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ESSA I Spac0020.jpg
Mission type Weather satellite
Operator ESSA/NASA
COSPAR ID 1966-008A
SATCAT no. 1982
Spacecraft properties
Manufacturer RCA Astro
Launch mass 304 kilograms (670 lb)[1]
Start of mission
Launch date 3 February 1966, 07:41:23 (1966-02-03UTC07:41:23Z) UTC[2]
Rocket Delta C
Launch site Cape Canaveral LC-17A
End of mission
Disposal Decommissioned
Deactivated 12 June 1968 (1968-06-13)[3]
Orbital parameters
Reference system Geocentric
Regime Low Earth
Semi-major axis 7,115.60 kilometers (4,421.43 mi)
Eccentricity 0.0083082
Perigee 685 kilometers (426 mi)
Apogee 803 kilometers (499 mi)
Inclination 97.94 degrees
Period 99.56 minutes
Epoch 7 December 2013, 20:11:52 UTC[4]

ESSA-1 (or OT-3) was a spin-stabilized operational meteorological satellite. Its name was derived from that of its oversight agency, the Environmental Science Services Administration (ESSA).


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 its 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.


  1. ^ "ESSA 1". National Space Science Data Center. Retrieved 8 December 2013. 
  2. ^ McDowell, Jonathan. "Launch Log". Jonathan's Space Page. Retrieved 8 December 2013. 
  3. ^ "ESSA". NASA Science. Retrieved 8 December 2013. 
  4. ^ "ESSA 1 (OT-3) Satellite details 1966-008A NORAD 1982". N2YO. 7 December 2013. Retrieved 8 December 2013. 

 This article incorporates public domain material from the National Aeronautics and Space Administration document "ESSA 1" (retrieved on 2009-03-05).

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