LUCI and MODS Mask Review

This page intends to describe the procedures to be followed from receipt of the mask design files from partner coordinators up to, but not including, installation of the masks in the instruments. For installation of MODS masks, see MODSMaskExchange.

Deadlines & Important Dates


For partner blocks between Nov 16 and Dec 16. Monday, October 24; LBTB (5); OSURC (5), INAF (5), AZ (0), ARGOS (6), D (1) Masks for the limited partner-wide ARGOS commissioning nights in December should be submitted to Sebastian Rabien according to the instructions in the recent Call for Proposals.

For partner blocks between Dec 24 and Jan 31, 2017 Monday, November 29; LBTB (6), OSURC (6), INAF (6), AZ (3), D (1)


Slit Mask Submisison Deadline: Wednesday, January 11, 2017 For 2017A, Partner Coordinators will let us know ahead of their science blocks for MODS what masks are needed, and ahead of scheduled LUCI cabinet exchanges what masks are to be inserted.

Guidelines for Partner Coordinators & Principal Investigators

For all submissions remember the following:

1) Please collect the mask design files from your PIs and send the batch to by the deadlines given above.

2) Please remind your PIs to use as many reference stars as possible.

3) If you are reusing masks that have already been cut in previous semesters, please provide us with the following information:

- The mask ID.

- The name of the LMS or MMS file. For LUCI programs, please resend the LMS files.

- PI name or mask name used.

4) Slit Separations: We routinely receive mask designs with slits packed way too close together, either in the vertical direction, or sometimes in both vertical and horizontal directions. As a rule of thumb, please keep any space between slits (and reference stars) to about 1.8 millimeters (about 3\x94). If slits are too close, you risk losing the bridge between them and creating a very strangely shaped slit. If you think it looks too close, it probably is too close. If you are not sure, please contact us (or have the PI contact us) before the deadline so that we can check the masks.

5) Please make sure PIs do not rename the LMS and MMS files to something other than what MMS or LMS produces. Both softwares allow unique names to be created (i.e. luci2.42.M81Targ1.lms) , there is no need to rename the files. This issue becomes a problem when using the LMS file to create scripts and can lead to downtime at the telescope when LMS names do no match what is in the script and/or provided to observers.

6) LUCI MASKS - If you would like duplicate masks produced to try LUCI-1 and LUCI-2 in Twinned ( or Duplex mode, i.e. same exact MOS Mask in each LUCI taking data simultaneously), please let us know and we will fabricate two copies. This is a shared-risk mode and there are no guarantees that duplex observations will be made (but it can't hurt to try!)

7) If you are not submitting masks for a 2016B deadline, please let us know and we may be able to use your allocation to help another partner use more masks for their science observations.


The set of LUCI and MODS masks design files that will be required for the upcoming set of partner blocks should be received from the partner coordinators 2-3 weeks in advance of the LUCI mask exchange for that set of blocks. This allows time for:
  • review of mask designs (1-2 days)
  • URIC to schedule cutting the masks
  • transport to the mountain (preferably on the Tuesday shift change before the LUCI pre-cool)
  • LUCI pre-cool (3 days before the mask exchange)

Mask Design files

The mask design software, LMS (for LUCI) or MMS (for MODS) outputs three files for each mask:
  • the lms or mms file: This is a text file which: starts with information on the image and catalog files used to create the mask; contains the 6-digit mask ID, which is the value of INS.MASK.ID and starts with a "5" for MODS and "9" for LUCI masks; describes the positions and sizes, in arcseconds and millimeters, of the slits, the alignment star boxes, the reference apertures, which are the set of 5 (MODS) or 6 (LUCI) small dots along the top edge of the mask; and, in addition to the position of the mask center and orientation, includes the positions of the guide star(s) and the reference stars (LUCI only).
The lms files are copied to the lucifer computer by LBTO staff. The mms files are needed on the obsN computers for observing, and are usually in the same directory as the acquisition, observation and calibration scripts for that mask; these are all copied to the obsN computers by the observers.
  • the gbr file: These are the files are sent to URIC. They can be displayed using the open-source Gerber viewer gerbv.
  • the epsf file: These are encapsulated postscript files that show the mask design. The epsf files do not show the ID number.

