UPDATE: The launch, originally scheduled for Tuesday, has been postponed due to a technical problem.

The L-1011 carrier jet with a Pegasus rocket attached. Photo: Orbital Sciences

The U.S. military is ready to launch an experimental research satellite this week chock-full of risky new technologies that could improve space missions of the future.

The $85 million Tri-Service Experiments Mission-5 will begin early Tuesday morning off Central California's Pacific coastline when an air-launched Pegasus rocket soars toward Earth orbit with the 551-pound satellite.

The Orbital Sciences-built rocket, gunning for its 15th straight launch success, will be carried 40,000 feet above the Pacific Ocean by its L-1011 carrier aircraft in a mission originating at Vandenberg Air Force Base, Calif.

Once inside the preset "drop box" 10 miles wide and 40 miles long, the rocket will be released. Five seconds later its first stage solid-fueled motor ignites to start the 14-minute, 32-second journey to space.

Tuesday's available launch window extends from 8:57 to 9:55 a.m. EDT (1257-1355 GMT). Officials are targeting 9:07 a.m. EDT (1307 GMT) for drop of Pegasus, said Capt. Kevin Benedict, the satellite's mission manager.

Seeing planes and communicating with lasers
Called TSX-5 for short, the 12-sided satellite carries a host of experiments incorporated within two distinct payloads: the Space Technology Research Vehicle-2 (STRV-2) and the Compact Environmental Anomaly Sensor (CEASE).

"It is a very complicated, interactive suite of experiments that are basically looking at aircraft detection through medium-wave means and laser communications, which I think is one of the highlights if we can get this to work," Benedict said of the TSX-5 mission that is part of the Space Test Program at Kirtland Air Force Base, New Mexico.

STRV-2 is a $43 million research effort sponsored by the Ballistic Missile Defense Organization featuring a half-dozen experiments from both the United States and United Kingdom.

Mission patch for TSX-5. Photo: USAF

The experiment attracting the most attention is an infrared telescope designed to spot flying aircraft from space.

Built by the Defence Evaluation and Research Agency for the U.K. Ministry of Defence, the Medium Wave Infra Red (MWIR) telescope that will attempt to see a number of different British military aircraft during scheduled tests when TSX-5 flies overhead.

Researchers will employ a technique called "frame differencing" in which two satellite images of the same area -- taken moments apart -- are compared to reveal a moving aircraft below. By deducing the subtle changes between the two MWIR images, the plane can be spotted, potentially giving direction and speed information, too.

The Civil Aviation Authority will assist in the tests by verifying the location of aircraft in U.K. airspace.

If successful, designers of future military satellites could use the detection technology to protect national security, and the telescope's new cooling system could be beneficial to other remote sensing spacecraft.

"The smaller, lighter and cheaper detection technologies being demonstrated on this mission will allow future satellites to be smaller in size," said Chris Dorn, MWIR operations manager. "This raises the possibility of launching multiple small satellites 'on demand' to deal with a future political, military or disaster situation."

Instead of deploying one large conventional satellite, a fleet of smaller craft would "provide for more frequent re-visits, while launching on demand ensures that the assets do not deteriorate in space before they are required," Dorn said.

This experiment requires TSX-5 be placed into a rather unusual orbit for its planned 6-month mission, which could be extended to one year.

The craft will circle around Earth in a highly elliptical orbit ranging from a low point, or perigee, of 221 nautical miles and high point, or apogee, of 994 nautical miles, inclined 69 degrees to either side of the equator.

"What we would like to have is a perigee over the U.K. (during) the summer months," Benedict explained. "With this unique orbit we have a low perigee over the U.K. where we can take our pictures with MWIR and the high apogee gives us more time to download the data."

The other major objective of TSX-5 is testing LASERCOM, a satellite-to-ground communications link using laser. It will work in concert with the telescope to relay the infrared images to Earth. This cutting edge demonstration has never before been attempted from an orbiting satellite, Benedict said.

The TSX-5 spacecraft. Photo: USAF

If the communications link works, the 35 to 50 megabyte image files will be transmitted swiftly via LASERCOM's one gigabyte downlink stream. However, should LASERCOM not function properly, there is a backup way of relaying the telescope data to Earth, Benedict pointed out.

"The future applications are just unlimited for communications from space if you are talking about one gigabyte downlink...and this could be fit on to other satellites," Benedict said. "With satellites nowadays, the downlink rate is very slow, very sluggish. This would help us in the future to increase that downlink."

In addition, the STRV-2 module carries other experiments including a system that will damp out any vibrations aboard the spacecraft to improve the telescope's picture taking; tests to examine the space environment around the satellite and prove all-composite structures can survive the riggers of spaceflight.

The second payload, CEASE, is a warning system of sorts that will detect electrically-charged particles and radiation in the area around the satellite, which can be harmful to the craft. The Air Force Research Laboratory sponsors the $4 million CEASE.

Satellite testbed to aid future craft
TSX-5 is the sixth in a series of the Air Force's Space Test Platform missions, following STEP-0 through 4. The program has dropped the STEP name in favor of Tri-Service Experiments because of the various branches of the military that participate in the missions.

Like its earlier predecessors, the TSX-5 mission is inherently risky because it is purely experimental. But it will serve as a pathfinder to prove the new technologies are sound before being used on more expensive satellites in the future.

"We are in the experimental business, we are research, test and development," Benedict said. "The payoff is very large compared to the risks we take and that is why do these types of experiments."

TSX-5 was built by Orbital Sciences, which is also conducting the launch for a total of $30 million.

"I think there will be joy in Mudville once this thing is launched. There are a lot of people that have been working on this for many years and they are ready to see it go."