Tuesday, May 25, 2010

STS-132 Timeline for landing attempts for Wednesday, May 26, 2010

DISCLAIMER: I am posting times according to NASA's auto-generated landing data found in http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts132/news/landing.html and http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts132/news/dol_pad.html. This may change due to any change deemed necessary by Mission Control Center. For the ground track maps and the landing data, use the above links respectively.

Revision B 5/26/2010 1AM (added MILA acquisition to timelines)

All attempts will be for Kennedy Space Center's Shuttle Landing Facility. All times Eastern Daylight Time. Timelines are after the Quick Explanation section.

Acronyms used:

TDRS: Tracking Data and Relay Satellite
fps, Kfps: Feet per second, thousand feet per second
KFT: Thousand feet
EI: Entry Interface
NM: Nautical miles, or knots
TAEM: Terminal Area (of) Energy Management
MACH: Speed of sound. (Example: Mach 2.5 means 2.5 times the speed of sound)
HAC: Heading Alignment Circle/Cylinder

Quick explanation:

Landing of an orbiter consists of safely entering back into Earth's atmosphere, and bleeding off the tremendous energy generated on the ascent to orbit, and by energy, it means mostly speed and altitude. This is accomplished by slowing down the orbiter just enough to let it drop into the atmosphere, and the atmosphere does the job of slowing things down. By entering with a high angle of attack (with the nose aimed 40 degrees up), it creates a higher effect of drag. Since reentry at such speeds (17 thousand MPH) causes friction against the thickening air, a high-temperature plasma engulfs the vehicle. The angle of attack allows for the orbiter's thermal protection tiles to act as a shield for the rest of the vehicle from the superheated air. A series of pre-programmed steep banks during this phase will help increase drag further, therefore slowing down more, and helps to steer the orbiter towards the landing site. Once at the landing site and at a normal flying speed, the commander must manage the orbiter's energy (speed/altitude) by steering it correctly towards the runway, since at this stage there are no engines. It is essentially a heavy glider, or as astronauts have affectionately dubbed it, a flying brick. This phase is known as TAEM. The orbiter reaches the HAC and travels along it, coming out of the circle at the correct altitude, speed and alignment for the final dive to the runway. The landing gear is armed as the orbiter does a steep dive towards a point slightly a mile before the runway. Once at 1750 feet, the commander pulls the nose up (this is a pre-flare maneuver) as the pilot deploys the landing gear. This is done to decrease the orbiter's sink rate as it approaches the runway. As the wheels near contact, the commander pulls up on the nose further (final flare maneuver) to decrease the sink rate further, allowing for a flawless, soft touchdown of the rear, main landing gear wheels. The pilot, under Mission Control's command (received while they were entering the TAEM), will either deploy the drag chute at this point (nominal chute), or after the nose gear touches down (late chute). The commander makes the nose drop gently until the nose gear contacts the runway. The chute is ditched when their ground speed drops below 60MPH. Usually there is no braking on the wheels until the runway's midpoint is reached. Eventually, the orbiter slows to a stop (wheelstop). This marks the official end of the mission, and the Mission Elapsed Timer is stopped.

Attempt #1 on orbit #186

7:36:53AM TDRS-W acquires Atlantis's signal

7:41:49AM Deorbit burn ignition (lasts 3m10s, speed change by 342 feet per second)

8:16:28AM Entry interface (Alt. 399.9 thousand feet, speed 24.9Kfps, range to landing 4363NM)

8:21:26AM First roll command (80 degrees to the left)
8:34:47AM Second roll comand (Roll Reversal, 58 degrees to the right. Speed 13Kfps)
Third roll command (2nd roll reversal to the left, speed 7Kfps)
Fourth roll command (3rd roll reversal to the right, speed 3Kfps)

8:35:14AM Merritt Island Launch Area tracking station has C-band radar acquisition of Atlantis


8:41:43AM MACH 2.5, TAEM (Alt. 83.6Kft, speed 2.5Kfps)
8:43:56AM MACH 1 (Alt. 50.1Kft, speed 0.9Kfps)
8:44:09AM HAC Interception (Alt. 46.7Kft, speed 0.9Kfps, turn angle 317 degrees)

8:48:14AM Main Gear Touchdown (generated ground track points to runway 33)

Attempt #2 on orbit #187

9:17:24AM Deorbit burn ignition (lasts 3m10s, speed change by 342 feet per second)

9:17:46AM TDRS-W acquires Atlantis's signal

9:51:15AM Entry interface (Alt. 399.9 thousand feet, speed 24.9Kfps, range to landing 4393NM)

9:56:11AM First roll command (80 degrees to the right)
10:06:31AM Second roll comand (Roll Reversal, 65 degrees to the left. Speed 18Kfps)
Third roll command (2nd roll reversal to the right, speed 9Kfps)
Fourth roll command (3rd roll reversal to the left, speed 4Kfps)

10:09:58AM Merritt Island Launch Area tracking station has C-band radar acquisition of Atlantis

10:16:28AM MACH 2.5, TAEM (Alt. 83.9Kft, speed 2.5Kfps)
10:18:41AM MACH 1 (Alt. 50.1Kft, speed 0.9Kfps)
10:19:12AM HAC Interception (Alt. 42.2Kft, speed 0.8Kfps, turn angle 280 degrees)

10:22:58AM Main Gear Touchdown (generated ground track points to runway 33)