ess. /3/i? : /t/jess /o7 NOAA Technical Memorandum NESS 107 DATA EXTRACTION AND CALIBRATION OF TIROS-N/NOAA RADIOMETERS Washington, D.C. November 1979 nnp^l NATIONAL OCEANIC AND / ■ IV/QQ ATMOSPHERIC ADMINISTRATION / National Environmental Satellite Service NOAA TECHNICAL MEMORANDUMS National Environmental Satellite Service Series The National Environmental Satellite Service (NESS) is responsible for the establishment and oper- ation of NOAA's environmental satellite systems. NOAA Technical Memorandums facilitate rapid distribution of material that may be preliminary in nature and so may be published formally elsewhere at a later date. Publications 1 to 20 and 22 to 25 are in the earlier ESSA National Environmental Satellite Center Technical Memorandum (NESCTM) series. The current NOAA Technical Memorandum NESS series includes 21, 26, and subsequent issuances. Publications listed below are available (also in microfiche form) from the National Technical Informa- tion Service, U.S. Department of Commerce, Sills Bldg., 5285 Port Royal Road, Springfield, VA 22161. Prices on request. Order by accession number (given in parentheses). Information on memorandums not listed below can be obtained from Environmental Data and Information Service (D822), 6009 Executive Boulevard, Rockville, MD 20852. NESS 66 A Summary of the Radiometric Technology Model of the Ocean Surface in the Microwave Region. John C. Alishouse, March 1975, 24 pp. (COM-7 5-10849 /AS) NESS 67 Data Collection System Geostationary Operational Environmental Satellite: Preliminary Report. Merle L. Nelson, March 1975, 48 pp. (COM-75-10679/AS) NESS 68 Atlantic Tropical Cyclone Classifications for 1974. Donald C. Gaby, Donald R. Cochran, James B. Lushine, Samuel C. Pearce, Arthur C. Pike, and Kenneth 0. Poteat, April 1975, 6 pp. (COM-75- 10676/AS) NESS 69 Publications and Final Reports on Contracts and Grants, NESS-1974. April 1975, 7 pp. (COM- 75-10850/AS) NESS 70 Dependence of VTPR Transmittance Profiles and Observed Radiances on Spectral Line Shape Parame- ters. Charles Braun, July 1975, 17 pp. (COM-75-11234/AS) NESS 71 Nimbus-5 Sounder Data Processing System, Part II: Results. W. L. Smith, H. M. Woolf , C. M. Hayden, and W. C. Shen, July 1975, 102 pp. (COM-75-11334/AS) NESS 72 Radiation Budget Data From the Meteorological Satellites, IT0S 1 and NOAA 1. Donald H. Flanders and William L. Smith, August 1975, 20 pp. (PB-246-877/AS) NESS 73 Operational Processing of Solar Proton Monitor Data (Revision of NOAA TM NESS 49). Stanley R. Brown, September 1975, 15 pp. (COM-73-11647) NESS 74 Monthly Winter Snowline Variation in the Northern Hemisphere From Satellite Records, 1966-75. Donald R. Wlesnet and Michael Matson, November 1975, 21 pp. (PB-248-437/6ST) NESS 75 Atlantic Tropical and Subtropical Cyclone Classifications for 1975. D. C. Gaby, J. B. Lushine, B. M. Mayfield, S. C. Pearce, and K.O. Poteat, March 1976, 14 pp. (PB-253-968/AS) NESS 76 The Use of the Radiosonde in Deriving Temperature Soundings From the Nimbus and NOAA Satellite Data. Christopher M. Hayden, April 1976, 19 pp. (PB-256-755/AS) NESS 77 Algorithm for Correcting the VHRR Imagery for Geometric Distortions Due to the Earth Curvature, Earth Rotation, and Spacecraft Roll Attitude Errors. Richard Legeckis and John Pritchard, April 1976, 31 pp. (PB-258-027/AS) NESS 78 Satellite Derived Sea-Surface Temperatures From NOAA Spacecraft. Robert L. Brower, Hilda S. Gohrband, William G. Pichel, T. L. Signore, and Charles C. Walton, June 1976, 74 pp. (PB-258-026/AS) NESS 79 Publications and Final Reports on Contracts and Grants, NESS-1975. National Environmental Satellite Service, June 1976, 10 pp. (PB-258-450/AS) NESS 80 Satellite Images of Lake Erie Ice: January-March 1975. Michael C. McMillan and David Forsyth, June 1976, 15 pp. (PB-258-458/AS) NESS 81 Estimation of Daily Precipitation Over China and the USSR Using Satellite Imagery. Walton A. Follansbee, September 1976, 30 pp. (PB-261-970/AS) NESS 82 The GOES Data Collection System Platform Address Code. Wilfred E. Mazur, Jr*. , October 1976, 26 pp. (PB-261-968/AS) (Continued on inside back cover) NOAA Technical Memorandum NESS 107 DATA EXTRACTION AND CALIBRATION OF TIROS-N/NOAA RADIOMETERS Levin Lauritson Gary J. Nelson Frank W. Porto Washington, D.C. November 1979 UNITED STATES .DEPARTMENT OF COMMERCE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION Richard A. Frank, Administrator National Environmental Satellite Service David S. Johnson, Director 4 ,*«5gw m ex O '^■ISP Digitized by the Internet Archive in 2012 with funding from LYRASIS Members and Sloan Foundation http://archive.org/details/dataextractioncaOOIaur CONTENTS 1. Introduction 1 2. Instruments 2 2.1 Advanced very high resolution radiometer (AVHRR) 2 2.2 TIROS operational vertical sounder (TOVS) 2 2.2.1 High resolution infrared radiation sounder (HIRS/2) . 3 2.2.2 The stratospheric sounding unit (SSU) 4 2.2.3 The microwave sounding unit (MSU) 6 2.3 Data collection and location system (DCLS) 7 2.4 Space environment monitor (SEM) 8 3. Real-time data transmission service 8 3.1 APT transmission characteristics 10 3.2 HRPT transmission characteristics 10 3.3 HRPT format 11 3.3.1 Detailed description of HRPT minor frame format ... 19 3.4 DSB transmission characteristics 19 3.5 TIP data format 19 4. Creation of instrument data bases 29 4.1 HIRS/2 29 4.2 MSU 33 4.3 SSU 36 4.4 AVHRR 38 4.5 Scan timing and geometry 39 5. Calibration 40 5.1 AVHRR 44 5.2 MSU 47 5.3 SSU 49 5.4 Calibration of HIRS/2 51 5.5 Application of calibration coefficients to earth view data 52 5.6 APT 52 Appendix A Temperature-to-radiance conversion A-l Appendix B TIROS-N B-l References R-l in TABLES 2-1. Spectral characteristics of the TIROS-N/NOAA AVHRR instruments 3 2-2. AVHRR instrument parameters 3 2-3. HIRS/2 instrument parameters 4 2-4. HIRS/2 spectral characteristics 5 2-5. SSU channel characteristics 6 2-6. SSU instrument parameters 6 2-7. MSU channel characteristics 7 2-8. MSU instrument parameters 7 3-1. Real-time data transmission characteristics 10 3-2. APT characteristics 11 3-3. APT transmission parameters .12 3-4. APT format parameters 13 3-5. HRPT characteristics 13 3-6. HRPT parameters 17 3-7. HRPT transmission parameters 17 3-8. HRPT minor frame format 20 3-9. DSB transmission parameters 24 3-10. DSB TIP parameters 25 3-11. Detailed description of TIP minor frame 27 4-1. HIRS/2 digital A data output 30 4-2. HIRS/2 channel word location 32 4-3. MSU scan line format 34 4-4. MSU bit formats for each IFOV 35 4-5. Acceptable scan angles 36 4-6. 30-word SSU data sampling (repeated 32 times per SSU scan) 37 4-7. Instrument scan timing parameters 39 4-8. Scan line timing of the TOYS instruments 40 IV FIGURES 3-1. TIROS-N/NOAA real-time systems data flow 9 3-2. APT video line format (prior to D/A converter) .... 14 3-3. APT frame format 15 3-4. APT sync details 16 3-5. TIROS-N/NOAA HRPT minor frame format 18 3-6. TIP minor frame format 26 4-1. TIROS operational vertical sounder HIRS/2 and SSU scan patterns projected on Earth 41 4-2. TIROS operational vertical sounder HIRS/2 and MSU scan patterns projected on Earth 42 5-1. Thermal temperatures 1 and 2 54 5-2. Thermal temperatures 3 and 4 55 5-3. Grey level equivalent blackbody temperature, 3.7 |j.m. . 56 5-4. Grey level equivalent blackbody temperature, 11.0 [im . 57 GLOSSARY ADC - analog-to-digital converter AM - amplitude modulated APT - Automatic picture transmission ARGOS - French abbreviation for their data collection and location system (Service ARGOS) AVHRR - Advanced very high resolution radiometer bps - bits per second CAL - calibration CDA - command and data acquisition ch - channel cm - centimeter Cmd. - command CNES - Centre National D' Etudes Spatiales CPU - central processing unit CV - command verification DAC - digital-to-analog converter dB - decibel dBm - decibels above (or below) one milliwatt DCS/DCLS - Data collection and location system DIG - digital DSB - Direct sounder broadcast EIRP - effective isotropic radiated power FM - frequency modulation fps - frames per second GHz - gigahertz GMT - Greenwich mean time GOES - Geostationary Operational Environmental Satellite HEPAD - High energy proton and alpha detector HIRS/2 - High resolution infrared radiation sounder, mod. 2 HRPT - High resolution picture transmission Hz - hertz ICT - Internal cold target/internal calibration target ID - identification IFOV - Instantaneous field of view IR - infrared ITOS - Improved TIROS operational system IWT - Internal warm target K - Kelvin temperature kbps - kilobits per second kHz - kilohertz km - kilometer LSB - Least significant bit m - meter MAX - maximum mbar - millibar Mbps - megabits per second MHz - megahertz MEPED - Medium energy proton and electron detector MI - modulation index VI GLOSSARY (CONTINUED) MIN - minimum |j.m - micrometer MIRP - Manipulated information rate processor MSB - Most significant bit msec - millisecond MSU - Microwave sounding unit mV - millivolt mW - milliwatt NESS - National Environmental Satellite Service NFAN - Noise equivalent radiance difference NEAT - Noise equivalent temperature difference No. - number NOAA - National Oceanic and Atmospheric Administration PMC - Pressure modulated cell pps - pulses per second PRT - Platinum resistance thermometer PT - point REF - Reference S/C - spacecraft SEC, sec - second SEM - Space environment monitor S/N - Signal-to-noise ratio SOCC - Spacecraft Operations Control Center SPM - Solar proton monitor sr - steradian SSU - Stratospheric sounding unit SUBCOM - subcommutation SYNC - synchronous TED - Total energy detector TEMP. - temperature Tgt . - target THERM. - thermal TIP - TIROS information processor TIROS - Television Infrared Observational Satellite TLM - telemetry TOVS - TIROS operational vertical sounder Vdc - volts, direct current VHF - very high frequency XSU - cross-strap unit Vll DATA EXTRACTION AND CALIBRATION OF TIROS-N/NOAA RADIOMETERS Levin Lauritson, Gary J. Nelson and Frank W. Porto National Environmental Satellite Service, NOAA Washington, D. C. ABSTRACT. The TIROS-N/NOAA series is the third generation of environmental satellites providing real-time data to direct readout users. This publication has been prepared for the direct readout user of the Automatic Picture Transmis- sion (APT) service, the High Resolution Picture Transmission (HRPT) service and the Direct Sounder Broadcast (DSB) service transmitted from these satellites. Information is presented that will enable users to extract from the te- lemetry streams data that are unique to a given sensor, to calibrate these data, and to develop an understanding of the accuracy and precision that can be expected of the calibrated data. 1 . INTRODUCTION This publication has been prepared for the user of the direct readout of the Automatic Picture Transmission (APT) service of the High Resolution Picture Transmission (HRPT) service, or of the Direct Sounder Broadcast (DSB) service from the TIROS-N/NOAA series spacecraft. It is intended to provide the information necessary to extract data from the telemetry streams that are unique to a given sensor, to calibrate these data, and to develop an under- standing of the accuracy and precision that can be expected of the calibrated data. Information is provided that will enable users with varying de- grees of hardware capability and interest to realize the maximum utility from their particular systems. For example, an APT user may be interested in only the service that provides low resolution image products. On the other hand, a station that is equipped to read out, decommutate, and process HRPT data may wish to develop and produce quantitative products. In either case, the informa- tion will enable the user to realize the maximum capability from his system. Much of the material contained in this document describing the TIROS-N/NOAA instruments, data frame formats, downlink character- istics, etc., has been published before. Schwalb (1978) describes the TIROS-N/NOAA A-G satellite series in detail in NOAA Technical Memorandum, NESS-95. Schneider (1976) describes TIROS-N ground receiving stations. This publication is an attempt to bring together, under one cover, the informational content of much of that material. 2 . INSTRUMENTS 2.1 Advanced Very High Resolution Radiometer (AVHRR) The AVHRR provides data for transmission to both APT and HRPT users. HRPT data are transmitted at full resolution (1.1 km); the APT resolution is reduced to maintain allowable bandwidth. The AVHRR for TIROS-N is a scanning radiometer, sensitive in four spectral regions; a fifth channel will be added on later satel- lites in this series. Deployment of four- and five-channel in- struments is as follows: four-channel instruments are planned for TIROS-N, NOAA-A, NOAA-B, NOAA-C and NOAA-E ; five-channel instruments for NOAA-D, NOAA-F, and NOAA-G. The APT system transmits data from any two of the AVHRR channels selected by command from the National Environmental Satellite Service (NESS) Spacecraft Operations Control Center (SOCC). The HRPT system transmits data from all AVHRR channels. To avoid future changes on the spacecraft and in the ground receiving equipment, the TIROS-N/NOAA series HRPT data format has been de- signed to handle five AVHRR channels from the outset. When operating with a four-channel instrument, the data from the 11-micrometer (jum) channel are inserted in the data stream twice so that the basic HRPT data format is the same for both the four- and five-channel versions. Table 2-1 lists the spectral characteristics of the four- and five-channel instruments and designates the spacecraft on which they are planned to be deployed. Table 2-2 is a listing of the basic AVHRR parameters. 2.2. TIROS Operational Vertical Sounder (TOVS) The TOVS provides data for transmission to both HRPT and DSB receiving stations. The data are transmitted in digital format at full instrument resolution and accuracy. The TOVS consists of three independent instrument subsystems from which data may be combined for computation of vertical atmo- spheric temperature and humidity profiles. These are: a. High resolution infrared radiation sounder mod. 2 b. Stratospheric sounding unit c. Microwave sounding unit Table 2-1. Spectral characteristics of the TIROS-N/NOAA AVHRR instruments Four-channel AVHRR, TIROS-N Ch 1 Ch 2 Ch 3 Ch 4 Ch 5 0.55-0.9 (im 0.725-1.1 y.m 3.55-3.93 (im 10.5-11.5 |im Data from Ch 4 repeated Four-channel AVHRR - NOAA-A . -B. -C . and -E Ch 1 Ch 2 Ch 3 Ch 4 Ch 5 0.58-0.68 (im 0.725-1.1 urn 3.55-3.93 |im 10.5-11.5 y.m Data from Ch 4 repeated Five-channel AVHRR, NOAA-D, -F, and -G Ch 1 Ch 2 Ch 3 Ch 4 Ch 5 0.58-0.68 y.™ 0.725-1.1 (jm 3.55-3.93 M m 10.3-11.3 (im 11.5-12.5 ym Note: Changes to the above deployment scheme may occur as a result of instrument availability or changing requirements. Table 2-2. AVHRR instrument parameters Parameter Calibration Cross track scan Line rate Optical field of view Ground resolution (IFOV) Infrared channel NEAT(2 Visible channel S/n( 3 (1 Va 1 ue Stable blackbody and space for IR channels. No inflight visible channel calibration other than space. ±55.4° from nadir 360 lines per minute 1.3 milliradians 1.1 km @ nadir <0.12 K at 300 K 3:1 @ 0.5% albedo 1) Instantaneous field of view 2) NEAT - Noise equivalent differential temperature 3) Signal-to-noise ratio 2.2.1 High Resolution Infrared Radiation Sounder (HIRS/2) The HIRS/2 is an adaptation of the HIRS/1 instrument flown on the Nimbus-6 satellite. The instrument, built by the Aerospace/ Optical Division of the International Telephone and Telegraph Corporation, Fort Wayne, Indiana, measures incident radiation in 19 regions of the IR spectrum and one region of the visible spectrum. Table 2-3 is a listing of the HIRS/2 parameters. Table 2-3. HIRS/2 instrument parameters Parameter Calibration Cross-track scan Scan time Number of steps Optical field of view Step angle Step time Ground resolution (IFOV)* (nadir) Ground resolution (IFOV) (end of scan) Distance between IFOV's Data rate Value Stable blackbodies (2) and space background ±49.5° (±1125 km) @ nadir 6.4 seconds per line 56 1.25° 1.8° 100 milliseconds 17.4 km diameter 58.5 km cross-track by 29.9 km along track 42 km along-track @ nadir 2880 bits/second *Instantaneous field of view Table 2-4 is a listing of the HIRS/2 spectral characteristics and noise equivalent differential radiance (NEAN's). Note: There will be some variation in the achieved parameters from one HIRS/2 instrument to another, particularly in the NEAN's. 2.2.2 The Stratospheric Sounding Unit (SSU) The SSU, which has been provided by the United Kingdom, employs a selective absorption technique to make measurements in three channels. The spectral characteristics of each channel are de- termined by the pressure in a carbon dioxide gas cell in the op- tical path. The pressure of carbon dioxide in the cells determines the height of the weighting function peaks in the atmosphere. SSU characteristics are shown in tables 2-5 and 2-6. Table 2-4. HIRS/2 spectral characteristics Channel Half power Maximum Specified Channel frequency p.m bandwidth scene NEAN (cm- 1 ) (cm -1 ) temperature (K) FM 3-7 1 669 14.95 3 280 3.00 2 680 14.71 10 265 0.67 3 690 14.49 12 240 0.50 4 703 14.22 16 250 0.31 5 716 13.97 16 265 0.21 6 733 13.64 16 280 0.24 7 749 13.35 16 290 0.20 8 900 11.11 35 330 0.10 9 1,030 9.71 25 270 0.15 10 1,225 8.16 60 290 0.16 11 1,365 7.33 40 275 0.20 12 1,488 6.72 80 260 0.19 13 2,190 4.57 23 300 0.006 14 2,210 4.52 23 290 0.003 15 2,240 4.46 23 280 0.004 16 2,270 4.40 23 260 0.002 17 2,360 4.24 23 280 0.002 18 2,515 4.00 35 340 0.002 19 2,660 3.76 100 340 0.001 20 14,500 0.69 1000 100% A 0.10% A NEAN in mW/(sr m 2 cm 1 ) Table 2-5. SSU channel characteristics Channel Central Cell Pressure of number wave no. pressure weighting function (cm~l) (mb) peak (mbar) NE&T mW/(sr m cm -1 ) -1 1 668 100 2 668 35 3 668 10 15 5 1.5 0.35 0.70 1.75 Table 2-6. SSU instrument parameters Parameter Calibration Cross-track scan Scan time Number of steps Step angle Step time Ground resolution (IFOV) (at nadir) Ground resolution (IFOV) (at scan end) Distance between IFOV's Data rate Value Stable blackbody and space background ±40° (±737 km) 32 seconds 8 10° 4 seconds 147 km diameter 244 km cross-track by 186 along-track 210 km along-track @ nadir 480 bps 2.2.3 The Microwave Sounding Unit (MSU) The MSU is a four-channel Dicke radiometer making passive meas- urements in the 5.5-fim oxygen band with characteristics as shown in tables 2-7 and 2-8. Table 2-7. MSU channel characteristics Parameter Channel frequencies Channel bandwidths NEAT Value 50.3, 53.74, 54.96, 57.95 GHz 200 MHz 0.3 K Table 2-8. MSU instrument parameters Parameter Calibration Cross-track scan angle Scan time Number of steps Step angle Step time Angular resolution Data rate Value Stable blackbody and space back- ground each scan cycle ±47.35° 25.6 seconds 11 9.47° 1.84 seconds 7.5° (3 dB) 320 bps 2.3 Data Collection and Location System (DCLS) The Data Collection and Location System (DCLS) for the TIROS-N/ NOSS series was designed, built, and furnished by the Centre National D'Etudes Spatiales (CNES) of France, who refer to it as the ARGOS Data Collection and Location System. The ARGOS