MODS: The Multi-Object Double Spectrographs

Overview

MODS1 and MODS2 are UV to nearIR Multi-Object Double Spectrgraphs that are mounted at the Direct Gregorian focal stations of the LBT. They were designed and built by The Ohio State University Department of Astronomy in Columbus Ohio.

Each MODS is a low- and medium-resolution spectrograph (R=100-2300) and imager working across the entire 330-1100nm band with a 6x6-arcminute field of view. Multi-object spectroscopy is accomplished using laser-machined focal-plane slit masks fed into the beam by a 24-position mask cassette. A beam selector below the slit carries a dichroic that splits the incoming beam into separate red- and blue-optimized channels (the dichroic cross-over wavelength is 575nm), each with its own collimator, grating, camera and detector, allowing simultaneous operation across the entire CCD band. The beam selector can also direct light into the red or blue channels alone, providing blue-/red-only modes to extend wavelength coverage across the dichroic cross-over wavelength as required. The MODS CCDs are custom-built 3x8K monolithic e2v CCDs; blue-coated standard silicon on the blue channel and extended-red coated 40-micron deep depletion silicon on the red channel.

MODS1 was delivered to LBT in May 2010 and was commissioned on-sky from September 2010 through May 2011. It began regular observing operations in September 2011.

MODS1 mounted on the LDG rotator - 2010 Sept 1

MODS2 was delivered in October 2013 and was installed on the telescope for initial testing on 2014 April 9. Full on-sky commissioning will commence during Fall 2014. Binocular operation will likely begin during 2015.

MODS1 and MODS2 on the LBT - 2014 April 9

MODS Support & Service Procedures

• Instrument Startup Procedure
• Liquid Nitrogen Fill Procedure
• Instrument Rotator Service Positions
• Mask Exchange Procedure
• Inspecting MODS masks
• MODS Calibration Lamp Exchange Procedure
• IMCS Collimator TTF Zero Point Calibration Procedure
• CCD Dewar Pump-Down Procedure
• Post-Shutdown Startup
• Instrument Support Utility Programs (modsMask, modsAGW, modsTemps, low power, no power)
• MODS UPS Failure Recovery
• The full procedure to shut down software services and computers, in the event of a power outage
  OLD MODS Computer Power Down Procedure

MODS Instrument Tables

• Currently Installed Slit Masks
• Camera Filters
• Gratings and Prisms
• MODS FITS Headers
• MODS Calibration Lamp Change Log
• MODS Micro LYNX Motor Controllers (Table & Service Log)
• MODS IMCS TTF and Camera Focus
• Log of MODS Field Lens Cleaning
• MODS agw.ini files and MODS-AGw "recommissioning"
• More on the way...

Troubleshooting procedures for MODS team & LBTO staff

• Observers should look on the sciops webpages for troubleshooting, but the information on the following page will be sorted into the above and the sciops web pages (2022-Dec) Troubleshooting for observers

MODS Observing Documents

• MODS Instrument Manual (4Mb PDF)
• MODS Observing Scripts Manual (2Mb PDF)
• Observing Planning Tools (on the MODS website at OSU)
• Looking at the Data
• MODS Instrument Calibration (OSU)

-- RichardPogge - 22 Sep 2010