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".


References:

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

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