DailyTech has provided extensive coverage of the developing story concerning the dead satellite US 193.  This spy satellite, loaded with toxic fuel and top U.S. surveillance technology threatens both as a safety concern and as a security concern, lest its fuel be released over a populated area, or its remains fall into the hands of China or other non-ally nations.  The U.S. Navy took the double threat from the satellite very seriously and plans to launch a missile strike to try to blow it out of orbit.

The tale of US 193, built by Lockheed Martin, began in December 2006, when it was launched and experienced power failure upon entering orbit.  With the power out, communication with the satellite failed and its orbit began to decay.  The satellite, estimated to be between 2,500 and 20,000 lbs by various sources will finally impact with the earth in a matter of weeks if its course is not altered.  It is currently unknown whether the satellite's trajectory takes it into a land or a sea impact, but this should be made clear in a matter of days.

The satellite carries a cargo of as much as 1,000 lbs of Hydrazine fuel.  Hydrazine is a highly toxic chemical which is frozen for use as rocket propellant.  The Centers for Disease Control and Prevention stated that Hydrazine exposure in the short term produces coughing irritated throat and lungs, convulsions, tremors or seizures.  In the long term it can cause liver, kidney and reproductive organ damage.  Its effects are similar to severe ammonia or chlorine exposure. 

Authorities currently believe that most of the full tank of Hydrazine would survive the atmospheric descent.  If it hits land, the impact would scatter the fuel in high concentrations over an area approximately the size of two football fields, by most estimates.  Wind and other factors could cause exposure on a smaller scale in surrounding areas.

The satellite also carries a state of the art imaging sensor and sophisticated computer systems which the U.S. Armed Forces fear would be dangerous if they fall into enemy hands.

The U.S. Navy’s window of opportunity to shoot down the satellite beings at 10:30 p.m. ET Wednesday, however, weather issues could delay the launch until Thursday.  The missile used will be fired from the USS Lake Erie, slightly East of Hawaii.  The Shuttle Atlantis safely landed today, so there is no danger on that front.

The Lake Erie is an Aegis-equipped cruiser.  Aegis is an advanced target tracking system used by the U.S. Armed Forces.  The USS Decatur and the USS Russell destroyers will help the Lake Erie in its mission as well.  The Decatur will pump the trajectory to the Lake Erie's systems, while the Russell will take backup trajectory measurements should the Decatur's systems fail.

The shootdown will be very costly.  The slightly modified SM-3 missile used will carry a price tag of around $10 million USD.  Experts heavily modified the Lake Erie's Aegis systems at a frantic pace.  Among the modifications made include improvements to the tracking system.  Aegis typically strikes "warm" targets, so its sensors/algorithms were modified in order to target the cool satellite.  The total shootdown will cost between $40 million and $60 million USD according to U.S. officials.

The satellite missile pair will have a combined velocity of 22,000 mph.  The satellite, about the size of the fuel bus, has a 3-4 foot fuel tank, which will be the missile's target.  The missile will be guided by "kinetic kill vehicle" deployed during launch, which will be the eyes of the missile as it tracks its target.  Aegis will adjust the missile's course as necessary.

There have been other successful shootdown attempts in the past.  The Chinese executed a sloppy missile destruction of a satellite, scattering debris heavily in orbit.  Some say the U.S.'s shootdown attempt is merely a chance for the Military to flex its muscle and one-up China.  However, the Military revealed it already has shot down a satellite successfully.  In 1989 a U.S. fighter jet travelling at an altitude of 80,000 feet launched a heavily modified surface-to-air missile, which successfully destroyed a U.S. satellite.  Gen. James Cartwright, vice-chairman of the U.S. Joint Chiefs of Staff says the Military is purely acting to avoid potential disaster.

The Navy hopes to hit the satellite hard, with no explosive charge, fracturing it as it enters low orbit.  By hitting it at a lower altitude, they hope the debris including the Hydrazine, will burn up harmlessly.  This way they can avoid populating the Earth's orbit with more space junk, a threat to both space shuttles and other satellites.

If the first missile misses, the ship has two more onboard.  The Navy may take a second shot if the first launch fails, and if they feel there is still time to make another attempt.