Navigation and Control
GNC software commands effect vehicle control and provide sensor
data needed to compute these commands.
Control System Hardware
Hard-wired to one of eight flight-critical MDMs.
Include IMUS, tacan units, air data probe assemblies, and more.
Consist of an all-attitude, four-gimbal, inertially stabilized platform.
Two star tracker units are part of the navigation system.
Optical Alignment Sight
Used if IMU alignment is in error more than 1.4 degrees.
Determine slant range and magnetic bearing to ground station.
Provides information on the movement of the orbiter in the air mass.
Scan Beam Landing System
Used during landing phase to determine slant range, azimuth and
elevation to landing runway.
Measure absolute altitude from the orbiter to nearest terrain within
beamwidth of orbiter's antennas.
Sense vehicle acceleration along lateral and vertical axes.
Rate Gyro Assemblies
Used by flight control system to sense roll, pitch and yaw rates
during ascent and entry.
Rocket Booster Rate Gyro Assemblies
Used as feedback to find rate errors from liftoff to SRB separation.
Used by flight crew to gimbal engines and OMS/RCS systems.
Used for manual control of translation along the longitudinal, lateral,
and vertical axes to control RCS.
Stick Steering Push Button Light Indicators
Indicate control stick mode.
Command orbiter rotation about the yaw axis by positioning the rudder
during atmospheric flight.
Used during ascent to vary thrust level of main engines; used during entry to
control aerodynamic drag.
Provide manual control for positioning body flap during entry.
Provide signals to GPCs, prohibiting execution of related software
commands while RHC is active.
Used to move the aerosurfaces in roll, pitch and yaw.
Receive commands during atmospheric flight, causing aerosurface
Composed of several software modules that interpret maneuver commands
and generate commands for the appropriate effectors.
OMS/RCS thrusting periods can be used to correct or modify the orbit
Black boxes are situated in several locations around the orbiter.