SpaceX wants to fly Internet satellites closer to Earth

SpaceX is in the process of revising its satellite Internet initiative, Starlink, and is now hoping to exploit some of its spacecraft at a lower altitude than originally planned. In a new document filed with the Federal Communications Commission (FCC), SpaceX is asking the agency to modify its license so that more than 1,500 Starlink satellites can operate at an altitude 600 km lower than originally requested.

SpaceX says this modification will make the space environment safer, as it will be easier to get rid of these satellites at this new altitude when they run out of fuel or can no longer operate properly in orbit. This update could also explain the unexpected behavior of two SpaceX Starlink test satellites, which remained in lower orbits than expected.

In March, the FCC approved SpaceX's license for the first phase of its ambitious Starlink initiative – the company's long-term plan to launch nearly 12,000 satellites into orbit to transmit the Internet coverage to the Earth. SpaceX initially requested FCC permission to launch 4,425 satellites in orbits ranging from 1,110 to 1,325 km. But with this new depot, SpaceX is demanding that 1,584 of these satellites, supposedly operating at 1,110 kilometers, be allowed to operate at 550 kilometers.

According to SpaceX, moving satellites to a lower altitude means doing more with less. Originally, the company said it needed 1,600 satellites to operate at an altitude of 1,110 kilometers, but their downsizing means that the company can achieve the same results with 16 fewer satellites. And the low altitude facilitates the disposal of these satellites once they are installed in space. At this height, particles in the Earth's atmosphere bombard the spacecraft faster, pushing them out of their orbit and dragging them towards the planet. And while going down, they burn in the atmosphere.

Image: YouTube / SpaceX

It is essential to ensure that these spacecraft emerge quickly from their orbits because of the large number of vehicles SpaceX wishes to put into orbit. A constellation of the size of Starlink could significantly increase the number of operational satellites in the space, thus increasing the risk of collision in the space. According to a recent NASA study, 99% of these satellites will have to be reliably removed from their orbit within five years of their launch, otherwise the risk of collision between satellites will increase considerably.

Desorbing a satellite usually involves bringing the vehicle to a low enough altitude with thrusters where the Earth's air particles and gravity pull the probe down so it burns. Now, with this new ranking, SpaceX will no longer need to significantly move 1,584 of its satellites to get rid of it. The atmosphere at 550 kilometers should do the business in a few years. It is also useful in case the spacecraft fails in orbit. Satellites that fail at high altitude could be transformed into non-operational space debris that would remain in orbit for long periods of time. At lower altitudes, they can still fail and the atmosphere will swallow them quickly.

And that could go a long way with the FCC, which has expressed concern about the reliability of these satellites and whether they will be debrided in time. In fact, when the FCC approved the Starlink initiative, it stated that "it would be premature to accept SpaceX's request based on its current orbital debris mitigation plan." However, SpaceX has nevertheless received the authorization provided that the company provides an updated plan. how he would desorb his satellites in time.

The new document could also explain the behavior of two of the SpaceX test satellites currently in orbit. In February, SpaceX successfully launched a pair of test satellites – TinTin A and B – to test the technology needed for the Internet project from space. However, satellites have not reached their final orbit in space. The goal was to insert the satellites at an altitude of 511 kilometers and, once all the systems of the vehicles checked, SpaceX would then bring the pair to an altitude of 1,125 kilometers with the onboard satellite thrusters. It would take about six months. The company detailed these plans in a letter to the FCC dated February 1, 2018, three weeks before the launch.

Image: Jonathan McDowell

But the satellites have never left about 500 km, according to Space_Track.org, a site using satellite tracking information provided by the Ministry of Defense. A diagram of the duo's position in time shows that the satellites are naturally lower in their orbit – probably because of the particles in the Earth's atmosphere that drag them down, according to Jonathan McDowell, an astrophysicist at the University. of Harvard, following a spaceship in orbit. In June and July, TinTin B slightly raised its orbit, suggesting a slight burn of its onboard thrusters. TinTin A barely moved, except for a small gust on October 17th.

This led to the speculation of a possible failure, which was reported for the first time by Intel Space Report, and SpaceX told the site that the satellites "were delivered to the planned orbit, communicated with ground stations, continue to communicate with ground stations and are still in service today."

In the case of today's FCC, SpaceX indicates that it decided to change the orbits based on what it had learned from operating TinTin A and B at a lower altitude. "Working at a lower altitude offers many attractive features in both nominal and unplanned scenarios," writes SpaceX in the rankings. The company said it would simplify satellite design and reduce signal latency to just 15 milliseconds, which "would be virtually invisible to almost all users," according to SpaceX.

However, SpaceX recognizes that there are disadvantages to the lower orbit. Since the atmosphere is slightly denser at this altitude, it also means that the spacecraft has to work harder to stay in orbit and not be trained too early on Earth. It will also reduce the Earth's surface that each satellite can cover at any given time. SpaceX will have to change the way the spacecraft transmits its signals.

The FCC still has to approve SpaceX's request, but the Commission has declared November "Space Month". It is possible that something will happen soon. In the meantime, SpaceX has announced its intention to launch its first batch of Starlink satellites in 2019. Under the terms of its FCC license, SpaceX must launch at least half of its 4,425 satellites (potentially 4,409 today). now) six years constellation complete in use. In October, Reuters Elon Musk, CEO of SpaceX, redesigned Starlink's management to meet the program's timelines more quickly.