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.
This, just completed for you:
N.A.S.A. Technical Briefing
Saturday, Feb. 1, 2003, transcript of a portion of yesterday's technical briefing to the press, at N.A.S.A., available Sunday, Feb. 2, 2003 online at the BBC, playable on RealPlayer. Go to position 37:00 on the "tape."
Milt Heflin, Chief Flight Director ---
8:53 A.M. EST --- Indication of off-scale low measure ... temperature measurements on the left ... the in-board and out-board hydraulic systems; this is loss of the temperature measurement; there wasn't any indication of high or low ... we just lost it.8:56 A.M. EST --- In the left main gear tire wheel well, uh brake line and tire temperatures - there we saw an increase. Now I need to tell you that during this time, the vehicle was performing fine; we hadn't ... no indications of any problem.
8:58 A.M. EST --- We had what we call bond-line temperatures. These are temperature sensors that are embedded in the structure of the vehicle; we have 'em all over the Orbiter. Um ... three of these termperatures on the ... again the left side of the vehicle ... um, left wing area ... the off-scale low reading again. This was not high indication, low indication, but we lost the, lost the measurements.
8:59 A.M. EST --- Left in-board and out-board tire temperatures ... and pressures ... uh off-scale low. Uh, about eight ... eight measurements, total during that time. One of these ... one of these measurements uh .. uh ... sensed on-board by the computers, gave the crew ... um ... a message ... an indication that they could look at, on their displays ... um ... and they ... [clears throat] ... they ... uh ... we think, they were acknowledging that measurement that they saw. Again, the vehicle was fine with no problems at that time.