SUBMITTED BY ARTHUR N1ORC - AMSAT A/C #31468

*Countdown Begins for STS-120 21 Octber 2007 *

An extensive staff of controllers, technicians and engineers reported for duty at NASA's Kennedy Space Center on Saturday as the countdown began at 2 p.m. EDT for the launch of STS-120. Liftoff is scheduled for 11:38 a.m. EDT Tuesday.

NASA managers overseeing the launch preparations for STS-120 said space shuttle Discovery is ready for two weeks in space.

"All of our systems are in good shape," NASA Test Director Charlie Blackwell-Thompson said.

The Italian-built Harmony module Discovery is carrying to the International Space Station is also in good shape, payload manager Glenn Chin said. The station segment weighs more than 31,000 pounds and will serve as a connecting point for laboratory modules from NASA and the European and Japanese space agencies.

Weather officer Kathy Winters pointed to some concerns that rain showers and clouds could interfere with Discovery's launch. She said there is a 60 percent chance of favorable weather at launch time.

Discovery's crew of seven astronauts arrived at NASA's Kennedy Space Center on Friday. They have been going through final checklists and preparations of their own for Tuesday's planned lift off.

Crew members Pam Melroy and George Zamka flew simulated space shuttle landings early Saturday morning aboard a Gulfstream business jet modified to mimic the flight characteristics of a gliding shuttle.

STS-120 is scheduled to return to Kennedy's Shuttle Landing Facility at 4:47 a.m. Nov. 6.

*Mission Information* + STS-120 Mission Overview http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts120/index.html + Harmony Node 2 http://www.nasa.gov/mission_pages/station/behindscenes/harmony_payload.html

+ Space Shuttle Discovery http://www.nasa.gov/centers/kennedy/shuttleoperations/orbiters/discovery-info.html