NASA Deep Space Network


The NASA Deep Space Network is a worldwide network of spacecraft communication ground segment facilities, located in the United States, Spain, and Australia, that supports NASA's interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the Solar System and the universe, and supports selected Earth-orbiting missions. DSN is part of the NASA Jet Propulsion Laboratory.

General information

DSN currently consists of three deep-space communications facilities located such that a distant spacecraft is always in view of at least one station. They are:
Each facility is situated in semi-mountainous, bowl-shaped terrain to help shield against radio frequency interference. The strategic placement of the stations permits constant observation of spacecraft as the Earth rotates, which helps to make the DSN the largest and most sensitive scientific telecommunications system in the world.
The DSN supports NASA's contribution to the scientific investigation of the Solar System: It provides a two-way communications link that guides and controls various NASA uncrewed interplanetary space probes, and brings back the images and new scientific information these probes collect. All DSN antennas are steerable, high-gain, parabolic reflector antennas.
The antennas and data delivery systems make it possible to:
  • acquire telemetry data from spacecraft.
  • transmit commands to spacecraft.
  • upload software modifications to spacecraft.
  • track spacecraft position and velocity.
  • perform Very Long Baseline Interferometry observations.
  • measure variations in radio waves for radio science experiments.
  • gather science data.
  • monitor and control the performance of the network.
Other countries and organizations also run deep space networks. The DSN operates according to the standards of the Consultative Committee for Space Data Systems, as do most other deep space networks, and hence the DSN is able to inter-operate with the networks of other space agencies. These include the Soviet Deep Space Network, the Chinese Deep Space Network, the Indian Deep Space Network, the Japanese Deep Space Network, and the ESTRACK of the European Space Agency. These agencies often cooperate for better mission coverage. In particular, DSN has a cross-support agreement with ESA that allows mutual use of both networks for more effectiveness and reduced risk. In addition, radio astronomy facilities, such as the Parkes Observatory, the Green Bank Telescope, and the Very Large Array, are sometimes used to supplement the antennas of the DSN.

Operations control center

The antennas at all three DSN Complexes communicate directly with the Deep Space Operations Center located at the JPL facilities in Pasadena, California.
In the early years, the operations control center did not have a permanent facility. It was a provisional setup with numerous desks and phones installed in a large room near the computers used to calculate orbits. In July 1961, NASA started the construction of the permanent facility, Space Flight Operations Facility. The facility was completed in October 1963 and dedicated on May 14, 1964. In the initial setup of the SFOF, there were 31 consoles, 100 closed-circuit television cameras, and more than 200 television displays to support Ranger 6 to Ranger 9 and Mariner 4.
Currently, the operations center personnel at SFOF monitor and direct operations, and oversee the quality of spacecraft telemetry and navigation data delivered to network users. In addition to the DSN complexes and the operations center, a ground communications facility provides communications that link the three complexes to the operations center at JPL, to space flight control centers in the United States and overseas, and to scientists around the world.

Deep space

Tracking vehicles in deep space is quite different from tracking missions in low Earth orbit. Deep space missions are visible for long periods of time from a large portion of the Earth's surface, and so require few stations. These few stations, however, require huge antennas, ultra-sensitive receivers, and powerful transmitters in order to transmit and receive over the vast distances involved.
Deep space is defined in several different ways. According to a 1975 NASA report, the DSN was designed to communicate with "spacecraft traveling approximately 16,000 km from Earth to the farthest planets of the solar system." JPL diagrams state that at an altitude of, a spacecraft is always in the field of view of one of the tracking stations. The International Telecommunication Union, which sets aside various frequency bands for deep space and near Earth use, defines "deep space" to start at a distance of from the Earth's surface.

