Quote:
Originally Posted by kinetic
So you go to the 'live tracking' servers that are using 'tracking' data for almost live updates,
then they clog up with too many users logging in at crunch time 
It would be great with all of the technology we have available for just the
average punter to log in and watch an almost live telemetry feed right down to the end. |
Hi Steve,
What "live tracking" servers?
For a piece of space junk that isn't transmitting any of its own telemetry, continual live tracking doesn't exist.
What the U.S. Air Force Space Command has to do for these types of objects is to model their orbits in software
fed by orbital elements and to update the orbital elements by observations either from C-band (5.4GHz) or
S-band (3GHz) radar or dedicated tracking telescopes.
As C-band and S-band, like an optical scope, is line-of-sight, fixes can be intermittent.
Take for example the deployment of the Space Command C-band station at Exmouth in West Australia which
has only been in operation for just over one year now.
Along with a 3.5m telescope being built at Exmouth, to the best of my knowledge, that represents the limited coverage
of the southern hemisphere.
A Space Command S-band installation is being built in the Marshall Islands and it will create a virtual radar beam wedge extending
about 3000km out into space and about 5000km wide at its widest point.
The Marshall Islands facility will be the key installation in the US's new "space fence" but one can appreciate that
in-between those times when one does not get a radar or visual fix on the object all one can do is extrapolate
using the software models.
So how did the USAF Space Command know Tiangong-1 had re-entered?
Though the details are unlikely to be published, one could speculate that the US would have detected the
infrared signature of Tiangong-1 as it burnt up in the atmosphere through its constellations of
classified missile early warning system satellites, such as their latest generation Space-Based Infrared System
(SBIRS) satellites.
Designed to pick-up the tell-tale signature of the heat plume from a missle launch, what are designated
as the SBIRS-High satellites are in a high geosynchronous orbits so that each "sees" at any one time
most of the Earth's hemisphere.
I've modelled and animated in the past the orbits of earlier generation missile survellaince satellites
and it's fascinating to watch as you place them in a orbit and impart a spin on them how they can scan the Earth.
Here is someone else's video depiction :-
https://www.youtube.com/watch?v=mDTnl4E9FiY
A large part of what Space Command must do everyday is make split second decisions on whether the detection
of an infrared signature is that of a meteorite, re-entering space junk or when it comes from the ocean like
where Tiangong-1 impacted, a nuclear warhead SLBM-launch from a Russian submarine.
There have been documented false alarms in the past where President's have been roused from their sleep
in case the United States needs to go to DEFCON 1 and order a retalitatory strike, only to find it was an oil well flare.
That the US announced the rentry of Tiangong-1 before the Chinese says a lot about the relativities of
sophistication between the two in global early warning systems despite both being nuclear-armed powers.
But as best as we know, even the US lacks a "hard real-time" tracking capability for re-entering space junk.
