The Starlink satellite constellation from SpaceX is still in test mode, but already generates 5 trillion data bytes per day and receives software updates every week.
These are a few of the nuggets from a Weekend Reddit "Ask Me Anything" session with the software team from SpaceX.
The main focus of the online chat was on SpaceX’s successful mission to send NASA astronauts Bob Behnken and Doug Hurley to the International Space Station in a crew capsule – but one of the team members, Matt Monsonswitched from Dragon to Starlink to take over development of the Starlink software.
Although SpaceX's headquarters are located in Hawthorne, California, most of the work relates to that Starlink satellites is performed at the company's factories in Redmond, Wash.
SpaceX tends to play its satellite cards close to the vest, also because the process of building a satellite system is "highly proprietary" – as one of the company's vice presidents, Patricia Cooper, said in a report filed with the Federal Communications Commission in 2016. For this reason, all nuggets about the work of Starlink are eagerly searched for by SpaceX fans and occasionally inquiring journalists.
The Reddit AMA this weekend attracted more than 7,000 questions and comments, and the engineers were only able to answer a few of them. This made it easy to avoid sensitive issues – for example, the schedule for adding satellite-to-satellite laser communication links to the constellation. Despite the limitations, Monson and the other developers shed light on Starlink's interior, including the following highlights:
- The technology used for the crew dragon screens also formed the basis for the user interface of the first two prototype Starlink satellites, which were launched in 2018. "It has grown a ton since then, but it was great to see Bob and Doug use something that was kind of familiar to us," Monson wrote.
- SpaceX relies on the Linux operating system in its satellites and rockets. "Every launch of 60 satellites contains more than 4,000 Linux computers," said Monson. “The constellation currently has more than 30,000 Linux nodes (and more than 6,000 microcontrollers) in space. And because we share a large part of our Linux platform infrastructure with Falcon and Dragon, they benefit from our more than 180-year vehicle test period in orbit. "
- Not everything went right with the Starlink software. “We have had many cases where a satellite has an error in orbit that we had never imagined, but that could stay safe long enough to debug it, find a fix or workaround, and improve a software -Update, ”wrote Monson. He said SpaceX typically updates the software on all satellites about once a week, "with a number of smaller test deployments taking place."
- Monson said, "We are currently generating more than 5 TB (5 trillion bytes) of data per day" for Starlink. "Detecting problems on board is one of the best ways to reduce the amount of telemetry that we need to send and store (only send if it is interesting). The warning system used is shared between Starlink and Dragon."
As of last week, SpaceX launched eight batches of 60 Starlink satellites, which form a constellation of approximately 480 spacecraft (some of which are out of service). There is a ongoing controversy over the visibility of the satellites and possible interference with astronomical observations. When the sky is clear, you can Use Heavens-Above.com as a guide to spot the satellite train traveling across the sky.
The broadband data network is is already being tested for military applications. Just last month, SpaceX and the U.S. Army made a deal for another three years of experimentation and evaluation. The limited commercial service could start later this year, although it is not yet clear how exactly the service will be marketed.
(embed) https://www.youtube.com/watch?v=giQ8xEWjnBs (/ embed)
After all, thousands of Starlink satellites could provide broadband Internet access to billions of people around the world. Other companies, from OneWeb to the Canadian bankruptcy process to Telesat in Canada and Project Kuiper on Amazon, are also committed to the satellite internet market. However, due to Monson's comments, they will have a lot of technical catching up to do.
Monson said his favorite moment at SpaceX came just over a year ago when the first batch of 60 satellites was used in orbit like a card game.
"We developed the all-at-once deployment mechanism, but it's difficult to model and we couldn't really be 100% sure that it would work properly," he wrote. "I remember sitting there lifting Falcon off the block thinking: OK. In an hour, we'll either be idiots trying something that obviously never would have worked, or geniuses doing what is obviously the right way to use a lot of satellites. Fortunately, it went well. "