Satellite and space debris tracking as a service

All spacefaring nations must work together on common issues, such as tracking the thousands of pieces of space debris that could stifle the commercialization of space.
Commerce Secretary Wilbur Ross

On February 2, 1989, the Soviet Union launched its Cosmos 2004 satellite and the Chinese launched a rocket on December 15, 2009. Cosmos 2004 is now defunct as is the third stage of that Chinese rocket, but both remain in orbit. They were long forgotten until recently when LeoLabs, a satellite tracking service, predicted that they had a good chance of colliding at 971 km over the sea near Antarctica.

It turns out that they did not collide but they came within 11 meters of each other. The two objects have a combined mass of 2,800 kg and were traveling at a relative velocity of 52,900 km/h. Imagine what would have happened had those massive objects collided at that speed. Since they are in a vacuum, the collision would have been silent, but large and small fragments would have been scattered into their own orbits, exponentially increasing the likelihood of future collisions.

The Chinese rocket scientists were not thinking about the possibility of a collision with Cosmos 2004 when they launched their rocket in 2009, but today, with SpaceX and others planning to launch thousands of broadband-service satellites into relatively crowded low-Earth orbit, the debris problem is obvious and daunting, but there are some promising developments. (For more on the extent of space debris click here and here).

Governments have been tracking the orbits of satellites and debris larger than 10 cm for some time but a new company, LeoLabs, is using phased-array radar antennas to track objects as small as 2 cm. In a recent interview, LeoLabs CEO and Co-Founder Daniel Ceperley, said their phased-array radar antennas are capable of tracking the approximately 250,000 orbiting objects that are greater than 2 cm within a 100-meter margin of error.  

LeoLabs antennas can switch direction in one millisecond, but since it is difficult to locate and establish control over satellites with only one or a few observations in the first hours and days after deployment, they offer a Launch and Early Orbit service in which they focus more time on the satellites and SpaceX is using that service.

While the first hours and days after deployment are critical, the risk of a collision persists as long as a satellite is in orbit so LeoLabs also offers a Collision-Avoidance service that will report possible collisions a week in advance and follow up with increasingly more frequent and more accurate notices during the week. This will give satellite operators time to test alternative collision-avoidance maneuvers using LeoLab's interactive maneuver-simulation service.

The Collision-Avoidance service works if a satellite operator is trying to avert a collision with debris or a defunct satellite, but if two active satellites are involved, both parties must be informed and able to communicate about planned maneuvers. SpaceX says Starlink satellites will be able to maneuver autonomously to avoid collisions, but what happens if the approaching satellite also maneuvers in the same direction?

Up to this point, I've been talking about terrestrial tracking of satellites and debris, but tracking can also be done from space. A while ago, I suggested that SpaceX might equip their satellites to detect debris while in orbit and they have some autonomous collision avoidance capability, but as far as I know, they have no plans for offering collision avoidance data or service to others.

Northstar, a space-based Canadian startup, plans to track satellites from orbit. They have contracted for three satellites that will be in polar orbits at an altitude of 575 kilometers and plan to launch at least three more batches of three each in different orbits by 2024.

Like LeoLabs, Northstar plans to offer tracking as a service. While Northstar is several years behind LeoLabs, it will use different technology. If successful, Northstar plans to track satellites from low-Earth to geostationary orbits. They will be able to use optical scanners since there are no problems with the atmosphere and weather in space and will have a wide view, enabling them to revisit objects frequently and quickly and accurately predict orbits.

The investment and operating costs may also be different than those of LeoLabs, but I don't know whether it will have cost more to build and operate the 12 LEO satellites Northstar plans to orbit in 2024 or the six radar tracking stations LeoLabs will have in operation next year.

(NorthStar and ExoAnalytic, which tracks satellites and debris with terrestrial optical telescopes, announced a partnership in April 2019, evidently intending to combine their observations, but there is no further mention of that on their Web sites and Northstar has changed it's business model which initially called for dual-use satellites combining both Earth observation and satellite tracing.)

As shown below, many nations now launch, own, and/or operate satellites. (The map is as of 2016 but the database at the site included 68 nations as of August 1, 2020). Whether the tracking is done from the ground or space, it is clear that global data must be shared and collision-avoidance protocols invented, standardized, and perhaps automated. (Holger Krag, director of the European Space Agency (ESA) Space Safety Programme Office hopes to like to demonstrate automated maneuver coordination by 2023).

Achieving global space law and regulation like we have for the seas seems like an impossible technical and political challenge -- exacerbated by the fact that many satellites and tracking services, like the recently completed US "Space Fence," are operated by military and security organizations -- but it must be done. There has already been a close miss between a Starlink satellite and Aeolus, an ESA satellite, in which a software bug led to a communication breakdown between the ESA and SpaceX.

