USA-193 has now been hit by a missile fired from a US warship near Hawaii.
The debris from the satellite will re-enter the atmosphere over the coming weeks.
It is not yet known whether the hydrazine fuel tank was ruptured by the missile,
which was the primary purpose of the firing.
USA 193 was launched on December 14th, 2006 from Vandenberg Air Force Base in California. The launch
vehicle was a Delta II. Shortly after reaching orbit, ground controllers lost the
ability to control the satellite, and have never regained it.
The exact design and purpose of USA 193 are, or course, closely guarded secrets, but
specialists believe it is probably a high resolution radar satellite which was
intended to produce images for the National Reconnaissance Office (NRO).
When and where will it hit the Earth ?
Now that the satellite has been broken up by the missile collision, the debris will come down
over wide area over the coming weeks as they are slowed by atmospheric friction.
Re-entry will happen when the pieces reach about 100km. The plot below shows the
decay of USA-193 before it was hit by the missile.
What are the risks ?
The risk to people on the ground was extremely low, and since the missile hit broke up the satellite into many
smaller pieces, the risk should be even lower. The Earth is large and two-thirds of it is covered by ocean. Most of the
satellite will burn up in the upper atmosphere, but a few large pieces are expected
to survive the re-entry and fall to Earth. It would be very unlikely for any of them to hit someone.
The main hazard was the hydrazine fuel which is very toxic, and hopefully the tank has been
ruptured by the missile and the hydrazine been dipersed into space. This was the main
reason given by the US government for the missile strike.
Where are the pieces of USA 193 now ?
You can see the current position of USA-193 would have been in the ground track below. The
missile strike created many pieces of debris, but they should be centred roughly on the
position below, although dispersing more and more as time goes by.
Can I see it before re-entry?
The following links show the predictions for USA-193, assuming it was not hit by
the missile, the first link shows just visible passes (ie in the night when the satellite
is sunlit) and the second link shows all passes, which could be useful if you wish
to try and see a re-entry fireball.
Visible pass predictions for your location
All pass predictions for your location