Storage of Mask Design files

Usually I store the mask design files for each month on my desktop in separate subdirectories under the directory Masks:
  • Masks/mmmYY/PARTNER/LUCI/ and Masks/mmmYY/PARTNER/MODS/
  • I create the directory Masks/mmmYY/GerberFiles/LUCI and copy the LUCI mask gbr files into it, and likewise, Masks/mmmYY/GerberFiles/MODS for the MODS gbr files.
  • I create the directory Masks/mmmYY/YYYY.MM and copy the LUCI lms files into it.

Review of the Mask Design files

The gbr files should be displayed and checked for the following:
Alignment Star Boxes: Number, Position and Size
  • Number: are there at minimum 2-3 boxes for alignment stars, within the 'acceptable' region, yet distributed well enough to determine rotational offset?
  • Region: 'acceptable' regions for alignment stars are:
    • for MODS, alignment stars should be within 2.5 arcmin of the field center. Stars more than than 2.8 arcmin off-axis should not be used because the optical distortions in this region are significant enough to affect precise centroiding.
    • for LUCI, any region is fine, but slits and boxes at X-distances greater than 1.25 arcmin from the X-center have worse focus (see below).
  • Size: Are the boxes sufficiently large?
    • Boxes should be larger twice the seeing FWHM in order to see the star profile well enough to center.
    • For MODS, boxes are usually 4" x 4", but it is not a requirement that they be that size.
    • When viewing the gbr files, the size of the box can only be gauged with reference to the slits. Most of the slits are 0.8-1" wide.
Slits: Positions and Overlap
  • Region:
    • For MODS, are most of the slits within a circle of radius 2.5 arcmin or 2.8 arcmin about the field center? (see attached image, modsgbrwcircles.jpg)
    • For LUCI, are most of the slits within a vertical band that is centered on the mask and has width 2.5 arcmin? (see attached image, lucigbr.jpg). This is the region where the cylindrically curved mask is in best-focus; outside of this region, the deviation between the mask surface and the spherical focal plane larger than 0.5mm, i.e. the slits are >~0.5mm out of focus.
    • There are almost always some slits outside these regions - for 'filler' targets or sky. If the majority of slits fall outside the acceptable regions, however, we should point this out to the PI.
    • Overlap or Stacking:
      • On LUCI and most MODS masks there cannot be slits and/or boxes which cover the same rows.
        • The exception are MODS masks for prism spectroscopy, for which there can be three slits that cover the same rows.
lms or mms files may be needed to check details:

The sizes of the boxes, and whether the boxes and slits are in the 'acceptable' regions can only be judged 'by-eye' when viewing the gerber files. A more careful look at these requires examination of the lms or mms files, either by searching for information in the text or by displaying these using the LMS or MMS software.
  • While the region where the LUCI mask is in best focus is rectangular, and limits can be roughly inferred with respect to the set of reference apertures along the top of the mask, it can be more difficult to locate the region of 'acceptable' image quality, within ~2.5-2.8 arcmin off-axis, on the gerber files for MODS masks. For this reason, especially in the early days of MODS observations, I found it helpful to run up MMS and overplot the mms files, as well as circles of 5 and 5.6 arcmin diameter, on a sky image.
  • Use of MMS or LMS:
    • Download the MMS or LMS software on your computer. These programs are not on the obsN computers. (Should they be?)
    • Run LMS or MMS (bin/ or bin/ where bin is a subdirectory of the directory created by unpacking the downloaded tar file.
    • On my desktop, MMS is in ~/mms_v160/. The graphics file to draw the 5 and 5.6 arcmin diameter circles is ~/mms_v160/circ5. The diameters of the circles are defined in pixels and so work only for images obtained from the ESO sky server. For images from other (e.g. CADC) servers, which have different pixel scales, the circles will be the wrong size in arcminutes.
Will the selected guide star cause vignetting by the guide probe?

