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21 July 2010A filter wheel mechanism for the Euclid near-infrared imaging photometer
The Euclid mission is currently being developed within the European Space Agency's Cosmic Vision Program.
The five year mission will survey the entire extragalactic sky (~ 20 000 deg2) with the aim of constraining the
nature of dark energy and dark matter. The spacecraft's payload consists of two instruments: one imaging
instrument, which has both a visible and a near-infrared channel, and one spectroscopic instrument operating in
the near-infrared wavelength regime. The two channels of the imaging instrument, the Visible Imaging Channel
(VIS) and the Near-Infrared Imaging Photometer Channel (NIP), will focus on the weak lensing science probe.
The large survey area and the need to not only image each patch of sky in multiple bands, but also in multiple
dithers, requires over 640 000 operations of the NIP channel's filter wheel mechanism. With a 127 mm diameter
and a mass of ~ 330 g per element, these brittle infrared filters dictate highly demanding requirements on this
single-point-failure mechanism. To accommodate the large filters the wheel must have an outer diameter of
~ 400 mm, which will result in significant loads being applied to the bearing assembly during launch.
The centrally driven titanium filter wheel will house the infrared filters in specially designed mounts. Both
stepper motor and brushless DC drive systems are being considered and tested for this mechanism. This paper
presents the design considerations and details the first prototyping campaign of this mechanism. The design and
finite element analysis of the filter mounting concept are also presented.
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Rory Holmes, Ulrich Grözinger, Oliver Krause, Mario Schweitzer, "A filter wheel mechanism for the Euclid near-infrared imaging photometer," Proc. SPIE 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, 77391A (21 July 2010); https://doi.org/10.1117/12.856941