Life-saving NASA Communications System Turns 20

NASA's Tracking and Data Relay Satellites (TDRS) don't just enable data from spacecraft to reach Earth - they provide internet and even telemedicine to researchers at the South Pole. The South Pole TDRS Relay (SPTR) system turns 20 years old on Jan. 9, 2018.

In the 1990s, the National Science Foundation (NSF) faced a communications challenge with more than a hundred scientists working at their Amundsen-Scott South Pole Station in Antarctica per year to study everything from meteorology to astrophysics to climate. The scientists were completely isolated at the remote station during the winter months from about mid-February to late October every year.

Airplanes could not land to transport people or data, in the form of tapes, off Antarctica. Researchers were limited in how they could communicate, relying mostly on high-frequency radio to connect with the outside world or send their research back to the U.S., and it was difficult to do in a timely manner.

Additionally, polar-orbiting satellites used the South Pole Satellite Data Link (SPSDL) to move low volumes of survey mapping data to McMurdo Station, but the flow of data back to the U.S. was nearly impossible with the existing communications systems.

NSF's Pat Smith, technology development manager for the Office of Polar Programs, turned to satellites in high-altitude, high-inclination orbits to solve the problem. Inclination is the angle of an orbit in relation to Earth's equator, which has zero inclination.

The higher the satellite, the smaller the angle needed to provide useful communications. Together with a team at NASA's Goddard Space Flight Center in Greenbelt, Maryland, he developed a way to use satellites in geosynchronous orbits (about 22,000 miles above the Earth's surface) that were past their primary missions to provide internet connectivity and file transfer services to the South Pole.

Smith and another team of experts began by adapting older weather satellites and experimental satellites to provide communications services, which gave Antarctica the equivalent of a dial-up connection. However, as data collection continued to become more sophisticated, they needed to transmit and receive more data at a time. In the early 1990s, the team gained access to newer spacecraft, which enabled much better communications to and from the South Pole, but the data rates were still low and services were limited.

That's when Smith heard about TDRS, which were designed to provide communications services to spacecraft. He began working with Mike "NASA Mike" Comberiate from Goddard to determine if the NSF could get access to those resources from a remote location on Earth.

TDRS could provide a much higher data rate than the previous satellites NSF used, meaning more data could be sent at a time. The TDRS system also had multiple systems in place for communications, meaning there were backup options in case any of the systems failed. To make TDRS work for the South Pole's needs, NASA built a communications antenna at the South Pole station and added a new system at White Sands Complex in New Mexico, where the TDRS operations center is housed, to provide this new type of support.

The first signal was sent via the South Pole TDRS Relay system on Dec. 12, 1997, and the system officially became operational on Jan. 9, 1998.

"Given the power of the TDRS satellites, we were able get, out of a little 6-foot antenna, data rates that we could previously only get a fraction of with a big 9-meter antenna," said Smith. A 9-meter antenna equates to about 30 feet, or five times the size of a 6-foot antenna.

Over the next several years, the system was used for numerous purposes besides providing general connectivity to the South Pole. In June 1999, the South Pole TDRS Relay played a critical role in providing telemedicine from the U.S. to the station's physician, Jerri Nielson, who had discovered she had breast cancer while isolated at the South Pole station during the winter. They helped her perform a self-biopsy and administer chemotherapy, saving her life. Doctors leveraged the system for telemedicine again in 2002 to assist in knee surgery for meteorologist Dar Gibson.

Additionally, the system supported news events from the South Pole in the late 1990s and early 2000s, including a live New Year's Eve broadcast from the South Pole in 2000.

"It's hard to enumerate all the current systems that this was the pathfinder for," said Comberiate.

"The SPTR system was so far ahead of everything else back then that it was unimaginable."

The system was a game-changer not just for connectivity from the South Pole, but for communications in many remote locations. The use of TDRS for internet connectivity evolved from the South Pole to other ground and ship-based systems for remote science webcasts, such as for eclipses in remote locations. TDRS not only provided data services for these activities, but demonstrated the potential for the use of internet technology to support NASA missions.

This culminated in an experiment, named the Low Power Transceiver Communications and Navigation Demonstration on Shuttle (LPT CANDOS), on the STS-107 space shuttle mission in 2003. LPT CANDOS provided network connectivity to the payload bay of the space shuttle using the same TDRS equipment developed initially for SPTR.

Since that time, the ability to use general internet has been added to the International Space Station and the Orion spacecraft. Future exploration and science missions will use a combination of IP and disruption-tolerant networking (DTN) as part of a solar system internet.

Over time, the SPTR system has changed and evolved. The original NASA equipment was replaced with upgraded NSF equipment, which was named SPTR-2 and became operational in June 2009. The SPTR-2 antenna has access to any TDRS spacecraft in view and can also relay science data through the Geostationary Operational Environmental Satellite (GOES) network in between TDRS visibility windows. GOES satellites use a different communications system to communicate than TDRS.

Every year, researchers develop instruments that collect even more data at a time and require higher data rates to stay in the forefront of their scientific fields. Astrophysicists working on cosmic background research at the South Pole station expect to collect as much as 300 megabits of data per day in the next few years, so SPTR must continue to evolve with these growing needs.

The National Science Foundation (NSF) funds and manages the U.S. Antarctic Program (USAP), which has three, year-round remote research stations in Antarctica. This partnership between NASA and NSF commissioned a first-of-its-kind satellite communications ground terminal at the NSF Amundsen-Scott South Pole Station. The South Pole TDRS Relay (SPTR) ground terminal was the genesis of what is today an important data communications link moving high volumes of scientific research data daily from NSF-funded astronomy and astrophysics programs.

The partnership for communications, now in its 20th year, continues with long-term TDRS access, enabling science discoveries at the frontiers of astronomy and astrophysics, supporting the operations of Amundsen-Scott South Pole Station and providing the important connections to family and friends for the isolated scientists and crew.

+ For more information about NASA's space communications networks, visit here

+ For more information about TDRS, visit here

+ For more information on USAP, visit here

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