[semi-OT] a sensor-related post of sorts [Fwd: active s/c IDed as asteroid 2001 DO47!]

Colleague forwarded this on to me, and I thought, in light of some of
the sensor discussion a few weeks (months???) ago (was it weeks or
months? I can't remember), some of the material herein might give
those interested in the periodic sensor discussions some material
to chew on (eg, this is a vacc-head-related post; delete and ignore
if you're only interest is being on the ground ;-)

Mk

Helen Hart wrote:
> 
> ------------- Begin Forwarded Message -------------
> 
> Date: Thu, 1 Mar 2001 20:46:16 -0700 (MST)
> Subject: asteroid 2001 DO47 not just artificial-- but alive!
> 
> This is a first! A still operational spacecraft getting an asteroid
> number. This is quite a demonstration of our surveylance capabilities!
One
> object, I think Cassini, was detected at about 9 million km by Jim
Scotti
> of UofA's Spacewatch, but he already had a good ephemeris for that
one!
> Hay, isn't that cheating?!
> 
> Of course this is just a little bit embarrassing too :-)
> 
> Richard
> --------------------------------------
> ANOTHER "ASTEROID" IDENTIFIED AS SPACECRAFT: LESSONS LEARNED FROM THE
> SG344 DEBACLE
> 
> >From Larry Klaes <lklaes@bbn.com>
> 
> WAIT, IT'S ONE OF OURS
> 
> >From Sky & Telescope, 28 February 2001
> http://www.skypub.com/news/news.shtml#wind
> 
> A puzzling "asteroid" designated 2001 DO47 turned out to be of
terrestrial
> origin. The Wind spacecraft was launched in 1994 to study the
interaction
> between the solar wind and Earth
> magnetosphere. This plot shows the probe's looping trajectory from May
1999
> to April 2000. Courtesy International Solar-Terrestrial Physics
program,
> NASA/Goddard Space Flight Center.
> http://www.skypub.com/news/images2001/010228news02.gif
> 
> Future historians looking back at the search for Earth-threatening
asteroids
> will find a footnote for events that unfolded last week.
> 
> It began on the evening of February 18th when a fast-moving object was
> spotted in western Cancer by the Arizona-based Spacewatch team - the
> patriarch of contemporary searches, which has been looking for
near-Earth
> objects (NEOs) with a 36-inch telescope since the 1980s.
> 
> During the next two days amateur and professional observers at more
than a
> dozen locations around the world tracked thetracked the 16th-magnitude
> object as it raced eastward crossing a Moon's diameter of sky every 90
> minutes.
> 
> What emerged from the data was a tiny object moving in what appeared
to be a
> strikingly Earthlike orbit around the Sun. Calculations suggested that
it
> had passed very near the Moon last August and would come within
360,000
> miles (580,000 kilometers) of Earth on February 23rd. The Minor Planet
> Center (MPC) in Cambridge, Massachusetts, assigned it the preliminary
> asteroid designation 2001 DO47.
> 
> While certainly an interesting object, 2001 DO47 posed no threat. Even
if it
> were headed toward Earth, its estimated diameter of only 10 meters
would
> have made it too small to survive a passage through our atmosphere.
> Furthermore, from the outset there were suspicions by the MPC staff
that
> 2001 DO47 might be artificial and thus more reflective than a typical
> asteroid making it smaller yet.
> 
> "We would have liked to check out the artificial possibility before
> announcing the object," notes MPC associate director, Gareth Williams,
"but
> our resident expert, [Sky & Telescope contributing editor] Jonathan
> McDowell, was observing in Arizona and initially out of reach."
> 
> The story took another twist when observations of the object made on
> February 23rd by John Rogers in California and the undersigned in
> Massachusetts - both members of the worldwide network of amateurs who
> measure positions of asteroids and comets - were internally consistent
but
> significantly out of step with the earlier sightings.
> 
> "2001 DO47 has switched on its engine," is how Williams described the
> situation to MPC director Brian Marsden, who concurred with Williams
that
> the object must be artificial.
> 
> By February 25th they heard from McDowell, who identified the mystery
> spacecraft as Wind, a NASA probe, and confirmed that an engine burn
had
> indeed been scheduled for February 23rd.
> 
> Launched on a mission to study the solar wind and Earth's outer
> magnetosphere in late 1994, Wind spends most of its time far from
Earth, but
> it also makes occasional swings by the Earth and the Moon during
orbital
> maneuvers. The spacecraft is 2.4 meters (7.9 feet) in diameter and 1.8
> meters (5.9 feet) high.
> 
> Marsden told Sky & Telescope that, inspired by the 2001 DO47 incident,
the
> MPC has now added the orbital information of about a dozen spacecraft
to its
> computers, which should help identify these objects when they turn up
in the
> data from NEO surveys.
> 
> - Dennis di Cicco
> 
> Copyright 2001, Sky & Telescope
> 
> ------------- End Forwarded Message -------------
> 
> --------------------
>   Helen M. Hart
>   hart@pha.jhu.edu
>   FUSE Science Operations
>   Bloomberg 140-C  410-516-4375
>   http://fuse.pha.jhu.edu/~hart/