DEVELOPMENT AND TEST PROGRAMME OF THE WHEEL MECHANISMS FOR THE MID INFRA-RED INSTRUMENT (MIRI) OF THE JAMES WEBB SPACE TELESCOPE (JWST)

摘要

In 2012 NASA will launch the JWST as successor of the Hubble Space Telescope. Four scientific instruments will investigate the near and mid infra-red range between 0.6 and 28.3 microns. The Mid Infra-Red Instrument (MIRI) allows for broad and narrow band imaging with low resolution spectroscopic and coronagraphic capabilities as well as for integral field medium resolution spectroscopy above 5 microns. For this large variety of astronomical observing modes the instrument is equipped with three wheel mechanisms for positioning various elements like filters, dichroics, gratings, prisms and coronagraphic masks in the optical beam. Prime requirements for these mechanisms are high reliability under cryo-vacuum conditions (～7K), long lifetime (> 5years), high vibration capabilities (～ 45G), high positioning accuracy (～ 5arcsec) and low heat dissipation (< 1mW). To reach these goals simultaneously in a short timeframe, MPIA has transferred experience and heritage from its previous involvements in ESA missions like ISO and HERSCHEL into early development models (DMs), which are presently in the assembly phase at MPIA. Their detailed design and qualification programme are in the focus of this paper.