During the next week, a wayward U.S. spy satellite will make
passes across North America and western Europe soon after sunset and should be
easily visible to the unaided eye.
That's if it doesn't get shot down first.
The falling satellite
is named USA 193. It was launched Dec. 14, 2006. It has been described as being
similar in size to a school bus and might weigh as much as 10,000 pounds. It
carries a sophisticated and secret imaging sensor but the satellite's central
computer failed shortly after launch, never reaching its final orbit, and the
Pentagon declared it a total loss in early 2007.
Since then, the satellite's orbit has been decaying — slowly
at first. But in recent weeks USA 193's nearly circular orbit has been rapidly
lowering. Currently, its altitude is approximately 160 miles (260 km) above the
Earth.
Unless a proposed plan by the Pentagon is enacted to shoot down USA
193 during the next week, the satellite could conceivably re-enter the
Earth's atmosphere and burn up sometime in mid-March.
Viewing opportunity
Today through Feb. 22, USA 193 will make a number of evening
passes over North America and western Europe. It's orbit is inclined
58.5-degrees to the equator, a setup that makes it readily observable from most
of the Northern Hemisphere.
During this period, USA 193 will move along a general
southwest-to-northeast trajectory and pass over a number of cities in the United States, southern Canada and western Europe.
To spot a specific satellite, you need to know when and
where to look.
Predictions for the times and locations of USA 193 are available at the Heavens Above website (www.heavens-above.com).
Based on this website's sighting information, USA 193 will be very favorably
placed for observation over a number of large cities, assuming it is still in
orbit around the Earth and weather conditions permit.
What to look for
To find satellites,
it's also helpful to know how to roughly measure the sky. Your clenched fist
held at arm's length measures roughly 10-degrees of the sky. (From the horizon
to the top of the sky (the zenith) measures 90-degrees.)
From Chicago, as an example, the spy satellite is predicted
to reach as high as 38-degrees above the horizon (nearly four fists) on Feb.
17. That same date, as seen from Orlando, Florida, an evening pass as high as
65-degrees is predicted.
From Boston and Seattle, nearly overhead passes are forecast
for (respectively) Feb.18 and Feb. 22. And on the latter date, London, England should have a fine pass, with USA 193 arcing as high as 77-degrees above the horizon.
It should be stressed that because of the rapidly changing
nature of its orbit, sighting information from Heavens-Above should be checked
frequently.
Those who
have seen the International Space Station
(ISS) flying across their local skies should be aware that USA 193 will appear noticeably fainter, since it's quite a bit smaller than the ISS. Yet,
at its brightest, the spy satellite still should rank as bright as the
brightest stars, at roughly first magnitude in astronomers parlance.
Also, since
the spy satellite is in a lower orbit than the ISS, expect USA 193 to move much more rapidly across your line of sight.
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