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Deorbit and Landing Preliminary Advisory Data (DOL PAD)


Automated DOL PAD For STS-XYZ - this data is for the STS-XYZ mission
Deorbit To KSC On Orbit N - deorbit will occur on the Nth orbit of this mission
Generated MET 000/00:00:00 - the Mission Elapsed Time in days/hours:minutes:seconds that this information was generated by computers in Mission Control.

Deorbit TIG - Time of Ignition - the orbiter will fire its orbital maneuvering system engines to slow itself down and begin its descent to Earth. The time of the deorbit burn is shown in both MET (days/hours:minutes:seconds) and Central time (Julian Day/hour:minute:second). The location over the Earth at which this event will occur is shown by Latitude (degrees:minutes) and Longitude (degrees:minutes). The altitude (H - height) of the event is given in nautical miles (NM) or thousands of feet (KFT). Note: To find statute miles, multiply nautical miles by 1.15. Velocity is shown in thousands of feet per second (KFPS). 1.47 feet per second equals 1 statute mile per hour. Comments Section - DV (delta velocity) is the change in velocity the burn will cause and DT (delta time) is the duration of the burn. XR is the crossrange, the distance away from what would have been the shuttle's normal orbital groundtrack that the shuttle will fly during its descent through the atmosphere in order to reach the landing site.

TDRS West AOS - The orbiter will be in range (Acquisition Of Signal) of one of the NASA Tracking and Data Relay Satellites (TDRS West). Comments Section - EI Minus is the time in minutes:seconds until Entry Interface occurs.

EI - Entry Interface - that point at which the orbiter begins to encounter the first effects of the Earth's atmosphere, usually at an altitude of roughly 400,000 feet. Comments Section - Range is how far away the orbiter is from the landing site in nautical miles (NM).

MACH 2.5 TAEM - the orbiter has decelerated to a velocity of two and one half times the speed of sound and has reached a phase of descent called Terminal Area Energy Management (TAEM). TAEM is the second of three phases that the shuttle's entry and landing process is divided into because of the unique onboard software requirements for each phase. The first phase of descent is labeled simply Entry and extends from five minutes before Entry Interface to the start of TAEM. TAEM is a phase that takes the orbiter from about 83,000 feet and two and half times the speed of sound to a point where the shuttle is at an altitude of about 10,000 feet and aligned with the runway centerline. Approach and Landing phase extends from 10,000 feet to touchdown on the runway.

MACH 1 - the orbiter has decelerated to a velocity equal to the speed of sound (approximately 740 miles per hour at sea level). The time that the shuttle commander takes manual control of the spacecraft's approach and landing usually coincides with the point that the shuttle has slowed to Mach 1. Comments Section - how many minutes:seconds after reaching Mach 1 before the orbiter reaches the HAC I/C point.

HAC I/C - The point at which the orbiter intercepts the Heading Alignment Cylinder, an imaginary cylinder created by the Microwave Scan Beam Landing System (MSBLS) that is installed at primary shuttle landing sites. The HAC is a tool to assist with guiding the shuttle's final approach to the runway. Comments Section - the shuttle normally performs a turn following the HAC as it aligns with the runway and rapidly descends. The turn angle refers to how much of a turn will be performed by the shuttle around the HAC as it aligns with the runway. The shuttle can turn as much as almost a full circle (360 degrees) before aligning with the runway and descending to touchdown, but the amount of turn required is usually between 200 to 300 degrees for most landings.

Landing - the scheduled landing time is given in both MET (days/hours:minutes:seconds) and Central time (Julian Day/hour:minute:second). Landing occurs just a little over an hour after the deorbit burn.

Roll Schedule - as the orbiter descends through the atmosphere to a level where air pressure has built sufficiently and slows to where heating has subsided somewhat, it begins a series of four steep banks to slow down. The shuttle, in essence, fishtails through the atmosphere as it descends to dissipate its speed. The first couple of banks that the shuttle performs can often be very steep, as much as 80 degrees, that result in the shuttle's side facing toward the ground. The second, third and fourth banks are referred to as "roll reversals," since they basically reverse the shuttle's roll angle, i.e. from 80 degrees left to 70 degrees right. It is important to understand that although the shuttle is performing these steep banks, its angle of attack -- the angle of its nose toward the oncoming air pressure -- is very high, at 40 degrees for much of the entry, to protect the spacecraft from the intense heat that is generated. The angle gradually decreases, i.e. the nose is slowly brought down, as the shuttle descends and slows.

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