SpaceX has started to launch Starlink satellites with laser links that will help provide broadband coverage in the polar regions. Elon Musk, CEO of SpaceX wrote on Twitter on Sunday, these satellites “have laser links between the satellites, so that no ground station is needed at the poles”.
The laser links are included in 10 Starlink satellites that have just entered polar orbits. The launch came two weeks after SpaceX received approval from the Federal Communications Commission to launch the 10 satellites in polar orbits at an altitude of 560 km.
“All sats launched next year will have laser links,” wrote Musk in another tweet yesterday, indicating that laser systems will become standard on Starlink satellites in 2022. For now, SpaceX is only including laser links on polar satellites. “Only our polar sats have lasers this year and v0.9,” wrote Musk.
Alaskan residents will benefit from polar satellites, SpaceX told the FCC in an application to change the orbit of some of its satellites in April 2020. The plan is “to ensure that all satellites in the SpaceX system provide the same low latency. services for all Americans, including those in places like Alaska that are served by satellites in polar orbits, “SpaceX said at the time. The satellites can serve home and US government users “in polar areas that are unreachable,” SpaceX said.
Starlink satellites communicate with ground stations, about 20 of which have been installed in the United States so far. A SpaceNews article described how laser links reduce the need for ground stations and provide other benefits:
Inter-satellite links allow satellites to transfer communications from one satellite to another, either in the same orbital plane or in an adjacent plane. These links allow operators to minimize the number of ground stations, since a ground station no longer needs to occupy the same satellite area as user terminals and extend coverage to remote areas where ground stations are not available. They can also decrease latency, as the number of hops between satellites and ground stations is reduced.
The 10 satellites were originally authorized by the FCC for altitudes in the range of 1,100-1,300 km. FCC approval allowing SpaceX to cut altitude in half will help reduce latency.
With polar orbits, also known as orbits synchronized with the Sun, satellites “pass through Earth from north to south instead of west to east, passing approximately over the Earth’s poles”, as explained by the European Space Agency.
“Space lasers have exciting potential”
In December, during an interview with Ars senior space editor Eric Berger, SpaceX president Gwynne Shotwell said the demonstration of laser communications in space was among the company’s most significant achievements in 2020.
SpaceX had revealed a few months earlier that it was testing space lasers for data transfer between satellites. Starlink engineers provided more details on a Reddit AMA in November; here’s an excerpt from our coverage at the time:
“The speed of light is faster in a vacuum than in fiber, so space lasers have exciting potential for low-latency links,” said the Starlink team on Reddit in response to a question about space laser testing. “They will also allow us to serve users where satellites cannot see a terrestrial gateway antenna – for example, over the ocean and in regions poorly connected by fiber.”
Space lasers won’t play a major role on Starlink anytime soon, however. “We had an exciting flight test earlier this year with prototype space lasers on two Starlink satellites that were able to transmit gigabytes of data,” wrote the engineering team. “But reducing the cost of space lasers and producing many of them quickly is a very difficult problem that the team is still working on.”
SpaceX seeks FCC OK for more polar satellites
In November 2020, SpaceX asked the FCC for a quick approval “to facilitate the deployment of 348 Starlink satellites in polar orbits synchronized with the Sun at a lower altitude,” the FCC said in its decision to approve 10 satellites. The FCC approved only these 10 because it is evaluating interference issues raised by other satellite companies.
“We found that the partial concession of ten satellites will facilitate the development and ongoing testing of SpaceX’s broadband service in high-latitude geographic areas in the immediate term, pending further action to address the arguments in the registry regarding granting the modification as a whole and total subset of polar orbiting satellites, “said the FCC order.
Amazon’s Kuiper, Viasat, Kepler Communications and Pacific Dataport urged the FCC to reject even a partial concession of 10 satellites due to the potential for increased interference with other non-geostationary satellite systems. But the FCC order said that SpaceX has committed to “operate these satellites on a non-harmful interference basis with respect to other licensed spectrum users until the Commission has decided on their complete modification.” A battle between SpaceX and Amazon is brewing, with Musk accusing Amazon’s attempt to “harm Starlink today for an Amazon satellite system that is, at best, several years in operation.”