Status: Conceptual Design Review
The Wide Field Optical Spectrometer (WFOS) will provide near-ultraviolet and optical (0.3 – 1.0 μm wavelength) imaging and spectroscopy over a more than 40 square arcminute field-of-view. Using precision cut focal plane masks, WFOS will enable long-slit observations of single objects as well as short-slit observations of hundreds of objects simultaneously. WFOS will use natural (uncorrected) seeing images.
WFOS will incorporate a robust structure to support the various components of the instrument and minimize instrument flexure. In addition, it will incorporate an enclosure to protect its components and provide a light tight environment for the optical elements. The basic design of the support structure and enclosure will also offer ready access to all configurable portions of the instrument, such as the ADC, slit masks, dichroics, filters, gratings, and detectors to facilitate set-up and maintenance. WFOS is being designed so as not to preclude additional functionality such as an integral field unit, a tunable filter for narrow-band imaging, and an interface to a possible future Ground-Layer Adaptive Optics system for improving the images delivered to the instrument, and thus allowing for higher-sensitivity observations.
WFOS has three modes of operation: direct imaging, single-object spectroscopy and multi-object spectroscopy. To achieve the maximum observing efficiency and maintain the TMT aperture advantage over current telescopes, it must be possible to switch between modes with minimal overhead, < 30 seconds for changing the disperser to a mirror (for imaging), or to change reflection grating and (if in ECH mode) cross-dispersing prism.