While in MMS or LMS, I also check the positions of the selected guide star(s). (This is not necessary, however, as a tool could be written to determine, from the lms or mms file, the distance of the guide star from the center of the field and output a warning if it is less than 1 arcmin (for LUCI) or 223" (for MODS). If a warning is output, then a closer look, or at least a notice to the PI, is warranted.)
    • The LUCI guide probe is 2 arcmin x 2 arcmin and extends from above the LUCI field (+Y in detector coordinates). See the image, AGw_shadow_onaxis.jpg. I usually do not check whether the guide star selected will cause vignetting.
    • The MODS guide probe is 2.5 arcmin wide x 1.5 arcmin high, with an arm extending downwards. See the attached image, MODSguideprobe.jpg, of page 30, which contains Figures 22 and 23, of the MODS Instrument Manual. If the guide star is greater than 223" below the center of the MODS field (in detector coordinates, so if PA=0, 223" south), then the probe will not vignette. If there is a star near the edge of the science field, I usually create an acquisition script using the mms2obs tool, and then run modsView on this script with the shadow option to overplot the shadow of the guide probe.
    • mms2obs and modsView are installed on the obsN machines at the summit.
    • mms2obs -m dual grating -e 60 mymmsfile, where mymmsfile.mms is the name of the mms file, and the -m and -e flags specify the instrument mode and acquisition exposure time, will create a set of three files, among which is the acquisition (mymmsfile.acq) file. For this purpose, the arguments do not matter ("dual grating" is fine even if the actual observation will be "red prism"), so long as they are syntactically correct.
    • modsView --mms mymmsfile.mms --shadow mymmsfile.acq will bring up ds9 and display a DSS image on which is overlaid the location of the slits (green) and alignment star boxes (magneta) as well as the guide star (cyan) and shadow of the guide probe (yellow).
For MODS: is the selected guide star greater than 3.5 arcmin off-axis?

For guide stars that are far off-axis, in particular at Y distances greater than ~3.5 arcmin below the field center, some columns of Shack spots are vignetted on the WFS image, and this tends to introduce trefoil and, generally, cause problems with collimation. Ideally, a guide star should be chosen as close to the center of the MODS field as possible, without, of course, causing any vignetting of slits.

Sending the gerber files to URIC

  • Create a zip file to email to Russell Cole and Larry Acedo at URIC. Their email addresses are each a concatenation of the first initial and last name, followed by at email dot arizona dot edu.
    • cd Masks/mmmYY/
    • zip -r GerberFiles

Copying the LMS files to the LUCI computer

  • cd Masks/mmmmYY/
  • scp -r YYYY.MM engineer@lucifer:/home/engineer/LMSfiles/

Quality checks of the cut masks

  • At URIC, a cursory look of the masks is done to ensure that all slits are cut.
  • At LBTO, visual inspection is made. The instrument specialists rigorously check each slit on a light table checking through a microscope, checking for castoff or any debris. See Inspection of LUCI Masks and Inspection of MODS Masks for details and a procedural outline.
  • MODS masks, after they are loaded, are imaged using the script The procedure is also outlined on the Inspection of MODS Masks page.

