December 17, 2017

21.09.11: Stalking the Re-Entry of UARS.

UARS…Have you seen me in orbit? (Credit: NASA/GSFC).

A unique re-entry event is about to occur this week, one that, if you’re lucky, you may need only your eyes to witness. UARS, the Upper Atmosphere Research Satellite has been on the shortlist for imminent re-entry over the next few days. Launched in 1991 from the payload bay of the Space Shuttle Discovery, UARS is a 6 ½ ton observatory built to study the Earth’s atmosphere, particularly the ozone layer. The satellite was decommissioned in 2005, and has since spent its maneuvering fuel. A debris avoidance maneuver for the International Space Station was conducted in 2010, and CALsky has pegged re-entry to occur on or around 02:30 UTC on September 24th.

UARS decay, predicted versus observed. (Via @UARS_Reentry)

Interestingly, various projections peg a re-entry at 12:00 UTC on the 25th, while observed passes peg an earlier re-entry at about 13:00 UTC on the 23rd… and well, you get the idea. Recent solar activity may be the culprit in hastening the satellites premature decay. We here at Astroguyz HQ are watching on every pass, both illuminated and in the Earth’s shadow; we just got sight of UARS this AM for the 1st time over Hudson Florida, and it was really moving, like USA-193 before its demise in 2008. Speaking of which, one wonders if the DoD is planning to bring down UARS preemptively on its final orbits, much like the aforementioned hydrazine containing satellite? Hey, I’m just sayin…

Can you see it? UARS near Jupiter this AM from Astroguyz HQ… (Photo by Author)

UARS was about half as bright as the planet Jupiter this AM, and we didn’t see any evidence of flashing, although observers worldwide have reported such, and a tumbling motion may evolve rapidly over the next few days. Heavens-Above was right on the money this mornings for predictions; for the US South-East, the next passes centered on Florida are;

21-Sep 20:54-20:58 EDT (in shadow)

22-Sep 06:12-06:16 EDT (illuminated)

22-Sep 20:26-20:30 EDT (illuminated-in shadow)

23-Sep 05:43-05:46 EDT (In shadow)

23-Sep 19:55-19:58 EDT (Illuminated-In Shadow)

24-Sep 05:10-05:13 EDT (In Shadow)

This will be the biggest object to re-enter since Mir and the largest uncontrolled re-entry since Skylab in the 1970’s, although we haven’t seen the attending hysteria connected with UARS that Skylab sparked. Are we a better informed, more intelligent public than we were in the days of Charlie’s Angels and the Love Boat, or are we simply more absorbed by the mis-adventures of Charlie Sheen and Lady Gaga? Whatever the case, our unofficial estimate is that there is about a 1-in-180 (24 hours x 60 minutes/about 2 passes a day of 4 minutes each) chance that UARS will re-enter over your horizon if you live between latitude 57 degrees north and south of the equator, which covers a good swath of the human species…follow @Astroguyz on Twitter for all the action-packed updates and keep watching the skies!

22.05.11: Meteoroids: Sandblasting Satellites?

0.84mm diameter strike on the window of Shuttle Columbia seen after STS-35. (Credit: NASA).

Next time you use your mobile or GPS to bounce signals off of a satellite, thank Stanford professor Ingrid Close… she and other researchers like her think about meteoroid strikes and their potentially crippling effects on spacecraft, so hopefully you don’t have to. [Read more...]