1. Facilities

UArizona ARO Submillimeter Telescope

UArizona ARO Submillimeter Telescope (SMT) - Mt. Graham

Equipment Summary and Status - last updated July 30 2019
  • East Longitude: -109 53 27.6
  • North Latitude: +32 42 07.2
  • Elevation: 3170.1 meters (10400.6 feet)
  • 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

UArizona SMT banks (Available)

  • The UArizona 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. The sideband separating receivers (SBS) output four IFs: horizontal (H) and vertical (V) polarizations for both the lower (LSB) and upper (USB) sideband. Dual sideband receivers (DSB) output two IFs: the H and V polarizations, respectively, for the combined LSB+USB sideband. For processing, the filterbank can select 1, 2, or 4 IFs of the maximum four IFs available by reducing the total bandwidth per IF.
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

SWRDS Digital Spectrometer

The Wideband Radio Digital Spectrometer (SWRDS) is an FPGA based backend spectrometer for the SMT. The spectrometer is in development but is available as a shared-risk instrument as features may initially not work properly. It operates concurrent and in parallel with the standard filterbank.

SWRDS has two main working modes:

  • A wideband mode capable of processing a maximum of 2 GHz of bandwidth per window and up to 2 spectral windows per polarization. This mode in the future will be expanded to a 4 GHz of bandwidth.
  • A multi-window mode that has up to eight spectral windows ranging from 32 to 256 MHz bandwidth per polarization that can be placed within the IF band, currently restricted to 2 GHz.

For both modes, optionally a Hanning taper can applied as part of the digital processing. This reduces the frequency resolution from 1.2 to 2.0 times the channel spacing, but results in less aliasing and channels that statistically are more independent. For its initial use, the default IF is 6 GHz for the 1.3mm receiver and 5 GHz for the 0.8mm receiver. Users that require a moderate shift of the IF are asked to contact the ARO Helpdesk. Ongoing developments aim to enable a tunable IF.

Wideband mode

Wideband is a fixed mode FFT with up to two dual-polarization windows. This mode is currently not steerable. The two windows are set to upper and lower sideband, respectively. Each window produces individual spectra for the horizontal and vertical polarizations. Thus, a total of up to 4 spectra will be produced. Table 1 shows the possible bandwidth and channel-spacing configurations for the SWRDS wideband mode.

Multi-window mode:

Multi-window mode is an adjustable FFT that produces up to eight equally sized spectral windows that can be placed within the 2 GHz upper or lower sidebands of the receiver. Each window can be independently steered. Each window produces individual spectra for the H and V polarizations. Thus, a total of up to 16 spectra will be produced. There are four resolution options available in this mode, and the mode will be applied to all available windows. Table 2 shows the possible bandwidth and channel spacing configurations for AROWS wideband mode. For general information on the multi-window mode, albeit with a 4 GHz IF, see the 12-meter's AROWS backend.

Observing Restrictions

Sun Avoidance: The UArizona 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:
ARO Helpdesk