Overview

• Mid-resolution echelle spectrograph
• Very low-resolution prism spectrograph
• Imager

Science drivers

• Echelle mode
  • kinematics of galaxies and galaxy clusters
  • QSO intervening gas studies
  • "long slit" kinematics of gaseous nebulae
  • stellar metallicities
• Low-D mode
  • High throughput survey work: quasars, radio and X-ray sources, etc.
    (redshifts, continuum shapes, identifications)
• Imaging mode
  • narrow-band QSO imaging
  • small field of view surveys
  • benefits from seeing < 0.5 arcsec

LRIS Similarities

• Cassegrain instrument

• Optical spectrograph (3900 Å - 1.1 µm, like LRIS-R)

• Imaging mode
• Choice of two resolutions (LRIS has many)
• Slit masks possible, though little used
  • smaller field of view
  • not a commissioned mode
  • only 3 or 4 slots available for masks

HIRES Similarities

• Cross-dispersed echelle (also like NIRSPEC high-resolution mode)
• Can use slit masks

Novel features

• "Space frame" design to isolate structure from environment and minimize flexure
• Open-loop flexure compensation control
  • simple formula predicts image movement
  • high-precision active collimator controls compensate

Also different

• Active servo mechanisms with "optical" (~8500 Å) encoder tapes.

• New control interface design ("Dashboard")
  • tcl/tk
  • highly customizable, although we don't use this feature much
• "Sealed" hatch and spectrograph body with positive air pressure to keep optics clean

Design Walkthrough

Following the light path from the telescope to the detector:

• entrance window and cover (AIR operated)
• triple wheel (SERVO)
  • only upper wheel in focus
  • five slots per wheel
  • holders (one per slot) can have one, two, or three filters or slit masks
  • special 9-position echelle slit mask with "dekker" in middle wheel to select active slit
• offset mirror for guide/acquisition field

Guider path:

• 8-position filter wheel (HIRES_style holders) (SERVO)
• remote camera focus
• PXL 2K x 2K CCD

Science path:

• Collimator (SERVO)
  • Three legs with ± 25 mm travel, encoded to 5 µm
  • Focus and flexure compensation
• Cross-dispersion prism #1 OR imaging fold mirror (AIR)
• Fixed cross-dispersion prism (#2)
• Echelle grating OR low-D fold mirror (AIR)
• Camera shutter (AIR)
  • "curtain shutter" design with 3 states: left, open, and right
• Camera lens
  • fluid-filled gaps between some elements
• Dewar
  • ion pump
  • 2K x 4K MIT/Lincoln Labs CCD

Instrument Walkaround

• Electronics boxes

• hatch
• cryo fill port
• access panels

Electronics and Computers

• Galil motor controllers (2); Renishaw encoder tapes

• Leach II CCD controller
• Ion pump controller (a la HIRES)
• Lantronics terminal server
• Separate CCD computer (esi5cb; UNIX)
• Low-level interface control (koki; UNIX)
• Instrument computer (kanaha; UNIX)

Interface demonstration

• Startup

• Features of GUI

  • Control
  • Detail panels
  • Low-level diagnostic panels
• Log file
• Configuration tool (replacement not created yet)
• Other tools
  • xshow
  • cshow
  • testAll
  • ct