ACIS ECS RTS CAPs - HOW-TO

Table of Contents

  1. Introduction

  2. Is it possible?
    1. Radiation considerations
    2. Selecting a comm: is there enough time?

  3. Determine Measurement Length
    1. Select CLD File
    2. Thermal Considerations

  4. Do you want to change the FP temperature setpoint?

  5. Information Collection
    1. Obtaining a CAP number
    2. Obtaining the CLD filename and checksum
    3. Obtaining the CLD filename and checksum for the FP setpoint change
    4. Obtaining an OBSID

  6. CAP Template Locations

  7. Filling in the CAP Template
    1. Filling in the timing portion of "Restrictions/Warnings/Notes"
    2. Filling in the fields for the FP temperature setpoint

  8. ACIS Ops review

  9. Emailing to capreview

  10. The CAP Review Itself

  11. CAP Execution, Non-Load Tracking, and Storing the CAP

1. Introduction

This document describes how to determine whether or not it's feasible to execute a Long Term ECS (LTECS) measurement during a spacecraft shutdown, and, if so, how to do it.

Consider executing a LTECS if the spacecraft has autonomously shut down or if a manual shutdown is imminent.

The list of links above is also the basic checklist you follow to determine if you can run the Long Term ECS, select a CLD file and number of chips to execute, fill out the CAP, review the CAP and execute the CAP.

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2. Is it possible to run a Long Term ECS CAP?

You can run a Long Term ECS CAP provided the following is true:
  1. The radiation environment permits running a CAP.
  2. There is "enough" time between the comm in which you plan to upload the procedure, and the end of the orbit and/or the time for Return to Science upload.
  3. There is enough time in the selected comm to execute the CAP.
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2a. Radiation Considerations

If the CAP is run, RADMON will be enabled for the measurement. So you need to determine if the radiation environment is benign enough to not cause an autonomous SCS-107.

So if we come up on COMM and SCS 107 has run, or if you know that we intend to manually run SCS 107 at an upcoming COMM, determine if the radiation environment permits an ECS RTS CAP to be executed. This consists of checking:

 *** NOTE: *** The Flight Director may ok the ECS run if the rates are close to the limits, and trending downwards. Check with the Flight Director to make that determination.

If the radiation levels are NOT below or close enough to the limits and trending downward, STOP.

If the radiation environment permits the measurment, proceed with the next step.

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2b. Is there enough time?

Before you begin composing an ECS RTS CAP, determine if there's enough time to execute a reasonable CAP. You need to assess:
  1. How much time is there until the end of the orbit?
  2. What are the plans (if any) for uploading the Return to Science load?
  3. Is there enough time in the comm you selected?

If the orbit ends in less than 4 hours, it's probably not worth it to run the LTECS. If the shutdown extends after the start of the next orbit, it may be worthwhile to run a LTECS then.

If there's time in the orbit to run a LTECS, then either use the information gleaned from the shutdown telecon to asses when the Return to Science might be, or discuss with the FOT the feasibility of getting a measurement in before a replan load is uplinked (maneuver or science).

It may be that the Return to Science load will be uplinked in the next comm, in which case you can't run a LTECS. If the Return to Science load won't be uplinked until at least the second comm from now, it may or may not be reasonable to execute a LTECS. It all depends upon when these comms are scheduled and what has to be done during the comms.

Try to determine if there will be enough time in the comm in which you intend to upload the Command Load. There is always some housekeeping that must be done by the OCC for each comm such as an SSR dump.
During a shutdown such as a Bright Star Hold (BSH), quite often there are other tasks to be done which must take precedence.

If done efficiently, the CAP can be completed through step 10 in 25-30 minutes. This allows you to confirm that the ECS science run has started correctly.

Comm opportunities in the present orbit can be determined via several ways:

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3. Determine the Measurement Length

If there is sufficient time to execute an ACIS ECS RTS CAP, then the next step is to determine the length of time the measurement should take. That tells you which CLD file to choose for this measurement.