I am amazed to find myself agreeing with and quoting a member of Trump's cabinet, Commerce Secretary Wilbur Ross, who said "all spacefaring nations must work together on common issues, such as tracking the thousands of pieces of space debris that could stifle the commercialization of space."

Update 4/27/2021

The Union of Concerned Scientists has updated the satellite database mentioned above. As of January 1 2021, 72 nations have launched and/or operated satellites and there were 3,732 in orbit. The need for global regulation and collaboration will increase rapidly as SpaceX and other low-Earth orbit satellite companies and governments launch mega-constellations.

Update 6/4/2021 

LeoLabs has received an investment of $65 million to add build new tracking stations and add services. The company was also named one of the 10 most innovative space companies of 2021 by Fast Company and their service was named the best space product of 2020 by Forbes Magazine.

Might satellite constellations learn to avoid debris with sensors on satellites?

There were no artificial satellites before Sputnik in 1957.
Today there are about 5,000 with plans for thousands more.

Space debris is problematical.

The European Space Agency (ESA) reported that as of January 2019 there were about 5,000 satellites in space and 1,950 of them are still functioning. Hopefully, those functioning satellites have fuel and thrusters that will enable them to de-orbit and (mostly) burn up in the atmosphere when their useful life is finished. The remaining 3,050 are slowly drifting, along with a lot of debris.

The ESA estimates that there have been over 500 break-ups, explosions, collisions, or anomalous events resulting in fragmentation and they estimate that there are 34,000 debris objects >10 cm, 900,000 from 1 to 10 cm and 128 million from 1 mm to 1 cm. NASA says there are more than 20,000 pieces of debris larger than a softball, 500,000 the size of a marble or larger and many millions so small they can’t be tracked. (watch: NASA's Animation Shows Massive Space Junk Around Earth)

In low-earth orbit (LEO), debris circles the Earth at speeds of about 7 to 8 km/s. However, the average impact speed of orbital debris with another space object is approximately 10 km/s and can be up to about 15 km/s, which is more than 10 times the speed of a bullet. At those speeds, a collision with a small object can do significant damage. This sounds like a disaster waiting to happen and the current and planned proliferation of LEO satellites increases the likelihood of a Kessler Syndrome event -- a cascade of collisions between satellites and the ensuing debris.

As Kessler says "The cascade process can be more accurately thought of as continuous and as already started, where each collision or explosion in orbit slowly results in an increase in the frequency of future collisions." If you aren't worried yet, watch the following short video or read Kessler's 1978 paper.

Kessler's warning was taken seriously and NASA and others have been working on debris mitigation policy and technology for years, but the silver bullet has not been found. The Space Surveillance Network tracks approximately 23,000 relatively large objects and you can query the database here, but what about the millions of objects that are too small to track?

The SpaceX press release for their Starlink Mission hinted at their collision-avoidance strategy, saying that

Each spacecraft is equipped with a Startracker navigation system that allows SpaceX to point the satellites with precision. Importantly, Starlink satellites are capable of tracking on-orbit debris and autonomously avoiding a collision.

That sounds promising, but autonomously resolving and recognizing a marble-sized object that is approaching at up to 15 km/s, computing its trajectory and firing thrusters to avoid a collision can't be done -- even by Elon Musk.

Relatively few debris objects can be tracked terrestrially, but a satellite might be able to recognize a piece of debris and transmit its characteristics to a terrestrial processor, greatly expanding the tracking database. SpaceX may be approaching this as a machine-learning problem in which the entire constellation, not individual satellites, is learning to avoid collisions.

That is pure speculation, but it was triggered by a few thoughts.

For a start, at the end of 2017, SpaceX delivered a space debris sensor (SDS) to the International Space Station. As shown in the following short video, the SDS is capable of monitoring the size, speed, direction, and density of small particles that impact it.

Elon Musk also has a strong interest in machine learning -- he was a co-founder of openAI and his Tesla cars act as sensors uploading driving data that is used for training autonomous vehicles.

Going out to the very end of the limb -- Musk is a fan of science fiction and speculation on the possibility of a swarm of man-made objects learning about existential risks is reminiscent of emergent intelligence in Asimov's fictional planet Gaia or Teilhard de Chardin's noosphere).

Musk opened his Tesla patents and, if SpaceX demonstrates the feasibility of this approach to debris avoidance (and perhaps one-day removal), I expect that he would share this technology with competitors like OneWeb and Telesat and the space agencies of all nations.

Like global warming, space debris is an example of a tragedy of the commons and is a threat to all nations. As the cartoon character Pogo said, "We have met the enemy and he is us." Ironically, global tragedies of commons can unite us.