Genevieve Poblano / Digital Trends Graphics
If you’ve followed SpaceX’s Starlink project to create global broadband Internet, you’ve noticed that the company regularly launches not just individual satellites, but entire batches of 60 satellites at a time.
These stacks form a network in the sky called a satellite constellation, which provides near-global coverage in ways that a single satellite cannot. And not only SpaceX uses this approach – there are satellite constellations that companies from Amazon to its subsidiary Kuiper Systems to Facebook are working on as part of their Athena project.
But not everyone is on board to launch so many satellites into the night sky. Astronomers in particular have complained that such constellations jeopardize their ability to collect data with telescopes and hinder scientific progress.
To understand the pros and cons of this complex problem, we spoke to two experts: Olivier Hainaut, astronomer and lead researcher on how satellite constellations affect astronomical observations, and Brad King, CEO of a company that makes propulsion systems for satellites in the US -Military deployed in constellations.
The good thing: What satellite constellations can offer, individual satellites cannot
One of the greatest advantages of the constellation approach is that networks can easily be updated over time. If a system has a single large satellite, that hardware can take years to build and develop. Once started, it is extremely difficult to add features or improve the hardware.
With a constellation of satellites, you can gradually improve the hardware at startup. For example, if a company starts deploying satellites and develops more accurate sensors after a few years, they can easily install and deploy the new sensors in the next row of satellites. The existing satellites can continue to work together and the fleet can be gradually upgraded.
So the constellations are constantly being updated, said King, the CEO of Orbion, a small propulsion company that is currently providing the propulsion system for the Defense Advanced Research Projects Agency’s blackjack satellite constellation.
“If you fly 100 satellites, you don’t fly 100 satellites and wait 10 years and then launch 100 more,” King said. “They continuously update the fleet at around 20% of the fleet per year.”
It also means they can weather budget cuts on long-term projects by reducing the overall fleet, rather than scrapping a project entirely. This is important with government programs that may run for a decade and then cut their budgets.
There are additional specific benefits to using constellations for governments and the military. “The main benefit is resilience,” said King. “What you can do with a constellation, you can’t do with one [satellite] is that you can be resilient to attack. If you have a very large, very valuable satellite in orbit and you have an opponent who wants to refuse to use that satellite by damage or other means, it really only takes one bullet to take this entire ability off.
“When there are multiple internet providers in a region, people can access the internet more freely without government restrictions.”
“If you instead let 100 satellites share this functionality, your depth of attack would have to be much deeper to compromise functionality. So it protects against attacks. It’s not a big, thick, juicy target that will trick an enemy into attacking it. “
Once a constellation is in place, it can be used for all kinds of communication purposes. SpaceX’s Starlink program aims to deliver global broadband internet that has many potential benefits. In addition to the potential to provide internet access to poor or rural areas with little or no internet service, being able to track planes and ships around the world could also be invaluable for security reasons. The availability of multiple Internet providers in one region could enable people to access the Internet more freely and without government restrictions.
The bad: why constellations have some astronomers in their arms
As with all technological advances, the launch of satellite constellations is fraught with problems. Last year there has been a sometimes heated debate between SpaceX and the astronomical community over the launch of Starlink satellites.
When satellites are launched, they can leave trails of light in the sky, especially at dusk. While some may find these trails beautiful, they can affect astronomical readings because they’re much brighter than the stars or galaxies astronomers are trying to observe. There is also a question of whether Starlink satellites, which are in particularly low orbit, are visible to the naked eye and will affect readings once they are present.
Around 19 Starlink satellites were imaged by DECam on the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO) shortly after its launch in November 2019, creating light pollution that negatively affected astronomers’ ability to observe the night sky . National research laboratory for optical infrared astronomy of the NSF / CTIO / AURA / DELVE
The International Astronomical Union issued a statement in the summer of 2019 and a follow-up in February of this year. Both expressed concern about the negative impact the proposed megaconstellations of communications satellites could have on astronomical observations, citing Starlink, the Iridium satellite constellation, OneWeb, and others.
SpaceX quickly addressed the problems Starlink was creating in optical astronomy and worked with astronomers to find a solution. First, they tried painting the satellites a darker color, which, while diminishing their appearance, was not enough to please astronomers. So they moved on to a new design that included a visor for sun protection.
“That’s really smart,” said Hainaut. “Because if the satellite is not illuminated, it is completely dark and invisible. This means that the visor can hide most of the satellite. The way the satellite is set up means you can have a sight where you can see the back of the sight when viewed from the ground so it’s dark and the entire bottom of the satellite is in shadow. This means that the satellite will be several orders of magnitude weaker. “
“The orbit overcrowding problem is becoming an increasingly important focus in the space community, with concerns about the amount of debris in orbit around our planet.”
SpaceX has also adjusted the angle of the solar panels attached to the satellite so that the illuminated part is not visible from Earth. Combined, these fixes should more or less solve the problem of the operational Starlink satellites interfering with ground-based optical astronomy.
There are also some problems with the satellites interfering with radio astronomy. There may be a problem called frequency bleeding, in which satellites emit small amounts of radio waves at frequencies above their primary operating frequency, which can cause problems for radio astronomers. There is generally a lot of background noise that radio telescopes have to deal with, and satellite constellations can help.
SpaceX is working with the astronomical community in this area too, and astronomers seem largely optimistic that a solution can be found.
The final problem with launching a large number of satellites is not an easy one to fix. The orbital overcrowding problem is becoming an increasingly important focus in the space community, with concerns about the amount of debris in orbit around our planet. Space debris can be extremely dangerous, threatening everything from the International Space Station to our potential ability to inexpensively launch satellites in the future.
The main approach to this problem has been for companies to ensure that they can responsibly desorb their satellites when they are no longer needed. If a Starlink satellite is nearing the end of its life or a satellite is faulty, disposal is relatively easy because the constellation is in low orbit. The satellites just need to be maneuvered into a lower orbit and they drop into the atmosphere and burn.
Other constellations may be in a higher orbit. In these cases, it is easier to send them into something called a cemetery orbit than it is to get them into the atmosphere. However, if a satellite fails in a higher object, it can stay there for a very long time. Some satellites are now being fitted with features like hooks that make it easier for another satellite to acquire and dispose of them.
The ugly: what kind of constellations does the future hold in store?
Hainaut stressed that SpaceX has made efforts well beyond its commitments to address issues Starlink has caused for the astronomical community and it is confident that these issues can be resolved. The problem is, given the increasing popularity of constellations and the arrival of more companies in the future, these new players will consider the night sky as well.
“[SpaceX is] They are really doing everything, beyond what they are legally obliged to do, to solve the problems, ”said Hainuat. “Astronomers have a very good working relationship with Starlink, but it’s not clear we will have the same relationship with others [companies]because it’s just a good will. “
SpaceX / Flickr
Can other companies be trusted to follow SpaceX’s lead? There are contracts and agreements in place on the uses of space, including issues such as the disposal of satellites at the end of their lives. However, many experts argue that these contracts need to be strengthened and that there must be consequences for companies that fail to adhere to them.
“The problem is, there is no governing body that can really apply penalties consistently,” King said. “There are strict guidelines and contracts, but enforcement is problematic.”
Satellite constellations like Starlink can enable fantastic new leaps in telecommunications, but we need to find a way to balance that ability with the need to study the night sky and understand the universe beyond our planet.
“Space is a public community that we all share,” said King. “As a society, a lot has to be worked out as the constellations multiply … Everyone and nobody owns space and we all want to share it.”