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Program: DSP

Also known as LS-3A

Defense Support Program also called IMEWS Integrated Multipurpose Early Warning Satellite (only for the 1st generation)

Military geostationary satellite program for early warning and detection of nuclear explosions.

Should be replaced by SBIRS in 2010.


Operator: 21St Space Wing
Peterson AFB, CO

Command and Control: 50th Space Wing
300 O'Malley Ave, Suite 24, Falcon AFB, CO 80912-3024, USA

External resources


First generation

The first generation (also called IMEWS) was composed of 4 GEO satellites launched between 1970 and 1973. Two ground stations were establish to receive its results: at Buckley Air Force Base in the US (Colorado) and in Nurrungar or Woomera, Australia. The satellites were located at approx 60°E (Indian Ocean), 135°W (Pacific Ocean) and a third one in that Atlantic Ocean region (80°W).

The satellites weighed approx 1000 kg, were spin stabilized and has 2048 IR detectors. The first launch on 6 Nov 1970 was a partial failure (vehicle problem) as the satellite was placed in elliptical orbit.

Second generation

The second generation was launched from 1975 onwards (number 5 to 13). The satellites had a double lifetime (3 years) which enabled the system to have in-orbit spares. A ground station was established in 1982 in Kapaun, Germany.

Satellites 10 to 12 were multi-orbit satellites that could also be launched in molnyia-type orbits to monitor over 81° latitude. However no satellite was flown in this orbit.

Third generation

From 1989 onwards (starting with number 14). From number 19 the satellites were considerably upgraded for better on-board processing and data transmission.

Carry a secondary payload which monitors nuclear explosions in the upper atmosphere.

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