STIS Cycle-25 Calibration Phase-1 Last Revised: June 01, 2017 Proposal ID: TBD (Cycle 24: 14826) Title: CCD Sparse Field CTE Internal PI: Sean Lockwood Co-I(s): --------------------------------------------------------------------------- # Orbit estimates are TOTAL for all of cycle-25; assume 52 weeks Total Prime Orbits: 0 External Parallel Orbits: 0 Internals or no-impact orbits: 50 Comments on orbit estimate: Orbits will occur between 01 November 2017 to 01 January 2018. --------------------------------------------------------------------------- Purpose: Re-establish an accurate correction for parallel register CTE losses that can be used for direct analysis of science data with negligible background. Do measurements for one gain setting (GAIN=1), alternating with GAIN=4 every-other-cycle. Description: The sparse field CTE will be measured via internal calibration lamp observations taken through narrow slits. The strategy of the test is as follows. Using the onboard tungsten lamp, narrow slit images are projected at different positions on the detector. At each position a series of exposures is taken alternating between the 'A' and 'C' amplifiers for readout. The further the charge needs to be shifted to be read out, the more charge it will lose. For the parallel CTE measurement, the test will use the the cross disperser slits: 0.05x31NDB and 0.05x31NDA. In order to test the effects of different bias voltages and readout timings, the whole series of exposures are executed once for GAIN=1 and once for GAIN=4 every-other cycle; this process requires a total of 50 orbits per cycle, which includes various sets of biases and darks. For the CTE pixel based correction, the test requires 8 orbits for darks read out with amplifier A. 43/50 orbits are < 1800s, with the remaining exceeding this limit by ~100s each in order to capture the full sequence of exposures required for best analysis. Accuracy: 1% Comments on Accuracy: CTE correction coefficients will be determined to a relative accuracy of 1%; photometry should not be limited to >1% accuracy after correction for CTE. Products: Determine slope for time dependent correction of CTE, possible update of ccdtab reference file, and inclusion in a summary ISR. --------------------------------------------------------------------------- # THE REST OF THIS FORM IS FOR INTERNAL USE --------------------------------------------------------------------------- # Target information (copy for each target) Target Name.............................: TUNGSTEN RA......................................: n/a Dec.....................................: n/a Flux (and units)........................: n/a Visibility window (if known or relevant): n/a Comment on choice of target.............: n/a # Table of exposures (copy for each exposure): Target or lamp..........................: TUNGSTEN FLAT Type of Acquisition.....................: n/a Detector for observation................: STIS/CCD Operating mode .........................: ACCUM Spectral Element........................: G430M Aperture................................: 0.05x31NDA Central Wavelength......................: 5471 Exposure Time...........................: {0.3, 0.6, 0.9, 2.3} s Number of Iterations ...................: 1 per position per amplifier per exptime BOP Predicted Local Count Rate for MAMA.: BOP Predicted Global Count Rate for MAMA: ETC PID IDs for Count Rates.............: Special Requirements or options.........: GAIN=1, POS=3.2-{0,1,2,3,4}, CCDAMP={A,C} Comments................................: Take exposures sequentially Flux groups: {0, 1, 2, 3} Target or lamp..........................: TUNGSTEN FLAT Type of Acquisition.....................: n/a Detector for observation................: STIS/CCD Operating mode .........................: ACCUM Spectral Element........................: MIRROR Aperture................................: 0.05x31NDA Central Wavelength......................: Exposure Time...........................: 0.3 s Number of Iterations ...................: 1 per position per amplifier BOP Predicted Local Count Rate for MAMA.: BOP Predicted Global Count Rate for MAMA: ETC PID IDs for Count Rates.............: Special Requirements or options.........: GAIN=1, POS=3.6-{0,1,2,3,4}, CCDAMP={A,C} Comments................................: Take exposures sequentially Flux group: 4 Target or lamp..........................: TUNGSTEN FLAT Type of Acquisition.....................: n/a Detector for observation................: STIS/CCD Operating mode .........................: ACCUM Spectral Element........................: MIRROR Aperture................................: 0.05x31NDB Central Wavelength......................: Exposure Time...........................: 0.3 s Number of Iterations ...................: 1 per position per amplifier BOP Predicted Local Count Rate for MAMA.: BOP Predicted Global Count Rate for MAMA: ETC PID IDs for Count Rates.............: Special Requirements or options.........: GAIN=1, POS=3.6-{0,1,2,3,4}, CCDAMP={A,C} Comments................................: Take exposures sequentially Flux group: 5 Target or lamp..........................: BIAS Type of Acquisition.....................: n/a Detector for observation................: STIS/CCD Operating mode .........................: Spectral Element........................: DEF Aperture................................: DEF Central Wavelength......................: Exposure Time...........................: 0 s Number of Iterations ...................: {3, 10, 11, 21} BOP Predicted Local Count Rate for MAMA.: BOP Predicted Global Count Rate for MAMA: ETC PID IDs for Count Rates.............: Special Requirements or options.........: GAIN=1, CCDAMP={A,C} Comments................................: Target or lamp..........................: DARK Type of Acquisition.....................: Detector for observation................: STIS/CCD Operating mode .........................: Spectral Element........................: DEF Aperture................................: DEF Central Wavelength......................: Exposure Time...........................: {60, 1100} s Number of Iterations ...................: {1, 2} BOP Predicted Local Count Rate for MAMA.: BOP Predicted Global Count Rate for MAMA: ETC PID IDs for Count Rates.............: Special Requirements or options.........: GAIN=1, CCDAMP={A,C} Comments................................: --------------------------------------------------------------------------- # Special needs of this proposal? Scheduling: Schedule between 01 November 2017 and 01 January 2018. Start on November 01, 2017. Visits should execute in order. Prerequisites: n/a PDB update? N On-board table update? N # Special Requirements: Real time? N Special commanding? N Quick Data turnaround? N Special timing required? N Other? N Describe (& justify) special requirements: ------------------------------------------------------------------------- # Link to Cycle 24 Science Fraction of science programs supported by this calibration: 31% of STIS total exposure time (cycle 24) --------------------------------------------------------------------------- Expected FTE weeks for analysis: 3 Required turnaround on analysis (weeks): 3 Data volume (Mb needed for analysis): 12 GB Special software needed for analysis? (Describe): A script to determine the flux and background, and fit CTE values. Description of analysis Plans: These CTI measurements are made using an "internal sparse field test", along the parallel axis. This test utilizes the ability of the STIS CCD and its associated electronics to read out the image with any amplifier, i.e., by clocking the accumulated charge in either direction along both parallel and serial registers. A sequence of nominally identical exposures is taken alternating the readout between amplifiers on opposite sides of the CCD. Amplifier A and amplifier C are used to check the parallel CTI at the gain=1 setting. Comparison of the charge readout using the A and C amplifiers yields a measure of the CTI. If there were no CTI, then the ratio of the signals read out using the two different amplifiers for a source at the same position would be identically 1.