Creating a Better Transmission System for Deep-Space Applications(Forwarded)

American Geophysical Union

Contact:
Harvey Leifert, +1 (202) 777-7507

For Immediate Release: 24 October 2005

AGU Release No. 05-37

Creating a Better Transmission System for Deep-Space Applications

WASHINGTON -- 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 implication, according to Scheffer, is that the
technology could enhance the range for the Search for Extraterrestrial
Intelligence (SETI) program and allow it to search for fainter signals
over a more extensive range than was previously economically possible.

The research was funded through Cadence Design Systems.

Title: "A Scheme for a High-Power, Low-Cost Transmitter for Deep-Space
Applications"

Author: Louis K. Scheffer, Cadence Design Systems, San Jose, California.

Citation: Scheffer, L. (2005), A Scheme for a High-Power, Low-Cost
Transmitter for Deep-Space Applications, Radio Sci., 40, TBD,
doi:10.1029/2005RS003243 .

Contact information for author:
Louis Scheffer, +1 408 944-7114