Sustainability in Orbit in the Age of Satellite Constellations

The first space race saw two nations rush to reach the moon with a single rocket. The 21st-century equivalent involves hundreds of one-way trips into orbit, as corporations compete to provide global connectivity with ‘mega constellations’ of satellites.

Sending anything into space has historically been a costly and complicated ordeal. But the burgeoning commercial space market with advances in rocket technology, particularly a more agile and vertical engineering approach, have increased competition and lowered the barrier to entry. Satellites are getting smaller and smarter too. Traditional satellites in GEO (geosynchronous orbit – around 35,786 km above Earth) have provided us with persistent communication services since the 1960s. Satellites in LEO (low Earth orbit – 500 to 2,000 km above Earth) promise lower-latency communications and higher bandwidth per user.

Now that realizing capability in orbit is more feasible than ever before, there are huge opportunities for companies tapping into the emerging market of space-based internet connectivity. Some of the names are familiar, including SpaceX, Amazon, and Facebook. OneWeb, Telesat, and the European Union are also in the race. All have their eyes on the important (and lucrative) goal of providing internet to those who have been left behind by the digital divide, whether due to economic status, government restrictions, cost of infrastructure, or just being in the middle of nowhere. There’s also an emerging market of government customers for companies who can provide global, high-speed coverage.

The satellite constellation approach involves a network of small satellites positioned relatively close to Earth, handing off connections between one another. With enough satellites in LEO, users get both low latency and consistent coverage. SpaceX currently has more than 1,400 Starlink satellites in orbit and beta testing of its Starlink network is underway. The constellation could grow to as high as 30,000 in the coming years.

The FCC approved Amazon’s Kuiper constellation in 2020, which will consist of 3,236 satellites and be focused, initially, on the US market. OneWeb – now owned by Indian conglomerate Bharti Global and the UK government following a bankruptcy filing in 2020 –  is back in the race and has started launching satellites into orbit with a total of 648 planned. Telesat’s 298-strong Lightspeed network is thought to be around two years from launch.

Clearly, there’s about to be an explosion in the number of active satellites. There are close to 2,600 currently in orbit. If all of the above plans come to fruition, there could be almost 40,000. This rate of change in Earth’s orbital environment is unprecedented. And its impact could extend far beyond the necessary endeavor of providing all with internet connectivity.

Adding greater entropy to Earth’s orbit

Earth’s orbit is already a dynamic environment populated with hundreds of thousands of objects traveling at high velocity.

The U.S. government actively tracks close to 23,000 of them, including 8,000 satellites and all sorts of other fragments that have resulted from prior collisions and breakups. There are thought to be over 500,000 items too small to track but large enough to cause damage to an active satellite or spacecraft. In 1978, NASA scientist Donald Kessler predicted that LEO could become a maelstrom of uniform fragments enveloping Earth. An exponential increase in the amount of orbital debris could make our space ambitions impossible to realize, from satellite activity to astronomy to exploration.

Thousands more satellites are scheduled for launch and it’s easy to imagine the situation spiraling out of control. There is significant pressure for commercial ventures to operate sustainably.

SpaceX and OneWeb’s hardware are designed to have a lifespan of four to five years. It could then be several years before they are deorbited and burn up in Earth’s atmosphere. But importantly, the acceptance that redundant satellites can no longer linger endlessly in orbit is factored into their design.

Starlink’s relatively low altitude of 550 kilometers should simplify the removal of old hardware from orbit - which is an ongoing process. OneWeb’s hardware orbits at an altitude of 1,200 kilometers. The company is exploring commercial options for removing failed satellites from orbit and a grappling fixture is built in to facilitate their capture in the future. Both companies can also maneuver hardware to avoid potential collisions. But the risk of running into an object that isn’t actively tracked – and the knock-on effect of those seemingly inevitable incidents – is set to increase as more satellites are sent into orbit.  

