Within the next decade, the number of satellites on orbit will increase by several orders of magnitude. With several operators proposing mega-constellations and a slew of rising startups preparing to deploy their own satellites, debates around the secondary impacts that this influx of crafts will have on both Earthly and Orbital operations. In some cases, the policy has not yet caught up to the pace of innovation. In order to properly plan for regulation and policy, it is important to fully understand the nature and scope of the challenges that come with building businesses in humanity’s next frontier, to effectively prioritize, plan, and act.
Challenge #1: Debris
One of the most discussed concerns around space is in regards to congestion, and the fear that a substantial increase in satellite count will increase the likelihood of collisions. This fear stems from a theorized phenomenon known as the Kessler effect, in which the accumulation of space debris contributes to the creation of more debris, effectively making certain parts of orbit unusable. The Russian ASAT test conducted in late 2021 made this fear top of mind for some space operators, as Russia destroyed one of its own, old satellites and created over 1,500 pieces of trackable debris in low earth orbit (LEO). The European Space Agency estimates that there are as much as 1 million pieces of debris between 1 - 10 cm, and around 36,000 objects greater than 10cm that are currently posing a threat to satellites and human spaceflight.
SpaceX’s Starlink is one of the largest constellations in orbit with over 1,800 satellites on-orbit and has absorbed most of the public’s attention. One report by Hugh Lewis, head of the Astronautics Research Group at the University of Southampton, found that Starlink satellites are involved in about 50% of close encounters in LEO, where a close encounter is defined as a situation where two spacecraft pass within a distance of 0.6 miles (1 km) from each other. Though LEO itself is about 2300 Km wide (1400 miles) and satellites are spread across various altitudes within that range, maneuvering is common in order for satellites to maintain their authorized orbit, avoid debris, and navigate around other satellites. To perform these maneuvers, Starlink satellites come with an automated collision avoidance system built-in, which allows the satellite to perform its own micro-adjustments to keep its orbit and avoid objects in space. This automated system makes it easy for SpaceX to manage such a large constellation, but a lack of transparency across operators clouds the forecasted location of these satellites. LeoLabs is one company attempting to address this problem by deploying a ground network of radars capable of tracking orbital debris with high resolution.
In regards to satellite-on-satellite collisions, the core issue here boils down to a lack of an “air traffic control”-type authority. In being able to map the precise location of objects in LEO, operators would not be left guessing what the real-time trajectory of a satellite may be. An automated collision avoidance system would further facilitate this process. As objects in LEO travel at speeds upwards of 25,000 km/h, even small debris (<10cm / <4in.) poses a strong risk to the life of a satellite.
“Our data shows that an active satellite is 10 times more likely to get hit by a piece of debris than another active satellite, and that number is going to grow to 100 times when we start tracking small debris. … Starlink, and all other satellite operators, are victims of the debris environment they find themselves in, rather than causes of the problem.” - Daniel Ceperley, CEO and Founder of LeoLabs
To mitigate this part of the equation, companies will need to make a proactive effort to deorbit their inactive satellites, and for the industry to identify solutions that can clean up debris from orbit. Additionally, efforts to establish a proper “air traffic control” in orbit are required for operators to safely and transparently navigate in space. Policy experts and researchers will need to set updated standards for accountability and “rules of the road” in orbit, taking into account collision avoidance technology, constellation size, and deorbit strategy. The industry is already moving in this direction, most recently exemplified by NASAs call for a risk assessment of the second-generation Starlink constellation, citing how a lack of rules and transparency can lead to compounding effects that result in a collision, though they did not oppose the next-generation constellation. The current V1 12,000 satellite constellation has been approved, the proposed V2 constellation will stand at 30,000 satellites, making a more in-depth evaluation the responsible thing to do to ensure the current system in place can scale. In that same vein, policy experts should be mindful of all other dynamics that could lead to a collision, such as understanding what type of asset is in question (rocket, active satellite, inactive satellite, etc.). Work is already underway here through the Space Sustainability Rating that is being put together by the European Space Agency, the World Economic Forum, and the MIT Media Lab. Until then, SpaceX has stated that their satellites are designed to deorbit on their own, and burn up in the atmosphere, posing no threat to the satellites in LEO as they reach the end of their service life.
