MODS Quick Reference Wiki Page

Notes on multi-slit mask preparation

The MODS optical design has some significant astigmatism at high field angles (in the corners of the images). At present the mos alignment algorithm has some difficulty measuring the centroids of the alignment boxes and sources. Until further notice, when designing MODS masks please limit the selection of the alignment sources to field angles <2.8 arcmin maximum (<2.0 arcmin preferred) radius from the center.

A future version of MMS will draw this circle on the design window to remind people. We'll need to have a pull-down menu to select the 5.6 or 5-arcmin circles.

Also, please note that the current alignment script measures the positions of the boxes as well as sources on the CCD images and therefore requires that boxes be cut around at least three alignment sources.

Start of the Night

Set up for Data Acquisition on obsN (N=2,3,4; the observer workstations in the control room)

• Log into LBTO workstation, obs2, using your partner account (INAF,LBTB,OSURC,AZ). You could login to obs3 or obs4, but obs2 is just next to the operator's console and the most obvious choice for setting up instrument control.
• Open a terminal window and type mods1 status. You will see a status panel. Everything but the mods1 gui should be open and owned by mods
• In the terminal window type mods1 start gui. This should launch the MODS Control Panel.
• Open another terminal window and type modsDisp. This will launch two read-only ds9 windows to display the most recent Blue and Red images, while the terminal window will display a table of the images as they arrive on the /newdata disk.
• In the MODS Control Panel, click on the Setup icon on the left sidebar to display the MODS Instrument Setup screen.
  • Enter the Observer/Project Information:
    • Observer Names (can be separated by commas and spaces). This goes into headers as the value for the keyword, OBSERVER.
    • Enter the Partner Name: OSURC, AZ, INAF, LBTB, LBTO. The name entered here goes into the headers as PARTNER and determines how the data will be archived. (Multiple partners can be listed, separated by commas but no spaces.)
    • Enter PropID
    • Enter PI Name, Support (SUPPORT), Telescope Operator (TELOPS) and a Comment describing the run.
    • Once all the necessary updates have been made, click Apply, then Save.
    • The Partner, PropID and PI Name will be overridden later by the parameters in the Archive blocks of subsequent MODS observing scripts.
  • Click "GetDate" on the right side of the Instrument Setup Screen to update the UT date in the image file names. Make sure it is the correct UT date for the night, if it is early in the afternoon in may still get yesterday's UT. And if you have taken data already with that UT date, click refresh and double check that the Blue and Red CCD filenames do not already exist Click "Apply".
• Click on the MODS1 icon to switch to the MODS1 Dashboard. This will be the screen to watch during observing.
• Open a third terminal window and cd into the directory which contains your observing scripts. There are three types of scripts that you will be running during the observations: imaging (.img) scripts, and acquisition (.acq) and observation (.obs) scripts for spectroscopy.
• On obs2 or another workstation, open a terminal window in which you will run modsAlign.
• Ask your support scientist or telescope operator to:
  • run modsWake
  • put MODS into Observing Mode. If the first preset is sent with the calibration unit in, the guider stage will not initialize correctly and the preset will not move the guide probe. Put MODS into observing mode and ask the telescope operator to restart GCS (they will know what to do... it is not uncommon for someone to forget to put the instrument into Observing Mode before the operator issues a test preset.

Pointing and Collimation Check

• At the start of the night, once dark enough, ask the telescope operator to slew to a bright star to correct pointing offsets.
• Ask the telescope operator to preset to a Persson star near your first target and collimate.

Running Scripts

• There are two programs to execute scripts:
  • Use acqMODS to run acquisition scripts
  • Use execMODS to run observation and imaging scripts.
• Usually these are run without any flags. You can see a list of options, however, by entering acqMODS or execMODS without any argument.
• Note that the MODS GUI must be running for these scripts to communicate with the system.

