.gov Name: anonymous Password: guest ftp> cd pub/MAS/data ftp> dir -rw-r--r-- 1 11421 20 868 Oct 14 09:16 00readme drwxr-xr-x 13 11421 20 512 Sep 1 1993 ASTEX drwxr-xr-x 3 11421 20 512 Mar 21 10:03 BOREAS-hall drwxr-xr-x 2 11421 20 512 Oct 5 1993 CEPEX drwxr-xr-x 18 11421 20 512 Oct 14 09:25 FIRE drwxr-xr-x ii 11421 20 512 Oct 20 10:14 SCAR-A drwxr-xr-x 3 11421 20 512 Jul 9 1993 TOGA The readme file contains information on MAS LEVEL-1B data processing status, and data availability for each experiment. In addition, directories have been created to hold summary and browse information for each MAS experiment. For example, to obtain browse and summary data for a particular ASTEX flight, enter the ASTEX directory by typing: ftp> cd ASTEX ftp> dir -rwxr-xr-x 1 11421 20 403 Aug 12 1993 00README.DOC drwxr-xr-x 2 11421 20 512 Apr 5 12:50 02jun92 drwxr-xr-x 2 11421 20 1536 Apr 5 12:55 04jun92 drwxr-xr-x 2 11421 20 1536 Apr 5 12:58 08jun92 drwxr-xr-x 2 11421 20 1536 Feb 2 09:17 17jun92 drwxr-xr-x 2 11421 20 1536 Oct 18 14:58 18jun92 drwxr-xr-x 2 11421 20 1536 Oct 18 15:01 19jun92 drwxr-xr-x 2 11421 20 1024 Feb 16 09:42 21jun92 drwxr-xr-x 2 11421 20 1024 Feb 16 13:14 22jun92 drwxr-xr-x 2 11421 20 1024 Oct 18 15:06 23jun92 drwxr-xr-x 2 11421 20 1536 Feb 9 06:55 29may92 drwxr-xr-x 2 11421 20 1024 Oct 18 15:09 31may92 Within each experiment directory there are a number of subdirectories. Each subdirectory contains data recorded on a particular day. The sub-directories are named with the day, month, and year to enable easy selection of a particular day of interest. Each sub-directory contains the flight summary (.sum) and browse (.gif) data for one MAS flight during the experiment. For example, enter the directory for 17 June 1992 by typing: % cd 17jun92 % dir -rw-r--r-- 1 11421 20 2307 Feb 2 09:12 92169.sum -rw-r--r-- 1 11421 20 39022 Feb 2 09:11 9216901i.gif 27

