Earth Radiation Budget Experiment 1. TYPE OF DATA 1.1 Parameter/Measurement 1.2 Unit of Measurement 1.3 Data Source 1.4 Data Set Identification 2. SPATIAL CHARACTERISTICS 2.1 Spatial Coverage 2.2 Spatial Resolution 3. TEMPORAL CHARACTERISTICS 3.1 Temporal Coverage 3.2 Temporal Resolution 4. INSTRUMENT DESCRIPTION 4.1 Mission Objectives 4.2 Key Satellite Flight Parameters 4.3 Principles of Operation 4.4 Instrument Measurement Geometry 5. DATA PROCESSING SEQUENCE 5.1 Processing Steps and Data Sets 5.2 Derivation Techniques/Algorithms 5.3 Special Corrections/Adjustments 5.4 Processing Changes 6. QUALITY ASSESSMENT 6.1 Data Validation by Producer 6.2 Confidence Level/Accuracy Judgment 6.3 Usage Guidance 7. CONTACTS FOR DATA PRODUCTION INFORMATION 8. OUTPUT PRODUCTS AND AVAILABILITY 8.1 Tape Products 8.2 Film Products 8.3 Other Products 9. DATA ACCESS 9.1 Archive Identification 9.2 Procedures for Obtaining Data 9.3 NCDS Status/Plans 10. CONTACTS FOR ARCHIVE/DATA ACCESS INFORMATION 11. REFERENCES 11.1 Satellite/Instrument/Data Processing Documentation 11.2 Journal Articles and Study Reports 11.3 Archive/DBMS Usage Documentation 12. RELATED DATA SETS 13. SUMMARY/SAMPLE 14. NOTES ENDOFTOC 1. TYPE OF DATA 1.1 Parameter/Measurement. Earth radiances and solar irradiances in the ultraviolet, visible, and infrared spectral bands are measured by two instrument packages: scanning and non-scanning, with characteristics listed in the following table: Earth Radiation Budget Satellite (ERBS), NOAA-9, and NOAA-10 ERBE Instrument Characteristics _____________________________________________________________________ Wavelength limits Channel (micrometers) Measurement _____________________________________________________________________ Fixed WFOV* 1 0.2 - 50.0 Total Radiance 2 0.2 - 5.0 Shortwave (SW) Reflected Fixed MFOV** 3 0.2 - 50.0 Total Radiance 4 0.2 - 5.0 SW Reflected Fixed Solar 5 0.2 - 50.0 Total Irradiance Monitor Scanning NFOV~ 1 0.2 - 50.0 Calibrated Radiance 2 0.2 - 5.0 SW Reflected 3 5.0 - 50.0 Longwave (LW) Emitted ______________________________________________________________________ * Wide Field-of-View ** Medium Field-of-View ~ Narrow Field-of-View 1.2 Unit of Measurement. Nonscanner measurements are in counts and W/(m**2). Scanner measurements are in counts and W/m**2-steradian. Albedo measurements are unitless. 1.3 Data Source. The Earth Radiation Budget Experiment (ERBE) is currently being flown on the Earth Radiation Budget Satellite (ERBS), and NOAA-10. ERBE was also flown on the NOAA-9 satellite. The NOAA-9 scanner failed January 20, 1987 and the NOAA-9 nonscanner failed November 7, 1988. 1.4 Data Set Identification. Raw Archival Tape (RAT) images are archived on optical disks. These disks contain located raw counts of all radiometric measurements, plus housekeeping data in counts and converted values, orbit data, and attitude data. 2. SPATIAL CHARACTERISTICS 2.1 Spatial Coverage. The spatial coverage differs with each channel and spacecraft, as described below. Wide-angle Channels: These two fixed channels continuously view the Earth disc. NOAA-9 and -10 measurements are continuous over the entire globe. ERBS, which precesses 4.95 degrees West per day, has a latitudinal range between 57 degrees North and South. Medium-angle Channels: These two fixed channels continuously view a circle of nominally 5 degrees radius at the top of the atmosphere. NOAA-9 and -10 measurements are continuous over the entire globe. ERBS, which precesses 4.95 degrees West per day, has a latitudinal range between 57 degrees North and South. Narrow-angle Channels: These three scanning channels continuously view small areas over the entire Earth. The cross-track scan width is approximately 40 kilometers (km) at nadir. In addition, ERBS has a 35% field-of-view (FOV) overlap along-track at nadir. 