The U.S. Air Force in October selected a package that provides mobile communications services, data relay from terrestrial sensors and friendly forces tracking as the payload aboard the fourth satellite in the TacSat series, according to a Defense Department official.

The all-telecom payload for the TacSat-4 mission won out over candidates that included a radar-imaging sensor that has been pushed by the U.S. Army, said Lloyd Feldman, assistant director of science and technology in the Pentagon’s Office of Force Transformation.

TacSat 4, tentatively scheduled for launch in late 2007, also will feature the prototype standardized satellite platform that the Air Force will be able to buy in bulk and adapt to a variety of future missions, Feldman said in an interview here at the Geoint 2005 S ymposium.

The TacSat effort is a series of missions intended to demonstrate that small, low-cost satellites can be deployed quickly to meet a pressing need of commanders in a theater of operations. It is a key component of a wider initiative championed by the Office of Force Transformation known as Operationally Responsive Space.

Equipped with relatively modest capabilities, TacSat satellites are designed to operate in concert with other platforms such as aircraft and be tasked from the field using the Secret Internet Protocol Network, or Siprnet, a classified version of the Internet available to the U.S. military.

“It’s about not building a Carnegie Hall every time you want to hear some music,” Feldman said.

The data relay, or “exfiltration,” payload on TacSat 4, for example, would pick up and retransmit tactically useful data from sensors on buoys or on the ground, Feldman said.

The TacSat 1 and 2 satellites will carry imaging sensors that cover a wide area at coarse resolutions and directly cue aircraft equipped with higher-resolution sensors for a closer look and identification. Those satellites also will carry radio-signal fingerprinting devices that will enable the military to immediately identify an object, be it a boat, aircraft or ground vehicle, whenever its signals are picked up in the future.

TacSat 2 also will carry a payload that will pick up and relay signals from identification beacon signals aboard ships, Feldman said.

TacSat 3’s main payload is a hyperspectral sensor and the satellite platform will have a standardized avionics package whose development is being managed by the Air Force Research Laboratory.

The Naval Research Laboratory in Washington and the Johns Hopkins University’s Applied Physics Laboratory in Laurel, Md., are leading the effort to develop the standardized TacSat platform that will be demonstrated on the fourth mission, Feldman said. Once proven, the Air Force Space and Missile Systems Center, which procures U.S. military space hardware, could solicit bids for multiple platforms.

Feldman said the cost of these platforms, which feature standardized payload interfaces, could fall between $8 million and $5 million, depending on the quantity ordered. A study by the Massachusetts Institute of Technology’s Lincoln Laboratory found that such a platform, weighing between 100 and 200 kilograms, could fulfill 80 percent of the TacSat mission requirements, Feldman said.

Of the four TacSat missions in the pipeline, only TacSat 1, utilizing a commercial Orbcomm satellite communications platform, has a launch arranged. It is slated to fly in early 2006 aboard Space Exploration Technologies Corp.’s Falcon 1 rocket, either from Vandenberg Air Force Base, Calif., or the Kwajalein Atoll in the Pacific.

TacSat 2, which utilizes hardware leftover from the Air Force’s canceled TechSat 21 experiment, has no assigned launcher even though it is slated to launch in late 2006. The same goes for TacSat 3 and TacSat 4, tentatively scheduled to launch in early and late 2007, respectively, Feldman said.

Warren Ferster is the Editor-in-Chief of SpaceNews and is responsible for all the news and editorial coverage in the weekly newspaper, the Web site and variety of specialty publications such as show dailies. He manages a staff of seven reporters...