Space NASA Communication Systems

a antenna of the Near Earth Network (NEN). picture courtesy NASA/JPL

As soon as the first manmade satellites were put into orbit around the Earth, the need to track and guide the craft and to collect science data brought to that radio tracking stations were used. 50 years ago, at the dawn of human spaceflight, the first astronauts were only able to communicate with mission control operators on Earth for about 15 percent of each orbit. Three networks eventually came to supporting the space communications for NASA. The Near Earth Network (NEN) supporting low Earth orbit missions with a periodical contact to Earth. The Space Network (SN) for the low Earth missions generally via the TDRSS system. And the Deep Space Network (DSN), supporting the distant NASA missions like the ones exploring the solar system. Together, the Deep Space Network, Near Earth Network and Space Network are managed and directed by the Space Communications and Navigation (SCaN) program office, which was created by May 2006. SCaN serves as the program office for all of NASA’s space communications activities. The SCaN, generally, is to implement the combination of NASA’s space communications and navigation infrastructure within the Office of Space Communications under the Space Operations Mission Directorate (SOMD) –now the Human Exploration and Operations Mission Directorate (HEOMD)- transitioning to a single, unified mission support architecture. NASA's Goddard Space Flight Center in Greenbelt, Maryland manages both SCaN’s Near Earth Network and Space Network, providing continuous, reliable space communications services to low-Earth orbit spacecraft, such as the ISS

The Near Earth Network (NEN)

The Near Earth Network (NEN), formerly known like the Ground Network (GN) provides tracking, communications, and data system services during pre-flight, launch, orbital, landing, and post flight activities for missions requiring periodic contact in certain orbital and suborbital locations, including Low Earth Orbit (LEO), geosynchronous Earth orbit (GEO), lunar, and highly elliptical orbits. It is managed by NASA Goddard Space Flight Center. Craft are sending their data to globally distributed tracking stations as they pass overhead. More than 40 NEN spacecraft customers in orbit from 99 to 22,000 miles above Earth’s surface and even in orbit around the Moon. In addition to their data transfer services, NEN antennas provide constant telemetry, tracking and command for the spacecraft, helping for taking care of satellites on their orbit, like adjusting the orbit or re-aligning the solar panels. NEN assets are located throughout the world. Network assets owned by NASA are located at Wallops Flight Facility in Virginia; McMurdo Ground Station in Antarctica; White Sands Complex, in New Mexico; and owned by NASA, but operated by UAF is the Alaska Satellite Facility (ASF) at Fairbanks, Alaska (ideal for communicating with polar-orbiting satellites). The NEN is managed, operated and maintained at the Goddard Space Flight Center. Team members are located at the Greenbelt and the Wallops Flight Facility campuses. NASA implemented its first ground-based communications network—the Manned Space Flight Network (MSFN)—in the 1960s. The MSFN was a worldwide communications network with stations primarily located at low-latitudes to support the Mercury, Gemini, and Apollo Programs. During this same decade, NASA also acquired management of the military’s Minitrack system, evolving it into the Satellite Tracking and Data Acquisition Network (STADAN) to support an emerging class of satellites requiring enhanced communications. During the 1970s then, NASA merged the MSFN and STADAN, forming the Spaceflight Tracking and Data Network (STDN) to support communications needs of manned and unmanned spacecraft missions. NASA expanded the STDN in the 1980s to provide crucial support to the Shuttle while the Agency developed the Space Network (SN). In the 1990s, following the larger involvement of NASA into Earth studies, ground based stations came to provide communications support to high-data-rate science missions. As a result, the STDN evolved into a set of stations initially called the Ground Network (GN), and more recently renamed as the NEN. The NEN, on the other hand, pioneered the call to partner stations (like the NOAA, or other space agencies) and to commercial tracking stations. Government-owned assets are used only to provide services when use of a commercial provider is not feasible or cost effective. For example, NASA-owned assets provide support to missions with unique communications requirements, such as the Shuttle. Currently, the NEN provides over half of its services using commercial and partner providers thus providing for a unique business model. The NEN is currently augmenting its ground station network to provide communication services for future U.S. spacecraft system. The Near Earth Network's Launch Communications Segment is constituted of one station in the KSC, one in Ponce de Leon (Florida) and one in Bermuda. Goddard commissioned the Launch Communications Segment to support the Orion spacecraft and the Space Launch System (SLS). After a recent installment of a new antenna in Alaska and plans to install several antenna in the southern hemisphere, the NEN is also developing new capabilities that will increase bandwidth and allow the network to keep up with growing data demands as new missions are launched. Next challenge will be the increase of bandwith through the use of laser datalinks

