... WFC3 Data Handbook > Chapter 8: Persistence > 8.1 Image Persistence . ... Image Persistence . Image persistence is a phenomenon commonly observed in HgCdTe IR detectors. It is an afterglow of earlier images that in the case of the WFC3 IR detector is present when pixels are exposed to fluence levels greater than about 40,000 electrons. ... As shown in the left panel of Figure 8.2 , the amount of persistence in the WFC3 IR detector depends strongly on the fluence of the earlier exposure. ...
... 3.7.2 calwf3 Examples . ... Retrieving Software and Input Data Files . ... Uncalibrated (raw) data files from the HDA . ... The raw image headers already contain the appropriate keywords that list the reference file names that were assigned during STScI pipeline processing. ... calwf3 ( ? ... This example uses the same data from Example 1 and illustrates the steps required to reprocess a WFC3 association after changing the bias reference file from the default value to a file specified by the user. ...
... WFC3 Data Handbook > Chapter 3: WFC3 Data Calibration > 3.6 When should I recalibrate my data? ... When should I recalibrate my data? ... When data sets are retrieved from the Hubble Data Archive (HDA) they are always reprocessed from scratch using the latest available calibration reference files and software updates. ... when running calwf3 with personal versions of reference files or when using new reference files downloaded from the WFC3 website not yet available in the pipeline, . ...
... WFC3 Data Handbook > Chapter 3: WFC3 Data Calibration > 3.5 Calibration of WFC3 Spectroscopic Data . 3.5 . Calibration of WFC3 Spectroscopic Data . WFC3 images obtained using any of the three grism elements require special handling during pipeline calibration. calwf3 processing of grism images does not include extraction or calibration of the spectra. ... The aXe software and documentation can be downloaded from: http://axe-info.stsci.edu/ . ...
... When processing an association, calwf3 retrieves calibration switch and reference file keyword settings from the first image listed in the asn table. calwf3 does not accept a user-defined list of input images on the command line (e.g., *_raw.fits to process all raw files in the current directory). ... Only those steps with switch values of ? ... The reference file for dark subtraction, DARKFILE , is selected based on the values of the keywords DETECTOR , CCDAMP , and BINAXIS i in the image header. ...
... WFC3 Data Handbook > Chapter 3: WFC3 Data Calibration > 3.3 Keyword Usage . ... calwf3 processing is controlled by the values of keywords in the input image headers. ... Table 3.3 provides a summary of the keywords used by calwf3 , specifying whether they function as input or output to the task(s) listed in column 2. ... wf3ccd,wf32d, wf3ir . Input . Primary . ... wf3ccd,wf32d, wf3ir, wf3rej . Output, Input . ... wf3ccd . ... wf3ccd,wf32d, wf3rej . ... wf3ccd,wf3ir . ... wf32d, wf3ir . ...
... WFC3 Data Handbook > Chapter 3: WFC3 Data Calibration > 3.2 Overview of calwf3 . ... calwf3 uses separate paths for processing UVIS and IR images, as listed in Table 3.1 . calwf3 automatically calls the appropriate tasks, but each may be run separately if the user desires some variation from the normal processing. wf3ccd and wf32d are used for processing UVIS images, while IR image processing is done with wf3ir . ... Figure 3.2 shows the calwf3 flow of data in the calwf3 pipeline . ... IR Images . ...
... 3.1.1 Image Processing Summary . ... Then the data products, as well as the raw data are stored by MAST (Mikulski Archive for Space Telescopes). calwf3 corrects for instrumental effects and generates calibrated frames, and AstroDrizzle corrects for geometric distortion, cosmic-ray rejection, and combines associated dithered images. ... Combine images and reject cosmic rays from CR-SPLIT and REPEAT-OBS exposures . ... Processing of single exposures . ... Processing of CR-SPLIT / REPEAT-OBS exposures ...
... WFC3 Data Handbook > Chapter 1: The WFC3 Instruments > 1.3 The IR Channel . ... The IR detector employs a 1024 x 1024 Teledyne (formerly Rockwell Scientific) low-noise, high-QE HgCdTe detector array with ~0.13 arcsecond pixels, covering a nominal 136 x 123 arcsecond field of view. ... Figure 1.3 shows a schematic of the IR channel aperture projected onto the sky with respect to the V2/V3 reference frame. ... For a thorough discussion of WFC3 geometric distortion, we refer the reader to Chapter 4 . ...