2.2 Spatial Resolution. The spatial resolution differs with each type of channel and spacecraft (ERBS and NOAA). The ERBS and NOAA wide-angle channels view the Earth disc with a FOV of 136 and 126 degrees, respectively. The medium-angle channels have footprints of approximately 5 degrees radius, or 1000 km, at the top of the atmosphere. The narrow-angle channels on ERBS have an instantaneous hexagonal FOV of about 3 x 4.5 degrees, which is equivalent to a 31 km cross-track x 47 km track footprint at nadir. The narrow-angle channels on NOAA have a 44 km cross-track x 65 km track. The solar channel has an unencumbered FOV which observes the entire solar disk. 3. TEMPORAL CHARACTERISTICS 3.1 Temporal Coverage. ERBS coverage began in October 1984 and is still continuing along with NOAA-10, which became operational in October 1986. NOAA-9 coverage began in January 1985 and ended in November 1988. The NOAA-9 scanner failed on January 20, 1987, the NOAA-10 scanner failed on May 22, 1989, and the ERBS scanner failed on February 28, 1990. The NOAA-9 nonscanner failed November 7, 1988. ERBE nonscanner measurements from NOAA-10 and ERBS are continuing (please see Item 14 concerning the ERBS nonscanner). The solar channel measures 20 minutes of usable data (about twice per month) during solar calibration periods. 3.2 Temporal Resolution. Five channels of the nonscanner provide 125 samples per second. The solar monitor's shutter cycles every 32 seconds during a solar calibration. All of the channels of the scanner were sampled every 0.033 second. 4. Instrument Description 4.1 Mission Objectives. The objectives of the Earth Radiation Budget Experiment (ERBE) are: (1) to determine for a minimum of 1 year the monthly average radiation budget on regional, zonal, and global scales, (2) to determine the equator-to-pole energy transport gradient, and (3) to determine the average diurnal variation of the radiation budget on a regional and monthly scale. 4.2 Key Satellite Flight Parameters. Nominal orbit parameters for ERBS are listed below: . Launch date October 5, l984 . Planned duration* 1 year . Actual duration Scanner failed 2/28/90 . Orbit Non-sun synchronous . Semi-major axis 6988 km . Normal Altitude 610 km . Inclination 57 deg . Nodal period 98 min . Equator Crossing time Precesses Nominal orbit parameters for NOAA-9 are listed below: . Launch date December 12, l984 . Planned duration 1 year . Actual duration Scanner failed 1/20/87 Nonscanner failed 11/7/88 . Orbit Sun-synchronous . Semi-major axis 7248 km . Normal Altitude 872 km . Inclination 98 deg . Nodal period 102.08 min . Equator Crossing time 1430 Local Mean Solar Time, ascending Nominal orbit parameters for NOAA-10 are listed below: . Launch date September 17, l986 . Planned duration 1 year . Actual duration Scanner failed 5/22/89 . Orbit Sun-synchronous . Semi-major axis 7211 km . Normal Altitude 833 km . Inclination 98 deg . Nodal period 101.2 min . Equator Crossing time 0730 Local Mean Solar Time, descending * The design life for all ERBE instruments is one year with a two-year goal. 4.3 Principles of Operation. The nonscanner package consists of four Earth-viewing channels, consisting of two MFOV channels and two WFOV channels, and a solar monitor. All five instruments are active cavity radiometers, with an accuracy of approximately 1% for spectral flatness and electrical substitution radiation detection. The Earth-viewing channels have two spectral ranges, one sensitive to all wavelengths and the other only to shortwaves by means of a high-priority, fused silica dome. Cavities are enclosed in modules which include filter domes and aperture limiters. The modules are mounted in an elevation beam, which can be rotated to point the detectors at the Earth, at the internal calibration sources, or at the Sun. The scanner package contains three NFOV radiometric channels, each of which consists of an F/1.84 Cassegrain telescope. All are located within a single, rotating scan-head which scans the FOV across-track. The scan head can also be rotated in azimuth at a slow rate. Each channel makes 74 measurements per scan. One channel does not have a filter and therefore absorbs all wavelengths. A second has a Suprasil-W1 filter which transmits only shortwave radiation. The third has a multilayer filter on a diamond substrate to reject shortwave and accept longwave radiation. 