Biomedical Engineering Reference
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ary 26, 2000, followed by two more on July 29, 2000. They served as inexpensive
on-orbit testbeds for DARPA-sponsored MEMS RF switches and low-power RF
networking technologies. Nano- and picosatellites are ideal for inexpensive, fast
turnaround missions; the DARPA picosatellites were designed, fabricated, and
tested within 6 months. Picosatellite development in the United States is spon-
sored by DARPA and AFRL under the MEMS-based Picosat Inspector program. A
number of flight demonstrations with increasing sophistication (MEMS inertial nav-
igation and propulsion) will evolve into a picosatellite inspector that can be ejected
from a host satellite.
CMOS, MEMS, and related fabrication techniques have provided small, low-
power sensors and imaging arrays on silicon dice that can be utilized for attitude
determination. The Honeywell HMC1023 three-axis magnetic sensor, for example,
can fit on a U.S. dime yet has a minimum detectable field of 85 microgauss, which
is more than sufficient to provide spacecraft orientation to within a degree with
respect to the Earth's local magnetic field. CMOS imagers such as the Agilent
HDCS-1020 active pixel imaging chip could readily be adapted for use in an imag-
ing Sun sensor with 352
288 pixel resolution; it could provide better than 1/3-
degree resolution over a 90-degree field of view. Swapping the CMOS photodiode
structure with polysilicon-aluminum micro-thermocouples, also available in the
basic CMOS process, would result in a thermal imaging system that could detect
the 300 K Earth against the 3 K background of space for use in an Earth horizon
sensor.
2
Nanosatellites can be fabricated using current techniques, but capable picosat-
ellites and smaller spacecraft will require higher levels of integration. System-on-a-
chip technologies, high-speed serial interfaces and networking, and increased
device density due to better packaging (e.g., flip chip-on-a-board) will enable cur-
rent-generation microsatellite electronics to fit within a cubic inch. Related attitude
sensors, MEMS inertial sensors, and propulsion systems could fit within a similar
volume for some applications, like the satellite inspector. Even smaller volumes
will be possible as IC device densities continue to improve.
AFRL currently has an exploratory program with three universities (Arizona
State University, the University of Colorado, and New Mexico State University) to
develop and test a cluster of three next-generation, toaster-sized nanosatellites for
launch from the space shuttle for operation in a distributed mode. Potential advan-
tages for such nanosatellite distributed arrays include reduced launch costs, in-
creased reliability (losing one satellite would not preclude use of the array), and
more rapid system development cycles. The really significant surveillance game-
changer would be a cluster of nanosatellites functioning in a manner that mimics
an antenna miles in diameter.
×
1
Underwood, C., V. Lappas, G. Richardson, and J. Salvignol. 2002. SNAP-1-Design, con-
struction, launch and early operations phase results of a modular COTS-based nano-satellite.
Pp. 69-77 in Smaller Satellites, Bigger Business? Concepts, Applications and Markets for
Micro/Nanosatellites in a New Information World. Boston, Mass.: Kluwer Academic.
2
Janson, S.W. 2002. Nanotechnology—Tools for the satellite world. Pp. 21-30 in Smaller
Satellites, Bigger Business? Concepts, Applications and Markets for Micro/Nanosatellites in a
New Information World. Boston, Mass.: Kluwer Academic.
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