The Space Network (SN)

The Space Network (SN) consists of the geosynchronous relay TDRS satellites as it provides the resources for global space-to-ground telecommunications and tracking coverage for low and near-Earth orbit robotic and human spaceflight missions, and had been born in the 1980s. TDRS satellites serve as switchboards that receive data from spacecraft in Earth orbit, science balloons of high altitude and launchers, which then relay the data to one of two stations on the ground. The SN was aiming to a comprehensive voice and data transmissions between Space Shuttles (and eventually the International Space Station) and Mission Control. Before the TDRS System became operational, communications between the ground and the Shuttle were possible for only about 15 percent of each orbit. The first TDRS satellite was launched by April 1983 aboard a Space Shuttle mission as, unfortunately, the first TDRS was placed into an improperly low orbit, and it took several months of the TDRS using its own fuel to achieve the proper geostationary position. The TDRS satellites are located in one of the three clusters operational set located on the Atlantic, Pacific and Indian ocean. The SN is managed by NASA Goddard Space Flight Center. The three antennas of the Space Network's ground segment, as located at the three ground facilities of the system, like at the White Sands Ground Terminal, are fixed in alignment with the Tracking and Data Relay Satellite System (TDRSS) constellation. In the case of a ground to a mission commmunication, data from the ground is relayed to one the TDRSS satellites which in turn relays that to the target spacecraft, and reciprocally in case of a mission to ground link, eventually reaching to a data center like the mission control in Houston. The network provides the resources for global space-to-ground telecommunications and tracking coverage for low Earth orbit and near-Earth robotic and human spaceflight missions. The Space Network Ground Segment includes facilities and systems located at the White Sands Complex at Las Cruces, N.M., Guam Remote Ground Terminal at Guam, and the Space Network Expansion East at Blossom Point, Md. The ISS and the Hubble Space Telescope are too relying upon the Space Network and launch vehicles and a variety of other science missions as the Space Shuttle program did also. In terms of the ISS, there also exists very high frequency (VHF) communications ground stations that backup the Space Network, and communicate with Soyuz spacecraft when out of Russia’s range. The SN is managed by NASA's Goddard Space Flight Center (GSFC) and its primary ground communications facility is located at the White Sands Complex in Las Cruses, NM. Currently, the Space Network can transmit 300 megabytes of data per second. That’s enough to fill two CD-ROMs a minute, more than 700 a day. In the next several years, NASA is working to increase the data rate to 600 megabytes per second

