... WFC3 Data Handbook > Chapter 5: WFC3-UVIS Sources of Error > 5.1 Gain and Read Noise . ... Gain and Read Noise . ... The average read noise level measured in the science area pixels of bias frames at the default gain setting are summarized in Table 5.2 . Scatter in the measurements, based on data acquired between June 2009 and July 2015, is ~1% or better, depending on the amplifier. More recent correction for 1x1 readnoise values are in WFC3 ISR 2015-13, other values are from WFC3 ISR 2013 . ...
... WFC3 Data Handbook > Chapter 4: WFC3 Images: Distortion Correction and AstroDrizzle > 4.2 Distortion Corrections and Image Combination . ... In order to produce images that appear uniform for uniform illumination, the WFC3 flat fields include the effect of the variable pixel area across the field. ... AstroDrizzle relies on the Image Distortion Correction Table ( IDCTAB ) and the Detector to Image Distortion Correction ( D2IMFILE, UVIS only) reference files for a description of the WFC3 distortion. ...
... WFC3 Data Handbook > Chapter 4: WFC3 Images: Distortion Correction and AstroDrizzle > 4.1 WFC3 Geometric Distortion . ... The WFC3 UVIS detector is tilted at ~21 degrees about one of its diagonals, producing a rhomboidal elongation of ~7%. ... WFC3-ISR-2013-14 ). ... The knowledge of geometric distortion of the WFC3-UVIS and IR is the backbone of the STSDAS software DrizzlePac / AstroDrizzle software (Gonzaga, et al ., 2012 ), which is currently installed in the STScI on-the-fly pipeline (OTFR). ...
... M. Robberto, C. Hanley, I. Dashevsky, T he reference pixels on the WFC3 IR detectors, WFC3 ISR 2002-06, http://www.stsci.edu/hst/wfc3/documents/ISRs/WFC3-ISR-2002-06.pdf . ... B. Hilbert, Snowballs? in the WFC3-IR Channel: Characterization , WFC3 ISR 2009-43, http://www.stsci.edu/hst/wfc3/documents/ISRs/WFC3-ISR-2009-43.pdf . ... Hilbert & Bushouse, H., WFC3/IR Bad Pixel Table: Update Using Cycle 17 Data, WFC3 ISR 2010-13, http://www.stsci.edu/hst/wfc3/documents/ISRs/WFC3-ISR-2010-13.pdf . ...
... Observations made when HST is pointing near the bright Earth limb can result in the left most ~200 columns of the detector being subjected to background levels up to twice as bright as that on the rest of the chip. ... The overall shape of this high background region is very similar from one affected image to another, but the brightness of the scattered light varies as the HST pointing approaches or recedes from the bright Earth limb. ... Figure 7.12: IR Image affected by scattered earth-shine. ...
... WFC3 Data Handbook > Chapter 7: WFC3/IR Sources of Error > 7.8 Pixel Defects and Bad Imaging Regions . ... Pixel Defects and Bad Imaging Regions . ... 7.8.3 Dead Pixels . ... All pixels found anomalous enough to potentially impact data analysis results are flagged and listed in the current bad pixel table reference file. ... In total, 3,358 pixels are flagged as dead (0.3% of the detector?s light-sensitive pixels), and are marked with a 4 in the bad pixel table (see WFC3 ISR 2010-13 for details). ...
... WFC3 Data Handbook > Chapter 7: WFC3/IR Sources of Error > 7.6 Count Rate Non-Linearity . ... From 235 stars in 47 Tuc observed with WFC3/IR in F110W and F160W and in similar bandpasses in NICMOS Camera 2, we measure a non-linearity of WFC3/IR of 0.011+/- 0.0023 and 0.010+/-0.0025 mag per dex 1 , respectively, over a range of 10 magnitudes (4 dex). ... This work found that the count rate non linearity of the IR detector is less than 0.01 mag per dex (see WFC3 ISR 2011-15 for the details) . ...
... WFC3 Data Handbook > Chapter 7: WFC3/IR Sources of Error > 7.5 Detector Nonlinearity Issues . ... 7.5.2 Non-Zero Zeroth Read Correction for Bright Sources . ... Figure 7.7 shows the measured signal up the ramp for a single pixel during a flat-field ramp. ... By measuring this difference for each pixel using a set of flat-field ramps, the non-linearity behavior of each pixel is characterized, and a correction produced. ... This correction will soon be updated to include a pixel-by-pixel correction. ...
