January 4, 2023
COS NEWSLETTERS

About This Article

In this STAN we discuss the availability of stenv as a replacement for Astroconda. We also describe COS posters to be presented at the 241st AAS meeting and announce a new version of the COS Data Handbook.

Availability of stenv as a Replacement for Astroconda

The Space Telescope Science Institute has released “stenv” to supersede Astroconda for its software distribution. stenv provides a common environment for both the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST) pipelines and includes most of the packages in Astroconda.

While Astroconda has served our community well for many years, more recently the vast number of versions with an ever increasing number of software packages would often result in Astroconda taking a very long time to resolve dependencies. Moreover, some Astroconda dependencies are fundamentally incompatible with Python versions >3.7. To better support our users, stenv employs pre-determined Conda environments that are verified compatible with Python versions from 3.8 to 3.11. Additionally, while Astroconda primarily uses Conda recipes to build and serve packages, which need to be updated separately from PyPI releases, stenv draws most of its packages directly from PyPI with pip (though it still requires use of a Conda environment for hstcal and fitsverify, which are provided by conda-forge). Support for Astroconda will end on February 1st, 2023.

Instructions for installing and using stenv can be found at https://stenv.readthedocs.io/. Questions can be directed to the help desk at hsthelp.stsci.edu.

 

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COS Posters at the 241st Meeting of the American Astronomical Society

Two COS posters will be presented at the AAS meeting. We invite all COS users to review these to find out about the latest developments and future plans for COS. Below we include links to the posters. Additionally, all COS posters are archived on the COS poster page.

462.01 Updated Status and Performance of the Cosmic Origins Spectrograph (T. Fischer and the COS Team)

The Cosmic Origins Spectrograph (COS), aboard the Hubble Space Telescope (HST), continues to provide critical observations of the ultraviolet universe in its thirteenth year of operation. We present a general status update for the instrument over the last 12 months. Specifically, we introduce the new Lifetime Position 6 (LP6) for FUV spectroscopy with COS as the default location for spectroscopy with the G160M grating and describe changes in resolution and an increase in overheads in comparison to other LPs. We also provide updates for users on changes to the CalCOS data calibration pipeline. Specifically, we detail the delivery of a new NUV Extraction Table to prevent an over-subtraction of science spectra in extended sources, providing a mean flux increase of 12% in these targets, and the adoption of new dark rates due to increased solar activity, providing count rate increases between 6-18%. Further, we detail recent updates to the ETC, incorporating the latest throughputs for all COS modes, including changes in sensitivity with time and changes due to improved FUV flux calibration.

462.02 Science with the Cosmic Origins Spectrograph into the 2030s (M. Rafelski and the COS Team) 

The Hubble Space Telescope's Cosmic Origins Spectrograph (COS) Far-Ultraviolet (FUV) microchannel plate detector's efficiency at converting incoming photons into detectable events decreases with usage. This depletion of the detector's gain (i.e. gain sag) results in unusable regions of the COS/FUV detector over time. To mitigate the effect of gain-sag and provide the community with access to un-sagged regions of the FUV detector, the location of the COS FUV spectrum is periodically moved to a new location in the cross dispersion direction on the detector (called lifetime positions or LP). Two recent developments should extend the life of COS into the 2030's. First, we now operate the FUV channel in a 'hybrid LP' mode, with different gratings and cenwaves at different positions on the detector. Second, regions at the top of the detector that are affected by light leak when wavelength calibration lamp spectra are obtained simultaneously can instead be used when wavecal spectra are obtained non-simultaneously at a different location on the detector with "SPLIT-WAVECALS," in use at LP6 and beyond. We currently operate the G130M 'blue modes' at LP2, G140L at LP3, G130M/1222 and G160M 'short exposures' at LP4, G130M at LP5, and 'long exposures' G160M at LP6. Together with future LPs above LP6, this strategy will enable COS to operate with all settings well into the 2030's, enabling ground-breaking science with both UV channels concurrently with JWST observations. 

 

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Release of Version 5.1 of the COS Data Handbook

Version 5.1 of the COS Data Handbook has been published. Major changes include discussion of the new lifetime position LP6 and the introduction of stenv as a replacement for Astroconda, as described above.

 

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