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Hubble Space Telescope
STAN - Feb 2010


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| STScI Analysis Newsletter (STAN)
| Cosmic Origins Spectrograph (COS)
| February 2010
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Visit the "New in the Last 45 Days" section of the COS website at http://www.stsci.edu/hst/cos for new information about COS.

This and previous issues of the STAN can be found at http://www.stsci.edu/hst/cos/documents/newsletters.

CONTENTS:

COS INSTRUMENT:

- Revised COS G140L 1280 CENWAVE setting for Cycle 18

- COS Capabilities between 900 and 1150 Angstroms

- COS Line-Spread Functions

- COS Wavelength Calibration Zero Points

- New PHATAB File for FUV TIME-TAG Data

- Update to MIRRORB Throughput: Impact on COS Imaging and   Imaging Target Acquisition ETCs

- COS NUV Detector Dark Rate

COS DOCUMENTATION AND USER SUPPORT UPDATES:

- COS Calibration Posters Presented at 215th AAS Meeting

- Recent COS Instrument Science Reports

- Updates to COS Web Pages

- New ETC Special Notices Page

- IHB Errata and Updates

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Revised COS G140L 1280 CENWAVE setting for Cycle 18

For Cycle 18, the G140L 1230 CENWAVE setting is being replaced by a new 1280 setting.

COS Capabilities between 900 and 1150 Angstroms

During SMOV, pre-launch expectations that COS could record low resolution spectra in the wavelength range 900-1150 Å were verified. This observing mode, using the COS G140L grating with the new central wavelength setting of 1280, is now available to the community for Cycle 18. Here we point out some of the issues involved with using this mode.

COS Line-Spread Functions

The on-orbit line spread function of COS when used in HST, differs signficantly from pre-launch estimates. This issue is thoroughly discussed in chapter 5 of the COS IHB, but as it is of importance for much of COS science that we review again here our current understanding of these line spread functions and their impact on planned observations.

Updates to the COS Wavelength Calibration

New dispersion and lamp template files have been delivered for all COS spectroscopic modes. These new reference files should substantially improve the zero-points of the COS wavelength calibration.

New PHATAB File for FUV TIME-TAG Data

The screening of COS FUV detector event pulse heights in CALCOS has been modified to reduce background artifacts.

Update to MIRRORB Throughput: Impact on COS Imaging and Imaging Target Acquisition ETCs

Analysis of post-SM4 COS MIRRORB data have revealed that the pre-SM4 throughput values adopted for MIRRORB were too high by a factor 1.7. A corrected MIRRORB throughput reference file was implemented within SYNPHOT in October 2009, and the Cycle 18 COS Imaging ETC and Imaging Target Acquisition ETC are using the correct throughput values.

COS NUV Detector Dark Rate

The COS NUV detector dark rate has increased since the initial measurements reported in the COS Instrument Handbook were made. We provide an update based on more recent data.

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COS Calibration Posters Presented at 215th AAS Meeting

A number of posters presenting COS instrument performance information were presented on January 5, 2010, at the 215th AAS meeting in Washington DC. The titles and links to copies of the COS posters can be found at http://www.stsci.edu/hst/cos/documents/215aas_posters.

Recent COS Instrument Science Reports

A number of new COS ISRs have been prepared summarizing results from SMOV and early Cycle 17 calibration observations. These can provide useful information for interpretation and planning of COS observations.

Updates to COS Web Pages

Since the release of the new COS Instrument Handbook, we have completed a review of the COS web pages. As part of this review, a number of links into the IHBs were corrected and revised to conform with the Cycle 18 versions. If you find any additional links which are broken or which appear to be misdirected, please forward your concern to help@stsci.edu so we can both point you to the correct information and fix any remaining errors on these pages.

New ETC Special Notices Page

Reports of bugs and other special notices relevant to the use of the Cycle 18 Exposure Time Calculators (ETCs) will be posted at http://www.stsci.edu/hst/observatory/etcs/release_notes.

IHB Errata and Updates

A list of the current errata for the COS Instrument Handbook.

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