... WFC3 Data Handbook > Chapter 7: WFC3/IR Sources of Error > 7.3 WFC3 Dark Current and Banding . ... WFC3 Dark Current and Banding . ... 7.3.2 Banding . ... In practice, the dark current behavior of the IR detector is dependent upon the timing pattern used to collect each observation and is not constant for the duration of a given MULTIACCUM ramp. ... The dark current calibration files are created from many dark observations, which are taken on a regular basis throughout each observing cycle. ...
... WFC3 Data Handbook > Chapter 7: WFC3/IR Sources of Error > 7.2 WFC3/IR Bias Correction . ... WFC3/IR Bias Correction . ... During calwf3 processing, the mean measured signal of the reference pixels in each read is calculated and subtracted from all of the science pixels on the detector for that read. ... WFC3 ISR 2002-06 details the method of reference pixel bias subtraction, while WFC3 ISR 2012-05 shows reference pixel behavior, and compares various methods of subtracting the reference pixel signal...
... WFC3 Data Handbook > Chapter 7: WFC3/IR Sources of Error > 7.1 WFC3/IR Error Source Checklist . ... WFC3/IR Error Source Checklist . In comparison to the previous IR detectors flown on the Hubble Space Telescope the WFC3/IR detector data is subject to many fewer problems; thereby simplifying the tasks of data reduction and analysis. We present and discuss the known error sources to allow careful data processing, which will result in improved results. ... Bias Subtraction ( Section 7.2 ) . ...
... WFC3 Data Handbook > Chapter 9: WFC3 Data Analysis > 9.5 References . ... Brown, T., et al, 2009 WFC3 SMOV Proposal 11451: The Photometric Performance and Calibration of WFC3/IR, WFC3 ISR 2009-30 . ... Kuntschner,H., M. Kummel, J. R. Walsh, and H. Bushouse, 2011, Revised Flux Calibration of the WFC3 G102 and G141 grisms, WFC3 ISR 2011-05 . Kuntschner,H., H. Bushouse, M. Kummel, and J. R. Walsh, 2009, WFC3 SMOV proposal 11552:Calibration of the G141 grism, WFC3 ISR 2009-17 . ...
... The normal method for taking WFC3 slitless spectra is to take a pair of images, one direct and one dispersed, of each target field, with no shift in position between the two. ... Spectra produced by the G280 grism are oriented in WFC3 images with the positive spectral orders to the left (lower x-axis pixel index) of the 0th-order spot, with wavelength increasing to the left. ... This step consists of identifying and cataloging sources from a direct image in the field of the grism image. ...
... 9.3.3 Impact of Guide Star Failure . ... There are three coordinate systems applicable to WFC3 images. First, there is the position of a pixel on the geometrically distorted raw image (RAW) or, identically, the position on the flat-fielded images (FLT) after pipeline processing through calwf3. Second, there is the pixel position on the drizzled images (DRZ) created by new ST software AstroDrizzle which corresponds to an undistorted pixel position on a tangent plane projection of the sky. ...
... 9.2.1 Photometric Systems, Units, and Zeropoints . 9.2.2 Aperture and Color Corrections . 9.2.3 Pixel Area Maps . ... As an example on WFC3/UVIS, the measured flux in F606W within an aperture of radius 0.4 arcseconds (i.e., 10 pixels) is 91% of the total flux and the flux within 2.0 arcseconds is 98% of the total flux. For WFC3/IR, the flux in F140W within an aperture of 0.4 arcseconds (i.e., 3 pixels) is 84% of the total flux and the flux within 2.0 arcseconds is 97% of the total flux. ...
... These tasks include tools for mathematical and statistical operations on science images and for analysis and display of raw and reduced data. ... Under this category are several tasks described in Chapter 3 of the Introduction to the HST Data Handbooks , msarith, mscombine, msstatistics, msjoin and mssplit , along with a few other tasks we describe below, ndisplay, markdq, mosdisplay, pstack, pstats, sampinfo, sampdiff, and sampcum . ... The sampdiff task automates this process. ...