The Mercator Advanced Imager for Asteroseismology (MAIA) is being designed particularly for asteroseismology
of hot subdwarf stars on the 1.2m Mercator Telescope. In order to achieve the required precision on the pulsation
amplitude ratios, the photometric variations must be measured simultaneously in several bands with respect to
constant reference stars in the field. MAIA is an optical imager to observe simultaneously in three color bands,
corresponding approximately with an SDSS u, g, r+i+z photometric system. The fully dioptric design uses
a common collimator, two dichroic beam splitters (cut-offs at 390nm and 550nm) and three cameras. Each
camera holds a fast frame-transfer CCD cooled down to -90°C with a compact Stirling cryocooler. All lenses
are axially and radially constrained by a calibrated spring load, with radial adjustment mechanisms to calibrate
the centering of each lens. The differential thermal expansion of the optical system is compensated by the
thermal expansion of the different materials in the mechanical mountings, resulting in a design that is insensitive
to thermal variations. Specific care has been taken to reduce the effect of manufacturing tolerances on the
performance of the instrument. The tilt angle of two of the beam splitters is adjustable in two dimensions to
compensate for remaining misalignment in the optical system. Finite element models have been constructed to
verify that the structural flexure and structural dynamics are within the requirements. A tool has been developed
to estimate the performance of the instrument based on the design parameters. Various commercial software
tools have been used to optimize the workflow in this complex system design.
The Mercator Advanced Imager for Asteroseismology (MAIA) is being designed particularly for asteroseismology
of hot subdwarf stars. In order to achieve the required precision on the pulsation amplitude ratios, the photometric
variations must be measured simultaneously in several bands with respect to constant reference stars in the
field. MAIA is an optical imager to observe simultaneously in three color bands, corresponding approximately
with an SDSS u, g, r+i+z photometric system. The fully dioptric design uses a common collimator, two dichroic
beam splitters (cut-offs at 390nm and 550nm) and three cameras. MAIA covers a wide field of view (FoV)
of 9.4' x 14.1' with a sampling of 0.27"/pix on the 1.2m Mercator Telescope. When replacing the collimator
and with a modest reduction of the FoV, its host can also be used on larger telescopes. Each camera holds a
fast-frame-transfer charge coupled device (CCD), cooled by three four-stage Peltier elements to -70 °C. The
mechanical design minimizes structural flexure. Selected optical elements are mounted in quasi-isostatic lens
mounts to minimize the effects of temperature variations.
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