E.15 The Cycle 28 Calibration Plan

The Cycle 28 calibration plan was executed from November 2020 through October 2021. The individual programs are listed in Table E.16 and are described in more detail on the WFC3 Calibration Plan webpage. Following the link to Cycle 28 Calibration, a similar table may be found with direct links to the phase II programs and observation dates. This information may alternately be accessed via the HST Program Information webpage by entering the Proposal ID.

The WFC3 Cycle 28 section also links to a PDF presentation summarizing WFC3 and comparing the Cycle 28 plan with the prior cycle. This document contains more details on the calibration justification and in many cases includes supporting figures with the latest results from regular monitoring.

The Cycle 28 calibration plan was designed to:

  • Maintain and update the standard reference files (biases, darks, linearity, CTE traps, UVIS anomalous QE pixels, post-flash)
  • Monitor the health of the instrument (throughput, gain, hysteresis, bad/hot pixels, sink pixels, CTE decline, stability of the post-flash LED, filter transmission, state of the CSM, number of IR blobs, wavelength and flux stability of the grisms)
  • Support new initiatives and obtain supplemental (non-routine) calibration data

In this cycle, the IR Grism Flux Monitor (program 16408) has been modified to:

  • Quantify sensitivity losses in the IR grisms by supplementing the annual GD153 data with two additional WD standards

Five new calibration programs will supplement the standard monitoring. These programs (16439, 16440, 16441, 16512, 16518) were designed to:

  • Check whether IR filters are losing sensitivity similar to the grisms by repeating prior scanned observations of M35 
  • Recheck the optimal background (post-flash) level, as CTE losses continue to grow

  • Measure the impact of CTE on very faint stars

  • Test for changes in the F110W sensitivity with time by leveraging off of prior observations of the M4 cluster.

  • Check the UVIS focus cross-calibration from F410M to F606W for 'despace' values below 2 microns.

The results of these calibration programs will be documented in Instrument Science Reports on the WFC3 website at:

Table E.16: The Cycle 28 Calibration Programs

Program IDTitle
16414WFC3 UVIS Anneal  
16393WFC3 UVIS Bowtie Monitor  
16394WFC3 UVIS CCD Daily Monitor Part 1
16395WFC3 UVIS CCD Daily Monitor Part 2
16396WFC3 UVIS CCD Daily Monitor Part 3
16397WFC3 UVIS CCD Unflashed (CTE) Monitor 
16398WFC3 UVIS Post-flash Monitor  
16399WFC3 UVIS CCD Gain Stability   
16400WFC3 UVIS CTI Monitor (EPER)  
16401WFC3 UVIS CTE Monitor (Star Cluster)  
16402WFC3 UVIS Traps with Charge Injection  
16403WFC3 IR Dark Monitor 
16404WFC3 IR Linearity Monitor  
16405WFC3 IR Gain Monitor  
16406WFC3 UVIS Shutter Monitoring     
16415WFC3 UVIS and IR Photometry 
16416WFC3 UVIS Time Dependent Sensitivity 
16407WFC3 IR Grism Wavelength Calibration
16408WFC3 IR Grism Flux Calibration
16409WFC3 UVIS Pixel-to-Pixel QE Variations via Int Flats 
16410WFC3 UVIS Internal Flats 
16411WFC3 IR Internal Flats  
16412WFC3 CSM Monitor with Earth Flats 
16413WFC3 Astrometric Scale Monitoring 
16439WFC3 IR Time Dependent Sensitivity
16440WFC3 UVIS CTE: A Completely Direct Approach to Model Pinning
16441Understanding How CTE Affects the Faintest Point Sources in WFC3/UVIS
16512WFC3/IR Time-Dependent Sensitivity in Staring Mode (Clusters)

WFC3 Focus Cross-Calibration