• Elimination of labor-intensive assembly steps (welding, wiring cable harnesses, and so on).
• Automated testing of systems and subsystems.
• Paperless documentation of designs, fabrication processes, and testing.

Semiconductor batch-fabrication techniques enable us to produce low-power digital circuits, low-power analog circuits, silicon-based radio frequency circuits, and MEMS, such as thrusters and acceleration sensors, on silicon substrates. By exploiting these fabrication techniques, as well as by developing laser-based techniques, we will be able to mass produce highly integrated satellites for a number of applications. These silicon satellites are an assembly of thick single-crystal silicon wafers that are monolithic elements (i.e., wafer-scale integrated systems) or ''circuit boards" that function as multichip modules (MCMs). The MCM approach is better for near-term, low-volume applications, whereas wafer-scale integration is better for longer-term, high-volume (thousands of units per production run) applications. Silicon satellites can range in mass from picosatellites (1 mg to 1 g mass), through nanosatellites (1 gm to 1 kg mass), to highly capable microsatellites (1 kg to 100 kg mass) that perform various missions with lifetimes ranging from a few days to longer than a decade.

Most spacecraft systems and subsystems can be manufactured on silicon substrates. The Command and Data Handling (C&DH) system, the "brain" of any satellite, is composed already of standard silicon-based digital electronics. The challenge now for silicon satellite design is to provide on-orbit radiation tolerance for silicon shielding thicknesses from 1 mm through 1 cm. This can be achieved by limiting orbit altitudes and inclinations, modifying transistor cell layouts (i.e., edgeless transistors), or incorporating radiation-hard process technologies, such as silicon-on-sapphire.

Silicon satellites will need radio frequency output power levels of between 1 mW and several watts at frequencies of between 500 MHz and tens of GHz. Today's silicon communications circuit technology, driven by the explosive growth in wireless personal communications systems, can be adapted readily for satellite communications from very high frequency (VHF; approximately 100 MHz at the bottom end) through S-band (up to 2.7 GHz). Higher frequencies will require gallium-arsenide substrates, but recent advances in high-resistivity silicon and silicon-germanium (SiGe) technology may allow all-silicon design for operation of up to 40 GHz.

MEMS technology is another enabling technology for silicon satellites. MEMS adds "muscle" and new sensing capability, allowing silicon satellites to perform the functions of larger traditional satellites. Guidance, navigation, and control (GN&C) functions will require micromachined sun sensors, Earth sensors, star sensors, accelerometers, gyros, thrusters, and/or magnetic torque rods. Accelerometers and gyros have been demonstrated already in the laboratory; the challenge is to improve their accuracy and/or performance to match more stringent spacecraft requirements. The Charles Stark Draper Laboratory