Sunday, December 19, 2021

The Russian anti-satellite demonstration -- a month later

It was a "demonstration," not a "test."

On November 15, Russia demonstrated its ability to destroy an orbiting satellite, Cosmo 1408, by hitting it with a direct-ascent rocket. In an earlier post, I noted the anti-satellite demonstration and speculated on why Russia may have done it and why the Chinese had not condemned it. In this post, I'll look at the evolution of the resulting debris cloud and say more about the possible motivation.

In the immediate aftermath of the collision, when the debris fragments were closely bunched, there was fear of a possible collision with the Chinese or International Space Stations, but over time, the fragments began to spread out, as shown below. (Click the image to enlarge it).

By November 16, LeoLabs had detected 288 debris objects, 253 of which are shown in the Gabbard plot on the left,. A Gabbard plot shows the altitude of the apogee and perigee and the period of each of the orbiting debris fragments. (The circled points show the apogee and perigee of one of the fragments). By December 7, more objects had been tracked and Jonathan McDowell generated the second plot. Its clear that the debris cloud is spreading out with time as more objects are detected and tracked. 
The December 17 visualization from LeoLabs shows the debris as completing a rough orbital plane. (I say it is approximately 591 objects because that was the number of orbiting objects in the satellite catalog on  December 17 and LeoLabs may have been tracking more since they have the ability to track smaller objects). The fourth image is a visualization of over 2,000 objects six months after a Chinese anti-satellite test in 2007. It foreshadows the ongoing spread of Cosmos 1408 debris.
By December 17, had tracked 604 objects, 13 of which had been driven to low altitudes and had already decayed. (One of those was from an earlier accident). The characteristics of the orbits of the remaining 591 debris objects are shown below:

The altitudes shown above are near those of many currently approved broadband constellations as well as numerous constellations for Earth observation, automotive, military, and other applications, not to mention apparent nut-cases like Rwanda's application for 327,230 satellites. Furthermore, higher altitude satellites will have to cross these debris orbits on the way up and the way down when they are retired.
Shortly after the breakup, LeoLabs predicted there would eventually be from 1,500 to 2,500 debris objects, but when Jonathan McDowell pointed out that the intercept was generally in the same direction as the satellite vector they reduced their estimate of the number of debris objects and increased expected apogees. While they expect fewer objects, the average mass and size will be greater and they will remain in orbit for longer times.
LeoLabs summed it up by stating that "this occurred at one of the worst possible orbits" and "there will be some potential collision risk to most satellites in LEO from the fragmentation of Cosmos 1408 over the next few years to decades." 
Was it a "test" or a "demonstration?
The Russians chose a relatively large satellite at a dangerous altitude for the "test." Cosmos 1408 had a mass of ~2,200 kg. It orbited with an apogee of 490 km and a perigee of 465 km and its radar cross-section was 8.63 m^2. The U.S. military classifies objects over 1 m^2 as large and  India chose a safer 283 km altitude for their 2019 test.
Russia warned on state television that this "test" showed they could blow up 32 GPS satellites with this new anti-satellite technology, and they tied it to their troop buildup on the Ukrainian border. (GPS satellites orbit at much greater altitude).
This was not Russia's first anti-satellite test. They had previously conducted 10 direct-ascent and 22 co-orbital tests. Ten of the co-orbital tests had hit targets and produced small amounts of debris and the direct-assent tests were preceded by technically similar anti-missile tests. Those were tests. This was a demonstration.
The debris from the destruction of this satellite will not trigger a Kessler syndrome or put SpaceX out of business today, but it reflects a defiant, irrational attitude that threatens the space commons. Imagine the impact of such a collision if it were to occur five or ten years from now.
Related links
Listen to this podcast interview of Brian Weeden of the Secure World Foundation. Weeden puts the Russian demonstration in its political and historical context and discusses efforts to achieve an international ban on the destruction of orbiting objects.
For a discussion of the difficulty of accurately tracking orbiting satellites and debris and acting in time to avoid collisions, check out The Dilemma of Space Debris by David Fikleman -- "This process is very much like quantum mechanics, in which an entity is described by a probability density and a future state can only be estimated statistically." (You can see the 2014 first draft of this article here).
Update 12/26/2021
LeoLabs has released a third assessment of the Russian anti-satellite demonstration. They focused on the above-cited recognition by Jonathan Mcdowell that this was not a head-on hypervelocity collision. The report estimates the number of fragments and the distributions of their size and mass, which will be refined as more objects are tracked.
They plan to continue tracking debris created by the collision and to refine their estimate of its impact, which is that "the statistical probability of collision for satellites with mission-terminating debris in the 300–800 km altitude range has likely doubled due to this event, and will remain high for many years."

Characteristics of non-hypervelocity and hypervelocity collisions 
Update 1/3/2022
Jonathan McDowell's Space Activities in 2021 presents a detailed recap of the year in space. This year's edition includes a December 31 update on the Russian anti-satellite demonstration. The Space Force is now tracking 904 debris objects and the total may eventually be more than twice that. 
McDowell also reports the number of breakups and debris events for the year. There were five in addition to the Cosmos 1408 demonstration. 

He also mentions newly cataloged objects from earlier breakups.

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