Our first rocket launch of the week was by SpaceX. On February 4th at 06:19 UTC, a Falcon 9 with yet another batch of Starlink satellites took off from SLC-40 at the Cape Canaveral Space Force Station in Florida. This was the 18th launch of the version 1.0 satellites.
The launch was originally scheduled for late January but was delayed several days to February 4th due to poor weather at the booster recovery zone. This is nothing new; Falcon 9 launches have been delayed in favor of booster recovery in the past. Boosters are expensive, and SpaceX really wants to get their money’s worth.
Speaking of reusing boosters, this launch featured the fifth launch of booster 1060 just 28 days after its previous launch, which was on January 8th. This was the fastest turnaround yet, beating the previous turnaround record of 37 days between Booster 1051’s seventh and eighth flights on SXM-7 and Starlink Mission 16. This is excellent progress towards SpaceX’s stated goal of a 24-hour turnaround for the Falcon 9.
For those of you keeping score at home: eight minutes after launch, 1060 successfully landed on the drone ship Of Course I Still Love You. Both of the fairings had previously flown. According to SpaceX, one flew on the GPS III SV03 mission, the other SAOCOM-1B, both were successfully retrieved from the water.
This was a dedicated mission so another sixty satellites were added to the mega-constellation, bringing the total number of version 1.0 satellites launched to 1,023 of a planned 1,440 in the first phase of the constellation. So far, that’s roughly 71% of the first shell filled.
Those 1,023 satellites do not include satellites from the very first launch in May 2019. SpaceX called those 60 satellites “version 0.9” and as of January 2021, only six are still operational. Several version 1.0 satellites have also been deorbited, either intentionally or as a result of losing control and being dragged back into the atmosphere uncontrollably.
Jonathan McDowell, an astrophysicist who also monitors satellites in orbit in his spare time (when he’s not working on Chandra), reports that as of late January 2021, fourteen version 1.0 satellites have been intentionally deorbited or had their orbit decayed uncontrollably. A further seventeen of the version 1.0 satellites are not raising their orbits.
Future phases of the constellation will lead to a total of over ten thousand spacecraft. The next phase of 1,228 will be inserted between five and six hundred kilometers at either 70- or 97.6-degree inclinations. SpaceX has further approval to launch 7,518 additional Starlinks to orbits between 335 and 345 kilometers and inclinations of 42, 48, and 53 degrees. SpaceX has asked for but has yet not received permission for an additional 30,000 satellites to add to the constellation.
These additional shells of Starlink satellites will use V-Band transponders unlike the Ka/Ku transponders of the first 1440. V-Band is a higher frequency than Ka/Ku which will allow for more bandwidth and greater throughput. It’s also an unlicensed band over most of its frequencies in most countries around the world, and these two things alone have made it a favorite in microwave line-of-sight communications, particularly for backhaul links where fiber isn’t an option to move a lot of data around.
Other than highly directional microwave links though, not a lot operates in this band, so there’s also not much interference to overcome, which is great for urban areas. However, the reason it’s not used much is that the band tends to be heavily absorbed by atmospheric oxygen and is also subject to rain fade (absorption by water, like when your satellite TV goes out when it’s raining). The oxygen absorption in these cases tends to act like sound-proofing, which muffles the signal. This is why it’s mostly been used for line-of-sight radio links of two kilometers or less. More power can help overcome these losses, but it can get prohibitive.
Starlink will benefit from coming more or less straight down through the atmosphere in most cases rather than at an angle, but it still remains to be seen how well this band will work on the ground. If nothing else, it could easily replace the intra-satellite laser links if those prove to be a technological bridge too far. Even if ground-level service proves impractical, the band may also still prove useful for in-flight data links for aircraft operating at altitude.
Is your brain full of too much Starlink info yet? Astronomers worry about the sky getting too full of moving points of light, but that is a longer story for another day.