provides a means for locating the position of fixed or moving platforms and for obtaining environmental data from them (e.g., temperature, pressure, altitude, etc.). Location information may be computed by differential Doppler techniques using data obtained from the measurement of platform carrier frequency received on the satellite When several measurements are received during a given contact with a platform, location can be determined. The environmental data messages sent by the platform will vary in length depending on the type of platform and its purpose. A technical discussion of the DCLS and the processing of its data is not included in this pub- lication. Detailed information concerning the DCLS, including technical requirements for platforms and criteria for use of the system can be obtained by writing to: Service ARGOS Centre Spatial De Toulouse 18, Avenue Edouard Belin 31055 Toulouse Cedex France 2.4 Space Environment Monitor (SEM) The SEM instrument consists of three independent components designed and built by the Ford Aerospace and Communication Corpo- ration. The instrument measures solar proton, alpha particle, electron flux density, energy spectrum, and the total particulate energy disposition at the altitude of the satellite. The three components are: a. Total energy detector (TED) b. Medium energy proton and electron detector (MEPED) c. High energy proton and alpha detector (HEPAD). This instrument is a follow-on to the solar proton monitor (SPM) flown on the ITOS series of NOAA satellites. The new instrument modifies the SPM capabilities and adds the monitoring of high energy protons and alpha flux. The package also includes a monitor of total energy deposition into the upper atmosphere. The instru- ment augments the measurements being made by NCAA's Geostationary Operational Environmental Satellite (GOES). A technical discussion of the SEM and the processing of its data is not included in this publication. Information can be obtained by contacting: U. S. Department of Commerce National Oceanic & Atmospheric Administration Environmental Research Laboratory Space Environmental Laboratory Boulder, Colorado 80303 3. REAL-TIME DATA TRANSMISSION SERVICE As mentioned previously, three separate real-time data services are available from the TIROS-N/NOAA series satellites. The data flow for these services, on board the spacecraft, is shown in figure 3-1; their characteristics are described in table 3-1. 8 z o H < Ki n£ as ACON TA 'HASE POLA 137.77 ui Q co -J i- oS < i > cc lil < s ai < _i Q HI H-uj 1- Z i- b; LU u. < Sco D 0Q F, H cc * o — 1— ~. LU 00 co £ — 00 -I t- cq a. < cc J I o «- < CM 1 1 1 1 1 CM CO 3 D 2 CO CC 8 CO 2 LU CO o Q X o Q o «£ C) O LU O CO LU CC CO LU oc £L LU CO a. h- CO h- m < O LU 00 O -i s ^ CO CO CO 00 S X. H «H Rj -P -a W s CD P M >> 0) CD E •H +J I H ccj CD < < O I w o cc I CO CD U P* faJD •H fc4 siN3wn«iSNi 3iva vj.va aaoi Table 3-1. Real-time data transmission characteristics System Characteristics APT VHF, AM/FM 2.4-kHz subcarrier HRPT S-band, digital, split phase 0.66 Mbps DSB (includes low-bit-rate VHF, digital, split phase 8.32 instruments such as TOYS) kbps 3.1 APT Transmission Characteristics Video data for transmission on the APT link (output at the rate of 120 lines per minute) are derived from the AVHRR high resolu- tion data. The digital outputs of two selected AVHRR channels are processed in the manipulated information rate processor (MIRP) to reduce the ground resolution (from 1.1 km to 4 km) and produce a linearized scan so that the resolution across the scan is essentially uniform. After digital processing, the data are time multiplexed along with appropriate calibration and telemetry data. The processor then converts the multiplexed data to an analog signal, low-pass filters the output, and modulates a 2400-Hz subcarrier. The maximum sub- carrier modulation is defined as the amplitude of gray scale wedge number eight (see figure 3-3), producing a modulation index of 87 ± 5 percent . Tables 3-2 through 3-4 and figures 3-2 through 3-4 identify the pertinent APT characteristics. 3.2 HRPT Transmission Characteristics All spacecraft instrument data are included in the HRPT trans- mission . Output from the low data rate system, TIROS information proces- sor (TIP) on board the spacecraft is multiplexed with the AVHRR data and becomes part of the HRPT output available to users. The low data rate system includes data from the three instruments of the TIROS operational vertical sounder (TOVS) and from the space environment monitor (SEM), the Data Collection and Location System (DCLS), and the spacecraft housekeeping telemetry. General characteristics of the HRPT system appear in- table 3-5. 10 Table 3-2. APT characteristics Line rate (lines per minute) Data resolution Carrier modulation Transmit frequency Transmit power Transmit antenna polarization Subcarrier frequency Carrier deviation Ground station low pass filter Synchronization 120 4 km nearly uniform Analog 137.50 MHz or 137.63 MHz 5 watts Right hand circular 2.4 kHz ±17 kHz 1400 Hz 7th order linear recommended 7 pulses at 1040 pps. 50% duty cycle for channel A; 7 pulses at 832 pps, 60% duty cycle for channel B 3.3 HRPT Format The HRPT format provides a major frame made up o frames. The AVHRR data are updated at the minor f the TIP data are updated at the major frame rate, three minor frames that make up a major frame will same TIP data. The HRPT is provided in a split-ph the S-band transmitter. The split-phase data, (1) positive during the first half of the bit period a during the second half of the bit period. The spl (0), is defined as negative during the first half and positive during the second half of the bit per critical parameters are given in table 3-6 and the frame format is shown in figure 3-5. f three minor rame rate while That is, the contain the ase format to , is defined as nd negative it-phase data, of the bit period iod. The HRPT HRPT minor Specific characteristics of the HRPT transmission system are detailed in table 3-7. 11 Table 3-3. APT transmission parameters Type of transmitted signal System output Frequency, polarization EIRP at 63° from nadir Antenna Gain at 63° from nadir Ellipticity Circuit losses Transmitter Power Carrier modulation index Premodulation bandwidth ±0.5 dB Frequency stability Subcarrier modulator Subcarrier frequency Subcarrier modulation index Post modulator filter, type 3-dB bandwidth Premodulator filter, type 3-dB bandwidth VHF, AM/FM 2.4-kHz DSB-AM 1.44-Hz video 137.50-MHz right circular polarization or 137.62-MHz right circular polarization 33 . 5 dBm worst case 37.2 dBm nominal -0.5 dBi, right circular polarization 4.0 dB, maximum 2.4 dB 5.0 watts minimum ±17, ±0.85 kHz 0.1 to 4.8 kHz +2 x 10~ 5 2400 ±0.3 Hz 87 ±5% 3-pole Butterworth 6 kHz, minimum 3-pole Butterworth-Thompson 2.4 kHz, minimum 12 Table 3-4. APT format parameters Frame Rate Format Length Line Rate Number of words Number of sensor channels Number of words/sensor chan Format Line sync format Word Rate Analog- to-digital Conversion accuracy Low-Pass Filter Type 3 dB bandwidth 1 frame per 64 seconds See figure 3-3 128 lines 2 lines/second 2080 Any 2 of the 5; selected by command 909 See figure 3-2 See figure 3-4 4160 per second The 8 MSB's* of each 10-bit AVHRR word 3rd order Butterworth-Thompson 2400 Hz ♦Most significant bits (MSB) Table 3-5. 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CO 4 4 5 5 6 6 7 7 CHANNEL A 128 VIDEO LINES 8 8 ' 9 9 10 10 11 11 12 12 13 13 14 T 14 15 15 16 16 TELEMETRY FRAME A TELEMETRY FRAME B ONE COMPLETE TELEMETRY FRAME Ml*=10.6% Ml=21.5% Ml=32.4% Ml=43.3% Ml=54.2% Ml =65.2% Ml=76.0% Ml =87.0% WEDGE WEDGE WEDGE WEDGE WEDGE WEDGE WEDGE WEDGE 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 ZERO MODULA THERM. THERM. THERM. THERM. PATCH BACK CHANNEL TION TEMP TEMP. TEMP. TEMP. TEMP SCAN ID WEDGE REFERENCE 1 2 3 4 Ml =0.0% 9 10 11 12 13 14 15 •Ml -MODULATION INDEX Figure 3-3. APT frame format 15 in 00 q d ii ii I i X z in +1 oo 2 X < 5 o 6 ii I z J CO 1 co T o CO CM CO CO 00 CM Q Z < Q < i CO •H -P o -i _l CD 1 o UJ UJ T3 1 UJ Z z CM CO _i Z < Z < CM -J X X CO T 2 CJ oo o 00 o 8 o UJ Q UJ UJ Q UJ H ft CM CM O O < O UJ oc UJ (0 II a, a. ^ J 8 < 03 1 1 v m l<3- o 7 o Z II > > CO t- 00 00 f\l 00 p UJ — 5 £2 CD U o z 3 •H N X o < oc UJ Q < co to o K cc"- ooc il o 2 rSCC CC < CO O UJ 2 s o P o o UJ z 55 Z S Oui 5 xcc =. Q X to I- UJ OS z< UI CC - 1 u. UJcc i° its OC Ui O "J II UJCflfe U a fan •H 18 3.3.1 Detailed Description of HRPT Minor Frame Format While figure 3-5 shows the identification and relative location of each segment of the HRPT minor frame, a detailed description of each of these segments appears in table 3-8. Bit 1 is defined as the most significant bit (MSB) and bit 10 is defined as the least significant bit (LSB). 3.4 DSB Transmission Characteristics The TIROS-N/NOAA DSB contains the TIP output. These data are transmitted at 8.32 kbps, split phase at either 136.77 or 137.77 MHz linearly polarized. Transmission parameters are summarized in table 3-9. The TIP output on the DSB contains a multiplex of analog house- keeping data, digital housekeeping data and low bit rate instrument data. The key parameters of the data format are contained in table 3-10. A detailed description of the TIP frame format is given in section 3.4. 