Guest editorial: Prevent space collisions
On February 10, an event happened in space that many thought was statistically impossible. Just before noon Eastern Standard Time, two satellites collided 470 miles above Siberia at a combined velocity of over 22,000 mph. As of July over 1,200 pieces of resulting debris, bigger than a softball are being tracked by the US Air Force's Space Surveillance Network (SSN). Many more pieces too small to track consistently were also created in the collision. These pieces ended up in one of the most crowded places in Earth orbit where many imaging and Earth-observing satellites are located.
There have been collisions in space before, but never between two payloads. The previous seven known unintentional collisions in space have all been between inactive satellites and either spent rocket stages or pieces of debris. This time, it was between an active Iridium satellite, part of the company's constellation of 66 (now 65) low Earth orbit communication satellites, and Cosmos 2251, an inactive Russian military communications satellite.
The most distressing aspect of this collision is that it could have been avoided. The positions of both objects were well known to the U.S. military through the network of radars and optical telescopes that make up the SSN. They also have existing procedures to screen satellites for possible collisions and provide advance warning to the satellite's owner-operator. However, due to resource limitations this screening is only done for a limited list of important objects such as the International Space Station and critical US national security spacecraft. Iridium was also well aware of the risk of collision to its satellites and had been working with the military to detect potential collisions until it stopped in 2008, stating that there were just too many close approaches to handle cost effectively.
The good news is that there are a variety of options that could help prevent scenarios like this in the future. One would be for the U.S. government to release its high precision tracking data to all satellite owner-operators, allowing them to perform their own collision warning analyses. To be useful, though, this data would have to be more precise than the low accuracy data the U.S. government already releases publicly.
A second option is to continue to keep the high accuracy data private and for the US government to perform collision warning for all owner-operators. This is entirely possible, but, would require a significant increase in the resources currently allocated, primarily in the number of trained analysts. It would also require a policy debate over whether or not the military is the right department to be performing this task, as well as what the inherent liability and legal issues are.
The third option is for the U.S. government to allow, and preferably support, the creation of an international civil space situational awareness system. This system would have the goal of providing the basic tools necessary to enable all space actors predict possible collisions and take avoidance measures. This includes positional data on objects in orbit, space weather data, and atmospheric density, plus the analytical tools to make decisions this data. It would also involve contributions of data on precise positions and possibly future maneuvers by commercial owner-operators.
Any of these three options would go a long way towards preventing future collisions like this one. However, they cannot prevent collisions between objects that are not under control. Of the more than 19,000 objects tracked by the U.S. military, fewer than 1,000 are active satellites and less than half of those are thought to have any maneuvering capability. This is why collision warning and avoidance needs to be combined with continued emphasis on minimizing the creation of new debris and research into eventually being able to remove debris from orbit. All three efforts are critical to ensuring the long term sustainability of space for all.
Brian Weeden is a technical advisor with the Secure World Foundation, an organization that focuses on the secure and sustainable use of space.