BEIJING, Sept. 3 (Xinhuanet) -- The number of participants in the Northrop Grumman Lunar Lander Challenge was reduced from nine to seven recently when Micro-Space and a so-called "mystery team" withdrew from the competition to design, build and successfully test a new lunar lander for NASA.

William Pomerantz, director of Space Projects for the X Prize Foundation in Washington, D.C. said Friday the ninth "mystery team" has elected to withdraw from the competition. The identity of that ninth competitor has been kept under wraps -- and continues to remain so, he said, as they have requested to maintain their anonymity.

Another team ─ Micro-Space of Denver, Colorado has missed a required benchmark ─ a Team Summit ─ making them ineligible to win prize money in 2007. The team will continue their development, however, and have a presence at this year's Wirefly X Prize Cup.

The field eligible to win the 2 million U.S. dollars in Lunar Lander Challenge prizes is now at seven competitors.

The Wirefly X Prize Cup '07 Holloman Air and Space Expo is being held Oct. 27-28 at Holloman Air Force Base in Alamogordo, New Mexico.

Meanwhile, Armadillo Aerospace ─ one of the seven remaining Challenge competitors ─ reports recent success. Armadillo rocketeers pulled off new tethered flights of their vertical takeoff/landing vehicle at the Greyson county airport north of Dallas.

"This is the first time we have taken a vehicle and done back-to-back 180-second flights on the same day, with the exact same vehicle configuration, John Carmack, head of Armadillo Aerospace, said.

(Agencies)