The Space Network Ground Segment Sustainment effort (SGSS) is updating NASA's Space Network ground communications infrastructure with new, state-of-the-practice technology. These upgrades involve the installation of an entirely new architecture in each Tracking and Data Relay Satellite System (TDRSS) ground terminal, which enables easier technology refreshes, simplified future expansions, and an increase in customer data rate capabilities, while lowering operations and maintenance costs. Furthermore, SGSS is developing the architecture to allow for extensibility and expandability. The SGSS Project has the responsibility to refurbish the three existing Space Network ground terminals at the White Sands Complex in New Mexico and in Guam. In addition, SGSS will build a new terminal at Blossom Point, Md. SGSS's new architecture is expected to be fully operational by late 2016. The SGSS Project Office at NASA Goddard manages the development effort for the ground terminals as the operation of the network is the responsibility of the Space Network Project at Goddard. The effort also includes expanding and improving the methods for Space Network user control centers to interface with the Space Network Ground Segment for data and service planning and control. A total of six first generation TDRS spacecraft were successfully placed into orbit from April 1983 through July 1995. The first TDRS satellite was delivered by the 6th Space Shuttle mission and the triangle shaped space network was completed in 1989 with the deployment of TDRS-4. The second generation of TDRS was launched 2000-2002 with three satellites. In later years, the TDRS-1 orbit inclination was increased allowing for communications through the satellite for portions of a day, with the North and South poles. NASA has contracted Boeing to build three additional follow-on TDRS spacecraft (the TDRS-K, TDRS-L and TDRS-M, as the first one launched by January 2013 and the following to launch in 2014 and 2015, respectively) replenishing TDRS-1 and TDRS-4, and expanding NASA's communication services. The retirement of any such satellite consists into excess fuel depletion, disconnecting batteries, and powering down the Radio Frequency Transmitters and receivers so that the satellite is completely and permanently passive and will never interfere with other satellites. Most recent TDRS spacecraft include several modifications from older ones, including redesigned telecommunications payload electronics and a high-performance solar panel designed for more spacecraft power to meet growing S-band requirements. Another significant design change, the return to ground-based processing of data, will allow the system to service more customers with evolving communication requirements. The TDRS system, generally, provides tracking, telemetry, command and high-bandwidth data return services for numerous science and human exploration missions orbiting Earth. These include the International Space Station and NASA's Hubble Space Telescope. Recent improvements announced by late 2016 also will increase the data rate capability as another TDRS spacecraft will add to that increase in 2017. Third-generation spacecraft are part of a complete network which, by early 2018, amounted to 10

The Deep Space Network or DSN

two of the three DSN 34-meter (111-foot) beam waveguide antennas at Goldstone, California. picture courtesy NASA/JPL

NASA's Jet Propulsion Laboratory in Pasadena, California, manages the DSN for SCaN. The predecessor to that deep space network was established in January 1958 when JPL, then under contract to the U.S. Army, deployed portable radio tracking stations in Nigeria, Singapore and California to receive signals from the Explorer 1, the first U.S. satellite. On December 3, 1958, JPL was transferred from Army jurisdiction to that of the new NASA agency and given responsibility for the design and execution of robotic lunar and planetary exploration programs. Until now that few small antennas were part of the Deep Space Instrumentation Facility originally operated by the U.S. Army in the 1950s. It officially morphed into the Deep Space Network on Dec. 24, 1963. Shortly afterward, NASA established the concept of the Deep Space Network as a separately managed and operated communications facility 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. Hence the DSN, like the provider for such services to various users, came to develop receivers, traking, telemetry and command system, digital signal processing and the various mean to control and track the craft launched into the solar system. A site had been chosen as soon as in March 1958, by the JPL, in the desolate Goldstone Dry Lake area at Fort Irwin in the Mojave Desert. Such a desert location was to provide an environment as free of radio noise as possible. As, until now, mobile tracking stations were used in the domain of the astronautics, the location in the Mojave Desert was the first place to harbour fixed antennas. The first of those was the 'Pioneer Station', an antenna built to communicate with the Pioneers 3 and 4 in December 1958 and March 1959, respectively. As further antennas and facilities -outside the USA included- were soon set up, the planners, since that time of the early 1960s, forecasted the permanent enhancement of the network to match the expanding space conquest, with the antennas growing in sizes and performance, accomodating NASA's various lunar and deep space missions. Even the Apollo program was managed by the facilities of the DSN (the images of the first Moon walk however were transmitted back from the Moon to the Parkes Observatory radio telescope, southeastern Australia). By the late 1970s, the network expanded its dishes' sizes as NASA was also exploring the concept of arraying antennas at the occasion of the Voyager missions. The DSN network was provided in 1964 with the 'Space Flight Operations Facility' (SFOF), a three-story building harbouring the Network Operations Control Center, which, further, kept communications -like it keeps doing today- with the other centers of the DSN worldwide. The best known workhorse antenna, the Goldstone, Calif. 230-foot (70-meter-wide) antenna became operational by 1966 as it was deviced to track missions which began venturing beyond the orbit of the Earth, featuring a 210-foot (64-meter-wide) dish, which was upgraded from 64 to 70 meters in 1988 to enable the antenna to track NASA's Voyager 2 spacecraft as it encountered Neptune and Uranus. The first task of the antenna was to track the Mariner 4 mission, which had been lost by smaller antennas once its historical flyby at Mars performed. That awarded it the name 'Mars antenna'. That antenna supported missions like the Pioneer, Cassini or the Twin Rovers at Mars. It's there that the famed Apollo 11, Neil Armstrong's famed communiqué 'That's one small step for man. One giant leap for mankind' was received and sent then on to American television sets while the images came through another antenna. It also helped radar-imaging nearby planets, asteroids and comets