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-rw-r--r-- 1 11421 20 41241 Feb 2 09:11 9216901v.gif -rw-r--r-- 1 11421 20 75311 Feb 2 09:12 9216902i.gif -rw-r--r-- 1 11421 20 64532 Feb 2 09:12 9216902v.gif -rw-r--r-- 1 11421 20 18146 Feb 2 09:12 9216903i.gif -rw-r--r-- 1 11421 20 19379 Feb 2 09:12 9216903v.gif -rw-r--r-- 1 11421 20 49289 Feb 2 09:12 9216904i.gif -rw-r--r-- 1 11421 20 43389 Feb 2 09:12 9216904v.gif -rw-r--r-- 1 11421 20 98800 Feb 2 09:12 9216905i.gif -rw-r--r-- 1 11421 20 98075 Feb 2 09:12 9216905v.gif -rw-r--r-- 1 11421 20 41049 Feb 2 09:12 9216906i.gif -rw-r--r-- 1 11421 20 28162 Feb 2 09:12 9216906v.gif -rw-r--r-- 1 11421 20 18944 Feb 2 09:12 9216907i.gif -rw-r--r-- 1 11421 20 18570 Feb 2 09:12 9216907v.gif -rw-r--r-- 1 11421 20 198545 Feb 2 09:12 9216908i.gif -rw-r--r-- 1 11421 20 182063 Feb 2 09:12 9216908v.gif -rw-r--r-- 1 11421 20 173019 Feb 2 09:12 9216909i.gif -rw-r--r-- 1 11421 20 162709 Feb 2 09:12 9216909v.gif -rw-r--r-- 1 11421 20 115572 Feb 2 09:12 9216910i.gif -rw-r--r-- 1 11421 20 111105 Feb 2 09:12 9216910v.gif -rw-r--r-- 1 11421 20 123971 Feb 2 09:12 9216911i.gif -rw-r--r-- 1 11421 20 123051 Feb 2 09:12 9216911v.gif -rw-r--r-- 1 11421 20 137309 Feb 2 09:12 9216912i.gif -rw-r--r-- 1 11421 20 136656 Feb 2 09:12 9216912v.gif -rw-r--r-- 1 11421 20 184931 Feb 2 09:12 9216913i.gif -rw-r--r-- 1 11421 20 161166 Feb 2 09:12 9216913v.gif The flight summary file (92169.sum) is an ASCII text summary (and therefore must be transferred in ASCII mode in FTP) of the flight lines processed for that flight. The name is formatted as yyddd.sum where yy is the year and ddd is the day of year. The contents of this file are shown below: MODIS AIRBORNE SIMULATOR (MAS) FLIGHT START OF FLIGHT LINE ....................................................... LINE TIME LAT LON SOLAR START HH :MM : SS DEG DEG ZEN AZIM HEADING ........................................... i 11:27:39 37.214 -24.754 31.5 106.6 126.35 2 11:32:26 36.831 -24.421 30.2 107.5 198.62 3 11:45:29 36.155 -24.434 27.5 109.8 126.42 4 11:48:26 36.031 -24.079 26.6 110.8 96.75 5 11:52:30 35.968 -23.536 25.4 112.5 107.87 6 12:05:43 35.630 -22.662 22.2 117.5 296.53 7 12:11:41 35.957 -22.895 21.5 120.2 116.74 8 12:21:21 35.777 -23.243 20.0 123.3 304.01 9 12:41:04 36.851 -25.025 18.6 132.1 125.78 i0 12:55:40 35.802 -23.544 15.0 142.9 192.26 ii 13:06:34 35.058 -24.057 13.4 148.3 20.87 12 13:14:28 35.886 -23.716 13.3 158.4 17.88 13 13:25:52 37.101 -23.440 13.8 171.6 296.18 NUMBER OF FILES FOR THIS FLIGHT = TOTAL NUMBER OF SCAN LINES DATE THESE FILES WERE PROCESSED = 25-Jan-94 DATE THIS LIST WAS CREATED = 25-Jan-94 LIME INFORMATION FOR 17-JUN-1992 END OF FLIGHT LINE ................................................. TIME LAT LON SOLAR SCAN HH : MM : SS DEG DEG ZEN AZIM LIMES ....................................... 11:30:35 37.016 -24.435 30.6 107.3 1098 11:38:12 36.213 -24.686 29.1 107.6 2169 11:46:48 36.065 -24.292 27.1 Ii0.i 495 11:52:05 35.977 -23.590 25.5 112.4 1370 11:59:06 35.747 -22.707 23.5 115.3 2473 12:08:16 35.754 -22.996 22.0 118.3 963 12:12:56 35.890 -22.750 21.1 120.8 464 12:35:39 36.642 -24.914 19.2 129.0 5367 12:54:08 35.952 -23.595 15.4 141.9 4898 13:02:50 34.996 -23.779 13.6 146.1 2693 13:14:13 35.865 -23.724 13.3 158.1 2872 13:24:06 36.933 -23.359 13.7 170.2 3619 13:37:23 37.695 -24.975 14.3 177.0 4325 13 32806 The *.gif files shown in the previous directory listing are the browse images in Graphics Interchange Format (GIF) for every 4th pixel on every 4th line from each flight line. These images contain one short-wave visible and one longwave infrared channel. They are contrast stretched and converted to GIF for distribution, and as such do not contain quantitative radiance information. 28

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There are 2 GIF image files per flight line, named 92170??v.gif and 92170??i.gif, where ?? is the flight line number, v denotes visible (VIS) imagery, and i denotes infrared (IR) imagery. The date corresponds to year and day of year as mentioned previously. The VIS and IR channels are selected such that the VIS channel is at around 0.68 microns, and the IR channel is at around 12 microns. Example browse images from the MAS flight on 17 June 1992 are shown on the following page (Figure 1). These were acquired over the Atlantic Ocean, off the coast of the Azores Islands. Stratiform cloud features are visible, with marine stratocumulus in the upper region of the image and continental stratocumulus in the lower region of the image. A cold cirrus cloud formation can be seen (as a black feature) in the infrared browse image in the upper portion. This feature is not distinct in the visible browse image. Public domain or shareware software packages to view GIF imagery on various systems are available from the following anonymous FTP sites: IBM[PC oak.oakland.edu, pub/msdos/gif/cshwl01a.zip Macintosh mac.archive.umich.edu, mac/graphics/graphicsutil/gifconverter2.37.cpt.hqx Unix[X ftp.x.org, contrib / xloadimage.4.1.tar.gz 29