4.4 Instrument Measurement Geometry. The nonscanner modules can be rotated to any of three positions: launch/internal calibration position (180 degrees), the solar calibration position (78 degrees), and the Earth-viewing (nadir) position (0 degrees). The WFOV channels view the Earth from limb-to-limb. The MFOV channels are designed to include approximately an Earth view of 10 degrees within the unencumbered FOV. The scanner package can rotate in azimuth between 0 and 180 degrees with an accuracy of 0.075 degrees. (The normal scan mode is cross-track.) The hexagonal IFOV of each channel has an an angular size of 3 x 4.5 degrees, the longer dimension being along the satellite ground track. 5. DATA PROCESSING SEQUENCE 5.1 Processing Steps and Data Sets. Telemetry, ephemeris, and altitude data are merged together by time per day and spacecraft, and put onto the Level I Raw Archival Tape (RAT) optical disk. In addition to merging the telemetry and spacecraft ephemeris data streams, each instrument's FOV is located at the top of the atmosphere where their viewing angles are computed. Radiometric counts are then converted to engineering units, and the results are stored on the Level-II Processed Archival Tape (PAT) optical disks. (PAT processing is completed by an inversion subsystem which identifies scene type, computes shortwave and longwave radiances, and estimates the radiant exitance at the top of the atmosphere for each measurement.) 5.2 Derivation Techniques/Algorithms. In-flight calibration is performed to ensure high accuracy of radiometric measurements. The design and calibrations of the ERBE instrument are based on the 1968 International Practical Temperature Scale and the World Radiometer Reference. There is at least one on-board calibration device for each channel. These devices, together with a space look which provides a near-zero radiance, give basic offset and gain information for periodic in-flight calibration of the instruments. The scanner measurements are converted, pixel by pixel, to radiances by use of spectral factors, and to radiant exitance at the top of the atmosphere by use of angular directional models. The nonscanner measurements are inverted by either a shape factor (SF) method or by a numerical filter (NF) technique. 5.3 Special Corrections/Adjustments. Concurrent development of a mathematical model for each instrument helps in the understanding of instrument response in ground and in-flight calibration conditions and in space operation. 5.4 Processing Changes. None. 6. QUALITY ASSESSMENT 6.1 Data Validation by Producer. None. 6.2 Confidence Level/Accuracy Judgment. A confidence level has not been determined for the ERBE data and there are no immediate plans to do so. Some effort has been made to assess the accuracy of selected parameters (such as longwave and shortwave); however, a rigorous error analysis has not been undertaken. 6.3 Usage Guidance. RATs Monthly Product Summaries (MPS) are currently produced which include an explanation of the data coverage for the month. Each summary explains why an archival disk was not produced, and what caused major data dropouts. Monthly Product Summaries will be produced for the other archival products. 