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STIS Cycle-20 Calibration Phase-1

Last Revised: Aug 23, 2012
Proposal ID: 13138
Title: CCD Sparse Field CTE Internal
PI: Svea Hernandez
Co-I(s):

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# Orbit estimates are TOTAL for all of cycle-20; assume 52 weeks
# 01 November 2012 to 01 January 2013

Total Prime Orbits: 0
External Parallel Orbits: 0
Internals or no-impact orbits: 74
Comments on orbit estimate: Orbits will occur between
01 November 2012 to 01 January 2013.


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# This section should be written with a GO audience in mind -- use
# Calibration plans in WFPC-2 handbook as a guide.

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 both GAIN settings
(1 and 4).


Description: The internal sparse field CTE will be measured via internal
calibration internal lamp observations taken through narrow slits.
The strategy of the test is as follows. If there is a CTE effect, charge
will be left behind as the image is shifted through pixels during
readout. The further the charge needs to be shifted to be read out,
the more charge it will lose. Because the A amp and the C amp read
out at opposite ends of the CCD, the ratio in image intensity
(A amp/C amp) should increase as the image position moves closer
to the A amp end (and further from the C amp end). For the parallel
CTE measurement, the test will use the the cross disperser slits:
0.05x31NDB and 0.05x31NDA slits, projected on different
parts of the detector via special commanding of the slit wheel. The
whole series of exposures are executed once for GAIN=1, and once
for GAIN=4 to test the effect of different bias voltages.

Accuracy: 1%

Comments on Accuracy: CTE correction coefficients will be determined
to a relative accuracy of 1%; photometry should not be limited to by >1%
accuracy after correction for CTE.

Products: Determine slope for time dependent correction of CTE, possible
update of ccdtab reference file, and a summary in the end of cycle ISR.




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# THE REST OF THIS FORM IS FOR INTERNAL USE
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# Target information (copy for each target)

Target Name.............................: n/a (internal)
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
Type of Acquisition.....................: FLAT
Detector for observation................: STIS/CCD
Operating mode .........................: ACCUM
Spectral Element........................: G430M
Aperture................................: 0.05x31NDA
Central Wavelength......................: 5471
Exposure Time...........................: 0.3s, 0.6s, 0.9s, 2.3s
Number of Iterations ...................: 1
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=1,4, POS=3.2-0,1,2,3,4
Comments: Take exposures sequentially

Target or lamp..........................: TUNGSTEN
Type of Acquisition.....................: FLAT
Detector for observation................: STIS/CCD
Operating mode .........................: ACCUM
Spectral Element........................: MIRROR
Aperture................................: 0.05x31NDB
Central Wavelength......................:
Exposure Time...........................: 0.3s
Number of Iterations ...................: 1
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=1,4, POS=3.6-0,1,2,3,4
Comments: Take exposures sequentially

Target or lamp..........................: BIAS
Type of Acquisition.....................:
Detector for observation................: STIS/CCD
Operating mode .........................:
Spectral Element........................: DEF
Aperture................................: DEF
Central Wavelength......................:
Exposure Time...........................: 0
Number of Iterations ...................: 2,3
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=1,4
Comments: Take exposures sequentially.

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# Special needs of this proposal?

Scheduling: Schedule between 01 November 2012 and 01 January 2013. Start on
November 01, 2012.

Prerequisites: n/a

PDB update? no
On-board table update? no

# Special Requirements:
Real time? N
Special commanding? N
Quick Data turnaround? N
Special timing required? N
Other? N
Describe (& justify) special requirements:


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# Link to Cycle 20 Science

Fraction of science programs supported by this calibration:
23% of STIS total exposure time.

List categories of science which can't be executed until after this proposal:
none
why:

List categories of science which are best performed contemporaneous with
this proposal:
none
why:

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Expected FTE weeks for analysis: 3
Required turnaround on analysis (weeks): 3
Data volume (Mb needed for analysis): 10.5Mb
Special software needed for analysis? (Describe): A script to determine
the flux and background. CTE_monitor.py

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 default gain=1 and 4 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.