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Visible (0.68 btm) browse image Figure 1. MAS Browse Images, 30 ii iiiii ¸ .....i! i!iiiiiiill!i¸ ,!i i, _ .... i_iili!iiii_iii_i ii!i_ii!ii!!iiiiiiiiiiiii_ii_i!iiil! i iiii!iiiii!!!!i!i!ii i i ii iiiiiii¸iiiiiiiiiii!iiiiiiiiii!iii............ .... • ................ iiii_i_iiiiiii_i_i_iiiiiii!iiiiiiiiiiiiiiiiiiiiii!!iIiiii!!i!!iii_iiiii_ii!ii!iiiiiiiiiiiiiiiiiiiiiiiii!!!i!i_iiiiiiiIiiiiiii iiiii!i!ii!i!ii!!!i!iii!il!i!!iiiiii!iii!!!!iiiiiiiiiilili!iiii!i!iii!ii_iiiiii!ii!!!ii!!ii!iiii!iiiiiiiiiiii_i_l_ll_i .......................i_i!i_i_i!i_i!i!!iiiiiiiiiiiiiiii!ii!!iiiiiiii!i!iiiiiiii!!!ii!i!iili!iiiiil!il!iiiiiiiiiiii!iii_iiiiiliiiliiliil_il@" " iiiiiiiiiiiiiiiii_i_i_i!iii_i_i_iiii___i_i_i!iiiiii_i_iiiiiiii_!iiiii_i_i_i_i_i_i_iiiiiiiii!i!iiiiiii_i_i_iiii!i_iiiiii!!i!iiiiiiiiiiiiii_iiiiiii_iii_iiiiiiiiiiiiiiiiiiiiiiiiiiIiiiI_i_''ii• iiii!iii!ii!iiiiiii!i!ii_iii_iii_i!iiiiii_iiiiiii!iiiiii!!iiii!i!ii_ii iiiii_i_i_iiiiiii ii!iiiiiliii!iiiii iii........ iiiiiiii_iiiii_i_!iiiii_i_i_!ii_i_iiiiiiii_iiiiiii_ii_iiiiiiiiiiii_i!i!iiiiiiiiii_i_iii_iiiiiii!i!iii!iiiiiiii!iiiii ii!iiiiilliil!ii!iiiii!iiiiiiiiiiiiiiiiiii!i!iiiiiiiii!iiiiiliiiiiiiiiiiiiiiii!i!iiiiiiiii!iiiiii_i@i."'i. . iiiiii!i_!i_!_iiii_iiiiiiiiiiii_iiiiiiiiiii_iii_i!!i_iiii_iiiiiiiiii!ii!!iiii!iii_iiiiiiii!i!iiiiiiiiiiiiii_iiiii...?..._iiIiiii _i_iiiiiii_iiiiiiiii!iiiii!iiiiiiii!iiiiiii!iiiiii®il Infrared (11.95 btm) browse image Flight Line 11, 17 June 1992

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1. MAS Contact List Below is a list of persons involved with the processing and analysis of MAS data. Paul Hubanks, MAS LEVEL-1B Processing Manager Research and Data Systems Corporation 7855 Walker Drive, Suite 460 Greenbelt MD 20770, USA (301) 982-3724, phubanks@ltpsun.gsfc.nasa.gov Liam Gumley, MAS LEVEL-1 Processing System Designer Code 913, NASA Goddard Space Flight Center Greenbelt MD 20771, USA (301) 286-8789, gumley@climate.gsfc.nasa.gov Tom Arnold, MAS VIS/NIR Calibration Code 913, NASA Goddard Space Flight Center Greenbelt MD 20771, USA (301) 286-4805, arnold@climate.gsfc.nasa.gov Michael King, MAS Principal Investigator Code 900, NASA Goddard Space Flight Center Greenbelt MD 20771, USA (301) 286-8228, king@climate.gsfc.nasa.gov Paul Menzel, MAS Principal Investigator NOAA/NESDIS 1225 W. Dayton St. Madison WI 53706 USA (608) 263-4930, paulm@ssecmail.ssec.wisc.edu Chris Moeller, MAS Investigator; calibration, geolocation, MCIDAS Space Science and Engineering Center, UW-Madison 1225 W. Dayton St. Madison WI 53706, USA (608) 263-9597, chrism@ssecmail.ssec.wisc.edu Jeff Myers, MAS LEVEL-0 Data Distribution High Altitude Missions Branch, NASA Ames Research Center Mail Stop 240-6 Moffett Field CA 94035, USA (415) 604-6252, jmyers@msmail.arc.nasa.gov Pat Grant, MAS Engineering High Altitude Missions Branch, NASA Ames Research Center Mail Stop 240-6 Moffett Field CA 94035, USA (415) 604-6393, pgrant@msmail.arc.nasa.gov 31

