[meteorite-list] Creating a Better Transmission System for Deep-Space Applications

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Oct 25 12:23:56 2005
Message-ID: <200510251622.j9PGMY311832_at_zagami.jpl.nasa.gov>

http://www.eurekalert.org/pub_releases/2005-10/agu-cab102405.php

Public release date: 24-Oct-2005

Contact: Harvey Leifert
hleifert_at_agu.org
202-777-7507
American Geophysical Union <http://www.agu.org>

Creating a better transmission system for deep-space applications

Recent advances in wireless computing technology could improve
deep-space missions like asteroid research and remote spacecraft
operations by changing the way signals are sent from Earth. A new method
designed to effectively deliver commands and instructions using hundreds
of millions of tiny transmitters linked together could also free the
giant satellite dishes currently used to send and receive the long-range
information for other applications. A research paper describing the
scheme for relatively simple high-power transmitters will be published
in the October issue of Radio Science, a journal of the American
Geophysical Union.

The technique is based on a principle known as a phased array, a method
to align a number of mini-transmitters alongside one another and direct
their combined beam into the sky. Such a system has previously been used
for military radar technology, but has only recently become cost
effective for civilian use because of improvements in consumer computing
technology, according to the paper authored by Louis Scheffer at Cadence
Design Systems. He indicates that the advantages from so many individual
transmitters, using designs similar to cell phone technology, could
include improved reliability and efficiency over currently used systems
while reducing the transmission costs associated with the mammoth
satellite dishes. Overall, he suggests that the net result could be
significantly lowered costs for space communications, more data from
science spacecraft, and an increase in planetary and deep-space research
that requires remote signals.

Currently, planetary radars and distant spacecraft communications need
transmitters with extremely high power, which has been accomplished by
combining a strong microwave source with a large reflective antenna.
This is now done with giant satellite dishes mechanically steered to a
point in the sky. NASA's Goldstone radar, for example, the agency's
sensitive, deep-space analysis radar, uses a 500 kilowatt transmitter
and a 70-meter [230-foot] reflector for tracking asteroids that may
collide with Earth. The large antenna is focused on only a small point
in space at a time, and must be adjusted--and occasionally shut
down--due to changing weather conditions. In addition, Scheffer points
out that while almost all of the world's largest antennas are used to
both send and receive, the powerful transmissions severely hinder their
ability to detect faint signals from space.

"Imagine trying to listen for a whisper while you are shouting,"
Scheffer said. "Also, these antennas are incredibly busy, so only a
small fraction of the possible science gets done."

He proposes a large, flat array of low-power transmitters printed on a
number of circuit boards and attached to an unmoving infrastructure on
the ground, controlled by computers, which can deliver an enormously
powerful beam in any direction, or even multiple directions at once. The
paper outlines the requirements of a new system that would offer
enhanced reliability, since a single failure would not affect the
overall signal, and improved maintenance costs because of its lack of
moving parts and weather resistance. The system Scheffer proposes is
designed solely to transmit, as is needed for planetary radar and
spacecraft control. The transmitters would also allow existing antennas
to operate in a more efficient receive-only mode.

If available mass-production manufacturing techniques used for
electronics can be assumed for the centimeter-sized chips, a transmitter
similar to the Goldstone radar could be constructed for nearly
one-quarter the cost, Scheffer reports. He notes that the significant
amount of research and work done in the field of phased array radars
renders the development of such a system plausible, though no previous
applications to earth and space sciences have been studied. He further
suggests that as computer chip technology continues to improve,
additional wavelength and smaller antennas are possible to further
improve the systems.

The first possible application would likely be for spacecraft command
and asteroid research to observe objects that may pose a threat to
Earth. A more speculative application, according to Scheffer, is that
sending powerful signals to distant stars is easier and cheaper than
previously thought. This dramatically reduces the cost of potential
interstellar transmissions, such as searched for by SETI.

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Received on Tue 25 Oct 2005 12:22:33 PM PDT