A concern for the astronomy community

There are also concerns about the impact all of these satellites could have on our ability to observe space. In August 2020, the American Astronomical Society (AAS) released a report concluding that the effects of large satellite constellations on astronomical research and the human experience of the night sky range from “negligible” to “extreme.” Admittedly, that’s a wide range of potential impact. It’s explained by many contextual factors: The time of day that observations are carried out, the design of the satellites in question, the number of satellites, and the altitude of their orbit.  

The main takeaway from the AAS report was that astronomy and satellite constellations are on an unavoidable collision course. The findings showed that LEO satellites disproportionately impact science programs that require twilight observations, which include searches for asteroids, comets, and objects beyond the solar system. During twilight, the Sun is below the horizon for observers on the ground but not for satellites in orbit overhead. These are illuminated, leaving disruptive streaks across the sky as images are captured.  

Satellites that are higher in orbit, such as the OneWeb system, threaten to interfere with astronomical observations even during the night’s darkest hours. Fortunately, the report highlighted a number of ways to reduce the disruption. The suggestions included restricting constellations to orbital altitudes below 600km, darkening satellites or using sunshades to dim their reflective surfaces, eliminating the effect of satellite trails on research by using AI for automated image processing, and making their orbital information available to any observers keen to avoid them.

SpaceX has been quick to offer potential solutions, first launching DarkSat, a version of Starlink satellites with painted surfaces that reflect light diffusely (with mixed success). And latterly developing VisorSats, which deploy a visor that shades the satellite’s antennas from sunlight to taper its reflectivity.  

These alterations are by no means perfect for astronomers, but they represent a very positive step from the makers of satellite constellations.

The emerging market for end of life services

As the race to supply satellite connectivity heats up, so too does the race to provide secondary services for this new wave of commercial operators. These include operations to extend the life of existing infrastructure and removal services should a satellite fall into disrepair.

In March 2021, Astroscale, a Japanese company specializing in satellite servicing and orbital sustainability, launched an End-of-Life Services demonstration (ELSA-d) mission. ELSA-d will demonstrate the core technologies necessary for docking with and removing debris from orbit.

Earlier this year, San Francisco startup Orbit Fab outlined plans to offer a range of products and services across the commercial space industry. These include satellite refueling, the first ‘Gas Stations in Space’, and a recently announced NASA partnership testing the grappling systems required to develop satellite servicing.

To date, virtually all hardware sent into orbit has been designed with obsolescence in mind. As a result, a viable service industry has taken time to develop. The way we think about in-orbit services is set to change rapidly. With companies and services focused on sustainable space operations, a shift in investment is coming: from building and launching new spacecraft to extending the life of existing hardware.

To say that space is a unique commercial environment is a huge understatement. There’s no margin for error, high costs, and a high barrier to entry for any company with orbital ambitions. On the other hand, those involved are playing their part in the most pioneering endeavors the world has seen. The excitement is only tempered by the necessity to develop solutions that are sustainable, that keep space open to us for the decades to come.

The future of space sustainability

Operations that result in restricted access to space – either through the physical barriers imposed by snowballing orbital debris or by undermining astronomical research – could ultimately leave us worse off. But this conversation is coming to the forefront for government and commercial leaders, and progress is now being made with plenty of opportunities.

Technology can be used to hold satellite owner/operators accountable, such as investments in better tracking and prediction models, and using web-based services to more quickly and efficiently communicate. Satellites will need to become more autonomous with better on-board decision-making using AI/ML to learn patterns of behavior and better predict maneuvers and future positions. Additionally, more tracking sensors can be added to satellites thanks to the miniaturization of components. And with the advances in rocket technology and resulting greater launch capacity, it’s possible to launch sensors into space to aid tracking and identification.

There are myriad opportunities and challenges that have yet to be thought of. Space is a very complex environment and is becoming increasingly more complex, but advancements in technology can secure our future in this frontier.

At Slingshot Aerospace, our vision is to accelerate space sustainability to create a safer, more connected world. In other words, we are committed to space sustainability as a principle driving space activities. We want to ensure that space is a safe environment for future operations of human space flight, scientific missions, commercial missions, and missions by emerging space actors.