the astronauts test fired Reaction Control System (RCS) thrusters. The RCS thrusters control the shuttle's orientation as it descends and begins its re-entry through the atmosphere. All astronauts gathered for a deorbit briefing a little after 11:00 UTC, just before their midday meal. The Thanksgiving dinner aboard Atlantis was more traditional than expected. Earlier in the day, astronauts carried out the Shuttle Exhaust Ion Turbulence Experiments (SEITE) burn. The burn was radial down (nose to the Earth) such that the burn plume was observed by the orbiting C/NOFS satellite. Later, the Shuttle Ionospheric Modification with Pulsed Localized Exhaust Experiments (SIMPLEX) burn was conducted, with the burn plume observed by the Arecibo ground station. All seven crew members took a break at 13:13 UTC for a 20-minute talk with news media representatives. During the chat they took questions from ABC Radio, WTVT-TV in Tampa and KCBS in Los Angeles. After setup on the mid-deck of a recumbent seat for Nicole Stott and stowage of the Ku-band antenna used for high data rate communications during the mission at 19:34 UTC. November 27 (Flight Day 12 – Re-entry and landing) The Shuttle crew awoke Friday at 05:28 UTC. With weather looking good at the Kennedy Space Center, and nothing standing in the way of landing, Flight Director Bryan Lunney gave the "go" signal to close the payload bay doors at 10:52 UTC. Mission Control also instructed the astronauts to begin "fluid loading" – a protocol that aids the astronauts' readjustment to gravity. The crew strapped into their seats at 12:37 UTC in preparation for a landing. NASA operators gave the "go" for the deorbit burn and at 13:37 UTC, flying upside down and backwards above the southern Indian Ocean just west of Indonesia, Atlantis fired its orbital maneuvering system (OMS) engines for 2 minutes and 47 seconds. The deorbit burn decelerated the orbiter by about 211 miles per hour, enough to lower its orbital perigee into the upper atmosphere. Atlantis encountered the first traces of Earth's atmosphere, known as "entry interface", at 14:12 UTC at an altitude of 399,000 feet flying over the Pacific Ocean. At 14:26 UTC, eighteen minutes before touchdown, the orbiter was travelling at Mach 22; nine minutes later the orbiter was "gliding" at Mach 6. The shuttle's ground track took it along the east coast of Mexico's Yucatán Peninsula, across the Gulf of Mexico and cross the Florida coast