Discovery astronauts were in an upbeat mood on their final day in space as they readied the shuttle to return to earth but remembered Columbia's 7 crew members, including India-born Kalpana Chawla, who were killed during re-entry 2 years back.
"Discovery is in absolutely great shape and I'm pretty confident about the entry (into the atmosphere) and I'm thinking about the landing," shuttle commander Eileen Collins said in interviews to TV stations from space.
As Collins and pilot James Kelly get a go ahead from the mission managers, they will fire up two orbital jets at 1310 IST for three minutes and seven seconds each to lose altitude to begin re-entry into the atmosphere.
Hurtling down to earth at a speed of over 25,000 kms per hour, the shuttle will conduct several acrobatic manoeuvres to slow down to about 300 kms per hour for landing at the Kennedy Space Centre, Florida at 1417 IST.
In the event of weather preventing landing, the shuttle will begin de-orbit burn about 90 minutes later.
The weatherman has forecast favourable conditions with good visibility and only a slight chance of showers over the water in the vicinity of the three-mile-long landing strip.
Discovery un-docked from the International Space Station on Saturday after re-stocking the orbital lab with supplies and clearing it of trash.
The shuttle astronauts Stephen Robinson and Soichi Noguchi carried out three spacewalks to test new shuttle repair techniques developed after the tragic Columbia disaster.