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| NEWS FLASH |
February 10, 2000 |
Pint-Size
Satellites Will Soon Be Doing Giant Jobs
With half-pound birds already in orbit, a
new era in space exploration, military technology, and telecommunications is
dawning
Russia's launch of basketball-sized Sputnik I in 1957 stunned the world
and ushered in the Space Age. But Sputnik was a behemoth compared to the two
satellites that sent their first signals back to Earth on Feb. 8. If Sputnik
went "beep," these tiny birds -- smaller than a deck of cards and weighing less
than half a pound -- are going "chirp, chirp." The signals from these fledgling
spacecraft, dubbed picosats, may also be the wake-up call for a new era in
communications, defense, and space research.
The experimental
spacecraft, the tiniest ever placed in orbit, were built by Aerospace Corp. as
part of a consortium funded by the Defense Adanced Research Agency (DARPA).
Connected by a gossamer tether to keep them in radio range of each other, the
picosats are now talking to each other as well as to a third picosat on the
ground over communications systems adapted from conventional cordless
telephones.
SMALLEST SATELLITE: Picosats launched on Jan. 26
weigh less than one-half pound each and measure 4 by 3 by 1
inches
CREDIT: Aerospace Corp.
| Their builders envision a not-too-distant
day when huge, multibillion dollar satellites may have lots of company in orbit.
They'll be joined by a chorus of inexpensive, mass-produced spacecraft that can
be spewed from motherships on demand -- and even soar off into deep space. "They
are a harbinger of all kinds of miniature satellites," says Ernest Y. Robinson,
a top engineer at Aerospace, who was co-author of a seminal paper that launched
the concept of tiny spacecraft at a meeting of the International Astronautical
Federation Congress in Graz, Austria, in 1993.
Packed into a mother
satellite constructed at Stanford University called OPAL, the
picosats were lofted on a four-stage booster from Vandenberg Air Force Base on
Jan. 26. The orbiting twins epitomize the National Aeronautics & Space
Administration's goal of building spacecraft that are "smaller, lighter, and
cheaper." And they are the closest that researchers have come to creating a
"satellite-on-a-chip."
FROM THE MOTHERSAT. Picosats rely on an advanced
technology known as MEMS, for microelectromechanical systems. These systems
integrate logic circuits and mechanical devices carved from wafers of silicon.
Earthbound examples of MEMS include air-bag triggers and ink-jet printer heads.
The primary goal of the present mission is to test MEMS radio switches
made by Rockwell Science Center in Thousand Oaks, Calif., and to demonstrate
that miniature satellites can be released from a mothersat by a command from the
ground, and then operate in space. Last July, the space shuttle Columbia carried
into orbit a test package of some 30 MEMS satellite components, such as sensors
and gyroscope control systems. The tiny devices were capable of such essential
functions for any spacecraft as navigation and control, sensing, propulsion,
computation, and thermal control.
The shuttle mission was the first test
in space of a novel propulsion system designed to allow tiny satellites to
maneuver in space. The device, developed by TRW, Aerospace, and the California
Institute of Technology under a $3.5 million DARPA contract, literally puts
thousands of tiny rocket motors on a computer chip. Each thruster is a silicon
box that measures about 700 to 1,000 microns on a side and is filled with a
propellant such as those used in automotive air bags.
 
ROCKET-ON-A-CHIP: Array of 19 tiny microthrusters
(left) is drawfed by a penny. But each produces produces 100 watts of
power for an instant when they are fired -- enough energy to maneuver a
small satellite (right)
CREDIT: Aerospace Corp.,
Caltech |
Microscopic
heating elements in the boxes ignite the propellant in response to a control
signal. The burning fuel bursts the thinner outer face of the box, providing a
tiny thrust like a rocket motor. Although each rocket element can be used only
once, arrays of thousands, even millions, of thrusters might keep a small
satellite on course for a few years. The engineers estimate that almost a
million thrusters could be packed into an area of just 16 square inches.
When all the components have been tested and judged "space worthy," the
engineers intend to combine them in slightly larger satellites capable of useful
work in space. Called nanosatellites and weighing from 2 to 20 pounds, they will
be powered by solar cells and have navigational capability.
BATTLEFIELD BOTS.
The Defense Dept., of
course, sees a great potential for nanosats. Satellites packed with various
types of nanosats could be placed in orbit until the small satellites are
needed. For example, a swarm of miniature satellites could communicate with
sensors on a battlefield and convey important surveillance and tactical
information. Or they could be used to destroy incoming ballistic missiles.
But Robinson and his colleague Siegfried Janson, a senior scientist who
coined the term nanosatellite at the Graz meeting in 1993, see many other uses.
They could pick up messages as they pass over one part of the globe, then
download them to a remote receiver. Networks of nanosats configured so there's
always at least one overhead at any time could carry telephone calls and data.
Janson says nanosats communicating with 10-meter diameter ground antennas could
transmit and receive data at the rate of 1 megabit a second. And arrays of
nanosats flying in formation could function as a giant antenna. "One day we may
see nanosatellite clusters used for Internet-in-the-sky applications," he notes.
Scientific applications also abound. Even though nanosatellites will be
limited to optics up about 10 centimeters in diameter, ground resolution will be
tens of meters in the visible-light range. Agricultural, mineral, and water
resources could be mapped and monitored continuously. Various nanosatellites
could look at different parts of the visible and infrared spectrum to produce
maps.
LIKE HANSEL & GRETEL. For its part, NASA is already planning an
experiment called the Magnetospheric Constellation to use nanosats to study the
interaction of the Earth's magnetic field with charged particles from the Sun.
In addition, future planetary probes might create a communications relay back to
Mother Earth by dropping off trailing nansosat relays as they plunge into the
distant reaches of the solar system.
The satellite scientists preduct
that the first full-fledged military and commercial nanosats will be zipping
through the heavens in 8 to 10 years. The effort just got a boost from President
Clinton, who included an 84% increase in nanotechnology funding in his 2001
budget request. Of the $227 million earmarked as the National Nanotechnology
Initiative, the Defense Dept. is slated to get $110 million in funding for
projects such as MEMS -- a 57% increase over the current budget.
The
drive to make satellites ever-smaller is hardly played out. Just when we've
added picosat and nanosat to our vocabulary, along comes "smart dust." A group
at the University of California at Berkeley has begun a DARPA-funded effort to
create MEMS particles, each no more than a cubic millimeter in size, that could
be lifted for brief intervals by microthrusters to monitor weather, air quality
-- or a battlefield.
So construction of the huge orbiting International
Space Station continues, and plans are drawn for establishing human bases on the
Moon and Mars. But a large part of the future may lie with the lightweights --
minuscule spacecraft that would fit in an astronaut's pocket and perhaps be as
tiny as grains of star dust.
For More Information:
Sound file of Sputnik's beeps
Background on small
satellites
Description of MEMS
technology from Sandia National Laboratories
By Alan Hall in New
York
EDITED BY DOUGLAS
HARBRECHT
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