STScI Logo

Space Telescope Imaging Spectrograph
Phase I: STIS/MAMA Fold Distribution

STIS Cycle-18 Calibration Phase-1

Last Revised:                  8/25/20
Proposal ID:                   12416
Title:                         STIS/MAMA Fold Distribution
PI:                            T. Wheeler
Co-I(s):                       A. Welty

---------------------------------------------------------------------------
# Orbit estimates are TOTAL for all of Cycle-18 

Total Prime Orbits:            0
External Parallel Orbits:      0
Internals or no-impact orbits: 4
Comments on orbit estimate:    2 orbit visits, repeated biannually

---------------------------------------------------------------------------
# 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 globally 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 special commanding and is the same for the FUV and NUV MAMAs with the exception of the gratings/aperture/lamp combinations used for flat field illumination. This proposal executes the same steps as cycle 17 proposal 11863 and is described in STIS ISR 98-02R.

Accuracy: 95%
Comments on Accuracy: Position of the peak in the fold distribution can be measured to about 5% accuracy from this procedure.

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

---------------------------------------------------------------------------
# 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: 64.7% of STIS prime exposures use MAMAs, 99.6% of STIS SNAP exposures use MAMAs.


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

---------------------------------------------------------------------------
# THE REST OF THIS FORM IS FOR INTERNAL USE
---------------------------------------------------------------------------
Observation summary: Globally illuminate the detector with a flat field. Monitor the valid event (VE) rate counter while various combinations of row and column folds are selected. The process is the same for the FUV and NUV MAMAs with the exception of the gratings/aperture/lamp combinations used for flat field illumination. 

# 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):
-------------------------------------------------------------------------
**** This list of exposures needs to be repeated once every 6 months ****
-------------------------------------------------------------------------
Note (1)
Bright Object Protection Considerations
  (a) This proposal uses aperture/mirror/lamp combinations which are designed 
      to produce count rates of ~100,000-200,000 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 150,000 counts 
      (130,000 counts are used due to ground system restrictions) in a 1.0 
      second interval, from its nominal value of 77,000 counts in a 0.1 
      second interval.
  (c) For the reasons discussed in (b) and to prevent light from entering the 
      hub area, this test should only be run with the STIS external shutter 
      closed.

Visit 1, Exposure 1: FUV Fold Test Setup
Target or lamp                          : Dark
Type of Acquisition                     : n/a
Detector for observation                : FUV MAMA (M1)
Operating mode                          : Data
Spectral Element                        : n/a
Aperture                                : n/a
Central Wavelength                      : n/a
Exposure Time                           : 240s 
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: Sequence 1-3 NON-INT
    Set SGM Threshold = 15000, Integration Period = 0.1 s
    Configure Mechanisms
    Turn on HITM2 lamp at 10mA current
    Special commanding: Instruction = EOFOLDSET1

Visit 1, Exposure 2: FUV Fold Test Accum
Target or lamp                          : Dark
Type of Acquisition                     : n/a
Detector for observation                : FUV MAMA (M1)
Operating mode                          : Accum
Spectral Element                        : MIRROR
Aperture                                : F25ND3
Central Wavelength                      : n/a
Exposure Time                           : 300s 
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: This image is a flat field exposure with the HITM2 using special
  commanding so that the lamp remains on after the exposure.

Visit 1, Exposure 3: FUV Fold Test
Target or lamp                          : Dark
Type of Acquisition                     : n/a
Detector for observation                : FUV MAMA (M1)
Operating mode                          : Data
Spectral Element                        : MIRROR
Aperture                                : F25ND3
Central Wavelength                      : n/a
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: SPECIAL COMMANDING BELOW                                       
    Set SGM Threshold = 130000, Integration period = 1.0 secs
(a) Collect counter samples during flat field illumination
    Collect 5 samples X events
    Collect 5 samples Y events
    Collect 5 samples Z events
    Collect 5 samples W events
    Collect 5 samples VE events
    Collect 5 samples EV events
    Collect 5 samples OR events
(b) Disable MAMA Folds: C2, C3, C4, C5, C6, R2, R3, R4, R5, R6
(c) Conduct fold analysis
    Collect 5 samples 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 5 samples events (EV) to check lamp stability
    Collect 5 samples Valid Events (VE) to check lamp stability
(f) Turn off HITM2 lamp
(g) Collect event counter data for detector dark count rate
    Collect 5 samples X dark events
    Collect 5 samples Y dark events
    Collect 5 samples Z dark events
    Collect 5 samples W dark events
    Collect 5 samples VE dark events
    Collect 5 samples EV dark events
    Collect 5 samples OR dark events
(h) At completion of procedure reset SGM to nominal operating level

    Special commanding: Instruction = EOFOLDTST1

Visit 2, Exposure 1: NUV Fold Test - Fold Test Setup
Target or lamp                          : Dark
Type of Acquisition                     : n/a
Detector for observation                : NUV MAMA (M2)
Operating mode                          : Data
Spectral Element                        : n/a
Aperture                                : n/a
Central Wavelength                      : n/a
Exposure Time                           : 240s 
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: Sequence 1-3 NON-INT
    Set SGM Threshold = 15000, Integration Period = 0.1 s
    Configure Mechanisms
    Turn on HITM1 lamp at 3.8mA current

Visit 2, Exposure 2: NUV Fold Test - Accum
Target or lamp                          : Dark
Type of Acquisition                     : n/a
Detector for observation                : NUV MAMA (M2)
Operating mode                          : Accum
Spectral Element                        : MIRROR
Aperture                                : F25ND3
Central Wavelength                      : NONE
Exposure Time                           : 120s 
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: This image is a flat field exposure with the HITM1 using special 
  commanding so that the lamp remains on after the exposure.

Visit 2, Exposure 3: NUV Fold Test - Fold Test
Target or lamp                          : Dark
Type of Acquisition                     : n/a
Detector for observation                : NUV MAMA (M2)
Operating mode                          : Data
Spectral Element                        : MIRROR
Aperture                                : F25ND3
Central Wavelength                      : n/a
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: SPECIAL COMMANDING BELOW
    Set SGM Threshold = 130000, Integration period = 1.0 secs
(a) Collect counter samples during flat field illumination
    Collect 5 samples X events
    Collect 5 samples Y events
    Collect 5 samples Z events
    Collect 5 samples W events
    Collect 5 samples VE events
    Collect 5 samples EV events
    Collect 5 samples OR events
(b) Disable MAMA Folds: C2, C3, C4, C5, C6, R2, R3, R4, R5, R6
(c) Conduct fold analysis
    Collect 5 samples 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 5 samples events (EV) to check lamp stability
    Collect 5 samples Valid Events (VE) to check lamp stability
(f) Turn off HITM1 lamp
(g) Collect event counter data for detector dark count rate
    Collect 5 samples X dark events
    Collect 5 samples Y dark events
    Collect 5 samples Z dark events
    Collect 5 samples W dark events
    Collect 5 samples VE dark events
    Collect 5 samples EV dark events
    Collect 5 samples OR dark events
(h) At completion of procedure reset SGM to nominal operating level

    Special commanding: Instruction = EOFOLDTST2

---------------------------------------------------------------------------
# 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:
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 the requirement of this test.

-------------------------------------------------------------------------
# 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):       none

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

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