January 8, 2024

About This Article

1. WFC3 at AAS 243! 

We invite all those interested in WFC3 photometry, calibration, and instrument updates to stop by the WFC3 iPosters at the upcoming 243rd AAS meeting. Presenters welcome any and all feedback on proposing, data analysis, documentation, and all other aspects of your experience with WFC3. 

Below, we provide abstracts and session information, and link to the presentation listings in the AAS meeting itinerary. Times are given in Central Time (CT).

Updates and Improvements to HST/WFC3 Photometric Calibration - Ky Huynh, Varun Bajaj, Annalisa Calamida, Jennifer Mack, Mariarosa Marinelli, Aidan Pidgeon, Debopam Som

Tuesday, January 9, 5:30 PM - 6:30 PM

Wide Field Camera 3 on the Hubble Space Telescope consists of two channels optimized for specific wavelength ranges: the ultraviolet-visible channel (UVIS) and the infrared channel (IR). A considerable amount of work is done to monitor the quality and photometric stability of UVIS and IR observations. We present new time dependent IR zeropoints that correct for sensitivity changes as a function of wavelength. We also present ongoing work to improve UVIS inflight flat field correction based on crowded field photometry using new aperture corrections, calculated with respect to the focus levels of point source functions.

HST/WFC3: Instrument and Calibration Updates for 2023 - A. O'Connor, J. Anderson, A. Pagul, K. Huynh, P. McCullough, B. Kuhn, A. Pidgeon, D.Som, S. Baggett, A. Calamida, J. Green and the WFC3 Team

Thursday, January 11, 1:00 PM - 2:00 PM 

The Wide Field Camera 3 (WFC3) is an instrument aboard the Hubble Space Telescope (HST), offering high-resolution UVIS and IR imaging capabilities as well as slitless grism spectroscopy. The WFC3 branch, part of the Instruments Division at the Space Telescope Science Institute (STScI), works to provide high quality data products and data analysis tools for observers, to support the performance and science operations of the two WFC3 detectors, and to assist observers. This poster provides a general overview of WFC3 updates, including new analysis results providing insight into instrument performance, updates to calibration products, and information on new tools available to observers. We discuss new WFC3 dither patterns, refined values for shutter repeatability in very short exposures, the first publicly available sky calibration frames for the WFC3/UVIS G280 grism data, new documentation, as well as proposal advice. We aim to provide relevant information to the astronomy community, as HST and WFC3 continue to operate at high efficiency and usage request rates remain high.

2. Cycle 32 Instrument Handbook Published

M. Marinelli

The Cycle 32 edition of the WFC3 Instrument Handbook has been published! Updates to the previous edition of the Handbook are described in Section 1.1, and include:

  • The latest IR detector sensitivity loss estimates (Section 7.8);
  • Discussion of the G280 background sky models delivered in 2023 (Section 8.2 & Section 8.5);
  • Information about currently available software for extraction and calibration of grism data (Section 8.5);
  • More recent references of science use cases and clarifying details about available software for designing spatial scanning observations (Section 8.6);
  • A new Overview section in Appendix E that includes a summary table of all WFC3 calibration plans and corresponding timespans;
  • A summary of the WFC3 calibration plan for Cycle 32 in Appendix E (Section E.18);
  • Updated information, plots, and references throughout the handbook, based on the eight Instrument Science Reports (ISRs) released in 2023;
  • Several figures and plots replaced with equivalent but higher-resolution versions.

A PDF version of the entire Handbook is linked at the top webpage (orange box in Figure 1). The web version is searchable using the Search box above the Table of Contents (blue box in Figure 1). For example, searching "single guide star" will produce a list of sections in which this phrase occurs. On the result page, the question mark icon in the search box provides descriptions of how to refine this search using logical statements, wildcards, etc. (Figure 2)

Figure 1: Web version of the Cycle 32 WFC3 Instrument Handbook. A PDF version is downloadable using the link in the top left corner, while the web version is searchable using the search box.
Figure 2: Results page from searching the online version of the WFC3 IHB for “single guide star”; overlain is the Search Help window, which appears when a user clicks the question mark icon in the search box.

3. Migration of WFC3 Library to HST Notebooks

F. Dauphin, J. Green, M. Dulude

STScI Curated Science Notebooks are a collection of Jupyter notebook repositories maintained by different STScI teams. The collections support HST, JWST, MAST, and others. HST Notebooks, a repository of HST-related notebooks, includes analyses for ACS, COS, DrizzlePac, NICMOS, STIS, and now WFC3. In order to better support users and manage our software, we are migrating all of our notebooks from WFC3Library, our current repository of WFC3 analysis notebooks, to HST Notebooks. Each notebook contains a requirement.txt file, which provides necessary installations to run the notebook. In addition, new notebooks will be directly added to HST Notebooks, and we will continue to update the community as they are added. Furthermore, WFC3Library will be officially deprecated as of January 2024 as all users should go to HST Notebooks for our analyzes instead.

4. Slitlessutils: A Python Package for Extracting and Simulating Wide-Field Slitless Spectroscopy for WFC3 and ACS

R. Ryan

We present 'slitlessutils', the new STScI-supported package for analyzing wide-field slitless spectroscopy observed with all active HST instrument/detector configurations: ACS/WFC; ACS/SBC; WFC3/IR; and WFC3/UVIS.  Slitlessutils uses a forward-modeling engine to determine the mapping between a direct image and its corresponding slitless-spectroscopic images.  When coupled with detector calibrations such as the sensitivity curve, flat-field, pixel-area map, etc., these transformation coefficients enable the user to extract one-dimensional spectra from slitless observations and also to simulate a slitless-spectroscopic scene.  Slitlessutils offers two methods for extracting the spectra, which are delineated by the assortments of available HST orients.  Specifically, slitlessutils implements the LINEAR method (Ryan, Casertano, & Pirzkal 2018) for fields with multiple orients, as well as an HSTaXe extraction for fields with a single orient.  Additionally, slitlessutils provides several utility functions to prepare observed spectroscopic data for analysis (e.g., astrometric updates, background subtraction, and cosmic-ray rejection).  

Slitlessutils is written entirely in Python and is publicly available on GitHub/PyPI with documentation on ReadTheDocs. The software distribution includes worked examples that demonstrate several of the key analysis options, such as simulating a simple field, extracting an isolated calibration star, etc.  This initial public release includes basic functionality for ACS/WFC and WFC3/IR; the documentation describes the additional capabilities (incl. full ACS/SBC and WFC3/UVIS support) that are under active development and are anticipated to be available in near-term updates.  We welcome feedback from the community on the performance and code enhancements through the HST Help Desk.

5. New Documentation 

ISR 2023-08: WFC3/UVIS: New Full-Well Saturation Map Reference File - I. Rivera, M. Marinelli, J. Mack

The complete WFC3 ISR archive is available here. Additional information about WFC3 calibration, performance, data analysis, software tools, and more can be found online.

Need help? stsci.service-now.com/hst

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