An experimental on-orbit rendezvous spacecraft launched by the U.S. Air Force April 11 will begin conducting up-close inspections of inactive satellites and spent rocket stages in six to eight weeks in a mission that critics charge is a prelude to placing weapons in space.

Some arms control advocates say the $80 million XSS-11 satellite — launched from Vandenberg Air Force Base, Calif., aboard an Orbital Sciences Corp.-supplied Minotaur rocket — is intended to demonstrate anti-satellite capabilities, a charge the Air Force denies.

Vernon Baker, XSS-11 program manager at the Air Force Laboratory’s Space Vehicles Directorate at Kirtland Air Force Base, N.M., said the intent is to pave the way for making on-orbit inspections for diagnostic purposes. The Space Vehicles Directorate built the satellite with Lockheed Martin Space Systems of Denver.

According to an article posted on the Air Force’s Web site, XSS-11 technology could one day help NASA collect samples of rocks and soil from Mars and bring them back to Earth.

In an April 15 interview, Baker added that Air Force officials have talked with NASA about applying lessons learned from XSS-11 to the development of tiny spacecraft that could be deployed from the space shuttle for diagnostic purposes.

The XSS-11 is a more sophisticated spacecraft than its predecessor, XSS-10, Baker said. The XSS-10 experiment, conducted in January 2003, featured a tiny satellite that app r oached the rocket hardware that carried it into space and took video imagery that was sent directly to ground-receiving stations.

The XSS-10 satellite, based on hardware built by Chicago-based Boeing Co. and assembled by the Air Force Research Laboratory, was designed to operate for about 24 hours, Baker said. XSS-11, by contrast, is designed to conduct experiments for at least one year, and can operate in a far more autonomous manner, he said.

At roughly 140 kilograms and about the size of a household dishwasher, XSS-11 is the smallest satellite ever built by Lockheed Martin, said Kevin Rummell, the company’s XSS-11 program manager.

Baker acknowledged that XSS-11 will demonstrate technologies for military space surveillance — monitoring the orbital environment — but rejected the notion that it is intended to lay the ground work for anti-satellite weapons.

Jeffrey Lewis, a research fellow in the Advanced Methods of Cooperative Security program at the University of Maryland in College Park, believes spacecraft capable of closing in on other orbital objects could be used to destroy enemy satellites.

Lewis operates a Web site called that features links to several documents that he says shed light on the anti-satellite nature of the XSS-11 mission.

One such document is a paper titled, “Military Microsatellites: Matching Requirements and Technology,” which was based on a study conducted in 1999 by the not-for-profit research firm Analytic Services Inc., or ANSER, on behalf of Air Force Space Command.

The paper, published by the American Institute of Aeronautics and Astronautics and distributed at the organization’s Space 2000 Conference & Exposition, in Long Beach, Calif., said the “single strongest recommendation of this report is the deployment, as rapidly as possible, of XSS-10-based satellites able to intercept, image and if needed, take action against a target satellite.”

Lewis noted that the XSS program has roots in Clementine-2, an asteroid-intercept mission conceived by the predecessor to the Pentagon’s Missile Defense Agency in the 1990s. In 1997, the administration of then-U.S. President Bill Clinton cited concerns that Clementine-2 would violate prohibitions against space-based interceptors in the 1972 U.S.-Soviet Anti-Ballistic Missile Treaty and killed the project using the line-item veto. Both the line-item veto and the Anti-Ballistic Missile Treaty have since been scrapped.

Lewis and other XSS program critics say they have no problem with the concept of on-orbit inspection, but are concerned that developing anti-satellite weapons will create a new arena for warfare and cause a proliferation of orbital debris that could indiscriminately damage or destroy satellites.

Meanwhile, the XSS-11 launch was the third orbital mission for the Minotaur rocket, which is based on Minuteman ICBM motors and hardware from the Pegasus rocket built by Orbital Sciences. The Dulles, Va.-based company provides Minotaur vehicles for both orbital and suborbital missions under contract to the Air Force.

Three more Minotaur space-launch missions are scheduled, and new versions of the vehicle are being developed for use as targets by the Missile Defense Agency, according to Orbital Sciences spokesman Barry Beneski.

The next orbital mission, scheduled for July, will deploy the STP-R1 research satellite for the Air Force.

A Minotaur also is slated to loft the Missile Defense Agency’s Near Field Infrared Experiment, another satellite that has been flagged by arms control advocates as a possible demonstration of space-weaponry.

The third scheduled Minotaur space-launch mission will deploy the Constellation Observing System for Meteorology, Ionosphere and Climate . The six-satellite constellation is a joint effort between the University Corporation for Atmospheric Research of Boulder, Colo., and Taiwan’s National Space Program Office. The constellation will perform weather prediction, climate research and solar storm monitoring.

Orbital also is pushing the Minotaur as an option for meeting the Pentagon’s anticipated need for responsive space lift, a term that refers to rockets that can be launched quickly to meet various near-term military contingencies. “The Minotaur is a good low-cost option for government satellites,” Beneski said. “Given advanced planning it can be very responsive to government needs.”