|
ESSA-6
ESSA 6 (or TOS-D) was a spin-stabilized operational meteorological satellite.[1] Its name was derived from that of its oversight agency, the Environmental Science Services Administration (ESSA). Details ESSA 6 had a mass of 299 kilograms (659 lb) at the time of launch. The satellite's electrical power was supplied by about 10,000 1x2 cm solar cells on the cover and 21 nickel-cadmium batteries. Two redundant wide-angle APT (Automatic Picture Transmission) cameras, mounted on opposite sides and perpendicular to the spin axis, captured images. This subsystem was a camera-transmitter setup, designed to transmit real-time daylight images of cloud cover to ground stations. It included two 2.54-cm vidicon cameras with 108° F/1.8 lenses, mounted 180° apart. Each orbit, the cameras captured four or eight images, with picture taking lasting 8 seconds and transmission 200 seconds. The 800-line images were transmitted at 137.5 MHz to local APT stations, with reticle marks on the images to assist with geographical alignment. Each picture covered a 3100 x 3100 km area with 4 km resolution at nadir, with a 30% overlap to ensure complete coverage.[2] The base featured crossed-dipole antennas for command reception, while a monopole antenna provided telemetry (136.500 MHz) and tracking (136.770 MHz) from the top. Spin rate was regulated to 10.9 rpm using a Magnetic Attitude Spin Coil (MASC), which interacted with Earth's magnetic field to maintain a stable spin axis normal to the orbital plane, within ±1 degree.[1] Mission ESSA 6 was launched on November 10, 1967, at 18:00 UTC, atop a Delta rocket from Vandenberg Air Force Base, California, USA. ESSA 6 had an inclination of 102.12°, and orbited the Earth once every 114.8 minutes. Its perigee was 1,410 kilometers (880 mi) and its apogee was 1,488 kilometers (925 mi).[3] The satellite performed normally after launch. The APT camera system was successful, operating nearly continuously until November 4, 1969 when the spacecraft was deactivated.[2] References
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
