[meteorite-list] Mystery Object to Reenter Earth's Atmosphere (WT1190F)

[Ron Baalke]

http://www.skyandtelescope.com/astronomy-news/mystery-object-to-reenter-earths-atmosphere-1103201534/

Mystery Object to Reenter Earth's Atmosphere
David Dickinson 
Sky & Telescope
November 3, 2015
       
WT1190F will burn up over the Indian Ocean on November 13th, giving researchers 
an unprecedented opportunity to follow its path - and figure out where 
it came from.

An unknown object is headed for a fiery demise over the Indian Ocean on 
November 13th - and observations so far show it might be a relic of the 
early Space Age.

The object in question is WT1190F, first observed by the Catalina Sky 
Survey in 2013. A couple years of observations have characterized its 
curious orbit: its highly eccentric path around Earth takes the object 
from its nearest point (perigee) of 21,221 kilometers (13,186 miles) out 
to an apogee of 655,370 kilometers, 1.7 times the distance between Earth 
and the Moon.

What Is WT1190F?

[Graphic]
A diagram depicting the looping orbit of WT1190F. The blue circle is the 
Moon's orbit. 
Bill Gray / Project Pluto

Studies from the International Astronomical Union's Minor Planet Centre 
and the European Space Agency's NEO Coordination Centre European Space 
Research Institute (ESRIN) suggest that WT1190F is probably a piece of 
discarded space junk from a Moon mission. Not only because of its orbit, 
but also because WT1190 interacts with solar radiation pressure in a way 
that suggests it has low density and might even be hollow - perhaps a 
rocket booster, solar panel, or SLA Panels (Spacecraft Lunar module Adapter 
panels used during the Apollo missions).

Calculations project WT1190F's reentry above the Indian Ocean, just south 
of Sri Lanka, on November 13th at 6:19 UT, 11:49 a.m. local time.

This event provides astronomers the chance to model a reentry from a highly 
eccentric orbit, so they can test similar scenarios involving incoming 
asteroids.

"The object is quite small - at most a couple of meters in diameter - 
and a significant fraction, if not all of it, can be expected to completely 
burn up in the atmosphere," says Tim Flohrer in a recent ESA press release.

To this end, researchers from the SETI Institute and the High Enthalpy 
Flow Diagnostics Group (HEFDIG) at the University of Stuttgart, Germany, 
will conduct airborne observations of WT1190F's atmospheric reentry using 
a specially equipped Gulfstream 450 jet supplied by the International 
Astronomical Center in Abu Dhabi.

ESA researchers led similar airborne operations to observe the reentry 
of Hayabusa, an asteroid sample return mission in 2010, as well as the 
reentry of ESA's ISS ATV-1 supply spacecraft in 2008. See the video of 
Hayabusa's reentry:

To date, researchers are unsure just what lunar mission WT1190F belongs 
to. It will probably remain a mystery unless astronomers can link it to 
earlier observations.

"We've managed to identify the object with one found in 2013," says Bill 
Gray (Project Pluto), who has been working with the PanSTARRS team to 
identify WT1190F and characterize its orbit. 'That got us a good enough 
orbit that Marco Micheli was able to find images taken in December 2012 
from PanSTARRS in Hawaii. So about all we can say at this point is, it 
was launched sometime before December 2012."

But the more observations of WT1190F, the better. WT1190F won't pose a 
good observational target for backyard observers - it's currently only 
at magnitude +21 near apogee, though it'll approach magnitude +15 pre-reentry, 
in range of large backyard scopes. Dedicated observers can generate topocentric 
ephemerides using the Minor Planet Center's Distant Artificial Satellite 
Observations (DASO) page.

Space Junk and Low-Flying Space Rocks

The Department of Defense's Space Surveillance Network (SSN) uses radar 
and optical sensors to track more than 21,000 satellites and space debris 
down to sizes of about 5 centimeters (2 inches) in low-Earth orbit. In 
farther-out geosynchronous orbits, SSN can track objects down to sizes 
of about 1 meter. But researchers can only recover objects in wider-ranging 
orbits using imaging. Small, faint objects on wider orbits are extraordinarily 
difficult to find, and their orbits, complicated by the gravitational 
effects of the Moon, are difficult to characterize.

Other near-Earth asteroid discoveries have turned out to be space junk 
as well: J002E3 was a Saturn V third-stage booster from the Apollo 12 
mission, and 2010 QW1 turned out to be part of the Chinese Chang'e-2 lunar 
mission. The reentry of WT1190F, however, marks the first time astronomers 
have observed such an object returning to Earth.

Good luck to the team watching for WT1190F's reentry on November 13th!

Further resources:

Read Bill Gray's FAQ page at Project Pluto for an in-depth discussion 
on WT1190F.

http://www.projectpluto.com/temp/wt1190f.htm