NIRSpec - the JWST Multi-Object Spectrograph P. Ferruit (ESA), S. Arribas (CSIS), S. Birkmann (ESA), T. Böker (ESA), A. Bunker (Oxford), S. Charlot (IAP), G. De Marchi (ESA), M. Franx (Leiden), P. Jakobsen (DARK), G. Giardino (ESA), R. Maiolino (INAF), H. Moseley (NASA), B. Rauscher (NASA), H.W. Rix (MPIA), M. Sirianni (ESA), J. Valenti (STScI), C. Willott (Ottawa) Abstract NIRSpec will be the first slit-based astronomical multi-object spectrograph to fly in space, and is designed to provide spectra of faint objects over the near-infrared micron wavelength range at spectral resolutions of R=100, R=1000 and R=2700. The instrument's all-reflective wide- field optics, together with its novel MEMS-based programmable micro-shutter array slit selection device and its large format low-noise HgCdTe detector arrays, combine to allow simultaneous observations of >100 objects within a 3.4’ x 3.5’ field of view with unprecedented sensitivity. A selectable 3” x 3” Integral Field Unit and five fixed slits are also available for detailed spectrosco- pic studies of single objects. NIRSpec is being built for the European Space Agency (ESA) by EADS Astrium as part of ESA's contribution to the JWST mission. The NIRSpec micro-shutter and detector arrays are provided by NASA/GSFC. In this poster we present the instrument status and show some results of its first ground calibration campaign under cryogenic conditions. NIRSpec Highlights Wavelength range: µm Spectral resolutions: R~100, R~1000, and R~2700 Field of view: 3.4 x 3.6 arcmin (9 arcmin 2 for MOS) Programmable slit mask: MEMS-based micro-shutter array Integral-field spectroscopy: 3”x3” image slicer 5 individual “long” slits for single-object, high-contrast spectroscopy All-reflective optics Athermal design based on ceramic material for structure and optics 8 Positions: 1. Clear (CaF 2 substrate) 2. Closed (for use with CAA) 3. Long Pass λ > 0.7 µm 4. Long Pass λ > 1.0 µm 5. Long Pass λ > 1.7 µm 6. Long Pass λ > 2.9 µm 7. TA A (1.0 < λ < 1.3 µm, for Target Acquis.) 8. TA B (0.8 < λ < 2.0 µm) Flight model shown Filter Wheel Re-Focussing Mechanism Penta-prism design Large focus range No lateral image shifts Flight model shown All-ceramic design: bench & mirrors of SiC Athermal, very low CTE at 37 K Light-weight, yet extremely stiff Polished to optical quality (flight model shown) Fore Optics Three Mirror Anastigmat NIRSpec field of view NIRSpec status and schedule First thermal vacuum calibration in February 2011 Excellent optical performances (see data below) Improved design of some mechanical interfaces Second ground calibration campaign in summer 2012 Thereafter delivery to NASA NIRSpec optical path Telescope aperture & PSFPSF at MSA & truncationPupil at gratingPSF at FPA & pixelisation 11 x 2 calibration lamps: Redundant lamps (telescopes) Telescopes combined with transmission filters for passband selection Temperature-monitored Fabry-Perot filters for dispersion calibration Rare-Earth filter for absolute reference Qualification model shown Calibration Assembly Spectrometer light shield 8 Positions: 1. R=100 Prism 2. R=1000 Grating ( µm) 3. R=1000 Grating ( µm) 4. R=1000 Grating ( µm) 5. R=3000 Grating ( µm) 6. R=3000 Grating ( µm)) 7. R=3000 Grating ( µm) 8. Flat mirror for imaging mode Grating wheel Focal Plane Assembly (FPA) 2 Teledyne SCAs (H2RG) 2048 x 2048 pixels 2 each Physical pixel size 18 μm Pixel scale 100 mas Thermally controlled Data locally digitized by 2 SIDECAR ASICs (below) Camera housing FPA Harness Radiator interface Collimator Optics TMA Coupling Optics Target alignment Microshutter detail Microshutter Sub-Assembly (MSA 4 MSA quadrants with 365x171 shutters each Physical slit size: 175 x 76 μm 2 Aperture size on sky: 460 x 200 mas 2 Total FOV: 3.4 x 3.6 arcmin 2 Mounting structure also houses the IFU IFU design Made from SiC Flight model shown actual size 110 cm ~ 3’ 7” Argon source, IFU and Fixed Slits, F070LP, G140MErbium source, IFU and Fixed Slits, F140X, G140M Extracted spectrum