Progress report on FORCAST grism spectroscopy as a future general observer instrument mode on SOFIA

We have implemented and tested a suite of grisms that will enable a moderate-resolution mid-infrared spectroscopic mode in FORCAST, the facility mid-infrared camera on SOFIA. We have tested the hardware for the spectral modes extensively in the laboratory with grisms installed in the FORCAST filter wheels. The grisms perform as designed, consistently producing spectra at resolving powers in the 200-1200 range at wavelengths from 5 to 38 microns. In anticipation of offering this capability as a SOFIA general observer mode, we are developing software for reduction and analysis of FORCAST spectra, a spectrophotometric calibration plan, and detailed plans for in-flight tests prior to commissioning the modes. We present a brief summary of the FORCAST grism spectroscopic system and a status report. © 2010 Copyright SPIE - The International Society for Optical Engineering

Quick-look reduction software for FORCAST grism mode on SOFIA

We have designed and fabricated a suite of grisms for use in FORCAST, a mid-infrared camera scheduled as a first-light instrument on SOFIA. The grism suite gives SOFIA a new capability: low resolution spectroscopy from 5 to 38 microns at resolving powers from R=200 to R=1200, without the addition of a new instrument. We have developed an IDL based spectral data reduction and quick-look software package, in anticipation of FORCAST grism spectroscopy becoming a facility observing mode on the SOFIA telescope. The package allows users to quickly view their data by extracting single-order and cross-dispersed spectra immediately after acquiring them in flight. We have optimized the quick-look software to reduce the number of steps required to turn a set of observations into a fully reduced extracted spectrum. We present a description of the philosophy of the data reduction software, supplemented with screen shots and examples in hopes of garnering feedback and critiques from potential end users, software developers, and instrument builders. © 2010 Copyright SPIE - The International Society for Optical Engineering

A silicon and KRS-5 grism suite for FORCAST on SOFIA

We have designed and fabricated a suite of grisms for use in FORCAST, a mid-infrared camera scheduled as a first-light instrument on SOFIA. The grism suite gives SOFIA a new capability: low and moderate resolution spectroscopy from 5μm to 37μm, without the addition of a new instrument. One feature of the optical design is that it includes a mode using pairs of cross-dispersed grisms, providing continuous wavelength coverage over a broad range at higher resolving power. We fabricated four silicon (n = 3.44) grisms using photolithographic techniques and purchased two additional mechanically ruled KRS-5 (n = 2.3) grisms. One pair of silicon grisms permits observations of the 5 - 8μm band with a long slit at R 200 or, in a cross-dispersed mode, at resolving powers up to 1500. In the 8 - 14μm region, where silicon absorbs heavily, the KRS-5 grisms produce resolving powers of 300 and 800 in long-slit and cross-dispersed mode, respectively. The remaining two silicon grisms cover 17 - 37μm at resolving powers of 140 and 250. We have thoroughly tested the silicon grisms in the laboratory, measuring efficiencies in transmission at 1.4 - 1.8μm. We report on these measurements as well as on cryogenic performance tests of the silicon and KRS-5 devices after installation in FORCAST

Optimizing the transmission of the GRAVITY/VLTI near-infrared wavefront sensor

International audienc

Design Of And Progress Towards The Gravity Wave-front Sensors

International audienceThe GRAVITY instrument is a beam-combining interferometer for the four telescopes of the VLT, and relies upon four near-infrared (1.4-2.4 micron) Shack-Hartmann style wave-front sensors to determine the atmospheric distortion due to atmospheric turbulence. The GRAVITY AO system will then drive the VLT's MACAO deformable mirrors to correct the wavefront, permiting 10 micro-arcsecond astrometry. We present the current design and status of the wave front sensor system, as well as future plans for integration and test

Design Of And Progress Towards The Gravity Wave-front Sensors

International audienceThe GRAVITY instrument is a beam-combining interferometer for the four telescopes of the VLT, and relies upon four near-infrared (1.4-2.4 micron) Shack-Hartmann style wave-front sensors to determine the atmospheric distortion due to atmospheric turbulence. The GRAVITY AO system will then drive the VLT's MACAO deformable mirrors to correct the wavefront, permiting 10 micro-arcsecond astrometry. We present the current design and status of the wave front sensor system, as well as future plans for integration and test

GRAVITY Coudé Infrared Adaptive Optics (CIAO) system for the VLT Interferometer

International audienc