WASHINGTON — After evaluating potential alternatives to its Transformational Satellite (T-Sat) communications system, the U.S. Defense Department has opted to proceed with the program as planned and intends to award a $15 billion prime contract to Boeing or Lockheed Martin by this winter, according to a U.S. Air Force spokesman.

The future of the Air Force’s next-generation secure satellite communications system became uncertain earlier this year when the Defense Department’s acquisition czar, John Young, ordered an analysis of alternatives that included beefing up the military’s prior-generation satellites and deploying smaller platforms with some of the capabilities envisioned for T-Sat.

That study has been completed and the Air Force plans to move on with the program as currently structured, the spokesman, Air Force Lt. Col. Mark Brown, said in an e-mail response to questions.

Lockheed Martin Space Systems of Sunnyvale, Calif., and Boeing Integrated Defense Systems of St. Louis are competing to build T-Sat; both companies are in the midst of risk reduction contracts that now total $650 million apiece and run through January. The contract award will come roughly one year after the Air Force previously planned; the contract extensions needed to keep the Boeing and Lockheed Martin T-Sat teams together during the interim are worth a total of $300 million.

Now that the Defense Department has chosen a direction for T-Sat, funding is the next hurdle. To build the system with the intended capabilities and stick to its 2016 target launch date for the first satellite, the Air Force needs Congress to appropriate more money for the program than the service requested for 2009, according to Loren Thompson, chief operating officer at the Lexington Institute, an Arlington, Va.-based think tank.

The Air Force requested $843 million for T-Sat for 2009 – about $385 million less than the service anticipated it would need for that year when it submitted its 2008 budget proposal. For 2009 through 2013, the latest Air Force budget plan anticipates spending $6.6 billion on T-Sat, compared to $10.7 billion during the same period under the previous plan.

The House Armed Services Committee has recommended fully funding the program at $843 million for 2009, while its Senate counterpart recommended adding $350 million to the president’s request.

The House Appropriations defense subcommittee marked up the defense spending bill July 30 but will not release most details until the full committee considers the bill, which is likely to occur in September, committee spokeswoman KirstinBrost said.

A statement issued by the subcommittee’s chairman, Rep. John Murtha (D-Pa.), said the panel added $300 million to the Air Force’s $404 million request for the Advanced Extremely High Frequency (AEHF) system, T-Sat’s predecessor. This money will be used to procure a fourth AEHF satellite, which Congress directed the Air Force to buy last year.

The Senate Appropriations Committee has not yet scheduled its defense bill markup.