Create the mask tables

  • LUCI: in Masks/MMMYYYY/YYYY.MM run to generate the table and related xml file.
    • ./
  • For and order specific list run to generate the table, YYYY.MM_lmsfiles.txt.
    • ./ order.txt where order.txt is an ascii file with one line per lms filename, e.g.
      • these will output two tables:
        • 2014.10_lmsfiles.txt
        • 2014.10_lmsfiles.xml
    • If there are <=21 custom masks for the block, then pointing mask, given ID 912345 and called "pointing" (see below).
      • There are 23 slots for custom masks in LUCI, and 1 should remain empty in case of problems.
    • Copy and paste the YYYY.MM_lmsfiles.txt table into the CurrentLuci1MaskList
    • scp the entire directory, containing the lms files and the 2 tables output by lmsextract, to the LMSfiles directory under the engineer account on the lucifer computer:
    • Upload the YYYY.MM_lmsfiles.xml table to the Mask Config GUI (see image below)
      • Double-click on the Mask Config GUI icon to bring up the MOS mask ID table.
      • In the upper left corner of this table, click File and select Open to bring up a browse window.
      • Browse into the directory LMSfiles/YYYY.MM, select the YYYY.MM_lmsfiles.xml table and click Open. This will upload the table.
      • At the bottom left of the MOS mask ID table, click Commit to make the change. This will also exit the Mask Config GUI.
  • MODS: in Masks/MMMYYYY/mmsFiles run (to be created - an equivalent of for the MODS slitmask table).
    • Copy the to the mods1 (or mods2) computer.
      • cd Masks/MMMYYYY/mmsFiles
      • scp mods@mods1:/home/mods/Config/MODS1/00Masks/

Loading the masks

  • LUCI
  • MODS. See MODSMaskExchange.
    • Copy the script to an obsN computer. From mods1:
      • cd
      • scp lbto@obsN:/home/lbto/SciPrep/MODS/

Storage of masks

  • MODS masks are stored on the mountain, in a file cabinet in the Instrument Lab, 116. These are organized into file folders by the last digit of the ID number. We often re-use MODS masks.
  • LUCI masks are typically cut before each mask exchange. Because of the need to load and pre-cool the next set of masks while the previous set of masks is still in the instrument, it is not possible to use the same mask from one month to the next. However, it is possible to load older masks that are already out of the instrument.

Database of mask file names

  • As yet, there is not a database of masks. However, given that we often do re-use MODS masks, and that the mask IDs for two different masks may be identical (rare, but there are about 2 such cases), it would be helpful to start a database which contains the mask ID, PI, gbr filename, lms or mms filename, date mask submitted or cut, other?

Special masks

  • Aside from the permanent masks, there are several 'semi-permanent' LUCI masks:
    • Pointing mask, given the ID 912345
    • Two 10 arcsec-wide-slit masks from LBTB, cut in Germany and of a thicker substrate than the other custom masks:
      • Single wide-slit, called sng_10asec_ls and given ID 987011
      • Double wide-slit, called dbl_10asec_ls and given ID 987022

-- OlgaKuhn - 05 Oct 2013

  • gerber file for LUCI mask with best-focus region noted:

  • MODS gbr file with 5 and 5.6' circles indicated:

  • LUCI1 AGw guide probe on-axis:

  • MODS AGw guide probe shadow (pg 30, Figs 22 & 23, of MODS Instrument Manual):

  • uploading the *.xml mask table into the LUCI1 Mask Config GUI:
I Attachment Action Size Date Who Comment
AGw_shadow_onaxis.jpgjpg AGw_shadow_onaxis.jpg manage 74 K 17 Oct 2013 - 23:45 OlgaKuhn LUCI1 AGw guide probe on-axis
MODSguideprobe.jpgjpg MODSguideprobe.jpg manage 46 K 17 Oct 2013 - 23:46 OlgaKuhn MODS AGw guide probe shadow (pg 30, Figs 22 & 23, of MODS Instrument Manual) manage 11 K 03 Dec 2014 - 20:16 JenniferPower manage 11 K 03 Dec 2014 - 20:15 JenniferPower  
lucigbr.jpgjpg lucigbr.jpg manage 38 K 10 Oct 2013 - 23:16 OlgaKuhn gerber file for LUCI mask with best-focus region noted
maskconfiggui.jpgjpg maskconfiggui.jpg manage 111 K 02 Dec 2014 - 17:40 OlgaKuhn uploading the *.xml mask table into the LUCI1 Mask Config GUI
modsgbrwcircles.jpgjpg modsgbrwcircles.jpg manage 55 K 16 Oct 2013 - 17:08 OlgaKuhn MODS gbr file with 5 and 5.6' circles indicated
Topic revision: r17 - 25 Oct 2016, BarryRothberg
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