Mar 16 2009
Another Close Encounter
For the second time in a week, the ISS folks are addressing what, if anything, to do about a close encounter with more space debris. Last week (3/12/2009), ISS crewmembers camped out in the Soyuz for a few minutes as a “yo” weight from a PAM-D upperstage less than 5 inches across ventured into ISS’ vicinity. Word that it was going to pass too closely for safety came too late to maneuver the ISS out of the way, so the crew waited in the Soyuz in case there was a critical impact. Fortunately, there wasn’t.
Before anyone gets too critical of USSATCOM, which tracks our debris, for the late notification, they might want to realize how difficult it is to track something ~10 cm across. Think about being able, from a ground station looking through the atmosphere, spot something whizzing by, several times faster than a bullet and hundreds of km above the surface of the earth. Now imagine it’s just five inches long.
Several factors combined to make this difficult. First, it’s small. Big honkin’ expended rocket boosters and stuff are easy to track, even without transponders, because, hey, they’re big and easy for radars to never miss. As you get smaller, though, only your best radars can catch stuff. Smaller yet, and they only catch stuff once in a while, say every third orbit or once or twice a week. What that means is that there is more uncertainty in its position. When you have lots of data on a debris item, i.e. you catch its position several times a day with several radars, you can be pretty sure you have a handle on its orbit and can predict well where it will be several days in advance with good confidence. Something smaller, with only a few and diverse data points to work with, it’s not so easy and predictions are less exact.
Additionally, this was on a very eccentric orbit, dipping into space that is affected by atmosphere and then moving into a very high orbit. That atmospheric friction changes the orbit, and, although that can be taken into account, it adds to uncertainty.
Today, yet another smaller bit of debris, this time from a Kosmos 1275 that broke up for reasons we’ve never entirely nailed down, also in an unusual orbit, also ~10 cm, is being discussed by the ISS team, to see if they should move out of the way. I believe, at this time, that they now believe it will pass by far enough away to preclude needing a maneuver, but, coming close on the heels of the other scare, it’s a pretty impressive reminder of the difficulties of hanging around in space cluttered with debris. And, as the ASAT detritis and fallout from theIridium collision work their way down things will only get worse.
Update: NASA did determine that the junk would be far enough away to be outside the danger zone and did not require a maneuver.
This is getting so bad with the all of the junk up there, they may have to place radar installations on orbiting platforms that operate on the principles of the air traffic control system, but use the level of detail that the National Weather Service uses for tracking storms / rain / snow.
I think the junk’s been up there for some time. For decades we trashed the place, disposing of all sorts of crud (not a scientific term, I know) on our way to the moon, etc. Now we’re just having to live with what we did…
Kind of reminds me of the trashing we’re doing of our own world a bit lower to the ground. And so many still don’t think it’s happening. Denial is convenient, but not so helpful when we actually have to live with the damage long-term.
mpaulin, they have been working with other resources to help get a handle on better ways to measure and characterize the environment. So far, each have their limitations, but that may be something to be mindful of in the future.
shakespeare, I so hear you. What amazes me is that, 50 years ago, the pollution pollution (the pollution that was readily visible and everywhere) was muc more pronounced than it is today. We bitched and moaned about how it was too hard to clean up until we were told: Clean it. And then it was cleaned with almost no impact to anyone, ONCE we were committed to it. Same thing with CFCs. When we tied the ozone layer degradation to CFCs, people bitched and moaned about how we could never give up CFCs unless we wanted to do away with refrigeration altogether.
And, guess what, we drastically reduced our production of CFCs internationally and almost overnight. It will take a while before they stop wreacking havoc on the ozone layer (long story and a different blog), but progress was noticeable. And the impact on most of us? Did you notice it?
I suspect, once we get committed, we’ll find that we can improve our efficiency and reduce our carbon output far less painfully than we ever imagined. Take, for example, this article in the NYT on Palm Desert California where people installed expensive solar systems with loans from the city (paid back through property taxes) that turned $1400/month energy bills into $500/YEAR bills. That’s pretty freakin’ cool. And there are several distinct and cost effective improvements in solar technology in the works that could drastically improve that original cost.
I can only imagine how difficult it is to track something that small in space.
Davida
Sure hope they get committed to it soon. It does seem that more people are paying attention than they were 10 to 20 years ago. Here’s hoping it is under control for your children or, at least, theirs.