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Space Telescope Imaging Spectrograph
Phase I: Slit Wheel Repeatability

STIS Cycle-18 Calibration Phase-1

Last Revised:	Ocrtober 20, 2010 
Proposal ID:	12410
Title: Slit Wheel Repeatability
PI:	W. Zheng
Co-I(s): M. Wolfe, R. Osten, C. Proffitt	

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# Orbit estimates are TOTAL for all of cycle-17; assume 52 weeks) 

Total Prime Orbits:             0
External Parallel Orbits:       0
Internals or no-impact orbits:  1
Comments on orbit estimate:     


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Purpose:                       
Test the repeatibility of the slit wheel by taking a sequence of comparison lamp    
spectra with grating G230MB (2697) and the three smallest long slits (52X0.2,       
52X0.1, and 52X0.05). This is a clone of Cycle 17 Program 11851.  

Description:                   
Verify the repeatability of the slit wheel for three STIS slits 
(52X0.2, 52X0.1, and 52X0.05) by taking images with the Pt/Cr/Ne LINE lamp and
the CCD detector. Use the G230MB (2697) grating with the CCD, and rotate the 
slit wheel among the 3 chosen slits. Detector: CCD Grating: G230MB (2697) 
Slits: 52x0.2, 52X0.1, 52X0.05 Grating A: 52X0.2 (10 seconds) Grating B: 
52X0.1 (10 seconds) Grating C: 52X0.05 (20 seconds) Sequence: 
A-B-C-B-C-A-A-B-A-C-B-B-A-B-C-B-C-C-A-B-A-C-B-A Forward motion: B - 4 times 
C - 6 times Backward motion: A - 6 times B - 4times No motion: A/B/C - 1 time.

Accuracy:                       0.1 pixel
Comments on Accuracy:           after removing the zero-order shift
Products:                       report

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# Link to Cycle 18 Science
# Use the GO + GTO Phase 1 exposure  listing and derived statistics
# posted on WWW.

Fraction of science programs supported by this calibration:     ~50% of STIS

List categories of science which can't be executed until after this proposal:
why:

List categories of science which are best performed contemporaneous with 
this proposal:
why:


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# THE REST OF THIS FORM IS FOR INTERNAL USE
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Observation summary: 
	    Take spectra of LINE lamp at various slit positions.

# Target information (copy for each target)

Target Name.............................:	LINE
RA......................................:	N/A
Dec.....................................:	N/A	
Flux (and units)........................:	N/A	
Visibility window (if known or relevant):	N/A
Comment on choice of target:   			

# Exposure list plan at the Phase I level. Be as complete as reasonable. 
# If possible information should be complete enough to allow easy 
# submission of a Phase 2 from this form. However, if you have to leave
# some of the fields blank below, or want to provide the information
# in another format, that is acceptable. (Make sure you do the BOP checking
# though, as this is a phase-1 issue.)

Table of exposures (copy for each exposure as appropriate/desired):

Target or lamp..........................: e.g. Pt/Cr/Ne LINE
Type of Acquisition.....................: e.g. N/A
Detector for observation................: e.g. CCD
Operating mode .........................: e.g. ACCUM 
Spectral Element........................: e.g. G230MB
Aperture................................: e.g. 50x0.2, 50x0.1, 50x0.05
Central Wavelength......................: e.g. 2697
Exposure Time...........................: e.g. 10, 20s
Number of Iterations ...................: e.g. 1
BOP Predicted Local Count Rate for MAMA.:  N/A
BOP Predicted Global Count Rate for MAMA:  N/A
ETC PID IDs for Count Rates.............:  N/A
Special Requirements or options.........:  NON-INT
Comments: perform once early in Cycle


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# Special needs of this proposal?

Scheduling: early in Cycle 18

Prerequisites: None

PDB update?               None
On-board table update?    None

# 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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# Analysis Plan

We will use the existing procedure (IRAF, IDL) developed during SM4 and Cycle 
17 to analyze the data.

Expected FTE weeks for analysis:                                1
Required turnaround on analysis (weeks):                        4
Data volume (Mb needed for analysis):                           24 CCD images 
     	    	       	   					at 10.5 Mb each =252  Mb 
Special software needed for analysis? (Describe):

Description of analysis Plans:	      

After processing by calstis, we will use IRAF script "findshifts" to check any 
possible small shifts between the spectral features obtained with the same aperture 
and various wheel movements. Another IDL script fits the data points and remove a 
zero-order component of timer variation. The residuals reflect the actual fluctuation
of the wheel misalignment over observation time.