Object Acquisition

• To acquire spectroscopic targets:
  • In the terminal window, type acqMODS scriptname.acq to run the acquisition script:
    • For science targets, this acquisition script will take first a slit image (SlitGO), second, a field image (AcqGO), and then pause to allow the observer to run modsAlign. For spectrophotometric standards, the acquisition script will take only a field image (AcqGO) before pausing for modsAlign.
  • If a long-slit acquisition: run modsAlign -l <slitimage.fits> <fieldimage.fits> (modsAlign will look for these images in /newdata, so all that is needed on the command line is the image filename).
    • position cursor at the slit center (and away from Y-center of the array, Y=590 is good) and click "x" then "q". The X-center will be fit and the slit position will be drawn on the second, field, image.
    • on this field image, position the cursor on the target and click "a" (if a centroid can be reliably determined) or "x" to take the cursor position. "q" will exit and compute the offset needed. If it looks reasonable, send it.
    • Once the offset is made, continue the script to make a blind offset, if indicated, and then to obtain a confirmatory thru-slit image.
  • If a 5" long-slit spectrophotometric standard star acquisition: run modsAlign -r <fieldimage.fits>
    • the -r option is new as of March 2012 and uses a reference position of the slit center (503,590).
    • the field image will be displayed with an outline of the wide slit and the reference position of the slit center, marked by a green cross
    • position cursor on star and click "a" (if a centroid can be measured) or "x" to take the cursor position. "q" to exit and make the offset.
  • If multi-object acquisition: run modsAlign <mmsfile.mms> <slitimage.fits> <fieldimage.fits>
    • the MMS file must be in the directory from which modsAlign is run
    • The slit image will be displayed and the observer should position the cursor on each box and click "x" (this will centroid on the box). Once all boxes are marked, type "q".
    • The field image is then displayed and a regions file depicting the boxes is overlaid. Mark, in the same order as the boxes, the alignment stars with an "a". When finished, type "q".
    • The offset in x, y and rotation will be printed and you will be queried whether to send or not. If reasonable, send with "Y" or "y".
  • Once the alignment is made, start the observation with execMODS scriptname.obs.
• To recover alignment if a preset must be canceled mid-observation:
  • If the shell goes into RIP state:
    • pause the current integration by typing "pause" in the Command line box at the bottom of the MODS Dashboard, or by clicking the Pause button(s) for the red and/or blue channels.
    • The OSA will recover the shell and the preset should normally not be canceled.
    • Once collimated, resume the integration by typing "resume" in the Command line box or by clicking the Resume button(s).
  • If the preset is canceled (difficult recovery from shell RIP or guide star lost):
    • stop the current integration. This will readout and save the exposure that was in progress, writing the correct, shorter-than-requested exposure time in the header.
    • copy the acquisition script into a recovery script, e.g. cp yourtarget.acq recover.acq
    • go into the directory from which the acquisition with modsAlign was done and cat the file mods_lastOffset. This file contains the last offset command: offsetpointing dtheta dx dy detxy rel for MOS or offsetxy dx dy rel for long-slit
    • Edit recover.acq to replace all of the contents of the Acquire: block with, on the first line, the contents of mods_lastOffset and on the second, slitGO. The recover.acq script should have an Acquire block like:

                  Acquire:
                      offsetpointing -0.2807 -0.228 -0.824 detxy rel
                      SlitGO 

    • acqMODS recover.acq will then execute the preset, followed by the offset that was needed to the do the alignment the last time, and take a thru-slit image.
    • copy the observation script to a recovery obs script, e.g. cp yourtarget.obs recover.obs and adjust the exposure time and/or the nimgs as needed to complete the observation sequence.
• To run imaging scripts
  • execMODS scriptname.img
    • Imaging scripts preset the telescope, lock on a guide star, then pause until you think the WFS is sufficiently converged (the WFE reported on the GCSGUI <~ 400 nm) to proceed
    • Template .img scripts can be created with the mkMODSImg program (part of modsTools), and then edited to add filter and dithering sequences as needed.

End of the Night

• Calibrations can be done at the end of the night or during a cloudy night. Calibrations need not be taken every night.
• These require the telescope at zenith, and the dome dark (except for the comparison lamp calibrations which can tolerate a light dome).
• Scripts for calibrations should be included with the submitted set of scripts for the observing block, but a set of template scripts may be found at the MODS Instrument Calibration web page and in ~MODSeng/modsScripts/modsCalib.
• Ask the support scientist or telescope operator to run modsSleep.

-- OlgaKuhn - 27 Sep 2011