Five large
parabolic (dish) antennas are located at the Goldstone site to handle the workload, since at any given time the DSN is responsible for maintaining communication with up to 30 spacecraft. The antennas function similarly to a home
satellite dish. However, since the spacecraft they communicate with are much farther away than the
communication satellites which home satellite dishes use, the signals received are much weaker, requiring a larger aperture antenna to gather enough radio energy to make them intelligible. The largest, a 70-meter (230 ft)
Cassegrain antenna, is used for communication with space missions to the outer planets, such as the
Voyager spacecraft, which, at 21.5 billion kilometers, is the most distant manmade object from Earth. The radio
frequencies used for spacecraft communication are in the
microwave part of the radio spectrum;
S band (2.29–2.30 GHz),
X band (8.40–8.50 GHz) and
Ka band (31.8–32.3 GHz). In addition to receiving radio signals from the spacecraft (
downlink signals), the antennas also transmit commands to the spacecraft (
uplink signals) with high power
radio transmitters (80 kW) powered by
klystron tubes. A major goal in the design of the station is to reduce interference with the weak incoming downlink radio signals by natural and manmade
radio noise. The remote
Mojave Desert location was chosen because it is far from manmade sources of radio noise such as motor vehicles. The
RF front ends of the
radio receivers at the dishes use
ruby masers, consisting of a bar of
synthetic ruby cooled by
liquid helium to 4.5 K to minimize the noise introduced by the electronics. When not needed for spacecraft communication, the Goldstone antennas are used as sensitive
radio telescopes for astronomical research, such as mapping
quasars and other
celestial radio sources;
radar mapping planets, the
Moon,
comets and
asteroids; spotting comets and asteroids with the potential to strike Earth; and the search for ultra-high energy
neutrino interactions in the Moon by using large-aperture
radio antennas. ==History==