Space Telescope Testbed
The MIT Space Systems Laboratory has designed and constructed a testbed whose structural dynamic response is similar to that of proposed next generation space telescopes: the Space Interferometry Mission (SIM) and the Next Generation Space Telescope (NGST). The research goal is to address challenges faced by NASAs Origins Program telescopes in areas related to dynamics and control, and to ensure that the results are applicable to these missions.
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The testbed is designed to be as satellite-like as possible, and is neutrally stable at its axis of rotation to enable a slew maneuver. A reaction wheel assembly mounted at the bottom of the spacecraft bus section is used to slew the testbed. Disturbances traceable to those anticipated for the next generation space telescopes are engendered by the reaction wheels.
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The performance of the testbed is measured with an optical metrology system. The phasing of the optical paths is measured with a 10 nm resolution laser interferometer and controlled through the staged actuation of two optical delay lines, mounted on two arms of the testbed. The pointing is measured by angle encoders, a three axis gyroscope assembly, and a high resolution CCD camera. Staged control of the pointing will be accomplished coarsely with the reaction wheels and finely by two piezoelectric fast steering mirrors. A real-time computer with a vector DSP board is used for the digital control.
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