Challenge #2: Deorbiting
One key aspect of this environment is the de-orbiting strategy of a satellite. Once a satellite reaches the end of its service life, satellites will enter what is called a “graveyard orbit”. For higher altitude satellites in GEO, satellites are elevated to an altitude 300km higher than GEO, well out of the way of operational orbits. For satellites in LEO, operators lower the altitude of the satellite so that it will naturally re-enter the atmosphere within 25 years. As the satellite falls through the atmosphere, the heat from air friction burns up the satellite, causing it to disintegrate before it ever reaches the surface. This option is only available to operators that can demonstrate that the probability of injury or property damage is less than 1 in 10,000. In the case that a satellite does not qualify for graveyard orbit, a controlled deorbit is instead performed, in which the satellite is maneuvered over a predetermined broad ocean area. As mentioned, Starlink satellites have always been designed well below the 1 in 10,000 threshold. But an updated design now shows that the satellites will be able to fully disintegrate, nearly eliminating their probability of injury or property damage. With a large number of Starlink satellites already orbiting over broad ocean areas, the risk is even further reduced. Though this reduces risk of physical injury of people on Earth and the risk of collision on orbit, it is important for future research to analyze the sustainability of such deorbiting strategies. Satellites contain a large amount of aluminum, which could remain in particulate form in the atmosphere after the satellite burns up. The idea of using a small amount of aluminum particles or aerosols in the atmosphere has long been theorized as a method to reduce the impacts of climate change by increasing the Earth’s albedo. In contrast, there are fears that this strategy could instead leave small, temporary holes in the atmosphere. Though the actual amount of aluminum necessary to impact this area in either direction is unknown. This area of space operations has largely remained unstudied in the past, as its impact was thought to be negligible by regulatory authorities. But with more satellites entering orbit, a reevaluation of this method would be the responsible thing to do. More research is required to fully understand the impact these strategies can have on the environment, and in which direction.
Alternative approaches to deorbiting are already being worked on. These solutions range from in-orbit spacecraft designed to transport dead satellites to a return craft, to craft that can implant themselves on dead satellites and allow satellites to be returned safely to Earth, without burning up in the atmosphere. A potential solution may include SpaceX’s own Starship rocket. One of the rocket’s proposed functions is to deploy satellites using its large fairing door, which is novel on its own and has potential to vastly change how the space industry operates. A secondary use of this fairing door could be to effectively swallow dead satellites and small debris, and bring it back down to earth to be disposed of, or recycled, properly. While the technology remains promising, it is still early, and only time and regulation will tell what option is most feasible, and sustainable.
Challenge #3: Astronomy
Another concern arising from the growth in LEO satellites has to do with the light pollution created by the vast amount of satellites. Common concerns here boil down to light reflecting off of the satellites impacting ground-based observation of the night sky. Though amateur astronomers can easily remove these faults in processing, scientific researchers must navigate this challenge differently. Market-leader SpaceX has made efforts to mitigate its impact, initially through its Darksat prototype, and now through installing visors to reflect light away from the Earth. A 2022 study conducted by the National Science Foundation-funded Zwicky Transient Facility (ZTF) found that this “Visorsat” design reduced the satellites reflectivity by a factor of about 4.6, with respect to the original design. This results in the satellites having an apparent brightness level of magnitude 6.8. While this is dimmer than even the faintest stars (magnitude ~6), it is just shy of the standards outlined by the SATCON1 workshop in 2020 that called for satellites to be at a magnitude 7 or fainter. As far as the streaks caused by these satellites, the same study found that roughly 18% of all twilight images (those taken at dusk or dawn) were affected. The team believes that once the constellation grows, it is likely that nearly all images taken by the facility will be affected, though non-twilight images are not expected to be affected. Despite this, ZTF notes that their science operations have not been strongly affected, as they report that a single streak impacts less than one tenth of a percent of the pixels in their images. For context, the ZTF exists to catalog and study cosmic objects such as supernovae and near-Earth asteroids.
