The SGSS project's newly modified 18.3m main mission antenna The SGSS project's newly modified 18.3m main mission antenna
The newly modified 18.3m main mission antenna at the White Sands Ground Terminal in White Sands, New Mexico. Credit: NASA
SGSS, SN 

Space Network Upgrades Pass Critical Milestones

By Matthew D. Peters

May 14, 2020

The Space Network Ground Segment Sustainment (SGSS) project began testing freshly upgraded antennas and communications electronics with several NASA missions at NASA’s White Sands Complex. This important leap forward is the latest in a large-scale upgrade effort for NASA’s Space Network, which will increase data rates, improve user coverage, reduce maintenance requirements and extend the network’s lifespan.

SGSS upgrades have converted ground system antennas to support dual-band capabilities, transmitting over both Ku- and S- band to and from NASA’s communications satellites, known as Tracking and Data Relay Satellites (TDRS). Previously, the antennas only supported the Ku-band frequency for communicating with a TDRS. Now, thanks to SGSS, the antennas can easily switch between the two bands when needed, ensuring TDRS communications services are not interrupted.

NASA is undertaking these enhancements to the network while it remains operational — a feat of engineering never attempted before. Much of the Space Network’s legacy technology is analog. The radio frequency signals to and from the relay satellite constellation must be carried over long analog paths before they are modulated and demodulated. With SGSS, the signals can be digitized right as they hit the antenna. This improves efficiency, enabling the system to use higher data rates and more efficient data transport systems.

With the antennas upgraded and ground electronics installed, SGSS was able to “shadow” one of the TDRS spacecraft. An upgraded antenna received the TDRS telemetry, ensuring the system could properly process it. After the successful shadow, SGSS was given permission to control the spacecraft.

SGSS engineers then used a separate but also newly upgraded antenna system and electronics to simulate TDRS users. The test antenna sent signals as if it were a NASA mission using Space Network services. The TDRS relayed those signals back to the main mission antenna, just as it would during actual operations. Once engineers successfully completed simulations, the system could start testing with user spacecraft.

“We knew from day one that the system would be capable of providing quality services to every Space Network user,” said Vir Thanvi, SGSS project integration manager. “The challenge was to make sure our implementations took into account every aspect of each user’s needs.”

Supporting the diverse needs of Space Network users is an extremely complicated endeavor. Each user has a document that outlines how their mission will interact with the system and the services they need, and that document is be updated as SGSS upgrades become operational. SGSS informed users of progress, sought feedback and ensured impacts to the user are minimized, despite changes to the system.

“SGSS upgrades are a big paradigm shift for missions,” said Thanvi. “The project took lots of time to educate each one on changes to the system, making sure each change was understood and each mission’s concerns were properly addressed as we coordinated testing.”

The Space Network provides continuous communications services to over 40 exploration and science missions in low-Earth orbit, allowing those missions to bring their data back to Earth. The SGSS project will modernize the Space Network’s ground segment, which first came online in 1983, and make critical infrastructure upgrades to this international asset.

The SGSS project is based at NASA’s Goddard Space Flight Center in Greenbelt, Md. Goddard’s Exploration and Space Communications projects division manages both SGSS and NASA’s Space Network with NASA’s Space Communications and Navigation program office providing programmatic oversight. To learn more about SGSS, visit: https://sgss.gsfc.nasa.gov.

By Matthew D. Peters
NASA’s Goddard Space Flight Center, Greenbelt, Md.