Weather Satellites: ESSA VII

ESSA VII - Environmental Science Services Administration Satellite VII

Launch date: August 16, 1968

Launch site: Vandenberg AFB, California

Launch vehicle: Two stage long tank Delta

PROGRAM OBJECTIVE:

To replace ESSA V and provide cloud cover photography to the US's National Meteorological Center for the purpose of preparing operational weather analyses and forecasts.

SATELLITE DESCRIPTION:

The spacecraft was an 18-sided polygon, 42 inches in diameter, 22 inches high and weighed 320 pounds. The craft was made of aluminum alloy and stainless steel then covered with 9100 solar cells. The solar cells served to charge the 63 nickel-cadmium batteries.

The two cameras were mounted 180 degrees opposite each other along the side of the cylindrical craft. The "cartwheel" configuration of the TIROS IX was selected as the orbital configuration of the operational series of ESSA satellites. Therefore, a camera could be pointed at some point on Earth every time the satellite rotated along its axis. The spacecraft operating system was the same as on the TIROS IX. The craft was placed in its planned sun-synchronous 102 degree inclination retrograde orbit. The satellite spin axis was rotated using the magnetic attitude control system into an alignment perpendicular to the orbital plane and tangent to the Earth's surface. The ESSA VII system transmitted images covering 2000 mile square areas with 2 mile resolution from every location once per day. Two arrays of radiometer sensors were also mounted 180 degrees apart to measure the global distribution of solar radiation reflected by the earth and the earth's atmosphere, as well as the long wave emissions from the earth (a contribution from the NIMBUS program).

ESSA VII remained operational for 571 days until deactivated by NASA on March 10, 1970.

PARTICIPANTS:

NASA, ESSA, RCA, US Weather Bureau, NMC.