3.5 TIP Data Format The format of a TIP minor frame is shown in figure 3-6. This figure identifies the relative location of the instrument data within each TIP minor frame. A detailed description of a TIP minor frame is given in table 3-11. Each TIP minor frame is composed of 104 eight-bit words. Bit 1 is defined as the most significant bit (MSB) and bit 8 is defined as the least significant bit (LSB). This format is retained for the DSB. When the TIP data are multiplexed into the HRPT data stream, two bits are added to each TIP word. This is described under Function, TIP data in table 3-8. These bits are the two LSB ' s of each 10-bit word and, once removed, produce a TIP frame identical to that of the DSB TIP. Each HRPT minor frame contains five unique TIP minor frames. HRPT minor frames 2 and 3 contain TIP data identical to that con- tained in the first HRPT minor frame. HRPT minor frames 1, 2, and 3 can be identified by examining bits 2 and 3 of data word 7 of the 103 word header, as previously defined in table 3-8. 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M 2*1 XTAL 4+ ANT. 1 BEARING TEMP ANT. 2 BEARINC TEMP 79} ^ Z < O 80| XTAL 4- MOTOR TEMP MOTOR TEMP jzJ 00 LU (SPACE) 88 1 -15 VOLTS RF CHASSIS RF CHASSIS 95 1 1 ■■ O z 96 1 5 VOLTS PROG TEMP PROG TEMP ■ 1 1 ' ' ■ ' 103| POS CNT (INTERNAL SCAN 12 SCAN TARGET) 104J E ZERO 105 1 106[ PROG TEMP 107) CH 1 REF 108| CH 2 REF 109| CH 3 REF 110 :h 1 REF SCAN POS X SCAN CNT (SCAN TO PROG TEMP ( 1 FOV 1 ) 34 Table 4-4. MSU bit formats for each IFOV Typical format for all words except word 8 LSB bit 1 D D D D D D D D D D D D Data 1 when in zero reference disable mode; at all other times for the first seven words indicates it is the first word in a scan; for all other words indicates that the word is a real word; occurs only for an all-zero word Scan position - line count, word 8 LSB bit 1 3RRREEEEEEEE Scan angle (position) data Scan line count (reset by 128-sec sync) 1 when in scan disabled mode; at all other times 1 when in zero reference disable mode indicates that this is the 8th word in the scan position indicates that this is not the first word in a scan indicates that the word is a real word 35 Table 4-5. Acceptable scan angles IFOV Scan Ang les 1 and 14 83 , 91, 90 2 94 , 95, 31 3 24 , 26, 27 4 20 - 21, 17 5 1 4, 5 6 8 10, 11 7 46 47, 15 8 35, 42, 43 9 38, 39, 36 10 48, 49, 53 11 60, 57, 56 Space (12) 163, 162, 171 Internal target (13) 200, 201, 202 Formation of the 112 words of MSU data must start when bit 15 has a value of 1 indicating that this is the first word of a scan line. The timing of the output of MSU data, relative to the TIP minor frames, varies slightly. Consequently, an MSU scan line will start at one of the TIP major/minor frame counters listed below, or within two minor frames thereafter. TIP major frame Minor frame 19 257 1 211 2 147 3 83 4 19 4 257 5 211 G 147 7 4.3 SSU 83 Each TIP minor frame contains cated in word positions 16, 17, words (e.g., 16 and 17), when t represent one data sample of ei Thus, each TIP minoT- frame cont data word contains 12 bits of i each 16-bit word. The lower or Before processing, the 12 bits bits. This can be accomplished by 16. Further discussions of six 8-bit words of SSU data lo- 32, 33, 76, and 77. Each two aken together as one 16-bit word, ther telemetry or radiometric data, ains three SSU data words. The SSU nformation, left justified, within der four bits are data value 0. of data should be right shifted 4 by dividing each 16-bit data word SSU data will assume a 12-bit word. 36 An SSU scan is 32 seconds in duration (1 TIP major frame or 320 TIP minor frames) beginning at each minor frame 0. The SSU pro- vides a complete sampling of data every second. Recalling that each TIP minor frame is 0.1 second in duration, and that each minor frame contains three SSU data words, this provides 960 data words per scan, at a rate of 30 words per second. Each second of data (30 words) contains two radiometric data samples for each channel. The radiometric data samples for channel 1 are located in words 16 and 28, for channel 2 in words 17 and 29, and for channel 3 in words 18 and 30. The identification of the 30 SSU words is shown in table 4-6. Digital words 1, 2, and 3 in table 4-6 are described as follows In digital work 1, bit 1 (LSB) identifies the mirror synchronous recovery status, and is normally 0. Bits 2-12 comprise an 11-bit second counter that is reset to at the beginning of the space view. Table 4-6. 30-word SSU data sampling (repeated 32 times per SSU scan) SSU Data Words Digital word 1 1 Digital word 2 2 Digital word 3 3 Space port temperature 4 Earth port temperature 5 PMC bulkhead temperature 6 Detector temperature 7 Black body thermistor 8 Black body thermistor 9 Cell temperature ch 1 10 Cell temperature ch 2 11 Cell temperature ch 3 12 Base plate temperature 13 Middle bulkhead temperature 14 Optics baseplate temperature 15 Radiometric sample ch 1 16 Radiometric sample ch 2 17 Radiometric sample ch 3 18 Thermistor reference 19 Mirror fine position 20 Black body PRT 21 PMC Amplitude ch 1 22 PMC Amplitude ch 2 23 PMC Amplitude ch 3 24 ADC calibration 5% of full scale 25 ADC calibration 50% of full scale 26 ADC calibration 90% of full scale 27 Radiometric sample ch 1 28 Radiometric sample ch 2 29 Radiometric sample ch 3 30 37 Digital word 2 contains instrument configuration information as defined below: Bit 12 (MSB) Power on/off ('1' = on) 11 Mirror inhibit on/off ('1' = on) 10 Calibration mode auto/manual ('1' = manual) 9 Calibration verification (normally '0*) 8 Mirror in position space view ('0' if in position) 7 Mirror in position blackbody ('0' if in position) 6 Mirror in position Earth view 1 ("0' if in position) 5 Mirror in position Earth view 5 ('0' if in position) 4 Mirror in position Earth view 8 ('0' if in position) 3 Mirror position correct (fine position sensor) yes/no ( ' ' = yes) 2-1 Channel identification for frequency reading 00 = channel 3 (1.4 mb) 01 = channel 1 (14 mb) 10 = channel 2 (4 mb) Digital word 3 contains information necessary for evaluating the pressure modulated cell (PMC) channel frequencies. A data value will be inserted into this position once every 32 seconds. This will occur at minor frame of each major frame. Word 2, bits 1 and 2, must be used with word 3 for proper identification of the PMC being sampled. An SSU scan line consists of eight, 4-second Earth/calibration dwell periods. During each dwell period, eight radiometric data samples are taken for each channel (2 per second). These eight radiometric data samples require additional process- ing to derive a final radiometric data value for a given dwell period. During normal operations, the SSU instrument repeats a calibra- tion cycle once every eight lines (256 seconds). A calibration cycle consists of one line of data, beginning at TIP major frame 0, minor frame 0. This line contains radiometric data samples taken while the instrument views space and the internal calibra- tion target. The remaining seven scan lines contain radiometric Earth view data samples. 4 . 4 AVHRR The AVHRR data are located in two sections of the HRPT minor frame. The radiometric calibration data and telemetry information are contained in the 103-word header. The radiometric Earth view 38 data are located in that portion of the minor frame labeled AVHRR VIDEO (figure 3-5, section 3.2). Each minor frame contains a com- plete scan line of AVHRR data from all five channels. The AVHRR video data are located starting at HRPT word 751 and contains 10,240 words (2048 ten-bit words per channel). These data words are multiplexed sequentially into the video portions of the minor frame according to table 3-8. Every five words represent one simultaneous radiometric sample from each of the channels. Space data and internal target data, required for calibration of the IR channels, are located in the header portions of the HRPT minor frame (figure 3-5). The order in which these data are multiplexed is shown in table 3-8, section 3.3. 4.5 Scan Timing and Geometry The purpose of this section is to provide the user with the information necessary to establish the timing and scan geometry relationships between the TOVS instruments. The timing relation- ships are shown in table 4-7. The start time of each instrument scan line can be derived by using the TIP 32-second time code that was described in section 3.4. Table 4-8 identifies the start of each instrument scan line relative to that time code. This table also identifies the major and minor frame numbers that correspond to the start of each scan line. Noted that the minor frame counters corresponding to the start of each scan are not the same for each instrument. For example, at the time cor- responding to major frame 0, minor frame (TC(0/0) in table 4-8), all instruments begin their scan sequence. However, the data that corresponds to the start of the HIRS/2 scan line appears in major/minor frame 0/1, for SSU in 0/0, and for MSU in 0/19. Since the TIP major frame count value cycles from to 7, table 4-8 can be expanded by replacing major frame values 0, 1, 2, and 3 with major frame values 4, 5, 6, and 7 respectively. Table 4-7. Instrument scan timing parameters Time between No. of Earth start of each Step and view steps Instrument scan line dwell time per line *ATime HIRS/2 6.4 sec 0.1 sec 56 0.5 sec MSU 25.6 sec 1.81 sec 11 0.9 sec SSU 32 sec 4.0 sec 8 2 sec *ATime - the difference between the start of each scan and the center of the first dwell period (see figures 7 and 8) 39 Table 4-8. Scan line timing of the TOVS instruments Scan start TIP major minor frame time (seconds) HIRS/2 SSU MSU *TC (0/0) +6.4 o/i + 12.8 0/65 +19.2 0/129 +25.6 0/193 0/257 *TC (1/0) 1/1 +6.4 1/65 + 12.8 1/129 + 19.2 1/193 +25.6 1/257 *TC (2/0) 2/1 +6.4 2/65 + 12.8 2/129 +19.2 2/193 +25.6 2/257 *TC (3/0) 3/1 +6.4 3/65 + 12.8 3/129 + 19.2 3/193 +25.6 3/257 0/0 i/o 2/0 3/0 0/19 0/275 1/211 2/147 3/83 *TC (n/0) is the time calculated from TIP major frame n and minor frame 0, where n=0 , 1, 2, and 3. Note: This timing table for major frames 0-3 repeats for major frames 4-7. Figures 4-1 and 4-2 show the relationship between the scan pat- terns of each of the TOVS instruments. All TOVS instruments scan in the same direction, Sun to anti-Sun It should be noted that the scan direction of the AVHRR instrument is opposite that of the TOVS instruments. 