BOSTON — With one of its major satellite projects approaching launch and another having recently been terminated, the U.S. Defense Advanced Research Projects Agency (DARPA) is seeking less money for space-related work next year than it has in its current budget.

DARPA is asking Congress for $224.55 million for space programs in 2008, a decrease of $29.4 million from its 2007 budget. DARPA’s total funding request is $3.09 billion, compared to a $3.12 billion budget for this year.

Budget justification documents posted on DARPA’s Web site show the agency’s space-related funding growing to $225.24 million in 2009; $246.44 million in 2010; $246.44 million in 2011; $249.47 million in 2012; and $258.86 million in 2013.

The 2008 request does not contain funds for the Orbital Express satellite refueling demonstration, which is expected to launch in March aboard an Atlas 5 rocket carrying a variety of military experiments. Orbital Express received $34.7 million in DARPA’s 2007 budget.

Boeing Phantom Works of St. Louis is the prime contractor for the Orbital Express demonstration, which was nearly terminated in 2004 after technical difficulties drove up its cost.

Jan Walker, a DARPA spokeswoman, said Air Force Space Command will assume responsibility for the Orbital Express satellites once the initial demonstration has concluded. The two organizations are in discussions regarding follow-on experiments, she said.

DARPA’s 2008 budget request also reflects the termination of the Innovative Space-Based Radar Antenna Technology effort, which was intended to develop a very large radar antenna that could be folded into a small package for launch and unfurled in space. The imaging resolution of a radar satellite is a function of its antenna, or aperture, size and its al titude; the higher a satellite’s orbit, the bigger its aperture needs to be to provide data of the same clarity. DARPA’s effort was aimed at developing antennas big enough to allow radar satellites to operate at much higher orbits, where they would have broader ground coverage.

DARPA requested $50 million for the antenna project in 2007, but Congress granted only $22 million. DARPA, which has spent an estimated $156 million on the research, canceled plans for a flight demonstration after the intended beneficiaries, the U.S. Air Force and National Reconnaissance Office, declined to help pay for it.

DARPA continues to pursue a variety of embryonic programs for in-space monitoring, space-capability assurance and launching small satellites.

These include the Tiny, Independent, Coordinating Spacecraft (TICS) program, which is intended to develop on-orbit inspection satellites so small — each would weigh between 1 and 10 kilograms — that they would be difficult to detect, according to the budget justification documents. DARPA envisions groups of TICS satellites being launched aboard larger spacecraft — to be deployed upon command, as needed — or by dedicated small rockets, the documents show.

The current budget for TICS is $4.8 million; DARPA is requesting $6 million for the work in 2008, and plans to ask for $7 million in 2009.

DARPA has not awarded any TICS-related contracts thus far, and is not discussing program plans at this time, Walker said.

DARPA’s 2008 budget request includes some space-related new starts, including the NanoPayload Delivery program, which would focus on technologies that would enable air-, ground- and sea-launched tactical missiles to serve as small satellite launchers. A combination of technologies for reducing drag and increasing thrust could enable modified systems including the High-Speed Anti-Radiation Missile, and AIM 7 and AIM 120 air-to-air missiles to launch 1- to 10-kilogram satellites to 200-kilometer orbits for as little as $100,000, according to the budget documents.

DARPA is seeking $4 million for the NanoPayload Delivery program in 2008, and plans to request $8.5 million in 2009.

Another proposed new start is the X-ray Communication in Space effort, for which DARPA seeks $2 million in 2008 and $5 million in 2009. The effort would focus on countering enemy attempts to jam or intercept signals from U.S. military and intelligence satellites, the documents say.

DARPA also has protection of commercial satellite signals on its agenda. The agency is requesting $5 million in 2008, and plans to seek $9 million in 2009, for the Space Situational Awareness and Counterspace Operations Response Environment program. That effort would bring together a variety of data used by ground systems to identify threats, propose countermeasures and verify the effectiveness of the response, according to the budget justification documents.