20-year-old Military Weather Satellite Wasn’t First of its Kind To Explode


WASHINGTON — The 20-year-old military weather satellite that apparently exploded Feb. 3 was not the first satellite in its production run to break apart after a long, otherwise successful run.

In April 2004, a 13-year-old Defense Meteorological Satellite Program (DMSP) spacecraft dubbed DMSP-F11 experienced a similarly catastrophic breakup that produced 56 pieces of cataloged space debris.

In contrast to DMSP-F13 — the 20-year-old, semi-retired satellite that Air Force Space Command told SpaceNews last week apparently exploded after its power subsystem experienced a sudden temperature spike — DMSP-F11 was no longer operational when it exploded.

Launched in 1991, DMSP-F11 had been taken out of service and “passivated,” a process that usually entails discharging the spacecraft’s batteries, burning off any remaining propellant, and releasing any compressed gasses.

“The [DMSP-F11] spacecraft was non-operational at the time of the event,” according to NASA’s History of On-Orbit Satellite Fragmentations, published in 2008. “The electrical power generation system had been passivated by discharging the batteries and disconnecting them from the charging circuit. Virtually no nitrogen remained on board due to a leak detected early in the mission. The only energy source assessed to be on the spacecraft at the time of the event was approximately 6 [kilograms] of hydrazine.”

Hydrazine is commonly used as a monopropellant in satellites.

While propulsion was identified as the “assessed cause” in the breakup of DMSP-F11 in 2004, Air Force Space Command is still investigating the Feb. 3 incident that turned DMSP-F13 into 43 new pieces of orbital debris.

“The satellite was nearly 20 years old and experienced what appears to be a catastrophic event associated with a power system failure,” Air Force Space Command said in a Feb. 27 statement. “An investigation is ongoing.”

Both DMSP-F11 and -F13 were built by Lockheed Martin Space Systems as part of the DMSP Block 5D-2 series of satellites. A total of nine Block 5D-2 satellites launched between 1982 and 1997.

The DMSP satellite that launched last March, and a final DMSP satellite tentatively scheduled to launch next year, were built as part of the six-satellite Block 5D-3 series.

According to NASA’s 2008 study, accidental collisions — usually with orbital debris — account for 1.5 percent of known satellite breakups while battery problems are believed responsible for less than 5 percent.

The most common causes are propulsion failures of one sort or another, accounting for 45 percent of known incidents.

Nearly 30 percent of known incidents are the result of deliberate actions, such as weapons tests — which experienced a 10-year hiatus until China shot down its own Fengyun-1C weather satellite in 2007 — and Russia’s series of self-destructing Cosmos spy satellites.

About 20 percent of break-ups go into the record books as cause unknown.