GOES Imager Instrument

The GOES I-M Imager is a five channel (one visible, four infrared) imaging radiometer designed to sense radiant and solar reflected energy from sampled areas of the earth. By means of a servo driven, two-axis gimbaled mirror scan system in conjunction with a Cassegrain telescope, the Imager's multispectral channels can simultaneously sweep an 8-kilometer (5 statute mile) north-to-south swath along an east-to-west/west-to-east path, at a rate of 20 degrees (optical) east-west per second.

The Imager consists of electronics, power supply, and sensor modules. The sensor module containing the telescope, scan assembly, and detectors, is mounted on a baseplate external to the spacecraft, together with the shields and louvers for thermal control. The electronics module provides redundant circuitry and performs command, control, and signal processing functions; it also serves as a structure for mounting and interconnecting the electronic boards for proper heat dissipation. The power supply module contains the converters, fuses, and power control for interfacing with the spacecraft electrical power subsystem. The electronics and power supply modules are mounted on the spacecraft internal equipment panel.

Imager Instrument                   Spectral Bands (micrometers)
  Characteristics
				|  1  |  2  |  3  |   4   |   5   |
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Wavelength (micrometers)	| 0.55| 3.80| 6.50| 10.20 | 11.50 |
				| to  |  to |  to |  to   |  to   |
Product				| 0.75| 4.00| 7.00| 11.20 | 12.50 |
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Clouds				|  X  |  X  |  X  |   X   |   X   |
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Water Vapor			|     |     |  X  |   X   |   X   |
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Surface Temp			|     |  O  |     |   X   |   O   |
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Winds				|  X  |     |  X  |   X   |       |
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Albedo & IR Flux		|  X  |     |  O  |   X   |   O   |
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Fires & Smoke			|  X  |  X  |     |   O   |   O   |
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X: Primary Spectral Channel
O: Secondary (supplementary) Spectral Channel
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Field of View Defining Element:  Detector
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Optical Field of View	:  Square
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5-Channel Imaging	:  Simultaneously
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Scan Capability		:  Full earth/Sector/Area
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Channel/Detector		Instantaneous Field of View (IFOV)
(1)	Visible/Silicon		:  1 km
(2)	Shortwave/InSb		:  4 km
(3)	Moisture/HgCdTe		:  8 km
(4)	Longwave 1/HgCdTe	:  4 km
(5)	Longwave 2/HgCdTe	:  4 km
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Radiometric Calibration	:  Space and 290K IR internal blackbody
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Signal Quantizing (NE'delta'T)	:  10 bits all channels
 	S/N			:  Minimum 3X better than spec
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Frequency of Calibration
	Space			:  2.2 sec for full disk;
				:  9.2 or 36.6 sec for sector/area
	Infrared		:  30 minutes typical
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System Absolute Accuracy	:  IR channel lte 1 K
				:  Visible Channel 5% of
				:  maximum scene irradiance
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System Relative Accuracy	:  IR channel lte 0.1 K
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Transmit Frequency		:  1676.00 MHz
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Additional informaton about the GOES satellites can be found at: NASA GOES Project Office, or at The CIMSS GOES Page

Revised: 15 December 1997