The Deep Space Network eventually came today to be composed of three facilities, located 120° in longitude apart, from Goldstone, California, to Australia, through Spain. Because of celestial mechanics and trajectories, the best spacecraft tracking requires stations located in both the northern and southern hemispheres as sites spread around Earth in terms of longitude allows a round-the-clock coverage. Semi-mountainous basins where three antennas are located are reducing radio frequency interference, making the Deep Space Network the largest and most sensitive science telecommunications system in the world. The Goldstone facility is located 45 miles (72 km) northeast of Barstow, California, as the Australia is 25 miles (40 km) southwest of Canberra and the Spain one 37 miles (60 km) west of Madrid. Each complex is harbouring one 34-meter (111-foot) high efficiency antenna, one or more 34-meter beam waveguide antennas (3 in Goldstone, 2 in Madrid, 1 in Australia) -a feature allowed for a better processing treatment of the data received, one 26-meter (85-foot), and one, giant 70-meter (230-foot) antennas. Such a network allows for a 24-hour activity, as the DSN, since its inception, passed from a 8 bits/s telemetry-one spacecraft at a time, to a multi-megabit telemetry, three dozen spacecraft, round-the-clock following. Such antennas are uploading the commands and navigation data to the craft currently in the solar system, as, on the other hand, they are receiving the images and science collected by them. The Deep Space Network too is accurately tracking the craft positions and velocities. All antennas at one site are remotely operated from a centralized signal processing center, with a first processing performed and data, then, transmitted to JPL for further processing. The centers may be networked, as the DSN, for some missions, even made use of the Very Large Array (VLA) radio telescope located on the plains of San Agustin, 50 miles (80 km) West of Socorro, New Mexico, or other great radio observatories. The newtwork today is a facility of the JPL, as it's the California Institute of Technology (Caltech) which manages and operates it for NASA. During its first year of operation, the network had communicated with three spacecraft - Mariner 2, IMP-A and Atlas Centaur 2 as with 33 missions today. Space agencies in Europe, Japan and Russia have also relied on the Deep Space Network when planning and communicating with their own missions over the decades

As far as the operating mode of the DSN is concerned, it has to be noted that the first phases of a flight, with a large angular momentum, always needed that stations be positionned in such a way to facilitate the tracking at that moment, as the large antennas could not perform the work. As those stations were first mobile -and some even of the size of a mere suitcase, with an associated dish antenna, they came later to be fixed, with, for example, the facility at the Ascension Island, Atlantic Ocean, in 1966. Those stations, due to that most missions launch eastwards, from the Kennedy Space Center, Florida, have their first telemetry data acquired from there, before their disappearance on the horizon. These data are transmitted to the acquiring stations further located along the trajectory of the craft. The radio frequency band that many NASA missions use to communicate, generally, is the S-band, as it is getting a bit crowded and noisy. The data rate able is at 90 megabits of data per second

