Orbital Sciences Corporation is handling launch integration for the Orbital/Suborbital Program, whose purpose is to achieve low-cost spacelift for small satellites. The program uses surplus Minuteman II solid rocket motors and upper stages derived from Orbital's Pegasus rockets.

Satellite Classifications

Satellites are classified according to weight. Picosats are under one kilogram (2.2 kilograms equal a pound), while nanosatellites range from 1 to 10 kilograms. Other classes are microsats, 10 to 100 kilograms; small sats, 100 to 1,000 kilograms; and standard satellites, 1,000 kilograms or more. The smallest category envisioned is the femtosat, less than one-tenth of a kilogram, a satellite that would handle very simple missions.

Tethering

The two orbiting picosats are to be tethered because they will communicate via micropower radios. The tether will keep them within range of each other for crosslink purposes. In addition, the tether contains thin strands of gold wire to facilitate radar tracking by U.S. Space Command. Concepts for the future involve optical communication via fiberoptic tethers and other cluster architectures for miniature satellites for which experience with tethers is useful.

Testing MEMS

The mission represents one of several programs for systematic testing and use of MEMS in space to be designed and implemented by The Aerospace Corporation.

In another program, Aerospace researchers and colleagues at other organizations are analyzing data from MEMS devices brought back from the space shuttle Columbia July 27 and are making plans for a MEMS mission to the International Space Station.

Nanosatellites

The picosat mission is helping to lay the groundwork for nanosatellite missions. Mass production using semiconductor technology and incorporating high-level building blocks called application-specific integrated microinstruments, or ASIMs, a description coined by Robinson, would characterize nanosatellite architecture and assembly.

ASIMs comprise MEMS and related electronics subsystems used to form standalone capabilities. They can be integrated to create various types of ultrasmall instruments, components and subsystems and -- ultimately -- complete systems and miniature satellites.

"The use of this technology for low-cost, reliable, integrated space systems applications is inevitable," Robinson said.

Future space architectures include cooperative constellations, sparse aperture antennas, local swarms of nanosatellites, inspection and service missions, and extremely flexible launch-on-demand options, which include gun and balloon-assisted launches.