U.S Spysat Orbital Debris Tracked

The results from that missile intercept of the out-of-whack USA 193 spysat continues to be assessed by orbital debris experts.

One of those experts is T.S. Kelso of The Center for Space Standards & Innovation in Colorado Springs. He operates CelesTrak that posts info on orbital debris.

Kelso’s “USA 193 Post-Shootdown Analysis” shows that the missile launched from the USS Lake Erie occurred 38.5 seconds after the rogue spacecraft rose above the horizon as seen from the ship.

A plot of debris from USA-193’s destruction. Credit: AGI.

So far, there are 45 pieces of leftover debris from the intercept that are cataloged. A plot for the event shows debris ranging from 104 miles (167 kilometers) altitude at perigee (low point) all the way up to 1,670 miles (2,689 kilometers) at apogee (high point).

Kelso notes that he will be adding an orbital lifetime analysis to assess how long this debris might continue to present an increased risk to satellites in low-Earth orbit.

In a follow-on item, the analysis of the orbital lifetime of the debris is admittedly tough to do, Kelso explains. The original USA 193 spacecraft was some 4.5 meters long and 2.4 meters wide, according to open sources. Given that — and a cylindrical shape — that would give it a volume of 21.4 cubic meters, he figures.

Furthermore, given a reported spacecraft mass of 5,000 pounds (2,300 kilograms), subtracting the fuel weight of an announced 1,000 pounds - all that equals to a dry mass of about 1,800 kilograms and yields an average density of 85 kg/m3.

Soooooo….taking into account the U.S. Department of Defense view that “no parts larger than a football survived the strike” - that means 11 inches long and 21 inches in circumference, based on the tape measure rolled across a regulation NFL football, Kelso says. Since the U.S. Space Surveillance Network typically cannot track objects smaller than 10 centimeter in size, these spysat fragments should range from 10-20 centimeter in diameter.

Soooooo…(part 2) all this suggests that the last of any 10-centimeter chunks should decay and fall into Earth’s atmosphere 53 days after the intercept; in the 20-centimeter fragment department, the last object decays 105 days after the intercept.

If any of the pieces are larger than reported, they will take progressively longer to decay, Kelso concludes.