NASA has expressed concerns over a planned constellation of broadband satellites from AST & Science.

AST & Science is a Texas-based company that plans to launch a constellation of satellites that will provide 4G and 5G broadband to cell phones. NASA, however, objects (PDF) to the company’s plans on two grounds.

First, the constellation will orbit approximately 450 miles (720 km) above the Earth. This is directly in the orbital range of the A-Train, “a group of ten NASA, USGS, and international partner (CNES, JAXA) missions that have a mean altitude of 705 km but have osculating altitudes between 690 and 740 km.”

The second issue is the size of AST’s satellites. Because the satellites will have massive antennas on them, each one will take up a 30 meter radius, as much as 10 times the size of an A-Train satellite. This would result in substantial course corrections and mitigations.

“Based on the results of a NASA CARA simulation tool, the number of mitigation actions required for a 30m hardbody radius (HBR) object in this orbit regime increases from ~2 to 6 per year—almost a tripling of what is observed presently,” writes NASA representative Samantha Fonder. “Second, the frequency of mitigation actions and associated planning efforts is of course multiplied by the number of spacecraft: for the completed constellation of 243 satellites, one can expect 1500 mitigation actions per year and perhaps 15,000 planning activities; this would equate to four maneuvers and forty active planning activities on any given day.”

Accounting for these course corrections would require an entirely new, automated communication system between the different satellites. Since many of the existing satellites are older models, the upgrades would be challenging and costly.

In contrast, SpaceX’s Starlink constellation orbits at roughly 340 miles (550 km), putting it well below the range of the A-Train.

This is not the first time concerns have been raised about the proliferation of commercial satellites. Astronomers have been voicing concern for some time over the impact these constellations will have on astronomy.