Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado Cosmic Origins Spectrograph Instrument Design and Capabilities

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado Hubble 4 th -generation instrument for Servicing Mission 4 (Spring 2004) Replaces COSTAR in Bay 4 New ultraviolet spectrograph with more than 10 times greater sensitivity than previous or existing UV instruments Will probe the formation of structure and evolution of matter in the Universe by studying the furthest objects and the intervening material PI Institution: University of Colorado Industrial Partner: Ball Aerospace, Boulder, Colorado Additional partners: UC-Berkeley, STScI, GSFC, SwRI, U. Wisconsin Web site:

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado COS Science Requirements The COS Science Goals require: –point-source spectroscopy at UV wavelengths –medium spectral resolution (R > 20,000) –highest possible throughput –broad wavelength coverage in one exposure These goals are met using a combination of: –Quasi-Rowland circle spectrograph design (FUV) with only 1 reflection –high-efficiency 1st-order holographic gratings –large-format, solar-blind detectors –HST’s capabilities large collecting area UV coatings excellent pointing stability superb image quality (after aberration correction) NUV channel to backup STIS and provide complementary observing capability

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado COS has 2 channels to provide low and medium resolution UV spectroscopy –FUV: Å, NUV: Å FUV gratings: G130M, G160M, G140L NUV gratings: G185M, G225M, G285M, G230L –All M gratings have a spectral resolution requirement of R  20,000 NUV MAMA Detector (STIS spare) Calibration Platform FUV XDL Detector OSM2: G185M, G225M, G285M, G230L, TA1 OSM1: G130M, G160M, G140L, NCM1 Aperture Mechanism: Primary Science Aperture, Bright Object Aperture Optical bench (not shown): re-use of GHRS bench

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado COS FUV Spectroscopic Modes Nominal WavelengthResolving Power Grating Wavelength  Range (R =  b Coverage a per Exposure G130M Å 300 Å 20, ,000 G160M Å 375 Å 20, ,000 G140L Å > 820 Å a Nominal Wavelength Coverage is the expected usable spectral range delivered by each grating mode. The G140L grating disperses the Å region onto one FUV detector segment and Å onto the other. The sensitivity to wavelengths longer than 2050 Å or shorter than 1150 Å will be very low. b The lower values of the Resolving Power shown are delivered at the shortest wavelengths covered, and the higher values at longer wavelengths. The resolution increases roughly linearly between the short and long wavelengths covered by each grating mode.

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado COS FUV and NUV flight detectors meet or exceed performance requirements (QE, resolution, flat-fields, etc.) FUV gratings: –FUV holographic gratings fabricated by Jobin-Yvon (France) on SVG/Tinsley substrates and coated at GSFC –Flight FUV gratings (G130M, G160M, G140L) have been delivered which meet or exceed requirements –G140L-blazed R&D effort on-going at J-Y could, if successful, deliver additional 30-50% throughput improvement for that mode

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado FUV Effective Area 3000 cm 2  1000 cm 2  Sensitivity ~ S/N = 10 in 10,000s for F = 1 x ergs/cm 2 /s/Å

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado COS NUV Spectroscopic Modes Nominal WavelengthResolving Power Grating Wavelength  Range (R =  b Coverage a per Exposure G185M Å 3 x 35 Å 18, ,000 G225M Å 3 x 35 Å 20, ,000 G285M Å 3 x 35/41 Å 20, ,000 G230L Å 1-2 x 500 Å a Nominal Wavelength Coverage is the expected usable spectral range delivered by each grating mode, in three non-contiguous strips for the medium-resolution modes. The G230L grating disperses the 1st- order spectrum between Å along the A&B stripes on the NUV detector. G230L also disperses the Å region onto one of the outer spectral stripes and the Å region onto the other. The shorter wavelengths will be blocked by an order separation filter and the longer will not register because the detector is solar blind. The G230L 2nd-order spectrum between Å may be detectable along the long wavelength stripe. b The lower values of the Resolving Power shown are delivered at the shortest wavelengths covered, and the higher values at longer wavelengths. The resolution increases roughly linearly between the short and long wavelengths covered by each grating mode.

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado NUV Effective Area 800 cm 2  200 cm 2  Sensitivity ~ S/N = 10 in 10,000s for F = 1 x ergs/cm 2 /s/Å

Cosmic Origins Spectrograph Hubble Space Telescope James C. Green University of Colorado Calibration Sub-system