WASHINGTON — Although the U.S. Air Force hasn’t concluded its investigation of the Feb. 3 incident that caused a 20-year-old military weather satellite to strew debris, experts say the public details are consistent with a catastrophic battery failure.
“It is not uncommon to have batteries overheat in space and eventually explode,” said T.S. Kelso, a senior research astrodynamicist at the Center for Space Standards & Innovation, a research arm of orbit-modeling software provider AGI.
Kelso, a retired U.S. Air Force colonel, spent most of his military career working on space programs, including stints as the operations chief for the nation’s GPS satellites in the 1980s and director of Air Force Command’s Space Analysis Center during the 2003 Space Shuttle Columbia accident investigation.
“Back when I used to run the GPS Block I constellation, we spent a lot of time on battery management and thermal maintenance to avoid these types of problems,” Kelso told SpaceNews March 3. “The fact that we’re seeing this in old DMSP satellites — that were built long before we appreciated the need to passivate energy sources like these—is not too surprising.”
Kelso first drew attention to a “debris event” involving Defense Meteorological Satellite Program Flight 13 (DMSP-F13) satellite Feb. 25 via a series of Tweets.
U.S. Air Force Space Command disclosed the loss of the satellite and debris event Feb. 27 in response to questions from SpaceNews.
In a statement provided at the time, U.S. Air Force Space Command wrote:
The Defense Meteorological Satellite Program Flight 13 reached end of life Feb. 3, 2015 at 2:39 p.m. (MST). The decision was made to render the vehicle safe after DMSP operators discovered a sudden spike in temperature in the power subsystem of the nearly 20-year-old weather satellite followed by an unrecoverable loss of attitude control. At approximately the same time, the Joint Space Operations Center identified a debris field near the satellite. The Center continues to track the debris and will provide conjunction warnings if required, although none have been issued to date.
The Feb. 27 statement said the Air Force had identified 43 pieces of debris from the incident.
Kelso said March 3 that the number of of trackable pieces of debris had since grown to 46.
CelesTrak now has TLEs for 20 more pieces of DMSP 5D-2 F13 debris, bringing the total for this event to 46 pieces.
— T.S. Kelso (@TSKelso) March 3, 2015
Ted Molczan, an amateur satellite observer and orbit analyst based in Toronto, said Air Force Space Command’s description of the incident supports the battery failure explanation — albeit one that observation data suggest left DMSP-F13 “mostly intact.”
Molczan bases this assessment on two factors: what’s left of the satellite remains fairly bright and the explosion did not alter its velocity by all that much — perhaps as little as 0.13 meters per second.
“The delta-V (change in velocity) of some of the ejected fragments was far greater, judging by their orbital elements issued by [U.S. Strategic Command],” Molczan told SpaceNews via email March 3. “Therefore, it seems likely that the total mass of the debris is a small fraction of that of the spacecraft.”
While an exploding battery has emerged as the likely proximate cause of DMSP-F13’s catastrophic failure, figuring out exactly why the battery exploded presents an additional layer of difficulty — especially for analysts who don’t have the same level of access as the Air Force’s space surveillance experts.
“Whether the temperature spike occurred due to some type of thermal runaway or was triggered by a small debris strike will be very difficult to determine, however, without access to the telemetry or orbital data for the DMSP payload,” said Kelso, noting that’s something the Air Force does not release.
“I think we’ll have to wait for the [U.S. Air Force] to conclude their investigation to have a better idea,” Kelso said.