Consider the gyro-telescope assembly. Artful design orders operations to bring precision just where it is needed. Elegance is simplification. Ruthlessly, agonizingly, these must be stripped away. An early problem in Gravity Probe B was telescope pointing, made difficult by floppiness in the dewar structure.
Simplicity marks the spacecraft.
Around the dewar as main structural elements are mounted electronics, a four-paneled solar array, batteries, telemetry , a sunshield for the telescope, and other support systems. Each of the three control systems requires a sensor and a source of thrust. Drag compensation is referred to the proof mass. Pointing is more subtle. For the rest of the orbit, the relativity gyroscopes provide the reference, keeping the telescopes aligned, ready to reacquire the star as it comes up over the horizon.