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1. References Arnold, G.T., M. Fitzgerald, P.S. Grant, and M.D. King, 1994a: MODIS Airborne Simulator Visible and Near-Infrared Experiment. NASA Goddard Space Flight 104600. Calibration - 1991 FIRE-Cirrus Field Center, NASA Technical Memorandum Arnold, G.T., M. Fitzgerald, P.S. Grant, and M.D. King, 1994b: MODIS Airborne Simulator Visible and Near-Infrared Calibration - 1992 ASTEX Field Experiment. NASA Goddard Space Flight Center, NASA Jedlovec, G.J., K.B. Batson, R.J. Atkinson, Technical Memorandum 104599. C.C. Moeller, W.P. Menzel, and M.W. James, 1989: Improved Capabilities of the Multispectral Atmospheric Mapping Sensor (MAMS). NASA Marshall Space Flight Center, NASA Technical Memorandum 100352. King, M. D., Y. J. Kaufman, W. P. Menzel and D. TanrG 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. 32

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REPORT DOCUMENTATION Form Approved PAGE OMBNo. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection collection of information, including suggestions for reducing this burden, to Washington Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management 1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE Anril 1994 4. TITLE AND SUBTITLE - MODIS Technical Report Series of information. Send comments re larding this burden estimate or any other aspect of this Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. 3. REPORT TYPE AND DATES COVERED Te.chnie._ 1 Memorandnm 5. FUNDING NUMBERS Volume 3, MODIS Airborne Simulator Level 1B Data User's Guide 6. AUTHOR(S) Liam E. Gumley, Paul A. Hubanks, and Edward 7. PERFORMINGORGANIZATIONNAME(S)ANDADDRESS(ES) Goddard Space Flight Center Greenbelt, Maryland 20771 Code 910 J. Masuoka 8. PEFORMING ORGANIZATION REPORT NUMBER 94B00065 10. SPONSORING / MONITORING 9. SPONSORING/ MONITORINGADGENCYNAME(S)AND ADDRESS(ES) National Aeronautics and Space Administration Washington, DC 20546-0001 11. SUPPLEMENTARY NOTES ADGENCY REPORT NUMBER NASA TM- 104594, Vol. 3 Gumley: Applied Research Corporation, Landover, Maryland (Formerly with Research and Data Systems Corporation); Hubanks: Research and Data Systems Corporation, Greenbelt, Maryland; Masuoka: Goddard Space Flight Center, Greenbelt, Maryland. 12a. DISTRIBUTION / AVAILABILITY STATMENT Unclassified - Unlimited Subject Category 31 13. ABSTRACT (Maximum 200 words) The purpose of this document is to describe Spectroradiometer (MODIS) Airborne Simulator 12b. DISTRIBUTION CODE the characteristics of Moderate Resolution Imaging Level 1B data, the calibration and geolocation methods used in processing, the structure and format of the Level 1B data files, and methods for accessing the data. The MODIS Airborne Simulator is a scanning spectrometer, which flies on a NASA ER-2, and provides spectral information similar to that which will be provided by the MODIS. 14. SUBJECT TERMS 15. NUMBER OF PAGES 48 User's Guide, MODIS Airborne Simulator; MODIS, Remote Sensing, Airborne 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIRCATION OF REPORT OF THIS PAGE Unclassified Unclassified NSN 7540-01-280-5500 16. PRICE CODE i 19. SECURITY CLASSIFICATION 20. LIMITATION OF AB_ iHACT OF ABSTRACT UL Unclassified Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. Z39.18

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