SAN FRANCISCO — NASA needs to raise $1.2 billion by late 2012 from the U.S. Department of Defense or other government agencies to ensure that its fleet of Tracking and Data Relay Satellites (TDRS) can continue to communicate with spacecraft in near-Earth orbit beyond 2016, according to a report from the Government Accountability Office (GAO).

NASA and prime contractor Boeing Space and Intelligence Systems are succeeding in building two new satellites for the Tracking and Data Relay constellation on schedule and under budget, according to the report. While those satellites, scheduled for launch in 2012 and 2013, will provide added capability to send digital video, voice and data communications from government spacecraft to ground stations, the overall TDRS constellation continues to age.

“Even with the successful launch of TDRS-K and -L, continuity of service for TDRS System can only be ensured for NASA and other government agency users through approximately fiscal year 2016 at current support levels,” according to the GAO report, “NASA: An Assessment of Selected Large-Scale Projects” released March 3.”

Since the first TDRS satellite was launched into geosynchronous orbit in 1983, NASA has relied on TDRS to provide communications links between ground stations and the international space station, space shuttle and science satellites. NASA and Boeing officials declined to identify the other U.S. government agencies that use TDRS to communicate with their own spacecraft and ground stations, but a 2010 NASA Office of the Inspector General report on the TDRS program cites the U.S. Department of Defense, Missile Defense Agency and National Science Foundation as customers.

The TDRS constellation includes eight satellites: six operational spacecraft and two orbiting spares. Five of the eight spacecraft belong to the first generation of TDRS satellites. They continue to function but are “getting rather old,” said Bob Hladek, Boeing’s TDRS program manager.

NASA has an option to buy two additional TDRS satellites as part of the fixed-price contract space agency officials negotiated with Boeing for the purchase of TDRS-K and -L. “However, in order to exercise the options for TDRS-M and -N, NASA would need a financial commitment of $1.2 billion from partnership organizations,” according to the GAO report. The option for TDRS-M expires Nov. 30, and the option for TDRS-N expires one year later.

NASA’s Space Communications and Navigation Program, based at the Goddard Space Flight Center in Greenbelt, Md., “is advocating within the agency for TDRS-M and -N through NASA’s 2013 Program Planning and Budget Execution cycle,” said spokesman Dewayne Washington. “An agency decision will be made later this summer.” NASA officials declined to provide any additional comments on plans to obtain funding from other government agencies for additional TDRS satellites.

“We would very much like to see NASA exercise those options if at all possible,” Hladek said. He noted, however, that all federal agencies are facing great challenges in obtaining funding for future projects.

Department of Defense and Air Force officials declined to comment on their use of TDRS or any plans to provide funding for the communications satellites.

NASA historically provided TDRS service to non-NASA missions on a reimbursable basis. In 2007, NASA negotiated a new cost-sharing arrangement with its outside partners.

While Boeing awaits a decision on TDRS-M and -N, company engineers in El Segundo, Calif., continue to build the TDRS-K and -L satellites and to update the ground network under a $700 million NASA contract awarded in 2007. Boeing has completed integration of the TDRS-K bus and payload, Hladek said. Early this year, company officials began electrical testing of TDRS-K, which will be followed this summer by environmental testing, he added. NASA plans to launch TDRS-K in December 2012 from Cape Canaveral, Fla., aboard a United Launch Alliance Atlas 5 rocket. TDRS-L is scheduled for launch aboard an Atlas 5 from Cape Canaveral in December 2013.

Boeing officials are obtaining the components needed to assemble TDRS-L. Company engineers will begin integrating the TDRS-L bus and payload as soon as testing is completed on TDRS-K, Hladek said.

The new satellites are similar to their predecessors, TDRS-H, -I and -J, but space technology has changed significantly since those satellites were built and launched in 2000 and 2002. “All the payload electronics are brand-new designs,” Hladek said. “We have learned how to build much more efficient and reliable components.”

For example, the satellite uses the latest generation of gallium arsenide solar cells, which are much more efficient than the solar cells used to power TDRS-H, -I and -J. “The TDRS-K satellite has fewer solar cells, but produces more power,” Hladek said.

Boeing also is updating the TDRS ground system software to accommodate the new spacecraft while it continues to send and receive data from the TDRS satellites already in orbit.

In the recent GAO report on NASA’s largest projects, the TDRS Replenishment Program stands out as an anomaly. A majority of the projects examined by GAO were over budget and behind schedule. In contrast, NASA’s TDRS replacement program was being completed for less money that the agency budgeted. In 2010, NASA estimated that it would cost $453.1 million to purchase TDRS-K and -L. Those figures were revised downward this year. In February, NASA reported total project costs for TDRS-K and -L of $434.1 million, nearly 4 percent less than expected due to an 8 percent drop in development cost. The estimated cost for TDRS-K and -L development fell from $209.4 million in 2010 to $192.2 million early this year, according to the GAO report.

Debra Werner is a correspondent for SpaceNews based in San Francisco. Debra earned a bachelor’s degree in communications from the University of California, Berkeley, and a master’s degree in Journalism from Northwestern University. She...