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Space Telescope Imaging Spectrograph
CCD Sparse Field CTE Internal

STIS Cycle-17 Calibration Phase-1 Template

Last Revised: October 19, 2009
Proposal ID: 11850
Title: CCD Sparse Field CTE Internal
PI: Michael A. Wolfe
Co-I(s): Rachel Osten
         Charles Proffitt
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# Orbit estimates are TOTAL for all of cycle-17; assume 8 weeks 
# 01 August 2009 to 01 October 2009

Total Prime Orbits:             0
External Parallel Orbits:       0
Internals or no-impact orbits:  64
Comments on orbit estimate:   Orbits will occur between
01 August 2009 and 01 October 2009.  


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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:  Reestablish 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 sparsefield 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 D amp and the B amp read 
out at opposite ends of the CCD, the ratio in image intensity 
(B amp/D amp) should increase as the image position moves closer 
to the B amp end (and further from the Damp end). For the parallel 
CTE measurement, the test will use the the crossdisperser 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:  ISR, algorithm for calibration and coefficients.   



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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 August 2009 and 01October 2009. Start on 
August 01, 2009.

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 17 Science

Fraction of science programs supported by this calibration: 60% of STIS

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_plot.pro, measure.pro, group.pro, cte.pro,
and trend.pro.

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 D (the default) and amplifier B are used to check the 
parallel CTI at the default gain=1 and 4 setting. Comparison of the charge 
readout using the D and B 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.