Frequency bands

The NASA Deep Space Network can both send and receive in all of the ITU deep space bands—S-band, X-band, and Ka-band. Frequency usage has in general moved upward over the life of the DSN, as higher frequencies have higher gain for the same size antenna, and the deep space bands are wider, so more data can be returned. However, higher frequencies also need more accurate pointing and more precise antenna surfaces, so improvements in both spacecraft and the DSN were required to move to higher bands. Early missions used S-band for both uplink and downlink. Viking had X-band as an experiment, and Voyager was the first to use it operationally. Similarly, Mars Observer carried a Ka-band experiment, Mars Reconnaissance Orbiter had a Ka-band demo, and Kepler was the first mission to use Ka-band as the primary downlink.
However, not all space missions can use these bands. The Moon, the Earth-moon Lagrange points, and the Earth–Sun Lagrangian points L1 and L2 are all closer than 2 million km from Earth, so they are considered near space and cannot use the ITU's deep space bands. Missions at these locations that need high data rates must therefore use the "near space" K band. Since NASA has several such missions, they have enhanced the Deep Space Network to receive at these frequencies as well.
The DSN is also pursuing optical deep space communication, offering greater communication speeds at the cost of susceptibility to weather and the need for extremely precise pointing of the spacecraft. This technology is working in prototype form.

History

The forerunner of the DSN was established in January 1958, when JPL, then under contract to the US Army, deployed portable radio tracking stations in Nigeria, Singapore, and California to receive telemetry and plot the orbit of the Army-launched Explorer 1, the first successful US satellite. NASA was officially established on October 1, 1958, to consolidate the separately developing space-exploration programs of the US Army, US Navy, and US Air Force into one civilian organization.
On December 3, 1958, JPL was transferred from the US Army to NASA and given responsibility for the design and execution of lunar and planetary exploration programs using remotely controlled spacecraft. Shortly after the transfer, NASA established the concept of the Deep Space Network as a separately managed and operated communications system that would accommodate all deep space missions, thereby avoiding the need for each flight project to acquire and operate its own specialized space communications network. The DSN was given responsibility for its own research, development, and operation in support of all of its users. Under this concept, it has become a world leader in the development of low-noise receivers; large parabolic-dish antennas; tracking, telemetry, and command systems; digital signal processing; and deep space navigation. The Deep Space Network formally announced its intention to send missions into deep space on Christmas Eve 1963; it has remained in continuous operation in one capacity or another ever since.
The largest antennas of the DSN are often called on during spacecraft emergencies. Almost all spacecraft are designed so normal operation can be conducted on the smaller antennas of the DSN, but during an emergency the use of the largest antennas is crucial. This is because a troubled spacecraft may be forced to use less than its normal transmitter power, attitude control problems may preclude the use of high-gain antennas, and recovering every bit of telemetry is critical to assessing the health of the spacecraft and planning the recovery. The most famous example is the Apollo 13 mission, where limited battery power and inability to use the spacecraft's high-gain antennas reduced signal levels below the capability of the Manned Space Flight Network, and the use of the biggest DSN antennas was critical to saving the lives of the astronauts. While Apollo was also a US mission, DSN provides this emergency service to other space agencies as well, in a spirit of inter-agency and international cooperation. For example, the recovery of the Solar and Heliospheric Observatory mission of the European Space Agency would not have been possible without the use of the largest DSN facilities.

DSN and the Apollo program

Although normally tasked with tracking uncrewed spacecraft, the Deep Space Network also contributed to the communication and tracking of Apollo missions to the Moon, although primary responsibility was held by the Manned Space Flight Network. The DSN designed the MSFN stations for lunar communication and provided a second antenna at each MSFN site. Two antennas at each site were needed both for redundancy and because the beam widths of the large antennas needed were too small to encompass both the lunar orbiter and the lander at the same time. DSN also supplied some larger antennas as needed, in particular for television broadcasts from the Moon, and emergency communications such as Apollo 13.
Excerpt from a NASA report describing how the DSN and MSFN cooperated for Apollo:
The details of this cooperation and operation are available in a two-volume technical report from JPL.