The countdown to the launch of STS-121, the latest mission for the space shuttle Discovery, will start today at 5:00 p.m. local time in Cape Canaveral, Florida. It will strike T-minus 0, if all goes as planned, at 3:49 p.m. on 1 July. It will be a greatly anticipated time among the scientists, engineers, and astronauts of NASA, as it will be only the second launch since the tragic loss of the Columbia crew in 2003 and the first since Discovery's last flight eleven months ago, in which potentially damaging debris from the external fuel tank nearly struck the shuttle on lift-off.
According to NASA, the debris problem has been addressed using new techniques, but this has not ended an internal controversy in the U.S. space agency over Discovery's current fitness for launch. As recently as yesterday, NASA administrators removed their director of engineering at the Johnson Space Center in Houston after reading a sympathetic e-mail note he sent to fellow engineers who had dissented with the decision to proceed with an early launch date.
The stakes for the current mission are so extreme that chief NASA administrator Michael Griffin has said he would likely cancel all future missions of the space shuttle program if this one were to end in complete failure. The space agency has plans for as many as 17 more shuttle missions, possibly including one to repair the disabled Hubble Space Telescope, before the fleet is retired in 2010, after which a new program of space vehicles will replace it (which we wrote about last September).
There are risks to every space flight, but rarely have they been stressed as forcefully as the previous and current Discovery missions. The crew of STS-121 seem confident they will manage to safely perform their duties in orbit and return to Earth without a hitch. "I really hope we can close the chapter [on Columbia]," Mission Commander Steve Lindsey (Col. USAF) told the Houston Chronicle. "It's really important we establish we can work through these problems."
In addition to Lindsey, the current crew of Discovery consists of Pilot Mark Kelly (Cmdr. USN), Mission Specialist Mike Fossum (Lt. Col. USAF Res.), Mission Specialist Lisa Nowak (Cmdr. USN), Mission Specialist Thomas Reiter (European Space Agency), Mission Specialist Piers Sellers (Ph.D.), and Mission Specialist Stephanie Wilson (NASA). Reiter will start the STS-121 mission but will leave it in orbit to join the International Space Station (ISS) as a third crew member.
According to NASA, Discovery's mission is planned to last about 12 days, ending with a 10:45 a.m. landing at Kennedy Space Center (KSC) on July 13. The crew will test new equipment and procedures to improve shuttle safety, as well as deliver supplies and make repairs to the ISS (the 18th such mission by the U.S.).
The countdown to Saturday's scheduled launch—which is already threatened by forecast weather conditions—is comprised of 43 hours of systems preparations and inspections. At a KSC countdown status briefing this morning, NASA Test Director Jeff Spaulding said: "We're tracking no issues in our preparation at this point. Our teams have been working tirelessly during this last year to help make this flight and all shuttle flights as safe as possible for the crews."
We wish this crew great success in their mission and a safe return home.