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Phase I: COS/NUV MAMA Fold Distribution

COS Cycle-18 Calibration Phase-1

Last Revised:                 8/25/10
Proposal ID:                  ?
Title:                        COS/NUV MAMA Fold Distribution
PI:                           T. Wheeler
Co-I(s):                      A. Welty
                              D. Sahnow (JHU)

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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: 2
Comments on orbit estimate:    1 orbit per visit, repeated biannually
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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: The performance of MAMA microchannel plates can be monitored using a MAMA fold analysis procedure that provides a measurement of the distribution of charge cloud sizes incident upon the anode giving some measure of change in the pulse-height distribution of the MCP and, therefore, MCP gain.

Description: While illuminating the detector with a flat field, the valid event (VE) rate counter is monitored while various combinations of row and column folds are selected. The process is implemented using a time-tag exposure and special commanding. This proposal executes the same steps as Cycle 17 proposal 11891 and is described in COS TIR 2010-01.
               
Accuracy: 95%
Comments on Accuracy: Position of the peak in the fold distribution can be measured to about 5% accuracy from this procedure.

Products: The Fold Analysis findings are reported to the COS Science Team and V. Argabright of Ball Aerospace after completion of analysis, typically one-two weeks after the execution of the test.

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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: 7.9% of COS prime exposures use the NUV MAMA, 5.9% of COS SNAP exposures use the NUV MAMA.


List categories of science which can't be executed until after this
proposal:                      None
why:                           n/a

List categories of science which are best performed contemporaneous with 
this proposal:                 None
why:                           n/a

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# THE REST OF THIS FORM IS FOR INTERNAL USE
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Observation summary: Illuminate the detector with a flat field. Monitor the valid event (VE) rate counter while various combinations of row and column folds are selected.

# 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

# 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):
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**** This list of exposures needs to be repeated once every 6 months ****
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Note (1)
Bright Object Protection Considerations
  (a) This proposal uses aperture/grating/lamp (FCA/G185M-1850/D2-10ma) 
      combination which is designed to produce count rates of ~1,000-2,000 
      count/sec. They should not be changed without consultation with the 
      P.I.
  (b) During the execution of the fold analysis some anode folds are 
      disabled. Consequently, the OR counter does not provide a true 
      representation of the OR count and so the Software Global Monitor (SGM) 
      does not trigger until the enabled folds provide enough counts to the 
      OR counter to trigger the SGM's threshold. To compensate, while the 
      fold analysis is running the SGM threshold is reduced to 100,000 counts 
      in a 1.0 second interval, from its nominal value of 20,000 counts in a 
      0.1 second interval.
  (c) For the reasons discussed and to prevent light from entering the hub 
      area, this test should only be run with the COS external shutter 
      closed.

Visit 1, Exposure 1: NUV Fold Test - Setup
Target or lamp                          : Dark
Type of Acquisition                     : n/a
Detector for observation                : NUV MAMA
Operating mode                          : Data
Spectral Element                        : n/a
Aperture                                : n/a
Central Wavelength                      : n/a
Exposure Time                           : 475.0 s 
Number of Iterations                    : 1
BOP Predicted Local Count Rate for MAMA : Note (1)
BOP Predicted Global Count Rate for MAMA: Note (1)
ETC PID IDs for Count Rates             : n/a
Special Requirements or options         : Special Commanding
Comments: Sequence 1-2 Same Alignment
    Set SGM Threshold = 15000, Integration Period = 0.1 s