"There is a small chance that we would miss an asteroid or another event hidden behind a satellite streak, but compared to the impact of weather, such as a cloudy sky, these are rather small effects for ZTF." - Dr. Tom Prince, Ira S. Bowen Professor of Physics, Emeritus, at Caltech
Given the well-characterized orbits of the Starlink constellation, scientists believe that software can be developed to help mitigate potential problems, such as a tool that can predict the locations of the Starlink satellites, thus helping astronomers avoid scheduling an observation when one might be in the field of view. Other tools could take this a step further and assess whether a passing satellite may have affected an astronomical observation, which would allow astronomers to mask or reduce the negative effects of the streaks. Though these findings are promising, they are particular to the ZTF itself, and more research is needed to better understand how other facilities may fare. With SpaceX continuing to refine their light pollution-mitigation designs, we remain hopeful that future iterations of the constellation will show a further-reduced impact.
Radio astronomers have a similar challenge around the fear of interference from LEO constellations, as the frequency bands used by satellites have some degree of overlap with upcoming bases planning to use telescopes to identify biosignals in far off planets. The SKA Observatory (SKAO) is one such center under construction that believes some of its operations could be made less efficient due to interference, though it believes there are mitigation efforts that can be implemented to reduce these effects. In February 2022, SKAO and the National Science Foundation’s NOIRLab were selected to co-host a center to implement these mitigation efforts, which are similar in nature to those of optical astronomers (satellite tracking, spacecraft design, software tools, etc.). As regulation currently ensures these facilities are radio-silent and free from cellular or other interference sources, it is likely that satellites will work to be compliant here as well.
Challenge #4: Spectrum
Wireless communications are built on the radio frequency (RF) spectrum. Meaning, for a satellite to communicate with a ground terminal and vice versa, the signal must travel through and mingle with a vast array of competing signals to close the connection. When unwanted RF signals disrupt the link between transmitter and receiver, interference occurs and can prevent reception altogether, resulting in temporary loss of a signal or a reduction in quality. One way people work to mitigate interference is by splitting up spectrum into different bands where different technologies or companies must receive authorization to operate in.
Spectrum allocation then becomes somewhat of a “land grab”, as not being authorized to send signals translates to not being able to do business in certain regions or entire countries. The authorization process is one that is dated and slow-moving, and oftentimes it is easier for operators to work through distribution partnerships to service regions, rather than go through the process starting from zero. This dynamic was exemplified early in 2022, when the Indian government halted Starlink pre-orders and forced the company to refund customers, as their spectrum license had not yet been approved. Shortly after, new LEO operator OneWeb would announce its distribution partnership to service India alongside Hughes, which has greatly accelerated the new entrant’s licensing process.
The fight for spectrum can sometimes evolve into legal battles as operators present and refute claims around interference, as shown by Dish and SpaceX’s ongoing dispute around the 12GHz band. Though this case remains to be closed as of February 2022, it is up to the FCC now to determine whether disputes such as this one stem from genuine technical concerns, or power dynamics. Part of the mystery around spectrum and interference stems from the approaches operators currently use to understand their network metrics such as coverage, capacity, and quality. The current industry standard is to collect data through crowdsourcing or to perform something called a drive test, in which a person drives around an area using special tools to map out the network and collect insights on the metrics in question. This approach simply cannot scale with the pace of SatCom or even cellular, as new areas receiving coverage may be extremely challenging, or impossible, to map this way. In addition, these surveys will only provide information on a single network, rather than map the use and coverage of spectrum in an entire region or geography. Aurora Insight is one company tackling this problem through its network level sensing technology that can completely remove drive testing from the equation. Moving away from dated practices towards better management of our networks could help companies and governments better navigate spectrum regulation in the future. As new networks grow and evolve, spectrum clearing efforts could have lasting impacts on companies trying to do business, with some initiatives costing companies as much as $3.3B.
The world is in the midst of the growing pains that come along with new technologies. With the introduction of new operators in space, the world is now working to match the pace of space innovation to ensure operations across industries can continue, and improve where historical inefficiencies have persisted. With both new and legacy SatCom operators entering LEO, all actors within the industry must work towards building solutions that are both compliant and sustainable with an evolving regulatory, and environmental, landscape. Supplementary to this, these solutions can only come to fruition with industry collaboration. With companies such as SpaceX already working with leading institutions and regulatory authorities to ensure a smooth deployment of their constellation, we remain hopeful that innovation across fields will only be maintained, or augmented, due to the introduction of new technologies in low earth orbit.