JPL Performs First Two-Antenna Uplink Experiment with Mars Global Surveyor

http://www.jpl.nasa.gov/news/features.cfm?feature=1057

JPL Performs First Two-Antenna Uplink Experiment
Carolina Martinez/JPL
(818) 354-9382
March 21, 2006

For the first time ever, NASA's Deep Space Network has used a pair of
smaller antennas to successfully send two simultaneous signals to a
spacecraft in deep space that were combined at the spacecraft to yield
greater signal power. Prior to this experiment, only single 34-meter
(111- foot) or 70-meter (230-foot) antennas had been used to uplink
signals. This is a significant first step for future uplink
capabilities
using multiple antennas known as arrays.

The recent experiment combined X-band signals from two 34-meter
(111-foot) antennas at the Goldstone complex near the Mojave Desert,
and
transmitted the combined signal to NASA's Mars Global Surveyor
spacecraft currently orbiting Mars. The Mars Global Surveyor spacecraft
received the combined signal, measured the combined power levels, and
verified the predicted power gain, as a result of the combining
operation.

The Deep Space Network provides the two-way communications link that
guides and controls spacecraft and returns images and other scientific
data to Earth. Currently, each Deep Space Network facility has one
antenna of 70-meter (230-foot) diameter, between two and seven 34-meter
(111-foot) antennas, and one 26-meter (85-foot) antenna. There are
three
deep-space communications complexes placed approximately 120 degrees
apart around the world: at Goldstone in California's Mojave Desert;
near
Madrid, Spain; and near Canberra, Australia. This configuration ensures
that an antenna is always within sight of a given spacecraft, day and
night, as Earth rotates.

Although previously downlink arraying has been performed, the lack of a
demonstrated ability to perform uplink arraying has limited the
potential use of antenna arrays. Antenna arrays have the potential to
create an equivalent very large antenna aperture by combining many
smaller antennas.

The successful demonstration of uplink arraying is significant because
it removes a serious obstacle to moving towards an operational arrayed
network for space communications, one that can be used for both uplink
and downlink.

For the technical write up on the experiment see:

http://deepspace.jpl.nasa.gov/dsn/features/uplink.html .