The Pentagon’s Office of Force Transformation is promoting the development of a common spacecraft frame that might someday be mass produced to reduce the cost of a proposed new approach to battlefield reconnaissance that calls for building and storing imaging satellites until they are needed by commanders.

The common satellite platform — or bus, as it is called — could fly in space for the first time as the backbone of an experimental imaging spacecraft called TacSat 3, according to U.S. Air Force Col. Jay Raymond, a strategist in the Office of Force Transformation.

Meanwhile, the Naval Research Laboratory (NRL) in Washington and the Johns Hopkins Applied Physics Laboratory in Baltimore are leading an industry and academic consortium that is developing a more advanced platform prototype for TacSat 4. The consortium started work in late March, said Mike Hurley, head of the spacecraft development section at NRL.

Congress has added money to the White House budget request in recent years to support the goal of storing satellites and instruments and launching them in response to tactical needs.

Congress added $20 million for the common platform work in 2005 and appears poised to add money in 2006 as well. The House Armed Services Committee added $30 million specifically for the common platform effort in its markup of the 2006 Defense Authorization Act. The Senate Armed Services Committee added $30 million for responsive payload work including the common platform.

The Office of Force Transformation began working on the concept of responsive satellites in 2003 with the goal of conducting a series of tactical satellite experiments that would cost about $15 million each.

The first of those experiments, TacSat 1, will test the ability of U.S. Pacific Command to control a low-power imager developed by NRL.

TacSat 1 had been scheduled to launch in January 2004 on the inaugural flight of Space Exploration Technologies Corp.’s Falcon 1 rocket, but the date has slipped several times due to issues uncovered with the vehicle during pre-launch testing.

The TacSat 1 launch is now slated for late July or August, following the launch of a Titan 4 rocket from Vandenberg Air Force Base, Calif. The Pentagon plans to follow TacSat 1 with the launch of TacSat 2, which will feature a more-capable imager, about six months later, Raymond said. Future launches in the series may take place on an annual basis, he said.

TacSat 3 will feature a hyperspectral imager developed by the Air Force Research Laboratory and the U.S. Army. The imager would focus on land targets, according to an information paper written by Raymond, Hurley and other officials involved with the TacSat program. The paper, titled “A TacSat Update and the [Operationally Responsive Spacelift/Joint Warfighter Space] Standardized Bus,” was distributed at the 3rd Responsive Space Conference in Los Angeles in late April.

TacSat 3 will incorporate more input from the U.S. armed services about the capabilities they would like to see tested, Hurley said. The Air Force, Army, Marine Corps and Navy all have a say in the payload selection on the TacSat series beginning with this experiment, he said.

The Pentagon is in the early phases of planning and selecting a payload for the fourth TacSat experiment, which would feature an improved prototype of the common platform, Hurley said.

The Naval Research Laboratory and the Johns Hopkins Applied Physics Laboratory are leading an industry and academic consortium that is developing the platform prototype for TacSat 4 and kicked off work in late March, he said.

The consortium’s work is also intended to generate a payload design guide for use with the common platform, according to the information paper. The military has developed similar guides in the past for unmanned aircraft that can host a variety of payloads.

The work on the platform for TacSat 4 is expected to form the basis for the purchase of a batch of perhaps five platforms for future payloads, according to the paper. The Air Force Space and Missile Systems Center in El Segundo, Calif., would lead the purchase of those platforms.

The price of small satellites such as those in the TacSat series will be significantly affected by how many the military buys, according to the information paper. Buying about 10 annually could keep the cost at an attractive level, according to the paper.

Agreement among the military services and NASA on a common platform could help drive down cost through the purchase of common hardware, according to the paper.