The Deep Space Network (DSN) is the system that is used to
communicate with NASA's spacecraft which have been sent beyond Earth
orbit. The DSN also supports selected Earth orbiting satellites, radio
and radar astronomy, and other observations.
The DSN is comprised of three Deep Space Communications Complexes
(DSCC's), the Network Operations Control Center (NOCC), and several
other facilities. The DSCC's are located approximately 120 degrees away
from each other at Goldstone in California's Mojave desert in the
United States, at Robledo near Madrid Spain, and at Tidbinbilla near
Canberra Australia. The NOCC is located in building 230 at the Jet
Propulsion Laboratory (JPL).
Each DSCC has a number of Deep Space Stations (DSS's), each of
which is a high gain parabolic reflector antenna dish with steerable
azimuth and elevation, and the associated equipment such as amplifiers
and transmitters. In addition, each DSCC has a Signal Processing
Center (SPC), housing computers and other equipment, administrative
offices, and a cafeteria.
Each of the three DSCC's has one 70 meter antenna, a number of 34
meter antennas, and one 26 meter antenna. The 70 meter antennas were
originally built as 64 meter antenna's, but were upgraded to 70
meters between 1982 and 1988 to support Voyager's Neptune flyby with
an additional 2 dB per antenna.
The 34 meter antennas have changed design twice. The first antennas
were build as 26 meter antennas, and later upgraded to 34
meters. These antennas have since been dismantled and replaced by a
new 34 meter design, except for one at Goldstone, which has been
converted into an educational facility.
The DSN has seven main systems. The first of these is the timing
system, which is used to keep all of the facilities in sync with each
other. Synchronization is accomplished by tracking microsecond offsets
and comparing local reference clocks at each site with reference
pulses from GPS satellites.
The tracking system uses the Doppler shift of incoming signals and
radar to keep track of spacecraft. This information is used to help
navigate spacecraft and to infer information about the space
environment, such as gravitation in the area of a spacecraft. It is
also used to predict where antennas should be pointed and at what
frequencies they can expect signals.
The telemetry system is used by spacecraft to relay information
about themselves to their flight projects. The DSN is responsible for
decoding and forwarding telemetry data to the flight project.
The command system of the DSN is used to relay commands to
spacecraft, and functions rather like telemetry in reverse.
The monitoring system is used to keep and eye on the health of
the DSN itself. The NOCC uses monitoring information to control their
operations, and some of the data is also forwarded to flight projects
(received signal strength, for instance).
Radio science performed using the DSN involves measuring changes,
such as Doppler shift, attenuation, scintillation, rotation, in
incoming signals. This information can be used to infer the properties
of the channel that the signal has traveled through.
Very Long Baseline Interferometry (VLBI) is also done using the
DSN. This involves the monitoring of an object in space by two or more
antenna. The signals from the antennas are correlated to produce a
fringe pattern. VLBI can be used to precisely locate a spacecraft or
produce a synthetic aperture images of objects.
Future additions to the DSN may include a constellation of
satellites orbiting Mars called Mars Network (Marsnet).
As a side note, the Parkes Radio Observatory in Australia is related to the Tidbinbilla site and was the subject of a movie aptly named "The Dish".
Deep space network homepage - http://deepspace.jpl.nasa.gov/dsn/
For much more detail, see: Basics of space flight, section III, chapter 18 - http://www.jpl.nasa.gov/basics/bsf18-1.html
Pictorial history of the DSN - http://deepspace.jpl.nasa.gov/dsn/history/album/album.html