The topic of Space Traffic Management (STM) has been discussed in everything from the US Senate to White House press briefings over the last few years, and particularly over the past few months. The lack of space traffic management policies is a recurring problem across government. You can’t manage what you can’t measure, which is one of the fundamental challenges that goes unaddressed. Correct discovery, identification and tracking of all elements within the management domain is a core principle of any STM system. All large debris must be contained in each low-Earth management area.
We have yet to develop the necessary technologies and systems to effectively anticipate conjunctions between active satellites and large debris objects. In other words, STM does not exist today, it is actually the “wild west”.
Near-Earth space is big, but is it big enough to ensure safe flight with the rapidly growing population of active satellite constellations and orbiting debris? General James Dickinson, head of the US Space Command, recently stated that his organization is tracking nearly 35,000 objects, a very small subset of the actual number of objects in low orbit. This number represents an increase of 22% compared to just a few years ago. Considering the total number of space objects, the challenges seem insurmountable, and they currently are.
As of September 2021, the European Space Agency’s Space Debris Office offered some relevant historical facts:
The number of satellites launched into Earth orbit is approximately 12,000, of which approximately 7,500 are still in orbit.
The number of successful rocket launches since the beginning of the space age in 1957 is about 6,100.
The number of still functioning satellites is about 4,700.
The number of large debris objects regularly tracked and cataloged by the US Space Surveillance Network is more than 29,000.
The number of lift-offs, explosions, collisions or anomalous events that led to fragmentation is over 600. The total mass of all space objects in Earth orbit is over 9,600 tons.
The number of orbiting debris objects larger than 10 centimeters in size, estimated by statistical models, is 36,500. There are 1 million objects between 1 and 10 centimeters in size and 330 million objects between 1 millimeter and 1 centimeter. Due to insufficient sensor coverage, one of the biggest challenges we face is full space domain awareness. This challenge is very different and more complex than air and sea area awareness. Yes, there are systems (either developed or under development), but none are integrated at a sufficient level to provide comprehensive awareness of the space realm. Most STM discussions focus on the roughly 35,000 objects tracked, but that’s only 0.01% of the total population. The threats to sustained space security lie in millions of untraceable objects.
Any multi-pronged approach to STM should include debris remediation to eliminate the 5‑centimeter and smaller objects from altitudes between 600 kilometers and 1,200 kilometers, as well as provide 4 pi steradian sensor coverage to detect and track larger objects. The biggest pollutant are the smaller, but sufficiently large objects that can damage operating spacecraft in single collisions. These orbiting wrecks are too small to track and the resulting damage to satellites cannot be verified or recorded. Still, there is ample evidence that such debris is the most dangerous due to its density, relative encounter speeds, and the fact that it cannot be tracked. It is the presence of these objects that will cause the most serious damage to satellites. The continuous and selective removal of parts of the 1 millimeter to 10 centimeter large objects is necessary for flight safety and permanent access to space. Therefore, sustained stability and safety in orbit requires removal operations that effectively and permanently limit the number of small objects.
Summary of the news:
- There is no perfect system for managing space traffic