NASA's Deep Space Network thus allows for the support of the interplanetary missions but, too, of radio and radar astronomy observations as the network also supports some Earth-orbiting missions. The Goldstone's 230-foot (70-meter) radar dish, for example, along with two of Goldstone's 112-foot (34-meter) antennas was used to radar-map the southern polar regions of the Moon, as a preparation for the LCROSS mission, providing a contiguous topographic detail over a region approximately 311 by 249 miles (500 by 400 kilometers). The DSN 70-meter-wide (230-feet-wide) radio antenna in Canberra, Australia is Voyager 2 main mean of communication at it will be undergoing critical upgrades. The repairs will benefit far more than Voyager 2, including future missions like the Mars 2020 rover and Moon to Mars exploration efforts. The DSN is the largest and most sensitive scientific telecommunications system in the world. The 230-foot antennas provide for capturing signals from missions as far as 10 billion miles (16 billion km) from the Earth or to pinpoint the position of a spacecraft billions of miles away to a accuracy of just a few yards! Radio, microwave signals coming from such faraway missions are very low, typically limited to a emission value of 20 watts, or about the same power required to light a refrigerator bulb as the engineers are obliged, in terms of the ability of a spacecraft to communicate, to a tradeoff between efficiency and weight. Thus the total signal arriving at a DSN antenna can be 20 billion times weaker than the power level in a modern digital wristwatch battery. The signal, further, is usually spread over an area with a diameter equal to about 1,000 Earth diameters as radio noice is heard too, leading to the DSN systems have to use varied methods to enhance and separate a mission's data. When a single antenna is unable to capture a spacecraft signal by itself, the network uses a technique called “arraying” to combine the signal from two or more antennas

By the date of 2025, following the recommendations of an independent study, NASA embarked on an ambitious project to replace its aging fleet of 70-meter-wide (230-foot-wide) dishes with a new generation of receiving and transmitting 34-meter (112-foot) antennas. The new antennas, known as Beam Waveguide (BWG) antennas will be first installed, for two of them, in Canberra, Australia and later in Goldstone and Madrid, Spain like part of the Deep Space Network Aperture Enhancement Project (DAEP). Such new installations will serve NASA during the next 5 decades. Deep Space Station 36 (DSS-36) in Canberra, Australia became operational on October 1, 2016 and is one of four 111-foot (34-meter) Beam Waveguide (BWG) antennas to be built as part of the DSN Aperture Enhancement Project, allowing to uplink and downlink larger amounts of science and telemetry, tracking, and command data back and forth from Earth. BWG antennas differ from conventional antennas in that the transmission and reception of multiple frequencies is facilitated by the rotation of a mirror situated beneath the antenna, in the pedestal room. The location of sensitive instrumentation and transmitters in the pedestal room rather than in the structure of the antenna makes BWG antennas less complicated and more flexible to maintain than conventional antennas. Such antennae also allow for multiple frequencies to be used by a same antenna and received by the turning of the mirror in the pedestal room below the antenna. Antennae are much easier and less costly to maintain and signals can be translated on the spot to readable information. The new antennae also can receive higher-frequency, wider-bandwidth signals known as the "Ka band." This band, required for new NASA missions approved after 2009, allows the newer antennas to carry more data than the older ones. By 2007, NASA had also installed a new Ka Band Antenna Network at the White Sands Test Facility, N.M., with three 18-meter dishes to meet the growing demand for ground stations to handle high volumes of science data generated by today’s new satellites. The Golstone Mars antenna endured a seven-month upgrade in terms of this horizontal and vertical motion assemblies, and resumed operations by November 2010 after one month of intensive testing and is now ready to help maintain communication with spacecraft during the next decade or two of space exploration, after 40 years of service. The historic dish is now responsible for tracking an entire fleet of missions. NASA further is looking for the next generation of space communications technology and laser comm may be the answer. Optical communications provide higher bandwidth, which allows for faster data flow and even opens the door to streaming high-def video from distant planets to ground stations on Earth. The Laser Communications Relay Demonstration (LCRD) mission will be put to the test in 2016. The SCaN, on a other hand, is also studying the feasibility of dedicated relay or science orbiters in the next 15-20 years in high Mars orbit (aerosynchronous). A new 112-foot antenna, the Deep Space Station-23 (DSS-23), is being added in Goldstone to the DSN and equipped with laser technology, scheduled to be completed by mid-2022