What does your friend think of these paragraphs from various NASA discussions on the WEB .?
One other tool used by navigation is a drag altitude software sensor, which uses a model of the atmosphere to correlate the drag acceleration measured by the IMUs to altitude. This measurement, then, is only as good as the atmospheric model on which it is based. The model is not perfect. However, it has been determined through testing and analysis that drag altitude data are important in keeping downrange and altitude errors bounded during the blackout portion of entry (from approximately 265,000 to 162,000 feet). During this time, the ground is unable to uplink state vector corrections to the orbiter, and TACAN data are not available because of the heat-generated ionization of the atmosphere around the vehicle.
When the orbital mission is completed, the orbiter's payload bay doors must be closed for entry; therefore, its Ku-band antenna must be stowed. If the antenna cannot be stowed, provisions are incorporated to jettison the assembly from the spacecraft so that the payload bay doors can be closed for entry. The orbiter can then transmit and receive through the S-band system, the TDRS in view and the TDRS system. After the communications blackout during entry, the space shuttle again operates in S-band through the TDRS system in the low- or high-data-rate mode as long as it can view the TDRS until it reaches the S-band landing site ground station.
The communications satellite deployed by that crew should reduce to two minutes the communications blackout that has made re-entry of manned spacecraft suspenseful since the Mercury flights.
In past flights, the blackouts lasted 15 minutes as the speeding spacecraft re-entered the atmosphere.
The space shuttle spacecraft transmits and receives through the S-band system, the TDRS in view
and the TDRS system; thus, the WSGT and MCC-H are in the low-data-rate mode until the
communications blackout in entry. After blackout, the space shuttle again operates in S-band
through the TDRS system in the low-data-rate mode during descent to as low a view as possible
until it reaches the S-band landing site ground station, which then transmits and receives in the
high-data-rate mode on S-band.
Communicatiopns with Columbia 11
PAO # 2: The NASA weather plane, M.E. 1, has reported the
current weather conditions. Conditions for landing are good.
Lab # 2: M.E.1, this is Columbia II. We copy, over.
Flight Dir: Commander, you will enter communications blackout in 20
seconds, over.
Commander: Roger, Control. Communications blackout confirmed, over.
(To shuttle crew) Entering blackout.
PAO # 1: The shuttle has entered a region of intense ionization
that prohibits radio communications.
(Engage in no radio communications with Mission Control. The
following lines are to be spoken over the Columbia II's internal
2-way radios.)
Pilot: Activating RCS roll thrusters. Adjusting altitude for
re-entry.
Lab # 2: External heating 600 degrees.
Pilot: RCS thrusters deactivating.
Lab # 1: External heating 900 degrees.
Commander: Extend elevators. Conduct first roll reversal.
(You have now left the region of high ionization and may resume
communications with Mission Control)
Med Off: Leaving Communications blackout. Control, do you read?
Over.
Flight Dir: We read you, Columbia II. We also have visual contact.
You are looking good, over.
PAO # 2: The shuttle has left the region of high ionization and
has resumed communications with Mission Control. Pilot Control, this
is Columbia II. We are ready to assume manual control, over.
Flight Dir: Roger, Columbia II. Deactivating computer guidance
systems. Happy landings, over.PAO # 2: The NASA weather plane, M.E. 1, has reported the
current weather conditions. Conditions for landing are good.
Lab # 2: M.E.1, this is Columbia II. We copy, over.
Flight Dir: Commander, you will enter communications blackout in 20
seconds, over.
Commander: Roger, Control. Communications blackout confirmed, over.
(To shuttle crew) Entering blackout.
PAO # 1: The shuttle has entered a region of intense ionization
that prohibits radio communications.
(Engage in no radio communications with Mission Control. The
following lines are to be spoken over the Columbia II's internal
2-way radios.)
Pilot: Activating RCS roll thrusters. Adjusting altitude for
re-entry.
Lab # 2: External heating 600 degrees.
Pilot: RCS thrusters deactivating.
Lab # 1: External heating 900 degrees.
Commander: Extend elevators. Conduct first roll reversal.
(You have now left the region of high ionization and may resume
communications with Mission Control)
Med Off: Leaving Communications blackout. Control, do you read?
Over.
Flight Dir: We read you, Columbia II. We also have visual contact.
You are looking good, over.
PAO # 2: The shuttle has left the region of high ionization and
has resumed communications with Mission Control. Pilot Control, this
is Columbia II. We are ready to assume manual control, over.
Flight Dir: Roger, Columbia II. Deactivating computer guidance
systems. Happy landings, over. |