7. CONTACTS FOR DATA PRODUCTION INFORMATION 7.1 ERBE Experiment Scientist and Science Team Leader Dr. Bruce R. Barkstrom Atmospheric Sciences Division Mail Stop 420 NASA/Langley Research Center Hampton, Virginia 23665 FTS 928-5676 (804) 864-5676 7.2 ERBE Data Management Team Leader Mr. James F. Kibler Atmospheric Sciences Division Mail Stop 423 NASA/Langley Research Center Hampton, Virginia 23665 FTS 928-5386 (804) 864-5386 8. OUTPUT PRODUCTS AND AVAILABILITY 8.1 Tape/Disk Products (The following data products are from ERBS, NOAA-9, and NOAA-10.) 8.1.1 Raw Archival Tape (RAT) Optical Disk (RAT or S-1), Level I Medium/Specification: 12-in. write-once-read-many (WORM) optical disks. "Earth Radiation Budget Experiment (ERBE) Data Management System Raw Archival Tape (S-1) RAT Users Guide". July 1985. Format and Content: The optical disks were created on Optimem drives in an Aquidneck system. The data were first generated on a CDC computer. All records are written in multiples of 8-bit bytes. The first file contains a header record. The second file begins with a scale factor record, an integer-to-real offset record, and a time adjustment record, followed by about 5400 16-second data records. All data are arranged in chronological order. Data Quantity/Rate: Each physical record contains 16 seconds worth of raw instrument radiometric data, raw and converted spacecraft and instrument housekeeping data, and locations of each measurement on the Earth. There is one tape per day per spacecraft and one optical disk per month. Status: Raw Archival data on optical disk are available as follows: ERBS: October 25, 1984 through February 28, 1990 NOAA-9: March 1, 1985 through July 31, 1987 NOAA-10: November 1, 1986 through March 31, 1989 Plans/Schedule: Data are being processed and will be archived chronologically. 8.2 Film Products. None. 8.3 Other Products. None. 9. DATA ACCESS 9.1 Archive Identification. Central Data Services Facility Code 933 National Space Science Data Center NASA/Goddard Space Flight Center Greenbelt, Maryland 20771 FTS 888-6695 (301) 286-6695 9.2 Procedures for Obtaining Data. Users may submit requests for data by letter, telephone, personal visit or through the NSI DECnet computer network at NSSDC::REQUEST. Data costs are dependent on affiliation and sponsorship of the user program. Data are free to NASA personnel. Communication with the NSSDC Request Coordination Office is advised before ordering. Researchers who reside outside the USA should direct their requests to: World Data Center A for Rockets and Satellites Code 930.2 NASA/Goddard Space Flight Center Greenbelt, Maryland 20771 USA (301) 286-6695 9.3 NCDS Status/Plans. NCDS provides access to the ERBE-S2 and ERBE-S4 data sets. 10. CONTACTS FOR ARCHIVE/DATA ACCESS INFORMATION Request Coordination Office Central Data Services Facility Code 933 National Space Science Data Center NASA/Goddard Space Flight Center Greenbelt, Maryland 20771 (301) 286-6695 Goddard DAAC User Support Office Code 935 NASA/Goddard Space Flight Center Greenbelt, Maryland 20771 (301) 286-3209 FTS: 888-3209 NSI DECnet: NSSDCA::NCDSUSO INTERNET: NCDSUSO@NSSDCA.GSFC.NASA.GOV 11. REFERENCES 11.1 Satellite/Instrument/Data Processing Documentation. a. NASA/LaRC. "Earth Radiation Budget Experiment (ERBE) Data Management System Raw Archival Tape (S-1) Users Guide." Hampton, Virginia. b. NASA/LaRC. "Earth Radiation Budget Experiment (ERBE) Data Management System Processed Archival Tape (S-8) Users Guide." Hampton, Virginia. 11.2 Journal Articles and Study Reports. a. Avis, L.M., R.N. Green, J.T. Suttles, and S.K. Gupta, 1984. "A Robust Pseudo-Inversion Spectral Filter Applied to the Earth Radiation Budget Experiment (ERBE) Scanning Channels." NASA Tech. Memorandum 85781, NASA Langley Research Center, Hampton, Virginia. b. Barkstrom, B.R., l984. "The Earth Radiation Budget Experiment Experiment (ERBE)." Bull. Amer. Meteor. Soc., 65:1170-1185. c. Barkstrom, B.R., and G.L. Smith, 1986. "The Earth Radiation Budget Experiment: Science and Implementation." J. Geophys. Res., 24:379-390. d. Barkstrom, B.R., et