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Deep Space Network

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New for July 2019:  In January 1958, the United States launched its first satellite, Explorer 1, with a Jupiter C rocket developed under the direction of Dr. Wernher von Braun. Jet Propulsion Lab (JPL) was contracted by the Army to track the new satellite. JPL did this by deploying portable radio tracking stations in Nigeria, Singapore, and California. When the Army launched Explorer 1, these stations received telemetry and helped mission controllers plot the spacecraft’s orbit. Incidentally, Explorer 1 launched the day the Unknown Editor was born. Thus, when we talk about Space, we often hear "In the Year of the UE" to give historical context.

Later that year, NASA was formed, and JPL became part of the new agency.  They set up the Deep Space Network (DSN) as a separately managed and operated communications facility so that each flight project wouldn't have to build and operate its own specialized space communications network.  

 

The Deep Space Network: 50 Years of Interplanetary WiFi  

Today, the giant radio antennas of the Deep Space Network support interplanetary spacecraft missions and provide radar and radio astronomy observations. The DSN consists of three facilities spaced equidistant from each other – approximately 120 degrees apart in longitude – around the world. These sites are at Goldstone, near Barstow, California; near Madrid, Spain; and near Canberra, Australia. Each complex houses one massive 70-meter (230-foot) diameter antenna, several antennas at  34 meters across, and one smaller 26-meter (85-feet) diameter antenna that is used primarily to track Earth-orbiting spacecraft.

70 meters

From the DSN website:

The 70-meter antennas are the largest and most sensitive DSN antennas, capable of tracking a spacecraft traveling tens of billions of miles (kilometers) from Earth.Weighing in at nearly 2,970 U.S. tons (2.7 million kilograms), the surface of this reflector is maintained to a precision of within half an inch (one centimeter) across its entire 41,400 square foot (3,850-square-meter) surface. This precision is crucial – even minor deformations would interfere with the antenna’s operations. A hydrostatic bearing assembly supports the antenna’s tremendous weight on three pads, which glide around a large steel ring on a film of oil the thickness of a sheet of paper.

34 meters

Each DSN complex also has multiple 34-meter (111-foot) diameter antennas.  The 34-meter antennas come in two types: a high-efficiency antenna and beam waveguide antenna. The beam waveguide antenna incorporates five high-precision radio frequency mirrors that reflect radio signals along a tube from the antenna to a room below ground. This design allows sensitive electronics to be in a climate-controlled equipment room instead of outdoors, at the center of the antenna dish. This configuration also simplifies maintenance and modification of the equipment as new technologies are developed.

Each of the three sites has one high efficiency antenna.  In addition, Goldstone has three 34-meter diameter beam waveguide antennas, Madrid has two, and Canberra has one.

26 meters

A special mount (an X-Y mount) allows these antennas to point low on the horizon to pick up the fast-moving Earth orbiters as soon as they rise into view. The maximum tracking speed is three degrees per second, which is the equivalent of tracking one full rotation of an Earth-orbiting spacecraft every two minutes.

The 26-meter antennas were originally built to support the Apollo missions, which sent human explorers to the moon between 1967 and 1972.

Frequency assignments

DSN uses S, X, K and Ka-band to communicate. Spacecraft distance is measured by turn-around time of a signal. Spacecraft velocity is measured by the doppler shift of the uplink.  The signal is known to within 1Hz. 

Frequency allocations in MHz
Band Designation Deep Space Bands (for space stations more than 2,000,000 km from Earth) Near Space Bands (for space stations less than 2,000,000 km from Earth)
up-link (Earth to Space) down-link (Space to Earth) up-link (Earth to Space) down-link (Space to Earth)
S band 2 110–2 120 2 290–2300 2 025–2 110 2 200–2 290
X band 7 145–7 190 8 400–8 450 7 190–7 235 8 450–8 500
K band * * * 25 500–27 000
Ka band 34 200–34 700 31 800–32 300 * *

* = No assignment or not supported by the DSN

For more information, check out the DSN Telecommunication Design Handbook, 201, Rev B., Frequency and Channel Assignments, available at 

https://deepspace.jpl.nasa.gov/dsndocs/810-005/201/201B.pdf

LNAs

The DSN has led research in large area antennas and low noise receivers.  The LNAs are cryo-cooled, every degree Kelvin is important.

https://descanso.jpl.nasa.gov/monograph/series10/Reid_DESCANSO_sml-110804.pdf

 

 

 

 

 

Author : Unknown Editor

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