Adaptive optics systems for ground-based imaging through the earth's atmosphere must generally measure and correct for path distortions within a time period ranging from 0.5 to 10 milliseconds. For most astronomical objects, this requires a wavefront error sensor of the highest sensitivity -- typically a system which employs hundreds of quantum-limited photodetectors devoted exclusively to this task. This paper will point out how the system problems for figure control of orbiting telescopes are quite different since the error sources have periods which typically range from hours to years. Thus error signal integration times can be thousands of times larger for the orbiting optics, and it is feasible and economically advantageous to use low sensitivity dither adaptive optics systems, employing single detectors at the image plane. We will compare three classes of dither systems for this application: 1) one-element-at-a-time step systems; 2) half-at-a-time step systems; and 3) parallel sinusoidal dither (multidither) systems. Several types of signal processing will be compared from a signal-to-noise viewpoint. Computer simulations will be employed to illustrate the system performance at marginal signal-to-noise ratios.