Starlink connections examined
February 8, 2022
A study from Dr Sergei Pekhterev (co-owner of Astra-Internet) shows that the bandwidth of each of Elon Musk’s Starlink low Earth orbiting satellites is carrying 16 data beams and can serve some 2080 users as each craft passes overhead.
Pekhterev has used Starlink data which states that each satellite covers about 380 square kms of the Earth’s surface below. The core data comes from Starlink’s recent Indian submissions published in December 2021. SpaceX, says Pekhterev, talks of 100 Starlink satellites per 300 sq. kms as being “optimal”. This helps explain Musk’s end-plan which is to populate his Starlink orbits with some 40,000 satellites.
Pekhterev explains that for 100 percent coverage of the rural US the Starlink system will need 1341 satellites.
There are two other relevant data points: the first is a direct quote from a SpaceX engineer earlier in January who said that they had 145,000 active Starlink subscribers. The other is that while Musk has stated (on January 15th) that 1469 Starlinks are operational and a further 272 are moving to their operational orbits.
That number has increased helped by recent launches (and ahead of the January 31st launch of another 49). Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, stated on January 30th that by his calculation 2042 Starlinks had been launched and 1871 remain in orbit. That number has now grown to 2091 craft launched, and some 1920 are working.
Pekhterev says that based on these new data, he tries to determine how many cells can be simultaneously served by
one Starlink 8 or 16 satellite. “[The] 8 beam [versions] corresponds to the option that only one polarization is used on the 2000 MHz Ka band feeder link, and 16 beams, that both polarisations are used on the feeder link, which allows you to form 16 beams of the Ku band, each at 240 MHz, taking into account the guard intervals between the beams and TT&C channels for the transmission of service information. Let me remind you that the Starlink terminal works only in one right polarisation.”
He suggests that as far as the US and Canada are concerned, the two key regions have some 96 Starlink satellites currently “visible” to its North American gateways.
A filing from SpaceX to the FCC on January 7th has also emerged in which the Musk company supplies further and better particulars to the FCC on its Gen-2 Starlinks, saying that it had now launched more than 1900 satellites and the system must now be considered as “built” as far as its original FCC application was concerned.