OT: UARS Re-entry

[David Entwistle]

I see that the Center for Orbital and Reentry Debris Studies now have their UARS page on line. The current (Prediction epoch 19 SEP 2011 @ 12:14:22.345 UTC) prediction is re-entry above the mid-southern Atlantic at 23 SEP 2011 @ 16:10 UTC ± 1 day, but that is sure to change.

Updated (most recent prediction at the bottom):

Predicted Reentry Time: 23 SEP 2011 @ 20:36 UTC ± 20 hours, Prediction Epoch: 20 SEP 2011 @ 13:23:32.685 UTC
Predicted Reentry Time: 23 SEP 2011 @ 20:00 UTC ± 14 hours, Prediction Epoch: 21 SEP 2011 @ 13:00:58.904 UTC
Predicted Reentry Time: 23 SEP 2011 @ 22:07 UTC ± 9 hours, Prediction Epoch: 22 SEP 2011 @ 11:06:13.249 UTC
Predicted Reentry Time: 24 SEP 2011 @ 00:58 UTC ± 7 hours, Prediction Epoch: 22 SEP 2011 @ 19:55:04.326 UTC
Predicted Reentry Time: 24 SEP 2011 @ 03:16 UTC ± 5 hours, Prediction Epoch: 23 SEP 2011 @ 12:02:08.552 UTC
Predicted Reentry Time: 24 SEP 2011 @ 04:04 UTC ± 3 hours, Prediction Epoch: 23 SEP 2011 @ 20:47:52.440 UTC
Predicted Reentry Time: 24 SEP 2011 @ 05:10 UTC ± 2 hours, Prediction Epoch: 23 SEP 2011 @ 22:15:19.271 UTC

Perigee height: 203 km, Apogee height: 220 km, Epoch (UTC): 13:23:32, Tuesday, September 20, 2011
Perigee height: 195 km, Apogee height: 209 km, Epoch (UTC): 10:03:58, Wednesday, September 21, 2011
Perigee height: 184 km, Apogee height: 195 km, Epoch (UTC): 08:09:47, Thursday, September 22, 2011
Perigee height: 173 km, Apogee height: 183 km, Epoch (UTC): 22:51:08, Thursday, September 22, 2011
Perigee height: 162 km, Apogee height: 170 km, Epoch (UTC): 10:34:22, Friday, September 23, 2011
Perigee height: 145 km, Apogee height: 150 km, Epoch (UTC): 22:15:19, Friday, September 23, 2011
Perigee height: 130 km, Apogee height: 135 km, Epoch (UTC): 02:37:01, Saturday, September 24, 2011

[David Entwistle]

Just back from watching for UARS during its last pass over the UK - nothing seen. I see the prediction is now for re-entry at 5:10 UTC + 2 hours on Saturday September 24th, 2011 and, where ever it is, it will not be seen from the UK, nor Ireland.

A job, for a rainy day, is to reconcile the orbital decay of UARS (mass 5668 Kg) with the basic atmospheric model applicable to meteoroid-entry calculations. A decaying satellite skims along the upper atmosphere so, although there are a number of challenges, its decay is an excellent tool for getting an idea of the atmospheric density in this dificult to study area. The predicted re-entry time is changing all the time due to changes in the solar radio flux (F10.7) and geomagnetic index. Both parameters indicate the energy being delivered to the upper atmosphere which in turn influence the atmosphere's scale height - how rapidly the atmospheric density decreases with height...

UARS Orbit Decay

[David Entwistle]

Contrary to some other reports, NASA are reporting UARS re-entry over the Pacific Ocean:

Update #15
Sat, 24 Sep 2011 08:46:42 AM GMT

NASA’s decommissioned Upper Atmosphere Research Satellite fell back to Earth between 11:23 p.m. EDT Friday, Sept. 23 and 1:09 a.m. EDT Sept. 24. The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite penetrated the atmosphere over the Pacific Ocean. The precise re-entry time and location are not yet known with certainty.

The video from Canada looks like sky lanterns and not a re-entry.