Tim Furniss/LONDON

ROCKWELL International has won back work to build US Air Force Navstar global-positioning- system (GPS) satellites. The California-based company has now won 73 of the 93 Navstar contracts let by USAF.

Up to 33 Navstar Block 2F spacecraft will be built by Rockwell through to 2012 under a contract worth about $1.3 billion. The first of the Navstar Block 2F satellites will be launched by a McDonnell Douglas Delta 2 in 2001.

Rockwell's principal team member will be Computer Sciences of Maryland, which will develop software modifications for the ground segment and assume the operational-control-system support role.

The team will initially build six spacecraft, modify the GPS ground-control segment and provide launch processing and support. The Block 2Fs, numbered 61 to 93 in the series, will double to 15 years the design life of the Navstars.

The preceding 20 Block 2R Navstars, numbered 40 to 60, with a first launch by a Delta 2 scheduled for 1997, are being built by Lockheed Martin Astro Space after the company won a contract in 1989, submitting a lower bid than that from Rockwell.

Rockwell had been the original builder of 12 Block 1 Navstars, winning a contract in 1974. The first Block 1 satellite was launched in 1978. The company also built the Block 2 Navstars, numbers 13-21, and Block 2A Navstars 22-40, three of which have yet to be launched.

The Navstar GPS first achieved full operational capability in April 1995, with a combination of Block 2 and 2A satellites. The first replacement satellite for the system was launched in March (Flight International, 10-16 April).

The Navstar constellation system consists of 21 operational craft and three in-orbit spares, circling the Earth twice a day in six planes in circular, 20,000km, 55¡-inclination orbits. The extended lifetimes of the Rockwell-built Block 2 and 2A launched so far resulted in the USAF reducing the Block 2F contract from an originally planned 51, to 33 craft.

Source: Flight International