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