NYT article about teeny, tiny satellites. Sorry if already posted.
November 9, 1999
Giant Hopes for Tiny Satellites
By WARREN E. LEARY
WASHINGTON -- The concept of less being more will take on new
meaning in space next month when the Air Force launches a fleet of
tiny experimental satellites made of miniature components --
diminutive machines that could one day work together in groups to replace or
supplement larger spacecraft.
Driven by economics and the desire to approach working in space in a
different way, researchers are exploring methods to make and use midget
spacecraft -- some weighing less than a pound and hardly larger than a pack
of playing cards -- that could be used alone to perform simple tasks or flown
in formations to execute more complex ones.
Interest in tiny satellites that can
distribute the duties and risks of
working in space has grown with
advances in microtechnology that are
reducing the size of machines and
components. For example, rapid
improvements in
microelectromechanical systems, or
MEMS, are allowing researchers to
produce switches, valves, levers,
gears and other machine components
that are too small to be seen by the
human eye. Space engineers say they
are harnessing such elements to make
bantam satellites with techniques similar to those used to produce computer
chips.
"The goal is to one day build a satellite on a chip," said Dr. Siegfried W.
Janson, a senior scientist with The Aerospace Corp., a private research
organization in El Segundo, Calif. "We're talking about fully integrated
satellites that could be mass produced cheaply by the hundreds and sent into
space in groups to perform a variety of tasks."
Satellites are generally classified by weight, with standard ones weighing a
ton or more, small satellites coming in between 200 pounds and a ton, and
microsats considered those that fall between 20 pounds and 200 pounds. The
new wave of smaller satellites that engineers see for the future are so-called
nanosatellites ranging from 20 pounds down to 2 pounds, and picosatellites
that weigh in at less than 2 pounds.
Janson said he envisioned producing satellites weighing as little as half a
pound that are assembled from layered silicon wafers containing sensors,
computing power, communications systems, mechanical devices and even
micro rocket thrusters. Swarms of such satellites, launched together on
single, inexpensive rockets, could replace more expensive single satellites for
some tasks, he said, or spread out to take on entirely new roles in space.
In addition to low cost, networks composed of dozens, if not hundreds, of
inexpensive tiny satellites could offer a new standard of reliability, proponents
say. If one or several of the machines in a formation fails, others in the group
could redistribute themselves and continue performing the assigned task, they
say, something not possible with a single-satellite mission.
Peter V. Panetta of NASA's Goddard Space Flight Center in Greenbelt, Md.,
agrees, saying there is growing interest in increasingly smaller satellites and
other spacecraft. "This isn't just a fad," he said. "A lot of people see this as
the future and are working toward the technical breakthroughs to make these
things possible."
Panetta, manager of NASA's Nanosat Technology Development Program,
said the agency hoped to have a constellation of 100 nanosatellites, weighing
as little as 2 pounds each, launched by one rocket on a single mission in
2008. This approach would be ideal for science missions requiring
measurements to be taken simultaneously from many locations, he said, such
as monitoring the amount of solar radiation absorbed by, and then reflected
from, the Earth.
As a step toward the goal of flying formations of nanosats, NASA announced
in August that it would sponsor the Nanosat Constellation Trailblazer mission.
This flight of three, 40-pound microsats, scheduled for 2003, will test MEMS
technology, formation flying and methods of operating several spacecraft as
a system to pave the way for future nanosat clusters, Panetta said.
Formations of nanosats could be the only way to study certain phenomenon,
he said, such as the dynamics of the magnetosphere, the area around the
Earth that traps high-energy particles from the sun in the planetary magnetic
field. This moving, tear-shaped region extends more than 150,000 miles from
the Earth in the direction away from the sun, he said, and only a network of
satellites could constantly monitor its changes.
Dr. Mark E. Campbell of the University of Washington in Seattle recently
completed a NASA-sponsored study of possible deep space missions for
clusters of pico or nano-sized spacecraft. Among the possibilities, he said,
are teams of semi-autonomous craft that could swarm around asteroids or
comets to make measurements and then assemble themselves into a
communications array to send the results back to Earth. Another possibility is
to send a mother ship to a planet that would release orbiting picosats that
would slowly drift down through its atmosphere and send data back to Earth
via the mother craft.
"My guess is that it will take 15 to 20 years to put together a system like this,
but this is where the technology is heading," Campbell said.
Engineers also envision jobs for single midget satellites, like launching one
along with each expensive, large spacecraft. If a problem arose with the main
spacecraft, the tiny satellite buddy could detach and examine the larger ship
to help ground controllers diagnose and fix the difficulty.
To test the concept of midget satellites in space, several picosats are
scheduled to be launched into Earth orbit early next month on the inaugural
launching of a new Air Force booster rocket. The rocket, formally called the
Orbital/Suborbital Program Space Launch Vehicle but nicknamed Minotaur,
uses the first two stages of decommissioned Minuteman II intercontinental
ballistic missiles and upper stages from Orbital Sciences Corporation's
commercial Pegasus rocket. The Air Force hopes to use surplus ICBM's as a
cheap way to launch small government payloads.
Among Air Force and university payloads offered a free ride on the first flight
is the Orbiting Picosat Automated Launcher, or OPAL, built by students from
Stanford University. The OPAL mother ship is to fire off a half dozen
pico-sized daughter satellites, including a pair built by the Aerospace Corp.
and the Pentagon's Defense Advanced Research Projects Agency.
The two battery-powered satellites in this pair, each weighing about a
half-pound and slightly larger than a pack of playing cards, are to be
connected by a 100-foot tether to keep them from drifting too far apart to
communicate with one another. The satellites will spend several days
communicating with one another and with a third picosat at a ground station
to see how they operate as a system, and testing an array of experimental
MEMS radio switches.
The tether between the craft contains a gold wire to help Earth-based radar
track the tiny objects, which raises the issue of old picosats becoming space
debris that could damage other craft through space collisions.
Panetta of NASA said designers were aware of the potential problem with the
tiny, hard-to-follow spacecraft and see it as an issue to address in mission
design. One approach, he said, is to put nano-thrusters on Earth-orbiting
satellites that could be fired at the end of a mission to slow the craft enough
to fall out of orbit and burn up in the atmosphere. "You don't want the
solution to one problem to create another," he said.
Copyright 1999 The New York Times Company |
