ESSA-1

ESSA-1 (or OT-3) was a spin-stabilized operational meteorological satellite. ESSA-1 was launched on 3 February 1966 at 07:41 UTC. It was launched atop of a Delta rocket from Cape Canaveral, Florida. The spacecraft had a mass of 304 kilograms (670 lb) at the time of launch. ESSA-1 had an inclination of 97.91, and an orbited the earth once every 100 minutes. Its perigee was 702 kilometres (379 nmi) and apogee was 845 kilometres (456 nmi).

ESSA-1 had a similar design to that of the TIROS satellite series. It was an 18-sided right prism, measuring 107 centimetres (42 in) across opposite corners and 56 centimetres (22 in). It had a reinforced baseplate, which carried most of the subsystems and a cover assembly (hat). ESSA-1 had approximately 10,000 1-cm by 2-cm solar cells, which charged 21 nickel-cadmium batteries. ESSA-1 was designed to take pictures of daytime cloud cover, record them and transmit them when it was in range of a ground acquisition station.

The satellite spin rate and attitude were determined primarily by a Magnetic Attitude Spin Coil (MASC). The MASC was a current Carrying coil mounted in the cover assembly. The magnetic field induced by the coil interacted with that of the Earth's magnetic field, and provided the necessary torque to maintain a desired spin rate of 9.225 revolutions per minute (rpm). Five small solid-fuel thrusters  mounted on the baseplate provided a secondary means of controlling the spin rate.

ESSA-1 operated normally until 6 October 1966, when the camera system failed. The spacecraft was fully deactivated on 8 May 1967, after being left on for an additional period of time for engineering purposes.

External links

• [1] the NSSDC ID for ESSA-1 from the NASA website