by Researchers have found that attempting to avoid collisions in orbit increases the risk of future collisions after each evasive maneuver. The reason? Current space traffic management methods cannot adequately cope with the increase in the number of satellites in space.
Analysts with the Pennsylvania-based company COMSPOC (short for “Commercial Space Operations Center”), after each satellite collision avoidance maneuver, space traffic operators and observers have only a rough idea of where their objects are.
The difference between a satellite’s assumed position and its actual position can be as much as 25 miles (40 kilometers). As a result, after that collision the predictions are less than accurate for several days.
“It’s hard to plan and decide what to do and take action when you have such large errors,” Dan Oltrogge, chief scientist of COMSPOC, told Space.com.
Related: The worst space debris events ever
With the increase in the number of objects in orbit – functional satellites and space junk both — it is easy to see why such uncertainties are cause for concern. For example, satellites of SpaceX Constellation An internet mega-constellation had to merge 25,000 collision avoidance maneuvers in the six month period between December 1, 2022, and May 31, 2023.
Experts think this number is likely to double in the half year between June 1 and December 1, 2023, as SpaceX continues to launch additional Starlink satellites at a steady rate. Constellation is now more than 5,100 active satellites, which is less than half of the planned 12,000 satellites of the first generation Starlink orbital network. But SpaceX has plans to expand its space fleet to more than 40,000 satellites in the future, and other operators have similar ambitions.
Soon, orbiting satellites World they may be forced to make millions of maneuvers to avoid collisions each year. With inaccurate data being entered after each such move, catastrophic crashes could easily occur.
In fact, one such collision has already occurred. According to a recent analysis by COMSPOC, the infamous 2009 crash The collision between the US commercial communications satellite Iridium 33 and Russia’s unconventional Kosmos-2251 occurred after Iridium operators instructed their craft to make two short thruster burns to adjust the satellite’s position on the day before the collision. But the US Air Force, which was responsible for monitoring space traffic at the time, did not know about these maneuvers and did not take them into account in their calculations of the trajectory of Iridium 33. The consequences were disastrous. Because of the collision between the two bodies, each with a mass of more than 1,540 pounds (700 kilograms), produced thousands of fragments of debris, the most hurtles around the Earth to this day.
“Didn’t know what the maneuvers were,” said Oltrogge. “When they made the predictions, the models showed a lost distance of about 230 meters [755 feet] during closest approach and a collision probability of 10-34, which has a very small chance of collision.”
RELATED STORIES:
— Photos: Images of space debris & cleanup concepts
— Space Junk: Tracking and removal of orbital debris
— Colliding space debris makes a ‘noise’ that could be heard from Earth
When COMSPOC analysts incorporated data about the two short thrusters into their equations that modeled the collision, they got a much more serious prediction. Unbeknownst to any of the parties involved at the time, the predicted distance dropped to 50 feet (15 m), and the probability of collision increased to 1 in 1,000.
If the Iridium operators had known about this much higher probability of collision at that time, they would have “certainly [have] accept[n] evasive action,” Oltrogge said.
Nearly 15 years after that collision — the second-worst space debris event in history — mainstream space situational awareness providers don’t routinely incorporate data about satellite maneuvers into their predictions, according to Oltrogge.
But other things have changed since 2009. At the time of that accident, there were only about 1,000 operational satellites and 15,000 known pieces of space debris in Earth orbit. Today, nearly 9,000 operational spacecraft share the planet’s orbit with more than 35,000 tracked pieces of space junk, and millions of pieces of debris too small to monitor.
“Today, we have a much higher chance for collisions,” said Oltrogge. “And with all these maneuvers, we see a lot of degradation in our spatial situational awareness data.”
But Oltrogge thinks there is already a solution to the problem. Commercial companies, including COMSPOC, have developed platforms that can incorporate maneuver data received from satellite operators. New types of sensors and smart algorithms can further improve the accuracy and timeliness of predictions.
“We have to do better, and we should do that holistically,” said Oltrogge. “We should explore many different aspects, including tracking smaller debris and fusing data together and increasing collaboration between satellite operators and space situational awareness data providers.”
