Landing Preliminary Advisory Data (DOL PAD)
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.
- 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.
- 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
- 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).
- 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.
- 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.
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.
- 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.