20 October 2004 Kite: status of the external metrology testbed for SIM
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Kite is a system level testbed for the External Metrology System of the Space Interferometry Mission (SIM). The External Metrology System is used to track the fiducials that are located at the centers of the interferometer's siderostats. The relative changes in their positions needs to be tracked to an accuracy of tens of picometers in order to correct for thermal deformations and attitude changes of the spacecraft. Because of the need for such high precision measurements, the Kite testbed was build to test both the metrology gauges and our ability to optically model the system at these levels. The Kite testbed is a redundant metrology truss, in which 6 lengths are measured, but only 5 are needed to define the system. The RMS error between the redundant measurements needs to be less than 140pm for the SIM Wide-Angle observing scenario and less than 8 pm for the Narrow-Angle observing scenario. With our current testbed layout, we have achieved an RMS of 85 pm in the Wide-Angle case, meeting the goal. For the Narrow-Angle case, we have reached 5.8 pm, but only for on-axis observations. We describe the testbed improvements that have been made since our initial results, and outline the future Kite changes that will add further effects that SIM faces in order to make the testbed more representative of SIM.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Frank G. Dekens, Oscar S. Alvarez-Salazar, Alireza Azizi, Steven J. Moser, Bijan Nemati, John Negron, Timothy Neville, Daniel Ryan, "Kite: status of the external metrology testbed for SIM", Proc. SPIE 5491, New Frontiers in Stellar Interferometry, (20 October 2004); doi: 10.1117/12.549797; https://doi.org/10.1117/12.549797


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