5 . CALIBRATION Williamson (1977) presents an excellent description of the methodology of calibration for satellite-borne radiometers. In general, the calibration processes involve exposing a radiometer to an extended source that has been calibrated against a primary or secondary standard of one of the national laboratories and establishing a relation between the output of the radiometer and the quantity of radiation (radiance) measured by the radiometer. 40 CI CD C T3 P o w CO S3 tH O O T3 •H CD -P +-> u o CD >-n o O CO •H d -P U d CD f-r-P CD P o a CO o PS o t-H CO H & CO • CO rH i -d ^ e a* CD Sh c£ ■H CM CO i— i n u 4-> fl CD 0> > T"J H ^ cd Ph o •H +-> u CD a u CD -P +-> o a CO o JH CO P CO CD •H 03 42 All the radiometers flown on the TIROS/NOAA series satellites undergo extensive prelaunch radiometric calibrations at the in- strument manufacturer's facilities to establish their stability, linearity of response, and sensitivity in output digital counts per radiance unit. Instruments operating in the thermal infrared and microwave regions of the spectrum are calibrated against pre- cision blackbody sources whose calibrations are, in general, trace- able to the National Bureau of Standards (NBS). Instruments oper- ating in the visible and near-infrared regions are calibrated against lamps whose output is viewed through the aperture of an integrating sphere. The calibrations for these lamps are also traceable to NBS. Prelaunch infrared (IR) calibrations are performed in a thermal/ vacuum environment to simulate the environment of space. During the thermal/vacuum exposure, calibrations are performed at several instrument operating temperatures (nominal ±10° C) to provide a measure of the deviation of the instrument's response as a function of temperature. Visible and near IR calibrations are performed at ambient temperature in air. A typical IR or microwave calibration will expose a radiometer to an extended blackbody source whose temperature is varied, in discrete steps, over the entire dynamic range of interest. In the visible, the intensity of the source is varied over the dynamic range of interest. The data recorded during these calibrations then form a baseline from which the accuracy and precision of the radiometer measurements can be determined. Analyses of prelaunch calibration data from each of the primary radiometers on the TIROS/ NOAA series satellites are performed at NESS. Information result- ing from these analyses, which affect the accuracy or precision of calibration, are provided in later sections. The extensive nature of the prelaunch calibration program not- withstanding, it is not sufficient to rely on such calibration data to achieve the accuracies desired from today's satellite-borne remote sensing devices. Brower (1977) pointed out that using such static calibration of the ITOS scanning radiometer (in the thermal IR region) yielded temperature differentials of 2°C to 4° C be- tween thermistor measurements and radiometric measurements of an onboard blackbody. (Radiometric measurements referred to are those made when the instrument itself views the blackbody.) Another factor to be considered is that satellite-borne radiom- eters are subject to performance degradations in orbit. Unless some method is provided to assess those degradations, the prelaunch calibrations may shortly become useless or, at best, will yield questionable results. Therefore, the TIROS/NOAA radiometers, have been designed to perform in-orbit calibrations routinely, at intervals during their scan sequences (in the IR and microwave regions only; no attempt is made to perform in-orbit calibrations in the visible region). 43 In-orbit calibration is accomplished by programming a given radiometer's scan mirror to view: space (near-zero radiance), and part of its housing, which is a designed blackbody. This onboard blackbody is maintained at approximately the operating temperature of the radiometer (15°C or 288 K) . Also, it is instrumented with temperature sensors whose outputs are multiplexed into the radiom- eter's telemetry. Thus, the zero radiance from the space look and the radiance from the 15°C onboard blackbody provide a two- point, in-flight calibration. Calibration of the onboard blackbody is generally performed dur- ing the prelaunch calibration program. One method of doing this (and the method preferred by NESS) is to use the instrument itself as a transfer standard. Once the output of the radiometer in counts per radiance unit, has been established (using a precision calibration blackbody), the onboard blackbody temperature sensor outputs are merely correlated with the output of the radiometer when it views the onboard blackbody. Since the radiometer is calibrated at several different temperatures, calibration curves representing radiometrically derived temperatures can be generated for each of the temperature sensors in the onboard blackbody. In the following sections, the calibration procedures employed by NESS are treated in detail for each of the TIROS/NOAA primary radiometers . 5 . 1 AVHRR The information required for producing AVHRR IR channel calibra- tion coefficients is located in the 103-word HRPT header. (See figure 3-5 and table 3-8.) Header words 18, 19, and 20 each contain a five-point subcommu- tation of the outputs of four platinum resistance thermometers (PRT) that monitor the temperature of the internal calibration target (ICT). Each of these words contain redundant information. Any one of these words, when extracted from five consecutive HRPT minor frames, produces a reference (REF) value and one sample of each of the four PRT ' s . The pattern is as follows: HRPT minor frame Parameter sampled n REF n+1 PRT1 n+2 PRT2 n+3 PRT3 n+4 PRT4 n+5 REF 44 The reference value can be easily identified since it will be the only output having a count value of less than 10. NESS aver- ages 10 samples from each PRT to produce a mean PRT count value for conversion to temperature units. The 30 words of internal target data (header words 23-52) provide 10 samples each for IR channels 3, 4, and 5. The 50 words of space view data (header words 53-102) provide 10 samples each for all five AVHRR channels. These data are multiplexed as described in table 3-8. NESS averages 50 samples of space and internal target radiometric data per channel to produce mean count values. To calculate the internal target radiance, it is first necessary to compute the target temperature. The conversion of PRT mean counts to temperature is accomplished by: 4 T ± (K) = ^aijXi j=0 where Xi is the mean count for PRTi where i = 0,1,2,3,4 aij are the coefficients of the conversion algorithm and Ti is the temper- ature of the internal target calculated from PRTi. For example, the conversion of PRTi count value (Xi) into temperature (K) is T X (K) = a lf0 +ai f i X i+ a 1>2 lj+a lf3 X~i+a 1)4 X ± The coefficients a^j are supplied in appendix B. The average temperature of the internal target is computed by T = y?jTj i=l where T is the average of the internal target temperatures (K) and bi is the weighting factor of each PRT (supplied in appendix B). The conversion of temperature, T to radiance units (N) is described in appendix A. 45 Let us assume, for the time being, that the output of each channel (in counts) is linear as a function of sensed radiance. Then: N = G X + I describes the relationship between counts and radiances where: N is the radiance of the target at count value X, G is the channel gain, and I is the channel intercept. The gain of each channel is calculated by: G = N sp ~ N T X sp ~ X T where G is the channel gain (radiance unit per count), N S p is the radiance_of space, Nrf is the radiance of the internal target and X S p and Xf are the mean output count values when the instrument views space and the internal target respectively. The intercept of each channel is calculated by: 1 ± = N sp " Gx sp In reality, the response of the channels in the 11 fj.m -p.12 m region (channels 4 and 5) are slightly nonlinear. This non- linearity is a function of the physical properties of the detectors employed in these channels. Since only a two-point calibration is possible in flight, a correction must be made to both the gain and intercept algorithms. This is accomplished by adding a correction factor to the N S p parameter. This correction factor is calculated from subsystem test data to provide the smallest temperature error in the range of 225 K to 310 K. A table of errors and corrected values for Nsp are presented in appendix B. The 3.5-ym region channel (channel 3) uses a different type of detector and does not require corrections. Calibration of the visible AVHRR channels (1 and 2) is not performed in flight. Subsystem data are evaluated, however, to produce coefficients for the calibration algorithm. A = GX + I where G and I are the gain and intercept of each visible channel, X is the count value output of the radiometer for each channel, and A is the percent albedo of the target. Coefficients G and I are supplied for channels 1 and 2 in appendix B. Also included in appendix B are spectral response curves for channels l and 2. 