The U.S. Air Force's incremental approach to developing and deploying its Transformational Satellite (TSAT) network is raising questions about the system's ultimate capabilities and cost.

Last year, Air Force officials talked of a five-satellite network for TSAT that not only would provide laser links between the spacecraft but also down to the ground as the network grew. The estimated cost for TSAT was about $18 billion.

But now officials refuse to talk about any ground-to-orbit laser link requirements, and the service won't comment on estimated total costs.

"The TSAT program is composed of different segments," Air Force program officials said in an email response to questions. "These include the TSAT Mission Operations System (TMOS), which was awarded in January of 2006; risk reduction and technology development activities that have been on-going since 2004; and the TSAT space segment, which has not yet been awarded."

Air Force officials said they would only discuss the first increment of the TSAT satellite program - the initial satellite, which has half the laser terminals and about a quarter of the processing throughput compared to what was initially planned. "Right now, the Air Force focus is still on the program of record, and executing the TSAT Block I capability," program officials said.

The laser links for that satellite would be used to communicate with other satellites. Satellite communications to the Earth's surface are to be done with RF signals. It would be too early, Air Force program officials said, to estimate the total TSAT cost now.

The two contractors vying to build the TSAT spacecraft -- Boeing and Lockheed Martin -- also refuse to discuss any ground-to-orbit laser link possibilities. Lockheed would only acknowledge an Air Force desire for laser links between the satellite and high-altitude aircraft, such as unmanned aerial vehicles (UAVs). As for cost, Lockheed said TSAT was a $10 billion "development program."

That cost could only cover basic development, according to John Edwards of Forecast International.

"When people say that TSAT is a $10 billion development program I think they are trying to describe the DOD RDT&E [research, development, test and evaluation] funding in the Air Force budget," Edwards said. "This amount totals approximately $10 billion between fiscal year '05 and fiscal year '11. This does not include actual spacecraft procurement [or] launcher procurement, nor does it include ground segment procurement costs, which, when added up, will total more than $16 billion.

"The GAO [Government Accountability Office] has estimated that it would cost $16 billion in May 2006 so it's safe to say that there has been some cost growth since that time," Edwards continued. "I believe that $18 billion is the more realistic figure and I wouldn't be surprised if it was actually slightly higher than that if all the spacecraft are indeed procured."

Edwards also said the recent refusals to discuss orbit-to-ground laser links are likely due to technical difficulties in developing such a capability.

"The ground-orbit laser comms portion of TSAT was one of the desired capabilities and the reason you may not be hearing about it so much is because the laser comms are considered to be the most technologically and fiscally challenging portions of TSAT. The first TSAT spacecraft will be far less capable than originally expected and not until the second and maybe even third spacecraft will we start to see some of the bells and whistles that were promised with TSAT."

Loren Thompson, space expert for the Lexington Institute, said the reason for a clamp down on discussions about that type of laser communications is because even the development of that capability is now considered classified.