Tim Furniss/LONDON
The US Air Force launched its fourth Milstar military communications satellite aboard a Titan IV Centaur booster from Cape Canaveral on 27 February after a series of technical delays.
The 5,000kg spacecraft was originally to have flown last April. Milstar F4 is the first in the series to operate a Boeing-built medium-data-rate (MDR) payload to complement the UHF and low-data- rate (LDR) payloads which flew on the first two operational satellites, designated Milstar 1s.
Milstar F3, the first with an MDR payload and the first designated a Milstar 2 series spacecraft, was stranded in a useless orbit after a Cenatur upper stage failure in 1999. The failure was caused by corrupted computer software - an embarrassment for Lockheed Martin and, at $800 million a satellite, potentially the most expensive unmanned launch failure yet. Two Milstar 2s are left to be launched.
The Lockheed Martin-Milstars incorporate five on-board technologies not found in previous military communications satellites, namely signal processing, signal routing, resource control, crossbanding and satellite crosslinks. The LDR payload has 200 user channels at data rates of 75-24,000 bits per second (bps).
Satellite-to-satellite crosslinks enable communications to support the secure, jam-resistant tactical and strategic multiservice system. The MDR provides a 1.5 million bps data rate for real time voice and data transmissions. It dynamically sorts incoming data and routes it to the proper downlinks.
It is estimated that the Pentagon has spent over $20 billion to develop the Milstar system, the effectiveness of which is doubted by some observers, who describe the satellites as a Cold War relic.
A report by the Congressional General Accounting Office has criticised the programme for deficiencies in software, communications and performance.
Meanwhile, the schedule to launch the Advanced Extremely High Frequency satellite in 2004 to replace Milstar 2s is already under pressure. The Lockheed-Boeing-TRW team was merged from competing bidders to ensure the schedule was accelerated by 18 months. The project will not now begin in April as scheduled.
Source: Flight International