|This article needs additional citations for verification. (December 2013)|
|Mission type||Weather satellite|
|Launch mass||304 kilograms (670 lb)|
|Start of mission|
|Launch date||3 February 1966, 07:41:23UTC|
|Launch site||Cape Canaveral LC-17A|
|End of mission|
|Deactivated||12 June 1968|
|Semi-major axis||7,115.60 kilometers (4,421.43 mi)|
|Perigee||685 kilometers (426 mi)|
|Apogee||803 kilometers (499 mi)|
|Epoch||7 December 2013, 20:11:52 UTC|
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 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 kilometers (379 nmi) and apogee was 845 kilometers (456 nmi).
ESSA-1 had a similar design to that of the TIROS satellite series. It was an 18-sided right prism, measuring 107 centimeters (42 in) across opposite corners and 56 centimeters (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.
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