*** IMPORTANT: *** You must make certain that all commanding from the procedure is totally complete BEFORE the EEF1000 time of the orbit in which you intend to run the CAP. ACIS must be shut down and safely stowed before the next EEF1000.

3a. Selecting the CLD file

We have command loads necessary to run an ECS for 1 through 24 and 39 hours.

The general procedure is:

  1. Select the comm during which you intend to upload the Command Load.

  2. Find the time that the comm ends.

  3. Find the time of OORMPDS in the interrupted load by looking for the next occurrence of 'OORMPDS' in the ACIS-LoadReview.txt file, which occurs AFTER the end of the comm you have in mind.

  4. Calculate the time difference between the OORMPDS and the end of the COMM pass. Round the number DOWN to the nearest integer hour
    (i.e., if there is 15 hr 45 mins between the end of the COMM pass and OORMPDS, round down to 15 hrs). This is the LENGTH OF ECS and tells you which CLD file to use.

  5. Find the time of the EEF1000 in the interrupted load.

  6. Calculate the time all CLD commanding ends:

    End Time of Commanding = END COMM TIME+ LENGTH OF ECS you selected

  7. If the Time of the end of commanding is on or before the daily load's EEF1000 time, then you can use that CLD file.

  8. If the End Time of Commanding is after the EEF1000 time, choose a command load with a shorter length and recalculate the time of the end of commanding.

  9. Check the thermal limits of the candidate CLD file

3b. Thermal Considerations

If the shutdown is a Full Stop, the spacecraft will eventually be moved to a tail sun orientation.
For that situation, you can refer to these 1DPAMZT, 1DEAMZT and FP TEMP plots which will show the long term (the science portion of one full orbit) settling temperatures of these MSID's after a safing action where HRC-S is in the focal plane, 3 FEPS are on, ACIS is not clocking, video boards are off and at a nominal roll.

To aid in determining the longest possible ECS run, the worst case scenario - Perihelion 2024 - plots and quick lookup tables are available at these links:

1DPAMZT and 1DEAMZT 3 Chip ECS Measurement Lengths

1DPAMZT and 1DEAMZT Plots for 3 Chip ECS Measurements at Perihelion, 2024

1DPAMZT and 1DEAMZT 4 Chip ECS Measurement Lengths

1DPAMZT and 1DEAMZT Plots for 4 Chip ECS Measurements at perihelion, 2024

A starting temperature of 17.0 degrees C is typical for shutdowns. However can run SimulateECSRun to determine if your run is safe. Documentation can be found here

If the LTECS duration is five hours or longer and the pitch angle is aft of (greater than) about 140, you can also check on the thermal performance of 1DPAMZT, per this ECS run thermal modeling memo. You may need to drop a CCD or two to reduce the temperature. After checking thermal considerations, choose whether to do an ECS run with six, five, or four CCDs.

Another option you have is to use the command-line tool simulate_ecs_run from ACISpy:

ACISpy simulate_ecs_run

See ACISpy activation instructions first!

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4. Do you want to change the FP temperature setpoint?

It may be the case that you want to change the ACIS FP temperature setpoint in order to take data at a specific temperature for calibration purposes. We have versions of the LTECS CAP which include the steps to change the ACIS FP temperature setpoint, perform the ECS measurement, and then change the setpoint back to the default value of -121 C. There are different CLDs files for the different temperature setpoints which are possible to set to, which are detailed below. If you do not want to change the FP temperature setpoint, you will choose one of the CAP templates below which does not allow for this option.

5. Information Collection

The next steps are to obtain:
  1. A CAP number for the CAP,
  2. The filename and checksum of the CLD file you've selected for the ECS run
  3. If applicable, the CLD filename and checksum you've selected for the FP temperature setpoint
  4. An OBSID for the ECS run.

5a. CAP Number

Determine the next available CAP number by calling the OC/CC on duty via their cell phone at 617-594-3640.
Ask them for the next available CAP number. This will be a 4 digit number.

