Attitude and Orbit Control Subsystem

Attitude Measurement Electronics

This diagram shows more detail of the connectivity between units within the AME. Click on an area of this image to obtain a more detailed description of the units of interest.

The Attitude Measurement Electronics uses inputs from the spacecraft Sun Sensors, Attitude and Orbit Control Electronics (AOCE) and ground commands to provide the spacecraft subsystems with refined Sun pulse information, and to control the position of the fuel regulation valves and heaters in the Reaction Control Subsystem. It also takes power from the AOCS power converters and provides power switching for other units within the AOCS. The AME supports the function of the AOCS failure modes by enabling autonomous closure of the Latching Valves.


Sun Sensor Conditioning Electronics

This unit processes the signals from the Cross-Beam Sun Sensors (XBS) and Meridian Slit Sun Sensors (MS). Raw Sun pulses are received from the sensors. The SSCE resolves the origin of the pulses given the power status of the sensor packages, and routes buffered signals to the correct input channels in the AOCE and spacecraft Data Handling Subsystem. The four sensors (XBS1, XBS2, MS1, MS2) can operate in several different combinations, depending on mission phase and intent.


Thruster Flow Control Valve and Latching Valve Drivers

These are 8 main and 8 standby power amplifiers, providing on-off power signals to the solenoids that control Flow Control Valve (FCV) position. The FCV drivers cause thruster firings in response to the logic signals coming from the AOCE. The FCV drivers are prevented from working if the Latching Valves (LV) are closed - this ensures that the closed section of pipe between the LV and FCV is not depleted of fuel.

Latching Valve Drivers are power amplifiers that provide power to the solenoids that control LV position, in response to telecommands or failure signals generated by the AOCE.


Catalyst Bed Heater Drivers

These power amplifiers each provide on-off power to a pair of thruster catalyst bed heaters. Catalyst bed heaters are paired:


Power Switches

The AME also takes 28V, 26V, 14V, and 7V power from the AOCS converters and provides 28V, 26V, 13V, and 5V power to the AOCS units.