46 5.2 MSU The parameters necessary for calibrating the MSU are provided with each scan line. Since each scan line contains only one sample for each parameter, an average of these data from several scan lines is used for the calculation of calibration coefficients. The location of the space and internal target radiometric data is defined in section 4.2 MSU. The calibration coefficients for a specific scan line are computed from an average of the data contained in 25 lines (12 lines prior to and 12 lines subsequent to that line for which coefficients are being computed). The relationship between input radiance and instrument output counts is not linear in the MSU channels. Since only a linear relation between radiance and instrument output counts can be derived from the in-flight data, a nonlinearity correction algorithm must be applied to each channel. The coefficients for this algorithm are produced by NESS for each instrument, using preflight subsystem calibration information and are supplied in appendix B. The algorithm is: C"= S d ± C i=0 where C is the radiometric count output, d. is the nonlinearity correction coefficient and C is the modified count value to be used in the linear algorithm. Each of the two inflight calibration targets has two PRT's that are used to determine the temperature of these targets. In-flight target (#1) is viewed by channels 1 and 2. The temperature of this target is derived from PRT 1A and PRT IB. In-flight target #2 is viewed by channels 3 and 4. The temperature of this target is derived from PRT's 2A and 2B. The output count values from PRT's 1A, IB, 2A and 2B are located in words 2 and 3 of IFOV's 8 and 9 (see table 4-3). The conversion of each PRT count output to temperature (K) requires the use of two algorithms, the first to convert counts to resistance (R) and the second to convert resistance to temperature (K). The first algorithm is: C T CAL LO R A " K + K l T^ CAL A HI - T A CAL LO for PRT 1A & 2A 47 or C R TV. CAL LO R B " K + K l Tb CAL HI - T B CAL LO f ° r PRT 1B & 2B where : RA is the resistance of PRT 1A or 2A; R B is the resistance of PRT IB or 2B; C A is the count value of PRT 1A or 2A; C B is the count value of PRT IB or 2B; K and K^ are the resistance conversion coefficients supplied in appendix B. T A CAL HI and T A CAL LO and T B CAL HI and T B CAL LO are the high and low calibration reference points for electronic systems A and B respectively. T A CAL LO, T B CAL LO, T A CAL HI and T B CAL HI are located in words 2 and 3 of IFOV's 1 and 2 as defined in table 4-3. The second algorithm, converting R to temperature is: 2 T = £ e^R 1 i=0 where T is the temperature (K) of the internal target as derived from the resistance (R = R A or R B ) and e^ are the temperature conversion coefficients for each PRT. The coefficients e± are supplied in appendix B. The temperature of target #1 is the average of the temperature derived from PRT's 1A and IB. The temperature for target #2 is the average of the temperature derived from the PRT's 2A and 2B. The target temperature used for the calculation of calibration coefficients is averaged over 25 scan lines. The conversion of these average temperatures to radiance units (Nrp) is described in appendix A. Channel gains are calculated by: N sp _ N T Qj — C - C" 48 where G is the gain of each channel, Ngp and Nip are_the radiance of space and the internal target respectively, and Cgp and Cm are the corrected count values of the space and internal target views averaged over 25 scan lines. The values of Nop are sup- plied in appendix B. Channel intercepts are calculated by: I = N sp - G Cgp 5.3 SSU During normal operation, calibration of the SSU instrument is performed once every 256 seconds. The scan sequence format for the SSU provides 32 seconds (1 line) of radiometric space and internal target view data followed by 7 scan lines of Earth view data. The SSU calibration line contains four dwell periods of space data followed by four dwell periods of internal target data. These data can be identified by examining bits 7 and 8 of digital word 2, defined in section 4.3, SSU. Each dwell period contains 8 radiometric data samples per channel spaced according to the following timing chart. Sample (s) Time (t) 1 4 sec 2 1 . sec 3 1.4 sec 4 2.0 sec 5 2.4 sec 6 3.0 sec 7 3.4 sec 8 4.0 sec The accumulation of these samples over a four-second dwell j period produces a linear relationship between output samples (counts) and time (seconds). The slope of this line is defined J as a RAMP (counts per sec). This RAMP is computed using the lease squares equation: I „.,_ 8 I ts - His RAMP 8 2 t 2 - (Zt) 2 where all the summations over the eight samples and s is the count output value from a data sample at time t. 49 An average of the four RAMP values from the space view and an average of the four RAMP values from the internal target view are used in the calculations of calibration coefficients. The temperature of the internal target can be calculated from the blackbody PRT data samples (word 21, table 4-6) during the last 12 seconds of the calibration line and during the entire 32 seconds of the other seven scan lines. The PRT provides the most precise measure of the internal target temperature. However, should the blackbody PRT fail, the data samples from the two blackbody thermistors (words 8 and 9, table 4-6) may be used to derive the internal target temperature. The temperature of the internal target calculated from the black- body PRT data samples is: T(K) = S a-jX 1 i=0 where sl± are the conversion coefficients contained in appendix 2, and X is the averaged PRT data value (in counts). It is suf- ficient to average only the last 12 seconds of each line to produce X. The temperature of the internal target calculated from the blackbody thermistor data samples is: T(K) = 3 _. 3 _. 2 b ± X 1 + Z c i Y 1 i=0 i=0 where b-[ and c-^ are temperature conversion coefficients for each thermistor contained in appendix B and X is the average of the blackbody thermistor (word 8 divided by the thermistor reference [word 19 J). Y is the average of the blackbody thermistor (word 9 divided by the thermistor reference [word 19]). Again, it is sufficient to average only the last 12 seconds of each line to produce X and ?. The internal target temperature is converted to radiance (N) as described in appendix A. Channel gains are calculated by: N SP _ N T RAMP sp _ RAMP T 50 where G is the gain of channel, Ncqp and Nn^ are the_radiance of space and the internal target respectively, and RAMPgp and RAMP™ are the average ramp value for the space and the internal target views. Channel intercepts are calculated by: I = N S p - G RAMPgp 5.4 Calibration of HIRS/2 During normal operation, calibration of the HIRS/2 instrument is performed once every 256 seconds (40 lines). Calibration is provided by viewing two internal targets and space. The tempera- ture of both internal targets, a warm target (IWT) (290 K) and a cold target (ICT) (260 K to 270 K), are determined from four ther- mistors embedded in each target. Because of large temperature gradients induced by solar effects throughout the orbit, the temperature of the ICT cannot be reliably determined with suf- ficient accuracy to improve the calibration. Therefore, only the IWT and space-view data are used for calculating calibration coefficients. Element 58 of each HIRS/2 line contains five samples of each of the four thermistors used to determine the temperature of the IWT (see table 4-1). The output of each thermistor is con- verted to temperature K by: T = I a i 3=0 J J where T is the temperature indicated by the thermistor, X is the average of 200 samples for that thermistor (40 lines x 5 samples per line), and a, are the conversion coefficients supplied in appendix B. ^ The temperature of the IWT (Tj WT ) is determined by averaging the temperatures derived from the four thermistors. The Tj^rp is converted into radiance (N) as shown in appendix A. The computa- tion of calibration coefficients requires that for each channel an average value of the space and internal warm target view data be computed. For that line containing space-view data, there are 56 samples per channel. Samples 1 through 8 contain data while the scan mirror is moving to the space target ana are, therefore, not usable. For that line containing IWT view data, all 56 samples per channel are usable. 51 The channel gains are computed by: N SP - N IWT G = - X SP ~ X IWT where G is the gain for each channel, N g p and N-r^m are the radi- ance of space and the internal warm target, Xg p is the mean _space value (in counts) of the 48 usable space data samples, and X IWT is the mean IWT value (in counts) of the 56 usable IWT data samples. The channel intercepts are completed by: I = N SP - GX SP 5.5 Application of Calibration Coefficients to Earth View Data The gains and intercepts as computed for each instrument (sections 5.1 to 5.4) are used to convert Earth view radiometric samples (Xg in counts) to calibrated radiance value's (N^). The algorithm is N E = G X E + I For the MSU, Xg is defined as the count value modified for instrument nonlinearity (C) (section 5.2). The calibrated radiance values Ng do not include corrections for atmospheric attenuation, slant path corrections, or other atmospheric phenomena. 5 . 