Instrumentation

Heterodyne Instrumentation

The JCMT currently has five heterodyne spectral instruments: HARP: a 16-pixel array receiver working at 345 GHz; ʻŪʻū: a single-pixel insert on Nāmakanui working at 230 GHz; ʻĀweoweo: a single-pixel insert on Nāmakanui working at 345 GHz; ʻAlaʻihi, a single pixel insert on Nāmakanui working at 86 GHz and primarily intended for VLBI.  In addition, Kuntur is a 690 GHz receiver from LLAMA which replaces ʻĀweoweo in the Nāmakanui cartridge for planned time-limited campaigns, usually in the winter. The backend for all of these heterodyne instruments is the ACSIS correlating spectrometer. 

Continuum Instrumentation

SCUBA-2 is the JCMT’s continuum camera. It has four 32×40 detector arrays at 850 and 450 micron, in total 10240 detectors. SCUBA-2 operations are currently paused.

Current Status

Last update: November 20th 2025.

Operational

• Nāmakanui – ʻŪʻū
• Nāmakanui – ʻAlaʻihi (86 GHz, undergoing commissioning)
• Nāmakanui – Kuntur (690 GHz commissioning work)
• ACSIS – backend digital spectronometer
• WVM – Water Vapor Monitor (for weather see here)

Temporarily unavailable due to engineering work

Anticipated time off the telescope is Nov 19th 2025 to ~Dec 20th 2025.

• HARP

Currently not installed

The ʻĀweoweo cartridge is being temporarily removed from the Nāmakanui cartridge as of November 7th 2025, and replaced with the 625 GHz cartridge Kuntur. The exact date to swap back has not been selected but is anticipated to be in Spring 2026.

• Nāmakanui -ʻĀweoweo 

Operations Paused

As announced to the JCMT community in 2025, operations with SCUBA-2 (and its polarimeter POL-2) are currently paused.

• SCUBA-2
• POL-2

Instrument	Comments
SCUBA-2	850 and 450 micron continuum camera. 5120 bolometers (4 sub arrays x 1280 bolometers) at each wavelength band. Currently about 3500 bolometers are working at each wavelength band. Operations currently paused.
HARP	325 – 375 GHz 16 detector SSB SIS array receiver Currently HARP cannot be tuned to frequencies 325-329 GHz LSB and 335 – 339 GHz USB. 14 of the 16 receptors (detectors) are operational; H00 and H14 are not operational. H04 and H13 have bad baselines for frequencies lower than 340GHz Receptor H04/R05 is unusable at frequencies below 332.5 GHz PIs with projects involving jiggle maps on extended sources may wish to review the central pointings and/or K-mirror orientations in their MSBs. The lack of these receptors hampers jiggle mapping. Work is ongoing to replace the broken receptors. The largest square fully sampled field of view with a HARP jiggle map is currently 1.5’x1.5′. If the full 2’x2′ jiggle field of view is required we recommend using a small raster instead (114″x114″ 1/4 array spaced basket weaved). This will be less efficient with a factor of about 1.5 in time. Sensitivity variations creating striping – worst at 13CO/C18O
ʻŪʻū	225 GHz single pixel 2SB receiver.
ʻĀweoweo	345 GHz single pixel 2SB receiver
ʻAlaʻihi	86 GHz single pixel receiver (anticipated to be used primarily for VLBI)
Kuntur	690 GHz single pixel receiver
ACSIS	16 channel correlator with up to 1.8 GHz bandwidth.
WVM	183 GHz water vapour monitor installed in receiver cabin. Measures the precipitable water vapour along the line of sight at 1.2 second intervals. Of the two WVMs available the black WVM is currently installed.

Not Operational/Retired:

Instrument	Comments
RxA	211.5 – 276.5 GHz Single Channel DSB SIS receiver In 2016 the mixer was replaced by an SMA mixer and as a result sideband ratios are different from 1.0 at certain LO frequencies. This was also the case for the replaced mixer. It is planned to apply corrections in the data reduction. After replacement of the old 1980s micro computer, frequency switching has not been implemented.
RxW	For D band observations SSB is strongly recommended even if DSB mode is possible. The DSB option has been removed in the latest OT version. For D band, channel A is displaced by 10″ on the sky from channel B (which is the tracking receptor). Localized baseline ripple in PSSW mode.