5b. CLD filename and Checksum

Once you have selected the number of chips and the duration of the ECS run, you must note the name of the CLD file and its checksum. The CLD files are located here:

Determine the checksum that corresponds to this CLD file. Write it down. This can determined in 2 ways:

  1. Run 'lrts [name of CLD file]' -- the second line in the resulting output will identify the CHECKSUM corresponding to the input CLD file

  2. Or scan the list-of-CLD-durations-and-checksums.txt file in the appropriate CLD file directory

    For example for the 4 chip cases: /data/acis/acis_docs/CAPs/CTI-CLDs/4chip/list-of-CLD-durations-and-checksums.txt

    ....to determine the appropriate CHECKSUM value given a CLD file.

5c. CLD filename and checksum to change the FP temperature setpoint

If you are not changing the FP temperature setpoint, SKIP THIS STEP.

If you are changing the FP temperature setpoint, you must decide which temperature you want to set the focal plane to and then pick the CLD file which corresponds to that temperature. It will specify the SCS slot that it must be run in, which also must be filled into the CAP.

Currently, the available setpoint CLDs, as well as their checksums and the SCS slots they use are:

Temperature CLD Filename SCS Slot Checksum
-120 C 1A_WS004_210.CLD 210 B36DE8C
-115 C 1A_WS042_249.CLD 249 B36960B
-110 C 1A_WS029_255.CLD 255 7369BB7
-109 C 1A_WS031_200.CLD 200 53664BA
-105 C 1A_WS019_230.CLD 230 8367AB5
-100 C 1A_WS034_242.CLD 242 7368EE8

These pieces of information will have to be entered into the CAP as shown below.

5d. OBSID

Determine the next available OBSID number by scrolling through:

/data/acis/acis_docs/CAPs/obsids-for-oac.list

As of this writing (February 23, 2023) the last OBSID used was:

62621 2023FEB22 J. ZuHone CAP1698, ACIS-I CTI RTS (4 chips, 14 hrs)

OBSIDs are not taken from the end of the file. They are obtained by scanning the file to find the last one used, and then taking the next open OBSID beneath that (as of this date that would be 62661).
The table is filled in from the top down. So the next available Obsid is 62620

Edit the file aading your ECS observation annd be sure to add a descriptive line for your ECS run in order to reserve the OBSID.

*** IMPORTANT: *** Send email to 'sot' indicating you have reserved that OBSID number for use in the ACIS ECS RTS CAP.

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6. CAP Template Location

You are now able to select the correct CAP template from acis_docs. The locations are as follows:

If you aren't changing the FP temperature setpoint:

If you are changing the FP temperature setptoint:

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7. Filling in the CAP Template

  1. Collect the information from the previous steps (e.g. CAP checksum, CAP number, OBSID, etc.), the time of the comm pass during which you intend this ECS measurement to begin, and the time of the next EEF1000 for the orbit.

  2. In the directory:

    /data/acis/acis_docs/CAPs/

    copy:

    CAPXXXX_acis<[blank]/i/s>_<#ofCCDs,identifier>_RTS_ECS_SCS.doc

    to:

    CAPNNNN_acis<[blank]/i/s>_<#ofCCDs,identifier>_RTS_ECS_SCS.doc

    where NNNN is the CAP number you obtained from the OCC, and for the number of CCDs, aimpoint choice, and chipset identifier (i.e., "ALT","A","B", where applicable for 3 or 4-chip runs).

    OR, if you are changing the FP temperature setpoint, then copy:

    CAPXXXX_mFPTEMP_acisi_<#ofCCDs>_RTS_ECS_SCS.doc

    to:

    CAPNNNN_mFFF_acisi_<#ofCCDs>_RTS_ECS_SCS.doc

    where NNNN is the CAP number you obtained from the OCC, FFF is the (absolute) value of the FP temperature setpoint you've chosen, and for the number of CCDs you've selected.

    Note that the current template files are symbolic links to their latest versions.

