6.2 Specifying a UVIS Observation
Using the Astronomer’s Proposal Tool (APT), it is relatively simple to specify the parameters for a UVIS observation. Detailed documentation of the specifications can be found in the Phase II Proposal Instructions. The parameters available to General Observers for the UVIS channel are the following:
- Configuration: always WFC3/UVIS
- Mode: always ACCUM
- Aperture: must be specified; see Section 6.4.4 and Section 6.4.5 for the dimensions, location, and reference point (target placement) of the full array and subarray apertures.
- Spectral Element: must be specified for each exposure; see Section 6.5
- Optional Parameters: the options include FLASH (to add a specified number of electrons per pixel to the image to reduce CTE losses; Section 6.9.2), CR-SPLIT (to split an exposure into a specified number of subexposures for cosmic ray rejection - but note that dithering provides improved calibrated science products over CR-SPLIT (see Appendix C), BIN (to perform on-chip binning by a specified number - but beware that this mode 1) increases the area affected by bad pixels and cosmic rays and 2) is not advantageous with post-flash; Section 6.4.4), BLADE (to minimize vibration effects in short <5 sec exposures by selecting shutter blade A; requires approval - see Section 6.10.4), and INJECT (to implement charge injection to reduce CTE losses - but the use of this option is not generally permitted for science observations; see Section 6.9.2).
- Special Requirements: see the Phase II Proposal Instructions for details of Special Requirements related to the timing of visits and for dithering and mosaicking. Also available is the exposure-level Special Requirement POS TARG for offsetting the target from the default reference point of the aperture (see Section 6.4.3 for a discussion of the UVIS channel coordinate systems, Section 6.4.5 for reference points, and Appendix C for the POS TARGs associated with the WFC3 patterns).
- Number of Iterations and Time per Exposure: the exposure time for the UVIS channel must be an integer multiple of 0.1 s, ranging from 0.5 to 3600 s, except that 0.6 s is not allowed (Section 6.7.1) and 0.7 s is slightly less favorable than 0.5 s or > 0.8 s (WFC3 ISR 2023-04).
-
WFC3 Instrument Handbook
- • Acknowledgments
- Chapter 1: Introduction to WFC3
- Chapter 2: WFC3 Instrument Description
- Chapter 3: Choosing the Optimum HST Instrument
- Chapter 4: Designing a Phase I WFC3 Proposal
- Chapter 5: WFC3 Detector Characteristics and Performance
-
Chapter 6: UVIS Imaging with WFC3
- • 6.1 WFC3 UVIS Imaging
- • 6.2 Specifying a UVIS Observation
- • 6.3 UVIS Channel Characteristics
- • 6.4 UVIS Field Geometry
- • 6.5 UVIS Spectral Elements
- • 6.6 UVIS Optical Performance
- • 6.7 UVIS Exposure and Readout
- • 6.8 UVIS Sensitivity
- • 6.9 Charge Transfer Efficiency
- • 6.10 Other Considerations for UVIS Imaging
- • 6.11 UVIS Observing Strategies
- Chapter 7: IR Imaging with WFC3
- Chapter 8: Slitless Spectroscopy with WFC3
-
Chapter 9: WFC3 Exposure-Time Calculation
- • 9.1 Overview
- • 9.2 The WFC3 Exposure Time Calculator - ETC
- • 9.3 Calculating Sensitivities from Tabulated Data
- • 9.4 Count Rates: Imaging
- • 9.5 Count Rates: Slitless Spectroscopy
- • 9.6 Estimating Exposure Times
- • 9.7 Sky Background
- • 9.8 Interstellar Extinction
- • 9.9 Exposure-Time Calculation Examples
- Chapter 10: Overheads and Orbit Time Determinations
-
Appendix A: WFC3 Filter Throughputs
- • A.1 Introduction
-
A.2 Throughputs and Signal-to-Noise Ratio Data
- • UVIS F200LP
- • UVIS F218W
- • UVIS F225W
- • UVIS F275W
- • UVIS F280N
- • UVIS F300X
- • UVIS F336W
- • UVIS F343N
- • UVIS F350LP
- • UVIS F373N
- • UVIS F390M
- • UVIS F390W
- • UVIS F395N
- • UVIS F410M
- • UVIS F438W
- • UVIS F467M
- • UVIS F469N
- • UVIS F475W
- • UVIS F475X
- • UVIS F487N
- • UVIS F502N
- • UVIS F547M
- • UVIS F555W
- • UVIS F600LP
- • UVIS F606W
- • UVIS F621M
- • UVIS F625W
- • UVIS F631N
- • UVIS F645N
- • UVIS F656N
- • UVIS F657N
- • UVIS F658N
- • UVIS F665N
- • UVIS F673N
- • UVIS F680N
- • UVIS F689M
- • UVIS F763M
- • UVIS F775W
- • UVIS F814W
- • UVIS F845M
- • UVIS F850LP
- • UVIS F953N
- • UVIS FQ232N
- • UVIS FQ243N
- • UVIS FQ378N
- • UVIS FQ387N
- • UVIS FQ422M
- • UVIS FQ436N
- • UVIS FQ437N
- • UVIS FQ492N
- • UVIS FQ508N
- • UVIS FQ575N
- • UVIS FQ619N
- • UVIS FQ634N
- • UVIS FQ672N
- • UVIS FQ674N
- • UVIS FQ727N
- • UVIS FQ750N
- • UVIS FQ889N
- • UVIS FQ906N
- • UVIS FQ924N
- • UVIS FQ937N
- • IR F098M
- • IR F105W
- • IR F110W
- • IR F125W
- • IR F126N
- • IR F127M
- • IR F128N
- • IR F130N
- • IR F132N
- • IR F139M
- • IR F140W
- • IR F153M
- • IR F160W
- • IR F164N
- • IR F167N
- Appendix B: Geometric Distortion
- Appendix C: Dithering and Mosaicking
- Appendix D: Bright-Object Constraints and Image Persistence
-
Appendix E: Reduction and Calibration of WFC3 Data
- • E.1 Overview
- • E.2 The STScI Reduction and Calibration Pipeline
- • E.3 The SMOV Calibration Plan
- • E.4 The Cycle 17 Calibration Plan
- • E.5 The Cycle 18 Calibration Plan
- • E.6 The Cycle 19 Calibration Plan
- • E.7 The Cycle 20 Calibration Plan
- • E.8 The Cycle 21 Calibration Plan
- • E.9 The Cycle 22 Calibration Plan
- • E.10 The Cycle 23 Calibration Plan
- • E.11 The Cycle 24 Calibration Plan
- • E.12 The Cycle 25 Calibration Plan
- • E.13 The Cycle 26 Calibration Plan
- • E.14 The Cycle 27 Calibration Plan
- • E.15 The Cycle 28 Calibration Plan
- • E.16 The Cycle 29 Calibration Plan
- • E.17 The Cycle 30 Calibration Plan
- • E.18 The Cycle 31 Calibration Plan
- • Glossary