6 APT The APT frame format is shown in figure 3^3. Space data for the selected channel (instrument output while viewing space) appear in each APT video line immediately following the syn- chronization pulses. All of the other data necessary to perform the calibration appear in the telemetry frame. The outputs of the four sensors, which monitor the housing blackbody target temperature, appear in telemetry points 10, 11, 12, and 13 (thermal temperature number 1 through 4, respectively), Each thermal temperature is repeated on eight successive APT video lines. Thermal temperature #1, for example, begins on line 73 and is repeated through line 80; thermal temperature #2 begins on line 81; #3 on line 89; and #4 on line 97. 52 The output of the instrument when viewing the housing black- body target appears in telemetry point 15 (back scan) that begins on APT video line 113. It must be emphasized that APT is processed AVHRR data. Two selected channels from AVHRR are time division multiplexed into an output data stream that has been processed to achieve both bandwidth reduction and geometric correction. This processing is accomplished in the digital domain before being converted to an analog signal for output on the APT transmitter. To effect calibration of the selected IR channel, the AVHRR calibration data must be related to the APT video signal. This is accomplished by determining the relative signal level using the eight wedge levels as a scale. A minimum signal level would be equivalent to telemetry point 9; a maximum signal would be equivalent to point 8. Calibration curves showing the relation- ships of the four housing blackbody temperature sensors to the eight-level wedge scale are presented in figures 5-1 and 5-2. The calibration procedure is as follows: a. Determine the temperature of the housing blackbody by normalizing (scaling) the output of thermal temperatures 1 through 4 to the wedge levels. Plot the values found on the appropriate graph (figures 9 and 10). There will be slight differences between the sensors in indicated temperatures because of thermal grad- ients induced in the blackbody by solar input energy and Earth albedo; therefore, an average of the four indicated temperatures will be a good representation of the effective blackbody tern- ] perature. b. Determine the IR channel output while viewing the black- body by scaling the data appearing in telemetry point 15 (back ] scan) to the eight-level wedge. c. Determine the IR channel output while viewing space by normalizing the data immediately following the synchronization | pulses to the eight-level wedge. d. On figure 5-3 (3.7-fo.m channel) or figure 5-4 (ll-[j.m channel) plot the normalized value determined in step 2 against the black- J body temperature found in step 1. e. On figure 5-3 or 5-4, plot the normalized value determined in step 3 against the minimum temperature shown on the graph I (240 K for the 3 . 7- ym channel and 150 K for the 11-ym channel.) The slope of a line connecting the two points plotted in steps 4 and 5 above is a measure of the response of the selected channel . 53 CO 4 -I UJ > (UJ UJ e> o UJ UJ _i < o CO >- UJ e> B^^i^^i^^^M^^M^M 43.3 % 0.0 % 280 285 290 295 TEMP. K 300 305 CO 4 -J UJ > UJ -J UJ 3 o o UJ UJ 2 -I < O CO >- I UJ cr o r t=4 b. TELEMETRY POINT II BEGINS ON APT LINE 81 THERMAL TEMP #2 CALIBRATION ;:£M -MM[ihMinffl#tHH{liirMnmlM :=FB m : tn u; I 280 285 290 295 TEMP. K 300 43.3 % 32.4 % 21.5 % 10.6 % 0.0 % 305 Figure 5-1. Thermal temperatures 1 and 2 54 43.3 % 280 285 290 295 TEMP. K 300 305 : II' 'IU UJ > UJ b. TELEMETRY POINT 13 BEGINS ON APT LINE 97 THERMAL TEMP #4 CALIBRATION . fffll!l! ;i fffl(tlttlttil|l^l h i 1H^tlMfittHfflltfMWWtl 280 285 290 295 TEMP. K :!r : _T " 43.3 % 300 32.4% 21.5 % 10.6 % I^JO.0% 305 Figure 5-2. Thermal temperatures 3 and 4 55 -I > UJ -J Ul o UJ UJ -J < o CO > UJ £C O ' LU - Z a < 3. S o <-i o CO GO U S> ~ 3 03 Ul o fc& N* CD o 1 UJ o i S CD £ - I to o (0 T3 i -i4 ! o 03 r— ( io £1 CD o (rf <* > s & CD o rH K> CD > CD H >j O CD a C\J • CO .. -O 1 LO — CD 3 fcuO .. 1 - - -r> h g Jo 8 JO lO Q O O O O 0) A CO S tfO- CM CM CM CM CM CM ( X ) 3MfUVH3dW31 56 CO -J UJ > UJ -J UJ e> Q UJ UJ < o CO > UJ o 1 .o. z < gj;:;::;::: .5^: > E 3. O UJ — nr _l N >-\ i O o UJ ^W M H og >( 1 — 1 UJ u . . . *-*" , .2 q S3 co i> +- ' 00 CD id CD P o CO >> T3 o E id i— i 3. -O o ■P — CD o i— 1 1 ** > •H ! 3 r CD L ° rH ! i*> CD CD rH 1 Pi ] o CD CVJ O : 1 . ; -T o 1 LO — CD 1 [ 3 ■H I 1 _..,...., - J- o Pm 8 m o ro O O ro O CM 1 o 00 CM 1 o CVJ o o o o oo oo io ^- ro cm — o com CM CM CM CM ^CM (X) 3df11VM3dW31 57 Note that scene temperature retrieved using this response curve may be in error by several degrees. For quantitative work, fac- tors such as instrument and modulation nonlinearities (±2 percent), and atmospheric attenuation must be considered. A separate set of calibration curves (figures 5-2 and 5-3) will be required for each new spacecraft in the TIROS/NOAA series and will be published in an APT information note. 58 APPENDIX A. Temperature-to-Radiance Conversion v n N T = N(T) / g(v, T) $ (v) dv / 2 -l where N(T) is the radiance (mW/(sr m cm ) ) of a blackbody at temperature T(K) . 3 (v x T) is the Planck function v is the wave number ( cm ) and (v) $ (v) = /% (v) dv *v i where $ (v) is the normalized response function and v. and v are the wave numbers at the limits of the response function < 40 30 20 10 Vyx/A n fi?R 0.5! i9 w 1 — n fifM 0.497 — ■-/ V 938 0.40 0.50 0.60 0.70 0.80 WAVELENGTH 0.90 1.00 Channel #1. AVHRR Spectral Response B-4 o a. CO < 100 90 80 70 60 50 Q. CO 111 > I- < u 40 cc 30 20 10 0.720 0.710 ' 0.695 7 / 0.60 0.70 0.80 0.90 1.00 WAVELENGTH 1.10 1.20 Channel #2. AVHRR Spectral Response B-5 II. MSU (Section 5.2) di - nonlinearity correction coefficients Channel do 35.54 26.85 20.47 22.23 dl d2 1 2 3 4 0.09303 0.09400 0.09639 0.09649 1.9666xl0- 5 1.7264x10-5 0.9941xl0- 5 0.9659x10-5 PRT count to resistance conversion 495.6 107.8 coe f f icients ej_ - PRT resistance-to-temperature conversion coefficients PRT 1A 2A IB 2B e Q 29.10 27.55 29.05 28.95 0.42596 0.42787 0.42710 0.42836 0.3187xl0- 4 0.3185xl0- 4 0.3206xl0- 4 0.3175xl0- 4 Normalized response functions Channel 1 2 3 4 N, p-Radiance of space Channel 1 2 3 4 v (cm ) c 1.6779 1.7927 1.8337 1.9331 N SP ( mW / s r M cm- 0.000086 0.000096 0.000084 0.000092 B-6 III. SSU (Section 5.3) a^ - PRT count-to-temperature (K) conversion coefficient a Q a x a 2 285.082 4.5542xl0- 3 9.6285xl0- 9 h-^ and c^ - Thermistor to temperature (K) conversion coefficient b Q bi b 2 b 3 375.969 -203.161 179.13 -85.16 c ci C2 C3 375.969 -203.161 179.13 -35.16 Normalized response function Channel v c (cm ) 1 668.988 2 668.628 3 668.357 IV. HIRS - (Section 5.4, Calibration of HIRS/2) IWT PRT count-to-temperature conversion coefficients PRT a a l a 2 a 3 a 4 2 Im'ilnl f'SJJSS^S-S 9 - 1543 4xlO"S 4.71066x10-11 6 . 83373X10"! 6 ? S 'SS !-5JJ2! X J2 q 9.15816x10-8 4.70945x10-11 6 . 85893xl0"16 3 301.425 6.51738x10-3 9.16252X10" 8 4 . 71175xlO-H 6 87601xl0"l 6 4 301.4035 6.52364x10-3 9.00018x10-8 4 . 71042xlO-H 6 '. 61634xl0"16 B-7 HIRS/2 Normalized response functions CHANNEL 1 \>X 0.64478E+03 A\) 0.155o9E+01 0.59S35E-03 .67337E-02 0.2 4056E+00 0.70848E-02 0«0 0.0 Q.1378 0E-02 0.65 33 1fc-O2 O. 13 744E+00 0e4b35«E-02 0.0 0.0 0.19^44C-02 0.10956E-01 0.4 22tt5t-01 0.30782E-02 0.0 0.0 0.22813E-O2 0.37600E-0I 0.16070E-01 0.19029E-02 0.0 0.0 0.37781E-02 0.10773E+00 0. 96671 E-02 0.14659E-03 0.0 $(V30) CHANNEL 2 0.&4963E+03 0.1734 8E+01 30 0.0 0.0 0.19493E-02 0.O6207E-01 0.57290E-01 0.11304E-02 0.3P53t>fc-0* 0. J899t>£-04 0. S3736E-02 0.7155 6E-0 1 0.3259bE-0 1 0.6794 Oh -0 3 0.61955E-04 0.24868E-03 Q.I5249E-0I 0.7 3453E-0S 0.I260 0E-01 0.20094E-03 0.55126E-04 0.54076E-03 0.3S984E-01 0.70 85IE-O1 0.37951E-O2 0.0 0.48187E-05 0.981 88 E-03 0.56572E-01 0.67441E-01 0.17191E-02 0.0 CHANNEL 3 0.b6239E+03 0.18372E+01 30 • 0.68609E-03 0.1&939E-O1 0.653I3E-01 0.25858E-01 0.99069E-03 0. 1293 9E-0 3 O. 1590 4E -02 0.2546SE-01 0.65012E-01 0.1264 3E-0I 0.77027E-0 3 0.25370E-03 0.2 956SE-02 0.35152E-01 0.6 095 3E-01 0.56397E-02 0.56020E-03 0.49S74E-O3 0.54024E-02 0.46499E-O1 0.54585E-O1 0.23E68E-02 0.34185E-03 O. 74091 E-03 0.10279E-01 0.58506E-O1 0.43027E-01 0.11728E-O2 0.49624E-07 CHANNEL 4 0.67213E+03 0.20952E+C1 30 © o 0' 0.59934E-03 0.15859F-01 0.5«>275E-Ol 0.1S455E-01 0.81771E-03 0. 1973 2E -03 0.7470 2E-0 3 0.2966 9E-O1 0.5462 7E-ai 0.69094E-02 0.66252E-03 0.26173E-03 0.93328E-03 0.43223E-01 0.5142 0E-01 0.28I03E-02 0.45631E-03 0.31839E-0 3 0.30657E-02 0.51285E-01 0.45299E-01 0.I2985E-02 0.23091E-03 0.43452E-03 0.71495E-O2 0.55779E-0I 0.30597E-01 0.95467E— 03 0.27196E-07 CHANNEL 5 0.6921SE+03 0.16462E+01 30 0.0 0.17055E-O2 0.37010E-01 0.58345E-01 0.24314E-01 0.0 0.3109 4E-O2 0.46951E-01 O.56076£-Ol 0. 14to77E-01 0.17603E-03 0.68216E-02 0.53012E-01 0.52079E-0I 0.79779E-02 0.42121E-03 0.1367SE-01 0.56768E-O1 0.45086E-01 0.42149E-02 0.73494E-03 0.25076E-01 0.58225E-0I 0.355I0E-01 0.2 2060 E-02 B-8 HIRS/2 Normalized response functions (continued) 0.1S867E-02 0. 1090 JE-O^ 0-516blE-03 0.17387E-03 0.21101E-07 CHANNEL 6 0.7O292E 403 0.20697E+01 30 0-0 0.10437E-O2 0.29015E-01 0.S3720E-01 0.88276E-02 0.7761 IE -03 O. 1068 ^E-G3 0.2434 6E-02 0.39 233E-O1 O . 49 32 9tL -0 1 0.3984t>E-0 2 0. 71617E-03 0.35175E-03 O.43927t-0£ 0.484I8E-01 0.43743E-01 0.18884E-02 0.48018E-03 0.54 7SSE-0 3 0.93891E-02 0.S5492E-01 0.33313E-0I 0.10136E-02 0.22767E-03 0.71655E-03 0.175 38E-O1 0.56534E-01 0.19285E-01 0.t>7S22E-03 0.26550E-O7 CHANNEL 7 0.71868E+03 0.2 1469E+01 3 0.0 0.60941E-03 0.3468SE-OI 0.4912 0E-01 0.8944t>fc-02 0.59123&-03 0. 1299vfc-03 0. 1317IE-02 0.4825 7E-0 1 0.4737t>L-01 0.4290 7E -02 0.4l487t-03 0.2S128E-03 0.24532E-02 0.49030E-01 0.4 2798E-0I 0.20t>24E-02 0.365 11 £-03 0.41487E-03 0.64535E-02 0.47343E-0 1 0.32 389E-01 0.1067IE-02 0.32464E— 03 0.47051E-03 0.1674 4E-01 0.48389E-01 0.18733E-01 0.79916E-03 0.S28 29E-07 CHANNEL 6 0.8S874E +03 0.29503E+0I 30 0.0 0.71324E-03 0.31854E-OI 0.30642L-0I 0.12560fc-01 0.54309E-03 0. 