al., 1989. "Earth Radiation Budget Experiment (ERBE) Archival and April 1985 Results." Bull. Amer. Met. Soc., 70:1254-1262. e. Barkstrom, B.R., et al., 1990. "Earth Radiation Budget Experiment Preliminary Seasonal Results." EOS, 71:297-312. f. ERBE Science Team, l986. "First Data from the Earth Radiation Budget Experiment (ERBE)." Bull. Amer. Meteor. Soc., 67:818-824. g. Green, R.N., and G.L. Smith, 1991. "Shortwave Shape Factor Inversion of Earth Radiation Budget Observations." J. Atm. Sci., 48:390-402. h. Green, R.N., et al., 1990. "Intercomparison of Scanner and Nonscanner Measurements for the Earth Radiation Budget Experiment (ERBE)." J. Geophys. Res., 95:11,785-11,798. i. Harrison, E.F., et al., 1983. "Orbital and Cloud Cover Sampling Analyses for Multisatellite Earth Radiation Budget Experiment (ERBE)." J. Spacecr. Rockets, 20:491-495. j. Harrison, E.F., et al., 1988. "First Estimates of the Diurnal Variation of Longwave Radiation from the Multiple-Satellite Earth Radiation Budget Experiment (ERBE)." Bull. Amer. Met. Soc., 69:1144-1151. k. Harrison, E.F., P. Minnis, B.R. Barkstrom, V. Ramanathan, R.D. Cess, G.G. Gibson, 1990. "Seasonal Variation of Cloud Radiative Forcing Derived from the Earth Radiation Budget Experiment." J. Geophys. Res., 95:18,687-18,703. l. Hartmann, D.L., and D. Doelling, 1991. "On the Net Radiative Effectiveness of Clouds." J. Geophys. Res., 96:869-891. m. Kopia, L., 1986. "Earth Radiation Budget Experiment Scanner Instrument." Rev. Geophys., 24:400-406. n. Luther, M.R., l986. "The Earth Radiation Budget Experiment Nonscanner Instrument." Rev. of Geophys., 24:391-399. o. Ramanathan, V., et al., 1989. "Cloud-radiative Forcing and Climate: Results from the Earth Radiation Budget Experiment." Science, 243:57-63. p. Smith, G.L., R.N. Green, E. Raschke, L.M. Avis, B.A. Wielicki, and R. Davies, l986. "Inversion Methods for Satellite Studies of the Earth's Radiation Budget: Development of Algorithms for the ERBE Missions." Rev. of Geophys., 24:407-421. q. Wielicki, B.A., and R.N. Green, 1989. "Cloud Identification for ERBE Radiation Flux Retrieval." J. Appl. Met., 28:1133-1146. 11.3 Archive/DBMS Usage Documentation. None. a. Olsen, L.M., J.W. Closs, and F.E. Corprew, November 1991. "NASA's Climate Data System Primer: Version 4.0." EOS DAAC, NASA Goddard Space Flight Center, Greenbelt, Maryland. 12. RELATED DATA SETS Information about related data sets may be accessed by specifying one of the following data set names within the search criteria screen of the Data Access subsystem of the NCDS: N6-ERB (Nimbus-6 Earth Radiation Budget, Level-1 data) N7-ERB (Nimbus-7 Earth Radiation Budget, Level-1 data) AVHRR-1B (NOAA Polar Orbiter Advanced Very High Resolution Radiometer) NOAA-HB (NOAA Heat Budget) 13. SUMMARY/SAMPLE Level I hardcopy data products are not available. 14. NOTES NOAA-9 was used as a test bed for software modifications after NOAA-11 developed gyroscope problems. While testing the software, a command error resulted in a complete shutdown of all instruments on-board the NOAA-9 spacecraft on May 21, 1991. The ERBE nonscanner instrument on-board NOAA-9 was powered up on May 22, 1991, followed by the detector heaters on May 23, 1991. The nonscanner elevation beam was undefined once the nonscanner was powered up, and attempts to command the elevation beam to its correct position were unsuccessful. Although the telemetry data showed that the ERBE instrument was in no physical danger, further command testing of NOAA-9 was discontinued because of NOAA operational conflicts. These operational conflicts came to an end July 16, 1991 and command testing was resumed in order to recover normal operation of NOAA-9. NOAA-9 resumed operation (without sensors) on July 25, 1991. Further testing of NOAA-11 software modifications occurred in late August to correct continuing gyroscope problems. *92/03/16