Weather Satellites: GOES 7

GOES 7 - Geostationary Operational Environmental Satellite 7

Launch date: February 26, 1987

Launch site: Cape Canaveral, Florida

Launch vehicle: Delta 3914

PROGRAM OBJECTIVE:

The satellite was designed to sense meteorological conditions from a fixed location above the Earth, and to provide this data to operational forecasters and private interests on the ground. It was designed to replace GOES 5 and provide continuous vertical profiles of atmospheric temperature and moisture.

SPACECRAFT DESCRIPTION:

The spacecraft was a cylinder 85 inches in diameter, 138 inches high and weighed 874 pounds. The sides of the cylinder were covered by 15,000 solar cells which, along with nicad batteries, provided the power for the craft. Contained within, but protruding from the base was the primary instrument - the VAS (Visible Infrared Spin Scan Radiometer (VISSR) Atmospheric Sounder) and its sunshade. This instrument provided both day and night imagery of cloud conditions as well as temperature and moisture profiles over the full-disk. Unfortunately, the dwell times of sounder versus imager do not permit these two operations to occur simultaneously; however, soundings are still available on an hourly basis.

The satellite also used despun S-band and UHF antennas to improve the relay of meteorological data from over 10,000 surface locations into a central processing center for incorporation into numerical weather prediction models, and to perform facsimile transmission of processed images and weather maps to WEFAX field stations. In addition, a Space Environment Monitor (SEM) and Data Collection System (DCS) similar to those on the previous GOES were installed.

GOES 7 was placed in a geostationary orbit directly over the equator over the Atlantic (75W) and was referred to as GOES-EAST. The satellite is still operational; however, it has been moved several times to cover both the west and east coasts of the U.S. due to the failure of the imager on GOES-WEST. The current position (112W) allows coverage of the US west coast, while the METEOSAT 3 geostationary satellite is currently being leased from the European Space Agency for coverage of the US east coast. Unfortunately, the spin of the GOES 7 satellite is no longer stable resulting in a 'figure-8' orbit which grows by 0.9 deg. latitude each year. After GOES-I was deployed in Spring of 1994, as GOES 8 (GOES-East), GOES 7 remained in geostationary orbit, at 105 W, and is still used for satellite communications.

PARTICIPANTS:

NASA, NOAA, Hughes Aircraft, McDonnell Douglas