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COS Cycle-20 Calibration Phase-1 Template

Last Revised: 21 September 2012
Proposal ID: 13125
Title: COS NUV Spectroscopic Sensitivity Monitor
PI: A. Bostroem
Co-I(s): R. Osten, C. Proffitt

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# Orbit estimates are TOTAL for all of cycle-20; assume 52 weeks)

Total Prime Orbits: 6
External Parallel Orbits: 0
Internals or no-impact orbits: 0
Comments on orbit estimate: observations 3 times a year: 3x1 for G230L, 3x1 for M modes


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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: Monitor sensitivity of each NUV grating mode to detect any change due to
contamination or other causes. The bare-Aluminum gratings on COS are known to
degrade with a rate which has been fairly steady since the start of on-orbit
operations. Another goal is to track time dependence of sensitivity as a function
of wavelength.



Description: Obtain exposures in all NUV gratings --- G230L, G185M, G225M, and G285M тАУ 3
times a year. We will monitor the following modes: G230L/2635, G230L/2950,
G185M/1786, G185M/1921, G225M/2186, G285M/2617, and G285M/3094. These central
wavelengths constitute the reddest and bluest central wavelengths containing only
first order light with the exception of G225M which remains unused in Cycle 20.
NUV usage continues to be minimal and the trends are stable, therefore we will
continue to monitor the central wavelength used in the previous cycle and cut down
the cadence to 3 times a year.

Track time dependence of sensitivity as a function of wavelength. Because of the
low usage of these modes, and their fairly stable rate of decay, we continue the
reduced monitoring introduced in Cycle 19. Additionally, due to the stability of
the COS NUV modes, we will reduce the monitoring from 4 times a year to 3 times a
year.

With the cuts described above, we will need 3 one orbit visits to monitor the
G230L, and 3 one orbit visits to monitor the G185M, G225M, and G285M gratings, for
a total of 6 orbits in Cycle 20.

Accuracy: SNR of 30 per resel at the central wavelength
Comments on Accuracy: G285M acheives SNR = 26 due to its rapidly deteriorating
sensitivity.
Products: ISR, Time-Dependent Sensitivity reference files


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# Link to Cycle 20 Science
# Use the GO + GTO Phase 1 exposure listing and derived statistics
# posted on WWW.

Fraction of science programs supported by this calibration:
6.5% of COS total exposure time.


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 WD1057+719 in G230L 3 times per year in central
wavelengths 2635, 2950.
Take spectra of G191B2B in the M-modes 3 times per year, covering one cenwave
of G185M, one of G225M, and two of G285M.

# Target information (copy for each target)

Target Name.............................: WD1057+719
RA......................................:
Dec.....................................:
Flux (and units)........................:
Visibility window (if known or relevant):
Comment on choice of target:

Target Name.............................: G191B2B
RA......................................:
Dec.....................................:
Flux (and units)........................:
Visibility window (if known or relevant):
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. G191B2B, or HITM
Type of Acquisition.....................: e.g. ACQ-PEAK
Detector for observation................: e.g. CCD
Operating mode .........................: e.g. ACCUM or TIMETAG
Spectral Element........................: e.g. G430L
Aperture................................: e.g. 50x0.5
Central Wavelength......................: e.g. 4300
Exposure Time...........................: e.g. 300s, crsplit=2
Number of Iterations ...................: e.g. 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.........: (e.g. GAIN=4; LOW-SKY)
Comments: (e.g. if monitoring, specify frequency)


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# Special needs of this proposal?

Scheduling: as indicated above

Prerequisites: (e.g., specific SMOV proposal; command development?)

PDB update? (Specify table name if known e.g. SIAF).
On-board table update? (Specify table name if known e.g. CCDBadPixelTable)

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

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# Analysis Plan

Expected FTE weeks for analysis: 5 weeks
Required turnaround on analysis (weeks): 1
Data volume (Mb needed for analysis): 0
Special software needed for analysis? (Describe): existing IDL programs

Description of analysis Plans: Use existing IDL code to make ratios of spectra with
those obtained at the beginning of the monitoring. After averaging in wavelength,
plots of these trends with time determine the time-dependent sensitivity. These values
are used to update TDS reference files.

Create code to make TDS reference file from IDLSAVE files produced in the analysis.
Update TDS table to have wavelength dependence.

To get the data and run scripts will take 3-4 hours per visit (L+M combined), so an upper limit of 12
hours for a quicklook analysis for the entire program. Making a new reference file will take
3-4 weeks for testing and documentation.