| Rate Gyro Assemblies
SRB contains two RGAs, with each RGA containing one pitch and one
yaw gyro. These provide an output proportional to angular rates
about the pitch and yaw axes to the orbiter computers and guidance,
navigation and control system during first- stage ascent flight
in conjunction with the orbiter roll rate gyros until SRB separation.
At SRB separation, a switchover is made from the SRB RGAs to the
The SRB RGA rates pass
through the orbiter flight aft multiplexers/ demultiplexers to
the orbiter GPCs. The RGA rates are then mid-value- selected in
redundancy management to provide SRB pitch and yaw rates to the
user software. The RGAs are designed for 20 missions.