The Advanced Very High Resolution Radiometer
(AVHRR):
A Brief Reference Guide

by David A. Hastings and William J. Emery
Section V: Spacecraft and Sensor Characteristics


Table of Contents:

APPENDIX

Spacecraft Characteristics, advanced TIROS-N/NOAA E-J series:

3.71 m long, 1.88 m diameter maximum. 1009 kg spacecraft mass (excluding expendables); 386 kg satellite payload (all instruments and support). 2.37 by 4.91-m solar array. 515 Watts minimum output; 475 Watts power requirement at full operation. Attitude Determination and Control System incorporates (1) Earth Sensor Assembly (for pitch and roll); (2) Sun Sensor Assembly (yaw); (3) three orthogonal gas-bearing gyros to measure change in attitude in three axes (a fourth canted gyro is available as a spare); (4) Four Reaction Wheel Assemblies which provide corrective torques; (5) two Roll/Yaw Torquing Coils and two Pitch Torquing Coils electrically dissipate roll/yaw and pitch angular momentum. On board computers and continuously updated ephemeris models transmitted from Earth assist this process.

Attitude normally maintained within 0.12 degrees, 0.2 degrees maximum. Attitude measurement accuracy approximately 0.1 degrees. Five digital tape recorders, each with 168 m of tape, for 45 MB of data, enough for a full orbit (110 minutes) GAC, 10 minutes LAC. Tapes designed for 25,000 passes on each transport unit. Data processing all digital (APT translated digital to analog). Two-Year design lifetime.

Nominal orbit:

Height        Inclination         Orbital Period       Orbital Increment        Orbits Reception
(km)*            (deg.)                  (min.)           (deg./deg. W)     Per Day         Time (min.)**

833 + 18.5    98.739+0.5              101.38             25.40          14.18                13.0

*    Difference between apogee and perigee less than 56 km.         
**  Time visible to an antenna directly under the orbital track, assuming interference when the  satellite 
is less than 5 degrees above horizon.
Sensor characteristics:

Optics: 20.3-cm diameter focal Cassegrain telescope.
Scan mirror: Ribbed beryllium; 29.46-cm major axis, 20.96-cm minor axis.
Scanner: 360 rpm 80-pole hysteresis synchronous motor with ribbed beryllium scan mirror.
Power consumption: 4.5 Watts maximum.
Cooler: Two-stage radiant cooler, Infrared detectors operate at 105k.
Data Output: 10-bit binary, channels simultaneously sampled at a 40 kHz rate.
Power: 28 Watts Maxim (total instrument).
Size: 79 cm by 28 cm by 41 cm maximum.
Mass: 30 kg maximum.
Detector Type: Silicon (Ch 1 & 2); InSB (Ch 3); HgCdTe (Ch 4 & 5).
Scan Angle: 55.4 degrees on either side of nadir.
IFOV: 1.3 milliradians.
RFOV: 1.1 km at nadir; 6 + km at edge of scan.
Image Width: 2048 pixels, about 2800 km.
Calibration: Blackbody surface inside spacecraft (290 K) and space (0 K) and space (no albedo) for reflected channels.

Channel #    Description                                Band Width                    IFOV****

     1*      visible (green) channel                    0.58  to 0.68 micrometers     1.39
     2       reflected infrared channel                 0.725 to 1.05 micrometers     1.41
     3       hybrid reflected/thermal infrared channel  3.55  to 3.92 micrometers     1.51
     4**     thermal infrared channel                   10.3  to 11.3 micrometers     1.41
     5***    thermal infrared channel                   11.5  to 12.5 micrometers     1.30
*     0..55 to  0.90 micrometer on TIROS-N.
**    10.5 to 11.5 micrometer on TIROS-N and NOAA 40-channel AVHRR/1 series.
***   No channel 5 on  TIROS-N and NOAA 4-channel series. Channel 4 data are repeated.
****  Instantaneous Field of View (in milliradians)

Satellite   Dates of Operation  Descending  Daylight    # of 
                                  Node     Acquisition  channels
 
TIROS-N     10/19/78-01/30/80   0300         AM          4
NOAA-6      06/27/79-03/05/83   0730         PM          4 
            07/03/84-11/16/86              
NOAA-7      08/24/81-02/01/85   0230         AM          5
NOAA-8      05/03/83-06/21/84   0730         PM          4 
            07/01/85-10/31/85              
NOAA-9            02/25/85      0220         AM          5
NOAA-10           11/17/86      0730         PM          4
NOAA-11     11/08/88-09/13/94   0140         AM          5
NOAA-12           09/01/91      0730         PM          5      
NOAA-14           12/30/94      0140         AM          5

ABSTRACT
INTRODUCTION
HISTORY OF WEATHER SATELLITES
THE AVHRR SENSOR
SENSOR HARDWARE
DATA INGEST, PROCESSING, AND DISTRIBUTION
OPERATIONAL AVHRR DATA PRODUCTS
DIRECT READOUT OF AVHRR DATA
APPLICATIONS OF AVHRR DATA
METEOROLOGY
OCEANOGRAPHY
TERRESTRIAL SCIENCES
SOME EFFECTS OF THE SATELLITE SYSTEM ON APPLICATIONS
THE FUTURE OF THE AVHRR
REFERENCES
Entire paper (a bit long at 45 kilobytes)
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