  3. Edit the copy of the template you just made and fill in the information you collected
    in the previous steps, replacing all instances of [INSERT] with their appropriate values.
    Leave the inserted information highlighted to help the FOT reviewers.

    Verify that the version number in the title box on page 1 matches that of the filename you obtained.

7a. Filling in the timing portion of "Restrictions/Warnings/Notes"

You have collected:
  1. The Comm Start Time,
  2. Comm Stop time,
  3. Length of the CAP in hours,
  4. The Obsid,
  5. The CLD file checksum,
  6. Time of RADMON DISABLE
  7. Interrupted load (e.g. FEB2023)
The start and stop times for the comm are in the standard YYYY:DOY:HH:MM:SS format, and the ecs_dur is the duration of the ECS measurement in hours.

The [INSERT] values to be filled in are explained below.


OK HERE IS WHAT YOU WRITE IN YOUR CAP:

7b. Filling in the fields for the FP temperature setpoint

If you are not changing the FP temperature setpoint, SKIP THIS STEP.

If you are changing the FP temperature setpoint, the following fields highlighted in yellow must be filled in from the table above:

Be sure to save a PDF version of your CAP for distribution. AGAIN, you must -replace- XXXX in the filename with the CAP number you obtained from the OCC. ALSO, if you are changing the temperature setpoint, you must also replace FPTEMP in the filename with the value of the focal plane temperature setpoint. The CAP checklist is now built into the CAP itself.

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8. ACIS Ops review

Once you have a draft CAP completed, circulate it to the ACIS team for review and comments. For ease of review, include comm start/stop times and duration, the duration of the ECS run, and the OBSID and CAP number selected in the e-mail. Also for smoother reviews, leave the yellow highlights of the inserted values

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9. Emailing the CAP to capreview

If the ACIS Ops review is successful, circulate the CAP and the checklist to the larger community (via 'capreview@ipa') and indicate you would like to hold a CAP review. Cc the announcement to acisdude, hrcdude, and the MIT folks: Peter Ford, Bev Fergason, Mark Bautz, and Bob Goeke (pgf, fergason, mwb, and goeke).

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10. The CAP Review itself

Things to emphasize during the CAP review:

  1. IMPORTANT: The FOT MUST include the following commands in the beginning of a replan load if it is to properly intercept an already running ACIS ECS RTS CAP:

    1. The replan load must contain commanding to terminate, disable and clear SCS 135--the SCS slot used to run the CAP.

      One can verify this by checking the backstop file for the following 2 commands: CODISAS1=135 and COCLRS1=135

    2. The replan load must also contain TWO ACIS Stop Science commands 3 seconds apart to terminate the ACIS ECS measurement.

  2. That the RADMON DIS executed in the CLD file occurs before the CLD file has completed. Mention that all CAP commanding must be completed prior to the load-scheduled EEF1000 time.

  3. That if the CAP is not interrupted by a science resumption load, that the verifiers in step 13 (or 15 through 21 in the case of changing the temperature setpoint) can only be checked if they occur during a comm.

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11. CAP Execution, Non-Load Tracking, and Storing the CAP

Once the CAP is approved, you will execute it at the appointed comm. When execution begins, be sure to note the time.

Generally you will be on 1165 with the OC in order to step through the CAP. You will want to have the following pages up on your browser:

  1. One of the Real Time Engineering web pages.

  2. One of the PMON web pages.

  3. The Chandra Snapshot page: Chandra Snapshot

The Snapshot page will display RADMON status, SIM position, OBSID, as well as other useful parameters.

Once the CAP execution is complete, you need to write up the Shift report for the CAP execution and add this CAP event to the "Non-Load Tracking File". This is a file that is used by various programs to incorporate the effects of running this CAP into the Thermal Models.

The instructions for running the Non-Load Event Tracker can be found here.

Finally, store the CAP (both Word and PDF versions) in acis_docs under /data/acis/acis_docs/CAPs, and commit it to the acis_docs git repository.

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Last edited: 02/20/2019

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