Greg -
I didn't see anyone else reply, so I'll try.
No, it's not coincidence. After the Iridium collision last year, the US Air Force decided it was in everyone's best interest for them to run conjunction analyses against many more space objects than they had previously analyzed, and report their predictions to system owners. Previously, their concern was primarily the US government's spacecraft, so we (in the amateur community) and many commercial operators never knew what was happening to our birds unless we did (or paid for) the work ourselves. But the collision (as well as the Chinese ASAT demonstration) showed that the resulting debris fields were a major hazard to everyone, themselves included. So they must have allocated more resources to the problem, as this is a massive undertaking. (Note that some reports say that the US has about 20,000 objects that are tracked and cataloged. In theory, this means propagating the ephemeris of all of these for some number of days and comparing all possible combinations across the time period of the analysis.)
Unfortunately, many (if not most) of the objects no longer have maneuvering capability. If a vehicle can maneuver, these warnings give them time to try and increase the separation prior to the predicted close approach. (You might have heard of some times when a space shuttle does one of these maneuvers.) But if you can't maneuver (as is the case with AO-51), all we can do is watch and wait.
Steve W3HF
Apr 13, 2010 01:45:32 AM, ko6th_greg@hotmail.com wrote:
Is it just a coincidence that these warnings seem to be coming pretty often recently, or did NORAD change their reporting procedures, or is all the junk up there getting to critical mass where nothing is safe? It seems like we're heading into a situation like nuclear fission, where you get enough stuff interacting, and it sets up a chain reaction of collisions.
Greg KO6TH
hi steve, thanks for an informative post. good to see the bb doing what it does best.
73 john g7hia
________________________________ From: Stephen Melachrinos melachri@verizon.net To: amsat-bb@amsat.org Sent: Wednesday, 14 April, 2010 0:22:34 Subject: [amsat-bb] Re: Space Debris:
Greg -
I didn't see anyone else reply, so I'll try.
No, it's not coincidence. After the Iridium collision last year, the US Air Force decided it was in everyone's best interest for them to run conjunction analyses against many more space objects than they had previously analyzed, and report their predictions to system owners. Previously, their concern was primarily the US government's spacecraft, so we (in the amateur community) and many commercial operators never knew what was happening to our birds unless we did (or paid for) the work ourselves. But the collision (as well as the Chinese ASAT demonstration) showed that the resulting debris fields were a major hazard to everyone, themselves included. So they must have allocated more resources to the problem, as this is a massive undertaking. (Note that some reports say that the US has about 20,000 objects that are tracked and cataloged. In theory, this means propagating the ephemeris of all of these for some number of days and comparing all possible combinations across the ti! me period of the analysis.)
Unfortunately, many (if not most) of the objects no longer have maneuvering capability. If a vehicle can maneuver, these warnings give them time to try and increase the separation prior to the predicted close approach. (You might have heard of some times when a space shuttle does one of these maneuvers.) But if you can't maneuver (as is the case with AO-51), all we can do is watch and wait.
Steve W3HF
Apr 13, 2010 01:45:32 AM, ko6th_greg@hotmail.com wrote:
Is it just a coincidence that these warnings seem to be coming pretty often recently, or did NORAD change their reporting procedures, or is all the junk up there getting to critical mass where nothing is safe? It seems like we're heading into a situation like nuclear fission, where you get enough stuff interacting, and it sets up a chain reaction of collisions.
Greg KO6TH
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Stephen Melachrinos wrote:
were a major hazard to everyone, themselves included. So they must have allocated more resources to the problem, as this is a massive undertaking. (Note that some reports say that the US has about 20,000 objects that are tracked and cataloged. In theory, this means propagating the ephemeris of all of these for some number of days and comparing all possible combinations across the ti! me period of the analysis.)
Computers are cheap, so actually propagating the ephemerides of those objects is the easy part.
The hard part is that the published elements are simply not accurate enough to reliably predict collisions -- or give sufficient reassurances that a collision won't occur.
TS Kelso has written some stuff about this on his website. See
http://www.celestrak.com/events/collision/
He's been doing his own conflict predicts for some time. He shows many close approaches that never result in a collision. Yet he did not rate a Iridium 33/Cosmos 2251 collision as especially probable before it happened because the TLE numbers simply aren't accurate enough.
participants (3)
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John Heath -
Phil Karn -
Stephen Melachrinos