Graham Warwick/WASHINGTON DC
The ambitions of the US Department of Defense (DoD) to renew its communications satellite constellations could be scuppered by funding challenges facing all its programmes.
The first issue facing the DoD is whether it can afford to replace the Milstar II satellite which was launched into an unusable orbit by a Titan IV booster in April. The US Air Force says a replacement will cost over $1 billion, although efforts are under way with manufacturer Lockheed Martin to find ways to reduce the price.
The EHF-band Milstar II is to be the backbone of the DoD's protected communications network, and the constellation was to consist of four operational satellites, with no spare. Three Milstar IIs remain to be launched, but without a replacement satellite "there will be a hole in capacity or coverage", says an industry source.
The last Milstar II is scheduled for launch in 2002, but the first follow-on Advanced EHF (AEHF) satellite is not planned to be in orbit until 2006.
Hughes and Lockheed Martin were selected in August to define the AEHF programme, expected to be worth over $2 billion. One will be selected in April 2001 to develop the system, with the launch of five satellites (including one spare) to begin in mid-2006.
Unlike the purpose-designed Milstar, the AEHF will be based on a commercial communications satellite to reduce costs. Lockheed Martin's proposal will be based on a militarised version of its A2100 bus.
The DoD is also looking at using commercial technology to reduce the cost of renewing its other communications satellite constellations. Lockheed Martin, for example, plans to offer its A2100 bus for the Wideband Gapfiller programme, intended to bridge the gap between the Defense Satellite Communications System (DSCS) and the planned Advanced Wideband constellation.
Four more Lockheed Martin-built DSCS III satellites remain to be launched by 2003, to extend the service life of the system. Three Wideband Gapfillers will be acquired for launch in 2004-5, to cover SHF-band frequencies and Ka-band tactical mobile communications and Global Broadcast System television payloads.
Advanced Wideband launches are planned to begin after 2006. Lockheed Martin says its offering could be based on the commercial Astrolink broadband satellite communications system it is developing with TRW and Alenia Spazio.
Completing the DoD's wishlist is the Mobile User Objective Sys-tem, intended to replace the current UHF follow-on constellation beginning around the middle of the next decade. This programme, led by the US Navy, is due to get under way early next year with concept studies, leading to development from 2003.
The system resembles a commercial mobile communications constellation. Lockheed Martin has teamed with Iridium developer Motorola and Teledesic to bid for the programme.
Source: Flight International
