Technical Information

SOAR subsystems

The Enclosure

  • Achieves precise heat control by means of forced ventilation through a small dome area, set above a small building.
  • Unusually enclosed design promotes highly accurate telescope tracking through its control of wind buffeting.
  • The building was designed in the US and constructed by local Chilean contractors.
  • The dome was built in Brazil, using fiberglass panels from a US firm.

The Mount and Drives

  • Built by Vertex-RSI Corp. in Texas
  • Uses rolling element bearings for both altitude and azimuth
  • Achieves very high pointing and tracking specs
    • < 2 arcsec rms blind pointing
    • < 0.2 arcsec rms offsetting error
    • < 0.2 arcsec rms tracking jitter
  • Pre-assembled and tested in factory
  • Thoroughly tested in its dome on Cerro Pachon before arrival of the optics system. Throughout 2002, a 10-inch telescope mounted on the side of the main telescope was used to debug and verify pointing and tracking.

4.1m primary mirror

  • Very high optical quality: 17 nm rms surface.
  • Low thermal mass
  • Primary mirror is 4 inches thick

Active optics system

  • 120-actuator control of primary
  • Secondary on active hexapod
  • Image analyzer permanently mounted at one instrument port.

Tip-tilt tertiary mirror

  • Rapid tip-tilt correction at all foci


  • Many instruments are permanently mounted
    • 2 Nasmyth clusters, 3 instruments each
    • 2 Folded-cassegrain foci
  • Rapid selection between instruments
    • 60 seconds to switch
    • At least two instruments are always ready.

SOAR Instruments

Goodman Spectrograph

view more
  • High-throughput optical spectrograph
  • High sensitivity in near-UV down to atmospheric cutoff
  • Built by the University of North Carolina, Chapel Hill (PI: Chris Clemens)
  • Detectors: two UV-optimized 2K×4K MIT/Lincoln Lab CCDs
  • High-throughput Volume-Phase Holographic (VPH) gratings
  • Up to R = 1400
  • Choice of long slit or aperture plate.
  • Designed for rapid readout mode for monitoring short-period variability.

Spartan Infrared Camera

view more
  • Near-IR imager combining wide field with high angular resolution
  • Built by Michigan State University (PI: Ed Loh) with substantial participation from Brazil
  • Initially two 2048x2048 HgCdTe detectors.
  • Two more detectors were added in 2005 for 4096×4096 pixels total
  • 1–2.5 micron sensitivity
  • 2 magnifications
  • 3×3 arcmin2 FOV with 0.043 arcsec pixels
  • Matched to SOAR's K-band diffraction limit
  • 5×5 arcmin2 FOV with 0.073 arcsec pixels

Optical Imager

view more
  • SOAR's first-light instrument
  • Built by CTIO (NOAO), PI: Alistair Walker
  • 2×2048×4096 E2V CCDs
  • 15 micron pixels
  • Atmospheric dispersion corrector.

OSIRIS IR Spectrometer/Imager

view more
  • Near-IR imaging spectrograph built by Ohio State University (PI: Darren Depoy)
  • On loan to NOAO
  • 1024×1024 HgCdTe array sensitive between 0.95 and 2.4 microns
  • Intended as SOAR's IR spectrometer
  • Spectroscopy in J, H or K with R = 1200, 3000
  • Cross-dispersed mode covering IJHK simultaneously at R ~ 1200
  • Also provides imaging with large (0.14 or 0.35 arcsec) pixels over 1.3 or 3.3 arcmin FOV
  • Is being slightly modified for use on SOAR (installing narrower slit)

IFU Spectrograph

view more
  • Integral-Field, bench-mounted optical spectrometer
  • Built by University of Sao Paulo, Brazil (PI: Jacques Lepine)
  • Integral-field unit (IFU) fed from a pickoff mirror near telescope focus
  • Three interchangeable angular scales via interchangeable fore-optics in telescope focal plane
  • Lenslets in 30×50 grid
  • Coupled by a 5m-long optical fiber to spectrometer mounted on telescope azimuth structure
  • Detector: two red-optimized 2K×4K MIT/Lincoln Lab CCDs
  • Roughly 3 CCD pixels/fiber
  • R = 1000–40,000