SpaceX has received FCC permission to launch 4,425 Starlink communications satellites between 1,110 and 1,325 km in altitude. SpaceX in a new filing is now requesting that 1,584 of those satellites be allowed at lower orbits of 550 km. Satellites at that orbit are at the upper reaches of the atmosphere and have naturally decaying orbits over several years. Starlink satellites at that elevation would therefore be easier to decommission. Satellites that fail would also fall into the atmosphere naturally.
When SpaceX received initial FCC approval, the permission was contingent upon SpaceX providing updated satellite decommissioning plans. The FCC is concerned about space debris. This new orbital plan by SpaceX may address some FCC concerns.
SpaceX’s two current test satellites, TinTin A and B, were launched into the lower orbits but expected to be boosted to higher orbits. That boost hasn’t happened, leading some observers to question whether the satellites failed. In fact SpaceX may be studying the lower orbits in greater detail.
Lower orbits would represent faster communications speeds, with latencies as low as 15 ms. Satellites would also potentially cover less of the planets surface, which would require modifications to their design.
More detailed reporting of SpaceX’s updated FCC filing is provided by The Verge.