SAFARI is a point source spectrometer for the SPICA mission, which provides far-infrared spectroscopy and high sensitivity. SPICA mission, having a large cold telescope cooled to 6K above absolute zero, will provide an optimum environment where instruments are limited only by the cosmic background. SAFARI is a grating-based spectrometer with two modes of operation, Low Resolution (LR), or nominal mode (R~300) and High Resolution, (HR) (R~2000-11000). The SAFARI shall provide point source spectroscopy with diffraction-limited capability in four spectral bands over 34-230μm and a field of view (FoV) on sky over 2’×2’. Due to the complexity of the optical design of the SAFARI instrument a modular design was selected. Four principal modules are defined: Calibration Module (CS), Input Optics Module (IOM), Beam and Mode Distribution (BMDO) and Grating Modules (GMs). The present work is focused in the last module. Dispersive optical systems inherently demand the need of volume allocation for the optical system, being this fact somehow proportional to the wavelength and the required resolving power. The image sampling and the size of the detector elements are key drivers in this optical modular design. The optimization process has been performed taking into account the conceptual design parameters obtained during this phase such as collimator and camera optics focal lengths, subsystem diameters and periods and AOIs of the diffraction gratings.
ELMER is an optical instrument for the GTC designed to observe between 370 and 1000 nm. The observing modes for the instrument at Day One shall be: imaging, long slit spectroscopy, slit-less multi-object spectroscopy, fast photometry, fast short-slit spectroscopy and mask multi-object spectroscopy. It will be installed at the Nasmyth-B focal station at Day One, but it has also been designed to operate at the Folded Cassegrain focal station. The physical configuration of the instrument consists of a front section where the focal plane components are mounted (cover masks and slits) and a rear section with the rest of the components (field lens, folder mirrors, collimator, shutter, filters, prisms, grisms, camera and cryostat). Both sections are connected through a hexapod type structure.
An accurate behavior model of the instrument has been developed to optimize the design of the structural parts. The geometry of the hexapod configuration has been adjusted to reduce the ratio between the lateral deflection of the rear section and its rotation in order to minimize the image motion due to the deflections of the instrument. Special effort has been devoted to the design of the drives of the four wheels, each one driven by a preloaded worm gear.