209706 -OA 0. 2068 0E-O2 0.2809 0E-0I . 29 34 OE -0 1 0.93453E-02 0.3O317E-O3 0.1 1557E-03 0.&3747E-02 0.23958E-01 0.23980E-01 0.57336E-02 0.2O612E-03 0.26923E-03 O.16130E-O1 0.23597E-01 0.18849E-01 0.29S80E-O2 0.98819E-04 0.42594E-03 0.27272E-01 0.26615E-01 0.15587E-01 0.I3I34E-02 0.79949E-08 CHANNEL 9 0.97327E+03 0-3S114E+01 30 0.0 0.3460&E-03 0.583S6E-02 0.30989E-01 0.10504C-01 0.43136E-03 0.0 0.44 63 7E-0 3 0. 13746E-01 0.30931E-01 0.4100 5E-02 0.3306 5E-03 0.32686E-04 0.58700E-O3 0.24057E-01 0.33060E-01 0.1639bE-02 0.2 1892E-03 0.1S474E-03 0.1I863E-02 O.30 8O6E-01 O.34 309E-O1 O.90045E-O3 O.10863E-03 0.23178E-03 0.26227E-02 0.31946E-01 0.24791E-01 0.48867E-03 0.75578E-08 CHANNEL 10 0-1 1664E+04 0.43724E+01 30 0.0 0.72668E-04 0.20591E-03 0.39377E-03 0.151 13E-02 B-9 HIRS/2 Normalized response functions (continued) 0.63529E-02 0.15338E-01 0.1569SE-01 0.72436E-02 • 1 45 7 3£ -03 0.1b43 8E-Ol 0.16610E-01 0. 1513 IE-0 J 0.4339fcE-02 0. 1221 4E-03 0.15287E-01 0.16912E-01 0.13897E-01 0.I3362E-02 0.t>?85t>L-OA 0.13630E-01 0.16326E-01 0.11770E-01 0.38562E-03 0.21571E-04 G.I40 88E-0S 0.15880E-01 Q.939fe4E-02 0.12278E-03 0.I0519E-08 CHANNEL 11 0.13002E+04 0.4<*690E+0l 30 0.0 0.4S338E-03 0.143*4E-0l 0.25140E-01 0.46482E-02 0.20551t-03 0. 1382HL-OJ 0.7341 9E-03 0. 19 3b it -O 3 0.2336SE-01 0.2180 9E-0 2 0. 1494 1E-03 0.2 l£>10t-03 0.14339E-02 0.22858t-01 0.20228E-01 0.8 2877E-03 0.98024E-04 0.31 74foE-03 0.33 733E-02 0.25275F-OI 0.14814E-01 0.408O5E-03 0.10751E-04 0.42389E-03 0.7t>183E-02 0.25850E-01 0.89935E-02 0.30361E-03 0.0 CHANNEL 12 0.13850E+04 0.fc»53 79E+01 30 0.0 0.13S4 2E-03 0.12855E-01 0.12240E-01 0.824S9E-02 0.I5221E-03 0. 1620tfc-04 0. I 745 IE -O 3 0. 12 99 7E -01 0. 1I051E-01 0.7837 0E-02 0.80740E-04 0.4 8341E-04 0.t>3797E-03 0.l239t>t-01 0.92167E-02 0.778E2E-02 0.37131E-04 0.91743E-04 0.28377E-02 0.11942E-01 0.79691E-02 0.40281E-02 0.21406E-06 0.11248E-03 0.91147E-02 0.12265E-01 0.80158E-;02 0.67062E-03 0.0 CHANNEL 13 0.21574E+04 0.2t>2 76E+01 30 0.0 0.93276E-03 0.34065E-O1 0.39833E-0X 0.33730E-02 0.18337E-03 0.30060b -04 0.21316E-O2 0.3901 7E-OI 0.30 79 Zfc-OI 0. 1501 IE -02 0.0 0.220 36E-03 0.53916E-02 0.454 38E-0J 0.2 15 72E-01 0.9O914E-03 O.O 0.38340E-03 0.12933E-01 0.49207E-01 0.12694E-01 0.72675E-03 0.0 0.60588E-03 0.24509E-01 0.4719IE-01 0.64428E-02 0.4580SE-03 0.0 CHANNEL 14 0.21713E+04 0.2O414E+01 30 0.0 0.37555E-03 0.91194E-02 0.A3988E-01 0.17690E-01 0.543*3E-03 0.0 O.S098t>E-03 0. 1892 5E-01 0.41861E-01 0.70879E-O2 0.413O3E-O3 0.24504E-04 0.87127E-03 O. 30354 E-Ol 0.40717E-01 O.26174E-02 0.23317E-03 0.13143E-03 0.18636E-02 0.39493E-01 0.39441E-0'1 0.12S28E-02 0.46055E-04 0.2546 I E-03 0.38958E-02 C43922E-01 0.32244E-01 0.71984E-03 0.83335E-09 B-10 HIRS/2 Normalized response functions (continued) CHANNEL 15 0.22007E+04 0.22966E+01 30 0.0 0-72901E-03 0.12594E-01 0.37675E-01 0.3 7b8SF-Ol 0.1t>9?7f -02 0.7973 3E-04 0.9511 1E-03 0. 1928 2E-01 0.3725 5E-0 1 0.338« 1F-f»i o» vOHb bfc -OJ 0.21621E-03 0.17292E-02 0.26297E-01 0.35665E-01 0.22589^—01 0.54J44t- 03 0.37126E-03 0.33 760E-O2 0.31995E-01 O.35300E-O1 0-10 ,e **»E— nt 0.16167E-03 0.57019E-03 0.67461E-02 0.36159E-01 0-36B50E-01 n ,«ni 17E— 02 0.8f766E~o 8 CHANNEL, lb .22042f-_ +04 0.4£552E+0I 30 0.0 0.29177E-03 0.b0880E-O2 0.24405L-01 0.54040E-02 .3^2£-lE-03 O. )4bl <*fc-04 • 38 86 VE -0 3 O . 1 1 78 3E -0 1 0.2584=fc-01 0.2O35^E-0i* 0. 20 18 2E -03 0.O?47E-04 0.19591E-03 0.13389E-02 0.22411E-01 0.27099E-O1 0.516A3E-03 0.0 O.27279E-03 0.28889E-02 0.23877E-01 0.14968E-01 0.37920E-03 0.42874E-12 CHANNEL 17 0.23206E+04 0.26448E+01 30 0.0 0.6b3 = 3E-03 0.20I72E-01 0.354166-01 0.13460E-01 0.4 38S3E-03 0.79b0«E-0b O. 12220t-0ii . 28 87 I E -0 J 0.35*3 8E-01 0.4541 5E-0e 0.3090 8E-O3 0.1312 7E-03 0.27046E-02 O.3*9£3E-0f 0.38234E-01 0.1999*E-02 0.1 39 71 E -03 0.29242E-03 0.59437E-02 0.37382E-O1 0.38 378E-O1 0.10384E-02 0.18749E-04 0.41079E-03 0.11609E-01 0.37032E-01 0.26748E-01 0.53769E-03 0.0 CHANNEL 18 0.24413E +04 0.44793E+O1 30 0.0 0.b22bOE-03 0.662O8E-O2 0.27bblE-0l 0.1 14S2E-01 0.506*7E-03 0.5605 IE -0 4 O. J004 0E-O2 O.89415E-0? 0.2840 2E-0 1 0.5789 0E-0 2 0.3b63 0fc-0 3 .16357E-03 0.19815E-02 0.1 1866t-01 0.25735E-01 0.27498L-02 0.1 5953 E-03 0.31492E-03 0.31389E-02 0.16394E-01 0.22139E-01 0.12093E-02 0.89575E-O5 0.4 3911E-03 0.48298E-02 0.22548E-01 0.17642E-01 0.51102E-03 O.O CHANNEL 19 0.24870E+04 0.10672E+G2 30 0.0 0.13096E-03 0.1b92*E-02 0.92284E-02 0.929 17E-02 0.12578E-03 0.82141E-05 0.1746 2E-03 0.36865E-02 0.8914BE-0 2 0.5819iE-02 0.H361 5E-0A O.3 2770E-04 0.24A*0E-03 0.648 39E-02 0.8 4298E-02 0.21922E-02 0.54912E-04 0.63039E-04 0.36272E-O3 0.83669E-02 0.82562E-02 0.72 760E-03 0.17244E-04 0.946 35E-04 0.77O0 8E-03 0.91290E-02 0.89863E-02 .33192E-03 0.0 B-ll Band-correction coefficients Channel v c 1 668.00 2 679.23 3 691.12 4 703.56 5 716.05 6 732.38 7 748.27 8 897.71 9 1027.87 10 1217.10 11 1363.69 12 1484.35 13 2190.43 14 2212.65 15 2240.15 16 2276.27 17 2360.63 18 2511.95 19 2671.18 .99986 .99979 .99962 .99991 .99993 .99974 1.00015 1.00013 .99978 .99903 .99982 .99948 .99969 1.00011 1.00032 1.00057 1.00025 1.00020 1.00175 .047 .067 .131 .015 .010 .092 -.101 -.252 .118 -.132 .136 .424 -.015 .041 .074 .143 .060 .110 .650 B-12 REFERENCES Brower, Robert L. , "DRIR Calibration," National Environmental Satellite Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce, Suit land, Maryland, 1977 Schneider, John R. , "Guide for Designing RF Ground Receiving Stations for TIROS-N," NOAA Technical Report, NESS 75, December 1976. Schwalb, Arthur, "The TIROS-N/NOAA A-G Satellite Series," NOAA Technical Memorandum, NESS 95, March 1978. Williamson, L. Edwin, "Calibration Technology for Meteorological Satellites," Atmospheric Science Laboratory Monograph Series, U.S. Army Electronics Command, White Sands Missile Range, New Mexico, June 1977. 0. S. GOVERNMENT PRINTING OFFICE : 1979 311-046/312 R-l J^ ~J (Continued from inside front cover) NESS 83 River Basin Snow Mapping at the National Environmental Satellite Service. Stanley R. Schneider, Donald R. Wiesnet, and Michael C. McMillan, November, 1976, 19 pp. (PB-263-816/AS) NESS 84 Winter Snow-Cover Maps of North America and Eurasia From Satellite Records, 1966-1976. Michael Matson, March 1977, 28 pp. (PB-267-393/AS) NESS 85 A Relationship Between Weakening of Tropical Cyclone Cloud Patterns and Lessening of Wind Speed. James B. Lushine, March 1977, 12 pp. (PB-267-392/AS) NESS 86 A Scheme for Estimating Convective Rainfall From Satelliue Imagery. Roderick A. Scofield and Vincent J. Oliver, April 1977, 47 pp. (PB-270-762/AS) NESS 87 Atlantic Tropical and Subtropical Cyclone Classifications for 1976. D. C. Gaby, J. B. Lushine, B. M. Mayfield, S. C. Pearce, K.O. Poteat, and F. E. Torres, April 1977, 13 pp. (PB-269-674/AS) NESS 88 National Environmental Satellite Service Catalog of Products. Dennis C. Dismachek (Editor), June 1977, 102 pp. (PB-271-315/AS) NESS 89 A Laser Method of Observing Surface Pressure and Pressure-Altitude and Temperature Profiles of the Troposphere From Satellites. William L. Smith and C. M. R. Piatt, July 1977, 38 pp. (PB- 272-660/AS) NESS 90 Lake Erie Ice: Winter 1975-76. Jenifer H. Wartha, August 1977, 68 pp. (PB-276-386/AS) NESS 91 In-Orbit Storage of NOAA-NESS Standby Satellites. Brtce Sharts and Chris Dunker, September 1977, 3 pp. (PB-283-078/AS) NESS 92 Publications and Final Reports on Contracts and Grants, 1976. Catherine M. Frain (Compiler), August 1977, 11 pp. (PB-273-169/AS) NESS 93 Computations of Solar Insolation at Boulder, Colorado. Joseph H. Pope, September 1977, 13 pp. (PB-273-679/AS) NESS 94 A Report on the Chesapeake Bay Region Nowcasting Experiment. Roderick A. Scofield and Carl E. Weiss, December 1977, 52 pp. (PB-277-102/AS) NESS 95 The TIROS-N/NOAA A-G Satellite Series. Arthur Schwalb, March 1978, 75 pp. (PB-283-859/AS) NESS 96 Satellite Data Set for Solar Incoming Radiation Studies. J. Dan Tarpley, Stanley R. Schneider, J. Emmett Bragg, and Marshall P. Waters, III, May 1978, 36 pp. (PB-284-740/AS) NESS 97 Publications and Final Reports on Contracts and Grants, 1977. Catherine M. Frain (Compiler), August 1978, 13 pp. (PB-287-855/AS) NESS 98 Quantitative Measurements of Sea Surface Temperature at Several Locations Using the NOAA-3 Very High Resolution Radiometer. Laurence Breaker, Jack Klein, and Michael Pitts, September 1978, 28 pp. (PB-288-488/AS) NESS 99 An Empirical Model for Atmospheric Transmittance Functions and Its Application to the NIMBUS-6 RIRS Experiment. P.G. Abel and W.L. Smith, NESS, and A. Arking, NASA, September 1978, 29 pp. (PB-288-487/AS) NESS 100 Characteristics and Environmental Properties of Satellite-Observed Cloud Rows. Samuel K. Beckman (in consultation). NESS 101 A Comparison of Satellite Observed Middle Cloud Motion With GATE Rawinsonde Data. Leroy D. Herman, January 1979, 13 pp. (PB-292-341/AS) NESS 102 Computer Tracking of Temperature-Selected Cloud Patterns. Lester F. Hubert, January 1979, 15 pp. (PB-292-159/AS) NESS 103 Objective Use of Satellite Data To Forecast Changes in Intensity of Tropical Disturbances. Carl 0. Erickson, April 1979, 44 pp. (PB-298-915) NESS 104 Publications and Final Reports on Contracts and Grants. Catherine M. Frain, (Compiler), September 1979. NESS 105 Optical Measurements of Crude Oil Samples Under Simulated Conditions. Warren A. Hovis and John S. Knoll, October 1979, 20 pp. NESS 106 An Improved Model for the Calculation of Longwave Flux at 11 m. P. G. Abel and A. Gruber, October 1979, 24 pp. F 5 PE Ti?i T | A .T E UNIVE RSITY LIBRARIES AQDD072Dmm7 NOAA—S/T 79-315