The Submillimeter Telescope

Submillimeter Telescope (SMT) - Mt. Graham

Equipment Summary and Status - last updated July 30 2019

  • Main reflector: paraboloid D=10 m F/D=0.35
  • Subreflector: hyperboloid d=0.69 m Fe/D=13.8
  • Focus: Nasmyth or bent Cassegrain foci (2-outside each elevation bearing)
  • Reflector:
    • Spaceframe support: carbon fiber reinforced plastic (CFRP) tubes with invar steel joints (3040 kg weight).
    • Panels: CFRP skin with aluminum honeycomb sandwich core (110 Kg weight).
    • Subreflector support: CFRP tube quadrupod (110 kg weight).
    • Surface accuracy is measured by holography observations.
      The surface has an average rms of 15 microns over the entire surface.
  • Secondary:
    • Single mirror - CFRP aluminum honeycomb sandwich.
    • Chopping mechanism - at 80% duty cycle:
      • 10 Hz with 4 arcminute throw.
      • 25 Hz with 25 arcsecond throw.
    • 16 mirror positions possible for raster scanning.
  • Mount:
    • Altitude/Azimuth - steel with thermal insulation.
    • Absolute pointing accuracy: 2” rms
    • Tracking precision: 0.2” rms
    • Azimuth range: +/-270°
    • Elevation range: -2° to 91°
      • Observational range: ~20° - 84°
    • Slew speed: 60° min-1
    • 41500 kg weight
  • Observing season: October - June
  • Efficiency: 71% +/- 5% at 216 and 228 GHz
  • Supports position-switching, beam-switching, on-the-fly mapping, and continuum observing

Front Ends

1.3mm Receiver (Available)

  • ALMA Band 6 (205 – 280 GHz)
  • Dual polarization, SBS
  • Typical Tsys@230GHz = 200-275 K
  • Best Tsys@230GHz = 130-160 K

0.4mm Receiver (Unvailable)

  • 602 – 720 GHz
  • Dual polarization, DSB
  • 80 K TRx

0.7mm Receiver (Unvailable)

  • 385 - 500 GHz
  • Dual polarization, SBS
  • 150 K TRx

0.8mm Receiver (Available)

  • 325 – 370 GHz
  • Dual polarization, DSB
  • Typical Tsys@345GHz = 600-900 K
  • Best Tsys@345GHz = 350-500 K

New 0.8mm Band 7 Receiver (In development)

  • ALMA Band 7 (275 – 373 GHz)
  • Dual polarization, SBS
 

Back Ends

SMT Filter banks (Available)

  • The SMT IF range is 4-8 GHz for all receivers except the 0.8mm receiver, which has an IF range of 4-6 GHz. The IF center frequency is tunable from 4.5-7.5 GHz.
mode bandwidth (MHz) resolution (khz)
1 IF 2000 1000
2 IF 1000 1000
2 IF 64 250
4 IF 512 1000
4 IF 32 250

Observing Restrictions

Sun Avoidance: The SMT requires a 45° Sun avoidance zone.

Observing: None.


Recently Fixed and Current Issues

Filters 1.0MHz: There are periods of instability in the IF down conversion stages that manifests itself in platforming. Problems appear worse in position-switching and on-the-fly observing modes.

Filters 250kHz: The instability noted in the 1.0 MHz filters also appears in these filters. This platforming step is located at the IF center frequency and can be avoided by offsetting the IF.

Position - switching mode: There is a standing wave present when using observing in position-switching mode, especially at the upper end of 1.3mm receiver observing band. This standing wave is not atmospherically induced but instead is related to the receiver/hardware.


For more information, please contact:
Dr. Remo Tilanus, Operations Manager ARO
rtilanus@arizona.edu