| ESSA 6 | |
| Names List: | TOS-D |
| Mission Type: | Weather |
| Operator: | NASA |
| Cospar Id: | 1967-114A |
| Satcat: | S03035 |
| Launch Date: | November 10, 1967, 18:00 UTC GMT |
| Launch Rocket: | Delta |
| Launch Site: | Vandenberg Air Force Base |
| Orbit Reference: | Geocentric orbit |
| Orbit Regime: | Low Earth orbit |
| Orbit Eccentricity: | 0.00498 |
| Orbit Inclination: | 102.12° |
| Orbit Period: | 114.82 minutes |
| Apsis: | gee |
| Programme: | ESSA program |
| Previous Mission: | ESSA-5 |
| Next Mission: | ESSA-7 |
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).
ESSA 6 had a mass of 299kg (659lb) 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 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.
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 1410km (880miles) and its apogee was 1488km (925miles).[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.