COMSPOC’s latest analyses of the Russian ASAT event
29 December 2021
Six weeks have elapsed since the Russian ASAT test occurred. Previous posts by COMSPOC's CSSI and others have examined the space objects currently tracked, how many of those have reentered, and why there might be slightly fewer fragments than can sometimes accompany such ASAT tests. Yet there are some critical questions that remain: Specifically, which satellites are placed at greatest risk, where can the debris fragments go in the short-term based upon the velocities they experienced, how much will collision probabilities (and therefore spacecraft operator flight safety workloads) increase in the long-term, and how long will such fragments remain in orbit. In this blog, we set out to answer all of those questions based on the latest published data.
Addressing the low(er) intercept velocity modeling challenge
While the Russian ASAT’s assumed collision speed of over 10,000 miles per hour sounds fast, ASAT intercept speeds can be as much as three times faster. The slower relative velocity of the Russian ASAT test makes it more challenging to model. Tools developed at COMSPOC’s Center for Space Standards and Innovation (CSSI) were calibrated by governing the spread velocity and number of fragments so that the simulated fragmentation (the white dots in picture below) better-reflects the envelope of the more than 600 publicly disclosed debris fragments actively tracked by the U.S. (represented by the orange trajectories).
Fig. 1: Comparison of Russian ASAT-generated debris fragment trajectory envelope (orange trajectories) with CSSI debris model representative fragments (white dots) 62 minutes after intercept.
Following calibration, CSSI’s debris risk analysis tools were used to assess where fragments from this event might go. This assessment helps analysts answer four key questions:
1) Which spacecraft were placed at greatest risk because of the ASAT test?
Which spacecraft, and which countries, were put at greatest risk by this ASAT test? CSSI’s tools estimated a relative risk for each active spacecraft as shown in the figure below. The ASAT test placed many key spacecraft (and indeed, the space infrastructure of many countries) at risk. Of special criticality and interest, the International Space Station (ISS) was ranked the 20th-most at-risk spacecraft out of the entire database of active spacecraft. The spacecraft that experienced the greatest risk occupied the same orbital plane as COSMOS 1408 (pre-destruction) and therefore transits the fragmentation volume on an ongoing basis.
Fig. 2: Estimated top 50 spacecraft placed at risk by the Russian ASAT test, sorted in descending order.
2)
Where do ASAT-generated debris fragments go?
People often wonder where fragments might go following a
catastrophic breakup event. By looking backward in time using the U.S. tracked
objects, it is possible to get an idea of the velocities imparted to each
fragment by the collision as shown in the figure below. Each line (scaled for
visualization purposes) is a 3-dimensional depiction of the spread velocity that
specific fragments experienced. Fragments are sent in all directions from the
target satellite, often at high relative speeds.
Fig. 3: Depiction of spread velocity vectors for ASAT-generated debris fragments based upon SSN-tracked orbits.
Ever wondered where debris fragments might go? This picture below
shows the volume of space that debris fragments may have occupied in the
24 hours following the destructive event. The colors of the volume denote how
likely fragments are to occupy this volume of space, with red being the highest
risk. The U.S. DMSP satellite was placed at particularly high risk, but the ISS
also flew through the debris volume twice per orbit.
Credit: COMSPOC/CSSI volumetric analysis, with rendering by AGI, an Ansys Company.
Fig. 4: Estimated volume of space occupied by debris fragments during first day following intercept, with color depicting the relative likelihood of a fragment occupying that portion of space.
3)
Increased space safety workload on spacecraft
operators
Satellite operators already spend a lot of time and effort to avoid space debris collisions. How much more will be required to avoid the new COSMOS 1408 fragments? The graph below shows (1) the estimated effort spent avoiding other active satellites (blue), (2) tracked debris prior to ASAT test (orange), and (3) the additional collision risk introduced by Russian ASAT debris (gray). Increases of up to 126% are observed at the ASAT test altitude (460 km), up to 20% for Earth-observing spacecraft, and up to 10% for the ISS. These safety degradations will increase at ISS altitude as the debris fragments gradually begin to reenter the Earth’s atmosphere.
Fig. 5: Comparison of estimated collision risk a spacecraft would experience as a function of altitude, caused by pre-intercept debris (orange), other active spacecraft (blue), and new ASAT-generated debris fragments (gray).
4) How long are the fragments likely to remain in orbit?
The plot below shows the estimated lifetime of the debris
fragments generated by the Russian ASAT test. Most fragments should reenter
within a couple of years, but until then, the collision risk will remain elevated.
Fig. 6: Estimated distribution of ASAT-generated debris fragment orbit lifetimes.