A small U.S. space company is developing tiny experimental satellites designed to detect and track the launch of ballistic missiles beginning shortly after take-off.

The Pentagon had planned to deploy a constellation of standard-sized satellites to perform these tasks, but that effort was scaled back to research and development work in 2002.

Poway, Calif.-based SpaceDev won a five-year contract worth $43 million in March 2004 to develop the Microsatellite Distributed Sensing demonstration.

A quarterly financial report filed by SpaceDev last June stated that the project involves the design, construction and operation of a cluster of three tiny satellites flying in formation for boost phase and mid-course tracking to support national missile defense. The satellites’ design includes a sensor built by the Space Dynamics Laboratory in Logan, Utah.

Jim Benson, SpaceDev’s founder and chief executive officer, declined to discuss the project’s details.

The Defense Department Space Experiments Review Board ranked the Microsatellite Distributed Sensing demonstration at number 14 on its priority list for space demonstrations seeking launch space last fall.

The Pentagon had planned to begin launching a constellation of low Earth orbit satellites for the same purpose called the Space Based Infrared System (SBIRS) Low in 2007, but scaled the effort back due to concerns about cost, schedule and effectiveness.

Current plans for that effort, now known as the Space Tracking and Surveillance System (STSS), call for the launch of two demonstration satellites, with less than $1 million requested in 2006 for the early work for an operational constellation that could begin launching in 2012, according to a Pentagon official.

The Defense Department already operates a constellation of missile warning satellites called the Defense Support Program, and plans to launch a follow-on system called SBIRS High in 2008.

However, the SBIRS High satellites are not particularly well suited for boost phase detection because they are in geostationary orbit 36,000 kilometers above the equator. There also are other elements of their sensors’ design that makes it difficult for them to pick up missile launches fast enough to cue systems that could intercept the targets during their boost phase, according to a source involved with the effort.

Missile defense advocates believe that the boost phase can offer the best chance for a successful intercept because the target rocket is unlikely to be able to deploy sophisticated countermeasures at that point in its flight.

Another advantage of boost phase defense systems is that they provide an opportunity to destroy enemy missiles before midcourse systems take their shot.

The Pentagon is developing two systems that could intercept missiles in their boost phase — a new rocket and an aircraft equipped with a high energy laser.

The tiny satellites under development at SpaceDev use a different method of spotting and tracking missiles than STSS, according to sources involved with the effort. STSS uses infrared sensors that zone in on the heat from a missile launch, while the microsatellites will use less-expensive optical sensors, the sources said.

Deployment concepts for the microsatellites also could point the way towards an operational system less expensive than envisioned under the SBIRS Low program, which Congress believed could have cost more than $20 billion. SBIRS Low was intended to provide global coverage, but an operational architecture with the microsatellites could involve placing them over specific areas of concern, according to the sources involved with the program.

Program officials hope to explore methods of placing the microsatellites in low orbits that could give them the longest possible looks at particular areas, the sources said. This could involve placing them in elliptical orbits, the sources said.

The Pentagon also hopes to save money with the microsatellites by narrowly focusing on their ability to detect and track missiles, the sources said. The Pentagon had planned to assign a variety of other missions, including technical intelligence, to the SBIRS Low satellites, which added to their complexity and drove up the cost, the sources said.

Program officials also hope to use as much commercially available equipment as possible with the microsatellites to keep their cost low, the sources said.