... WFC3 Data Handbook > Chapter 1: The WFC3 Instruments > 1.2 The UVIS Channel . 1.2 . The UVIS Channel . ... CCDs, with ~0.040 arcsecond pixels, covering a nominal 162 x 162 arcsecond field of view. ... Minimum UVIS exposure time is 0.5 sec. ... Cosmic rays affect all UVIS exposures, therefore observations should be broken into multiple exposures or dither patterns whenever possible, to allow removal of cosmic rays in post-observation data processing. ...
... WFC3 Data Handbook > Chapter 1: The WFC3 Instruments > 1.1 Instrument Overview . 1.1 . ... WFC3 comprises two channels, each optimized for a specific goal: . ... Light coming from the HST Optical Telescope Assembly (OTA) is intercepted by the flat 45 degree WFC3 pick-off mirror (POM) and directed into the instrument. A channel-select mechanism (CSM) inside WFC3 then diverts the light to the IR channel via a fold mirror, or allows the light to enter the UVIS channel uninterrupted. ...
. WFC3 Data Handbook V. 4.0 . help@stsci.edu . WFC3 Data Handbook > Chapter 1: The WFC3 Instruments . Chapter 1: . The WFC3 Instruments . 1.1 Instrument Overview . 1.2 The UVIS Channel . 1.3 The IR Channel . WFC3 Data Handbook > Chapter 1: The WFC3 Instruments .
... 5.6.1 Full Well Depth . ... 5.6.4 Shutter Stability . 5.6.5 Fringing . ... Conceptually, full well depths can be derived by analyzing images of a rich starfield taken at two significantly different exposure times, identifying bright but still unsaturated stars in the short exposure image, calculating which stars will saturate in the longer exposure and then simply recording the peak value reached for each star in electrons (using a gain that samples the full well depth, of course). ...
... WFC3 Data Handbook > Chapter 5: WFC3-UVIS Sources of Error > 5.5 Image Anomalies . ... Ghosts appear as images of the pupil formed from the light of a bright target in, or near the UVIS detector FOV. ... Further details concerning these ghosts may be found in WFC3 ISR 2007-09. ... Specifically, in full-frame, unbinned UVIS readouts, the CT level is ~2x10 -4 of the source when the target is in quadrants A or C and about 8x10 -5 when the target is in quadrants B or D ( WFC3 ISR 2009-03 ). ...
... WFC3 Data Handbook > Chapter 5: WFC3-UVIS Sources of Error > 5.4 Flat Fields . ... Flat Fields . 5.4.1 Ground Flats . ... Revised flat fields for the complete set of 42 full-frame filters were computed from on-orbit data and delivered on December 14, 2011 for use in the WFC3 calibration pipeline. The flat fields in use prior to this date were derived from ground test data, and these were found to contain a set of four internal window reflections affecting ~45% of the detector field of view. ...
... WFC3 Data Handbook > Chapter 5: WFC3-UVIS Sources of Error > 5.3 Dark Current, Hot Pixels, and Cosmic Rays . ... Dark Current, Hot Pixels, and Cosmic Rays . 5.3.1 Dark Current . ... The number of hot pixels increases over time due to on-orbit radiation damage; periodic anneal procedures, where the UVIS detector is warmed to ~20C, successfully fix about 90% of the hot pixels. ... Figure 5.2 shows the number of hot pixels as a function of time since the installation of WFC3 on HST. ...
... WFC3 Data Handbook > Chapter 5: WFC3-UVIS Sources of Error > 5.2 Bias Subtraction . ... For example, a single-chip readout (the largest possible subarray) read out through amp A must be calibrated with a superbias constructed from single-chip bias frames read out through amp A; similarly, science data read out through amp B must be calibrated with a superbias constructed from bias frames read out through amp B. WFC3 Data Handbook > Chapter 5: WFC3-UVIS Sources of Error > 5.2 Bias Subtraction . ...