Invisible NASA Network Transports Satellite Secrets to Earth

Estimated reading time: 4 minutes

Around the world in 80 days? When Jules Verne wrote the novel, that seemed an impossible speed, but almost 150 years later, a NASA team has reduced the trip to minutes for data coming from some of today’s spacecraft.

Based out of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the Near Earth Network (NEN) serves as a conduit for information from spacecraft in low-Earth orbits, geosynchronous orbits, and even lunar orbits to the scientists who will study and use it on the ground.  

An orbiting observatory such as the Hubble Space Telescope collects huge amounts of data continuously, including both science observations and spacecraft health information, such as battery voltages and operational data. The missions of the Hubble Space Telescope and other satellite missions are not complete unless science observations and spacecraft health data are returned to the earth and processed.  There are no internet hook-ups, phone lines, or fiber optic cables in space to route the data to earth. That’s where the NEN comes in.

The NEN receives transmitted data from orbiting satellites like the Global Precipitation Measurement (GPM) mission, the Lunar Reconnaissance Orbiter (LRO), the Geostationary Operational Environmental Satellite (GOES) missions and more. Large antennas placed at numerous longitudes and latitudes around the world connect with much smaller antennas onboard the spacecraft as they pass overhead. Once received by ground stations, the information is distributed worldwide to stakeholders continuing their important science work and engineers evaluating how well the satellite is operating.

"The spacecraft has to be at a point in its orbit where the antenna can actually see it," said NEN engineer Ryan Turner. "It is as if you and I could only talk to each other if we could visually see each other, but if you walk around the corner, our conversation stops."

The ground stations receive data stored on spacecraft hard drives, which have a much smaller capacity than necessary to store a satellite’s lifetime of data. This data passes through a communication system that is capable of distributing it around the world to those in need of the data.

Engineers operating the NEN routinely schedule the connections between spacecraft and ground stations known as passes, referring to when the spacecraft passes above the ground stations to enable a connection opportunity. This is a huge responsibility with the 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. The team must ensure no two spacecraft are scheduled to connect with an antenna at the same time, which could overwhelm the system. If a pass is missed, the team must reschedule the pass for another ground station in the area while they ensure the antenna is ready to receive new data. Sometimes changing the location of a pass is not possible, and the spacecraft must hold onto its data for another pass. Over the course of a year, the NEN receives data from more than 54,000 passes, a dramatic increase from when the NEN was first established as the ground network more than 50 years ago during the Apollo era.

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