The tethered pair of "picosatellites," designed by The Aerospace Corporation under a project funded by the MEMS (microelectromechanical systems) Technology Office of the Defense Advanced Research Projects Agency (DARPA), were launched Wednesday from Vandenberg Air Force Base, Calif., aboard a new Air Force booster for small satellites.

The tiny DARPA/Aerospace Corp. satellites are the smallest such satellites with active capabilities ever to be launched.

Each of the DARPA/Aerospace Corp. picosats is smaller than a deck of cards and weighs less than one-half pound. These picosats are platforms for validating MEMS and also will demonstrate how mass-produced nanosatellites will operate in constellations in the future.

For satellites of this size, the DARPA/Aerospace Corp. picosats have unprecedented features and capabilities. For example, in addition to validating MEMS technology, they are able to communicate with each other and a third picosatellite at the ground station, as well demonstrate the principles of miniature satellites flying in a constellation. Another distinctive feature is the use of patch antennas which allow for omnidirectional signals between the picosats and limit the "envelope" of space they occupy.

They were housed in the OPAL mother satellite built by Stanford University students and taken aloft by a converted Air Force Minuteman II ballistic missile. The historic mission thus combines proven missile technology with pioneering satellite technology. The booster is formally called the Orbital Suborbital Program Space Launch Vehicle. It combines rocket motors from the Minuteman II and Pegasus XL launch vehicles. Minotaur is the booster�s informal name.

OPAL, which stands for Orbiting Picosat Automated Launcher, was one of several small satellites aboard the OSP/Minotaur launch vehicle. OPAL carries a total of six picosats, four built by students and amateur space enthusiasts. OPAL is being tracked by the US Space Command's Space Surveillance Network based at Colorado Springs.

After the OPAL orbit is precisely determined and the satellite is over the ground station operated by SRI International at Menlo Park, engineers from The Aerospace Corporation will request that student operators at Stanford�s Space Systems Development Laboratory transmit a command to eject the DARPA/Aerospace Corp. picosats.

Meanwhile A team of engineers from The Aerospace Corporation visited Stanford Thursday to assist students in troubleshooting procedures and set up for communicating with OPAL.

Team leader Steve Hast said that because OPAL was in "a slightly different orbit than predicted," release of the picosats will be delayed. They originally planned for a release of the DARPA/Aerospace Corp. picosats from OPAL Saturday evening with the ejection of four student-built picosats to follow.

Because OPAL is a "tumbler," that is, has no attitude control, it is uncertain in which direction the DARPA/Aerospace Corp. picosats will be ejected at the time of release either Sunday morning or evening. This is where support provided by the Space Surveillance Network is crucial. The network will track the DARPA/Aerospace Corp.

picosats with the help of thin gold strands inserted in the tether that will keep the two picosats close enough to communicate via a micropower radio. The gold strands will help make the satellites locatable by radar.

The radios were designed by Rockwell Science Center, Thousand Oaks, Calif., with funding by DARPA and in collaboration with UCLA. They are based on digital cordless telephone technology.

When the DARPA/Aerospace Corp. satellites are released from OPAL they will begin transmitting a beacon signal that Aerospace engineers at the Menlo Park ground station will attempt to pick up with a 50-meter dish. Distinguished Engineer Ernest Y. Robinson of The Aerospace Corporation said Space Surveillance Network tracking of these picosatellites is important, "because they are a harbinger of emerging technology associated with all kinds of fully functional miniature satellites (which will present tracking challenges)."

Robinson said he was "elated" at the OSP/Minotaur launch Wednesday because this increases the probability that a second launch of the OSP/Minotaur booster carrying an Air Force MightySat 2.1 satellite and planned for mid-June will go on schedule.

MightySat 2.1 will carry picosats designed by The Aerospace Corporation that are similar to the ones aboard the OPAL satellite. But with the more sophisticated MightySat 2.1 satellite built by the Air Force Research Laboratory at Kirtland AFB, New Mexico, an important demonstration of the capability of storing miniature satellites for later release on command will be possible.

A key feature of the picosats and of planned mass-producible nanosatellites is the use of MEMS for miniature integrated space systems. The Aerospace Corporation and other organizations have already experimented with MEMS in space. The corporation assembled a package of 30 MEMS devices�such as microthrusters, gyros, and accelerometers�for flight on the shuttle Columbia (STS-93), which returned them from space last July.

The Aerospace Corporation has been heavily involved in research into miniature satellites for a number of years and formally advanced the concept of nanosatellites at the 44th International Astronautical Federation Congress in Graz, Austria, in 1993.

Picosat Mission

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Satellite Launch To Boost DTH In India
Calcutta, India (SPX) Dec 28, 2005
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