ROBERT SIEGEL, host:
From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.
MICHELE NORRIS, host:
And I'm Michele Norris. NASA is tracking at least 500 orbiting pieces of debris from a Russian intelligence satellite. The satellite mysteriously exploded in March. Another piece of it broke apart last month, and some of the debris has come close to the International Space Station, as NPR's David Kestenbaum reports.
DAVID KESTENBAUM: The Russian satellite was a huge thing, probably three tons, with long solar panels. It's a model the Russians have been launching the 1970s. Analysts refer to them as electronic ocean reconnaissance satellites. The thinking is they monitor U.S. Navy transmissions to figure out where ships are, and the satellites have a strange habit of sometimes breaking up at the end of their missions.
Mr. JONATHAN McDOWELL (Harvard Smithsonian Center for Astrophysics): They undergo these mysterious spasms.
KESTENBAUM: Jonathan McDowell is an astronomer at the Harvard Smithsonian Center for Astrophysics.
Mr. McDOWELL: And what's unusual about this latest one is that there's so much debris, much more than in any previous explosion of a satellite of this type. So here we have hundreds of pieces of debris and quite a lot of them are going to be at high altitudes, where they're likely to stay in orbit for longer and cause more of a traffic hazard to other people using space.
KESTENBAUM: Officially, NASA categorizes the cause of the satellite's demise as unknown. Gene Stansbury at NASA's Johnson Space Center says some of the debris is in the vicinity of the International Space Station.
Mr. GENE STANSBURY (NASA): And in fact in recent days there have been a couple of instances where there have been pieces that looked like they might come close enough that the space station would have to possibly plan a maneuver to avoid the debris.
KESTENBAUM: But later tracking indicated the debris would pass at a safe distance. Stansbury says NASA has catalogued over 500 pieces, but those are just the ones they can detect, larger than a couple inches.
Mr. STANSBURY: The worry is things that are smaller than what the network can track. In those cases, you don't have any warning if one would come close, but again, don't want to over-exaggerate the risk from that.
KESTENBAUM: Russia is a major partner in the effort to build the space station. Stansbury says NASA has contacted Russian officials about the debris from these satellite breakups in the past but hasn't really gotten anywhere.
Mr. STANSBURY: They just haven't responded.
KESTENBAUM: Jonathan McDowell at Harvard says most analysts think that the Russians are ordering these satellites to self-destruct, an old practice of trying to keep them out of enemy hands.
Mr. McDOWELL: It does seem like the initial explosion happens as it's flying within the range of the Russian tracking stations, which leads one to imagine that it's them sending a radio signal going blow up now.
KESTENBAUM: The Russians used to do this during the Cold War, he says, but recently, most satellites have gone quietly. He says there's always been a mystery to the break-ups when they happen. Like this one, they sometimes explode multiple times. It's possible the later convulsions are due to leftover fuel igniting. He can't see why you'd need to blow something up three times.
Mr. McDOWELL: And I've been kind of thinking for 20 years, like what are these things up to, and I have not been able to come up with a good explanation.
KESTENBAUM: Gene Stansbury at NASA says he hears the Russians are retiring this perplexing model of satellite and may not ever launch one again. The Russian embassy did not return a phone call for comment. David Kestenbaum, NPR News.