3 research outputs found
MOSFIRE, the multi-object spectrometer for infra-red exploration at the Keck Observatory
This paper describes the as-built performance of MOSFIRE, the multi-object spectrometer and imager for the Cassegrain focus of the 10-m Keck 1 telescope. MOSFIRE provides near-infrared (0.97 to 2.41 μm) multi-object spectroscopy over a 6.1' x 6.1' field of view with a resolving power of R~3,500 for a 0.7" (0.508 mm) slit (2.9 pixels in the dispersion direction), or imaging over a field of view of ~6.9' diameter with ~0.18" per pixel sampling. A single diffraction grating can be set at two fixed angles, and order-sorting filters provide spectra that cover the K, H, J or Y bands by selecting 3rd, 4th, 5th or 6th order respectively. A folding flat following the field lens is equipped with piezo transducers to provide tip/tilt control for flexure compensation at the <0.1 pixel level. Instead of fabricated focal plane masks requiring frequent cryo-cycling of the instrument, MOSFIRE is equipped with a cryogenic Configurable Slit Unit (CSU) developed in collaboration with the Swiss Center for Electronics and Microtechnology (CSEM). Under remote control the CSU can form masks containing up to 46 slits with ~0.007-0.014" precision. Reconfiguration time is < 6 minutes. Slits are formed by moving opposable bars from both sides of the focal plane. An individual slit has a length of 7.0" but bar positions can be aligned to make longer slits in increments of 7.5". When masking bars are retracted from the field of view and the grating is changed to a mirror, MOSFIRE becomes a wide-field imager. The detector is a 2K x 2K H2-RG HgCdTe array from Teledyne Imaging Sensors with low dark current and low noise. Results from integration and commissioning are presented
MOSFIRE, the multi-object spectrometer for infra-red exploration at the Keck Observatory
This paper describes the as-built performance of MOSFIRE, the multi-object spectrometer and imager for the Cassegrain focus of the 10-m Keck 1 telescope. MOSFIRE provides near-infrared (0.97 to 2.41 μm) multi-object spectroscopy over a 6.1' x 6.1' field of view with a resolving power of R~3,500 for a 0.7" (0.508 mm) slit (2.9 pixels in the dispersion direction), or imaging over a field of view of ~6.9' diameter with ~0.18" per pixel sampling. A single diffraction grating can be set at two fixed angles, and order-sorting filters provide spectra that cover the K, H, J or Y bands by selecting 3rd, 4th, 5th or 6th order respectively. A folding flat following the field lens is equipped with piezo transducers to provide tip/tilt control for flexure compensation at the <0.1 pixel level. Instead of fabricated focal plane masks requiring frequent cryo-cycling of the instrument, MOSFIRE is equipped with a cryogenic Configurable Slit Unit (CSU) developed in collaboration with the Swiss Center for Electronics and Microtechnology (CSEM). Under remote control the CSU can form masks containing up to 46 slits with ~0.007-0.014" precision. Reconfiguration time is < 6 minutes. Slits are formed by moving opposable bars from both sides of the focal plane. An individual slit has a length of 7.0" but bar positions can be aligned to make longer slits in increments of 7.5". When masking bars are retracted from the field of view and the grating is changed to a mirror, MOSFIRE becomes a wide-field imager. The detector is a 2K x 2K H2-RG HgCdTe array from Teledyne Imaging Sensors with low dark current and low noise. Results from integration and commissioning are presented
The integral field spectrograph for the Gemini planet imager
The Gemini Planet Imager (GPI) is a complex optical system designed to
directly detect the self-emission of young planets within two arcseconds of
their host stars. After suppressing the starlight with an advanced AO system
and apodized coronagraph, the dominant residual contamination in the focal
plane are speckles from the atmosphere and optical surfaces. Since speckles are
diffractive in nature their positions in the field are strongly wavelength
dependent, while an actual companion planet will remain at fixed separation. By
comparing multiple images at different wavelengths taken simultaneously, we can
freeze the speckle pattern and extract the planet light adding an order of
magnitude of contrast. To achieve a bandpass of 20%, sufficient to perform
speckle suppression, and to observe the entire two arcsecond field of view at
diffraction limited sampling, we designed and built an integral field
spectrograph with extremely low wavefront error and almost no chromatic
aberration. The spectrograph is fully cryogenic and operates in the wavelength
range 1 to 2.4 microns with five selectable filters. A prism is used to produce
a spectral resolution of 45 in the primary detection band and maintain high
throughput. Based on the OSIRIS spectrograph at Keck, we selected to use a
lenslet-based spectrograph to achieve an rms wavefront error of approximately
25 nm. Over 36,000 spectra are taken simultaneously and reassembled into image
cubes that have roughly 192x192 spatial elements and contain between 11 and 20
spectral channels. The primary dispersion prism can be replaced with a
Wollaston prism for dual polarization measurements. The spectrograph also has a
pupil-viewing mode for alignment and calibration.Comment: 13 pages, 10 figures. Proceedings of the SPIE, 9147-5