The Cosmic Origins Spectrograph (COS) was installed on the Hubble Space Telescope (HST) in May 2009. COS is designed to perform high-sensitivity, medium- and low-resolution spectroscopy of astronomical objects in the 1150-3200 Å wavelength range. COS significantly enhances the spectroscopic capabilities of HST at ultraviolet wavelengths, providing observers with unparalleled opportunities for observing faint sources of ultraviolet light. The primary science objectives of the mission are the study of the origins of large scale structure in the Universe, the formation and evolution of galaxies, the origin of stellar and planetary systems, and the cold interstellar medium. More information and documentation on the Cosmic Origins Spectrograph can be found at CASA, the University of Colorado's Center for Astrophysics and Space Astronomy, Ball Aerospace, and the Experimental Astrophysics Group at the University of California - Berkeley.

COS News New COS Instrument Handbook (January 6, 2010) The COS Instrument Handbook for Cycle 18 has been released. COS ETC Update Oct 24, 2009 New versions of the ETC have been released for all instruments. These include updated throughput measurements based on SMOV results. More information will be available soon at http://www.stsci.edu/hst/cos/software/etc/ COS LSF Preliminary analysis of COS SMOV data suggests that the COS on-orbit spectroscopic line spread function (LSF) is different from what was observed during pre-launch ground testing. Mid-frequency zonal polishing errors in the HST primary and secondary mirrors result in extended wings and a slightly broader and less deep core in the COS LSF. This effect is larger at shorter wavelengths, and it may impact some COS FUV science. Most NUV observations should only be minimally affected. We are currently in the process of better characterizing this effect as a function of wavelength using on-orbit data. We will provide the observers with more quantitative information in the near future.

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		ISR 2010-03: COS Near-UV Flat Fields and High S/N Determination from SMOV Data Describes the process of determining and results of the COS NUV high S/N flat field reference files from data taken during SMOV4 T. Ake 04 Feb 2010 (pdf) STAN - Feb 2010 G140L 1280 CENWAVE, COS between 900-1150 Angstroms, COS LSF, new PHATAB file, Updates to MIRRORB Throughput, NUV Dark Rate, Wavelength Calibration, documentation, and User Support. Cycle 18 IHB Errata. COS+STIS Team 01 Feb 2010 (html) Update to MIRRORB Throughput: Impact on COS Imaging and Imaging Target Acquisition ETCs Lower throughput for MIRRORB P. Goudfrooij 29 Jan 2010 Revised COS G140L 1280 CENWAVE Setting for Cycle 18 Describes new 1280 setting Proffitt 29 Jan 2010 COS NUV Detector Dark Rate Report on recent increases in NUV MAMA dark rate D. Sahnow 29 Jan 2010 COS Spectroscopy between 900 and 1150 Angstroms Using COS Below 1150 Angstroms D. Massa 29 Jan 2010 Updates to the COS Wavelength Calibration New Dispersion and wavecal templates for COS NUV & FUV spectra C. Oliveira 29 Jan 2010 New PHATAB File for FUV TIME-TAG Data Changes in pulse-height screening for COS FUV TIME-TAG Data D. Sahnow 29 Jan 2010 COS Line-Spread Functions Describes wings of LSF P. Ghavamian 29 Jan 2010 ISR 2010-02: SMOV Absolute Flux Calibration of the COS FUV Modes Describes the processes used to determine the absolute flux calibration of COS FUV point source spectra D. Massa 28 Jan 2010 (pdf) ISR 2010-01: SMOV Absolute Flux Calibration of the COS NUV Modes Describes the processes used to determine the absolute flux calibration of COS NUV point source spectra D. Massa 28 Jan 2010 (pdf)