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Emergency maneuver by ISS to avoid debris underlines why space traffic management is crucial

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ISS collision space traffic management

The International Space Station (ISS) had to carry out an emergency avoidance maneuver to avoid a potential collision with an “unidentified object”. The incident saw NASA chief Jim Bridenstine tweeting his frustration while making a case for space traffic management.

“The Space Station has maneuvered 3 times in 2020 to avoid debris. In the last 2 weeks, there have been 3 high concern potential conjunctions. Debris is getting worse! Time for Congress to provide @CommerceGov with the $15 mil requested by ‪@POTUS for the Office of Space Commerce,” Bridenstine tweeted.

Earlier, the ISS had conducted two maneuvers – on April 19 and July 3 — to avoid potential collisions. The maneuver in April was triggered by a high-risk conjunction with a breakup fragment generated from the Fengyun-1C (FY-1C) anti-satellite test conducted by China in 2007, according to Orbital Debris newsletter from NASA. The July maneuver was to avoid an object with International Designator 1987-079AG and SSN# 27923, which was generated from the explosion of a SOZ (Sistema Obespecheniya Zapuska, “Launch Support System”) ullage motor, or SL-12 auxiliary motor, in 2003, it added.

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What happened on Sept 22

The September 22 maneuver was done roughly at 5.19 pm EDT. Using the ISS Progress 75 thrusters and with NASA and Russian flight controllers working in tandem to conduct a 150-second reboost to avoid the collision, NASA said. Themaneuver used the Russian Progress resupply spacecraft currently docked to the aft end of the Zvezda service module, an earlier statement from NASA had said. 

The maneuver raised the station’s orbit out of the predicted path of the debris, which was estimated to come within 1.39 kilometers of the station with a time of closest approach of 6:21 pm EDT.

Even though the crew was not in any danger, because of the late notification of the possible conjunction, the three Expedition 63 crew members were directed to move to the Russian segment of the station to be closer to their Soyuz MS-16 spacecraft as part of the safe haven procedure out of an abundance of caution, NASA said.

While the space agency didn’t give the details of the debris, space activities and launch commentator Jonathan McDowell said on Twitter that the object that ISS avoided was from the breakup of Japan’s H-2A F40 rocket stage. At 2221:07 UTC it passed within a few km of ISS at a relative velocity of 14 6 km/s, 422 km over the Pitcairn Island  in the South Pacific.

“Orbit data for ISS this morning shows it moved from a 419.2 x 420.4 km orbit to a 419.3 x 421.2 km one. The change moved the ISS physical position by about 5 km by the time of the H-2A debris encounter,” McDowell’s another tweet said. He also added that this was possibly the quickest collision avoidance burn planned for the ISS as  the warning came only that day.

Why space traffic management is critical

In recent times, experts have warned about the increasing number of objects, especially the upper stages of rockets, in the Earth’s lower orbits, leading to collision risks.

According to the Union of Concerned Scientists, which maintains a database of active satellites in orbit, there were a total of 2,666 satellites in space as of April 1, 2020. Of these 1,918 were in LEO. Also, there are more than double that number of satellites that are dead or lost. And then there are rocket stages, or even nuts and bolts left behind by astronauts, not to mention the millions of smaller, harder-to-track objects such as flecks of paint and bits of plastic. ESA estimates the total number of space objects in Earth orbit around 29,000 for sizes larger than 10 cm, 670,000 for sizes larger than 1 cm and more than 170 million for sizes larger than 1 mm!

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Any of these objects can cause damage to an operational spacecraft. For example, as per ESA, a collision with a 10-cm object would entail a catastrophic fragmentation of a typical satellite, a 1-cm object would most likely disable a spacecraft and penetrate the ISS shields, and a 1-mm object could destroy sub-systems on board a spacecraft.

The OECD has warned in a recently published report that economic and societal vulnerabilities to space hazards, in particular debris, are growing. For satellites in geostationary orbit, such a damage could amount to an estimated 5-10% of the total mission costs, which could be hundreds of millions of dollars. In LEO, the relative costs per mission could be even higher than 5-10%.

The cost of inaction, however, would be far greater. Enough debris in orbit could ultimately lead to the “Kessler syndrome” — a theoretical scenario in which the density of objects in LEO due to Space pollution is so high that collisions between objects could cause a cascade, each collision generating further debris that increases the likelihood of further collisions. OECD says this could be “an ecological tipping point that may render certain orbits unusable”, severely impacting weather forecasting, climate monitoring, Earth sciences and space-based communications.

Whose job is it in US

That is why space traffic management is a critical area for governments. In the United States, this has traditionally been managed by the Department of Defense. However, as the number of objects in orbit increased, it was felt that space situational awareness as a service from Defense was no longer adequate.

As part of Space Policy Directive-3, in 2018, the responsibility for Space traffic management activities was transferred to the Department of Commerce. Recently, a Congress-commissioned panel under the National Academy of Public Administration (NAPA) reaffirmed that the Office of Space Commerce at the Department of Commerce was the best suited civil agency to perform such tasks. There hasn’t been much progress on this front owing to lack of funding.

Bridenstine in his tweet urged Congress to release the $15 million funding that Commerce Department had advocated for Office of Space Commerce work as part of its latest budget proposal.