Visit 1, Exposure 2: NUV Fold Test - Fold Test
Target or lamp                          : D2 lamp
Type of Acquisition                     : n/a
Detector for observation                : NUV MAMA
Operating mode                          : Data
Spectral Element                        : NCM1FLAT, G185M
Aperture                                : FCA
Central Wavelength                      : 1850
Exposure Time                           : 2300s
Number of Iterations                    : 1
BOP Predicted Local Count Rate for MAMA : Note (1)
BOP Predicted Global Count Rate for MAMA: Note (1)
ETC PID IDs for Count Rates             : 
Special Requirements or options         : Special Commanding
Comments:
    Configure Mechanisms
    Turn on D2 lamp at 10mA current
 SPECIAL COMMANDING BELOW
    Set SGM Threshold = 100000, Integration period = 1.0 secs
(a) Collect counter data during flat field illumination
    Collect 60 sec W events
    Collect 60 sec X events
    Collect 60 sec Y events
    Collect 60 sec Z events
    Collect 60 sec OR events
    Collect 60 sec EV events
    Collect 60 sec VE events
(b) Disable MAMA Folds: C2, C3, C4, C5, C6, R2, R3, R4, R5, R6
(c) Conduct fold analysis
    Collect 60 sec VE for following 19 combinations of MAMA folds:
        (1) Enabled: C2, R2; Disabled: C3, C4, C5, C6, R3, R4, R5, R6
        (2) Enabled: C2, R3; Disabled: C3, C4, C5, C6, R2, R4, R5, R6
        (3) Enabled: C3, R2; Disabled: C2, C4, C5, C6, R3, R4, R5, R6
        (4) Enabled: C2, R4; Disabled: C3, C4, C5, C6, R2, R3, R5, R6
        (5) Enabled: C3, R3; Disabled: C2, C4, C5, C6, R2, R4, R5, R6
        (6) Enabled: C4, R2; Disabled: C2, C3, C5, C6, R3, R4, R5, R6
        (7) Enabled: C3, R4; Disabled: C2, C4, C5, C6, R2, R3, R5, R6
        (8) Enabled: C4, R3; Disabled: C2, C3, C5, C6, R2, R4, R5, R6
        (9) Enabled: C3, R5; Disabled: C2, C4, C5, C6, R2, R3, R4, R6
       (10) Enabled: C4, R4; Disabled: C2, C3, C5, C6, R2, R3, R5, R6
       (11) Enabled: C5, R3; Disabled: C2, C3, C4, C6, R2, R4, R5, R6
       (12) Enabled: C4, R5; Disabled: C2, C3, C5, C6, R2, R3, R4, R6
       (13) Enabled: C5, R4; Disabled: C2, C3, C4, C6, R2, R3, R5, R6
       (14) Enabled: C4, R6; Disabled: C2, C3, C5, C6, R2, R3, R4, R5
       (15) Enabled: C5, R5; Disabled: C2, C3, C4, C6, R2, R3, R4, R6
       (16) Enabled: C6, R4; Disabled: C2, C3, C4, C5, R2, R3, R5, R6
       (17) Enabled: C5, R6; Disabled: C2, C3, C4, C6, R2, R3, R4, R5
       (18) Enabled: C6, R5; Disabled: C2, C3, C4, C5, R2, R3, R4, R6
       (19) Enabled: C6, R6; Disabled: C2, C3, C4, C5, R2, R3, R4, R5
(d) Enable MAMA folds C2, C3, C4, C5, C6, R2, R3, R4, R5, R6
    at completion of exposure.
(e) Check lamp stability by checking EV and VE
    Collect 60 sec events (EV) to check lamp stability
    Collect 60 sec Valid Events (VE) to check lamp stability
(f) Turn off D2 lamp
(g) Collect event counter data for detector dark count rate
    Collect 60 sec W dark events
    Collect 60 sec X dark events
    Collect 60 sec Y dark events
    Collect 60 sec Z dark events
    Collect 60 sec OR dark events
    Collect 60 sec EV dark events
    Collect 60 sec VE dark events
(h) At completion of procedure reset SGM to nominal operating level

    Special commanding: Instruction = ELFOLDTST

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# Special needs of this proposal?

Scheduling: This proposal should execute in the spring and fall every year. The exposures listed are for one execution only so the number of exposures per year is twice this number.

Prerequisites           : None

PDB update?               N
On-board table update?    N

# Special Requirements  : Y
Real time?                N
Special commanding?       Y
Quick Data turnaround?    N
Special timing required?  N
Other?                    N
Describe (& justify) special requirements: Special commanding is required to implement this test.

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# Analysis Plan

Expected FTE weeks for analysis:                        0.2
Required turnaround on analysis (weeks):                  2
Data volume (Mb needed for analysis):                   n/a
Special software needed for analysis? (Describe): Special software has been developed to bin and analyze the data.

Description of analysis Plans:  (1-2 paragraphs):       

The analysis will be carried by the Engineering Team when the engineering science data become available approximately two days after each visit. The time-tag images are also examined for unusual spatial or temporal features. The fold test results are reported to the COS Science Team and V. Argabright of Ball Aerospace.