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STIS Cycle-20 Calibration Phase-1

Last Revised: August 31, 2012
Proposal ID: 13148
Title: STIS FUV-MAMA Flats
PI: Elena Mason
Co-I(s): Charles R. Proffitt

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# Orbit estimates are TOTAL for all of Cycle-18

Total Prime Orbits: 0
External Parallel Orbits: 0
Internals or no-impact orbits: 11
Comments on orbit estimate: 11 single-orbit visits to build S/N

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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:
This program is aimed at obtaining FUV-MAMA flat-field observations to
create a new p-flats with a SNR of ~100 per (low resolution)
pixel. The flats are obtained with the Krypton-lamp and the MR grating
G140M, similarly to the cycle 17 and 18 programs. However the exact
instrument setup (slit width and central wavelength) might change
depending on the desired count level (which will be close to the
internally allowed global rate limit).

Description:
Past experience and observations have shown that ~11 visits are
sufficient to create a cumulative image with ~2500 counts/pixel (high
resolution mode, equivalent to ~10000 count/pixel in low resolution
mode). We will start taking exposure with the setup G140M/52x0.1/1470
(as in the cycle 18 program) and move to G140M/52x0.1/1420 as soon as
the global rate has decreased below 180000-190000 counts/sec (maximum
allowed is ~280000 count/pixels). On the basis of past experience
exposures will be at least 4740 sec long. Hence, all orbits exceed the
1800 s execution time. Different visits will have different slit
offsets in order to illuminate the pixels which are normally shadowed
by the slit bars.


Accuracy: 1.0%
Comments on Accuracy: Accuracy is per low-res pixel (2x2 high-res
pixels)
Products: combine this and past cycle frames to produce a new
reference p-flat and and ISR, as applicable.

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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.............................: NONE (Kr lamp)
RA......................................: N/A
Dec.....................................: N/A
Flux (and units)........................: <=280000 count/s
Visibility window (if known or relevant): N/A

Comment on choice of target: Standard lamp for flat-field exposures.

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

Target or lamp..........................: Krypton
Type of Acquisition.....................: N/A
Detector observation....................: FUV-MAMA
Spectral Element........................: G140M
Aperture................................: 52x0.1
Central Wavelength......................: 1470
Exposure Time...........................: 11x4740 S = 869 M
BOP Predicted Local Count Rate for MAMA.: 0.2 count/s/low-res pixel
BOP Predicted Global Count Rate for MAMA: ~220000 count/s
ETC PID IDs for Count Rates.............: [see comments]
Special Requirements....................: SLIT-STEP=-3360, -1680, 0, 1680, 3360

Comments:

Count rate based on observations from program 12417. Count rate will
change as soon as the instrument setup will be modified.

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# Special needs of this proposal?

Scheduling: About 1 visit per month, to allow inspection of the frames
and timely change of setup as necessary and to avoid waste of orbits
in case of lamp failure (as happened in the past).

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

PDB update? No
On-board table update? No

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

As the lamp illumination declines, we are obligated to change the
central wavelength and/or slit width in order to compensate, and so to
preserve the limited lamp lifetime. In case special commanding is not
available for the required setting, on-board table update will be
required.

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# Link to Cycle 18 Science

Fraction of science programs supported by this calibration: 50% of
STIS total exposure time.

List categories of science which can't be executed until after this proposal:
None.

List categories of science which are best performed contemporaneous with
this proposal:
None.

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# Analysis Plan

Expected FTE weeks for analysis: 4
Required turnaround on analysis (weeks): 16
Data volume (Mb needed for analysis): 100
Special software needed for analysis? (Describe): existing IDL code

Description of analysis Plans: (1-2 paragraphs)

Global count rates and engineering data will be examined to determine
the extent of lamp degradation, and whether it matches predictions
from current on-orbit experience. Flats will be combined, and a
solution for the slit illumination and spectral distribution of the
lamp will be derived and removed to create P-flats.