GLT receiver cartridges - 86, 230 and 345 GHz.

Receiver cartridges – 86, 230 and 345 GHz.Nāmakanui (“Big-Eyes”) is a heterodyne receiver unit making use of the ALMA “insert” concept for a dewar that can hold three single-receiver inserts. These inserts are used singly when observing (i.e. only one at a time). This configuration mirrors that of the Greenland Telescope (GLT)  instrumentation (see here for link to the SPIE paper describing the GLT instrument).

Nāmakanui (an 86, 230 and 345 GHz instrument) was built by a team at ASIAA (Taiwan) and is on loan the to the JCMT as a spare for the GLT.  Nāmakanui was delivered to the facility in August 2019 with installation at the telescope in September 2019. First light was achieved early October.  Currently observatory staff are commissioning  the `Ū`ū (230 GHz) receiver prior to working on the other inserts.


The three heterodyne receiver inserts work at 86, 230 and 345 GHz, and are named `Ala`ihi (“Squirrelfish”), `Ū`ū (“Soldierfish”) and `Āweoweo (“Big Eye”) respectively. The 86 GHz insert is a dual polarization, 1-sideband mixer. The 230 and 345 GHz inserts have dual polarization 2-sideband mixers, producing four Intermediate Frequencies (IFs) with bandwidths of 4 – 12 GHz each (although this may be restricted to 4 – 8 GHz initially). Aweoweo (345 GHz) will be capable of supporting IFs in the 5 – 9 GHz range. Please note that, at present, the ACSIS IF system only supports IFs of 4 – 7.3 GHz.

The 230 and 345 GHz mixers are identical to those used by ALMA. More technical details on the 230 GHz mixer are available here. The most recent public user information on these receivers is given in Sections 4.2.4 and 4.2.5 of the ALMA Technical Handbook. Due to each insert having a separate optical path (TMU position), only one receiver/frequency range can be used at any one time.

`Ū`ū (230GHz)

Current Status: Commissioning

The accessible `Ū`ū frequency range is currently anticipated to be 212 – 274 GHz. Use of ACSIS with the new 230 GHz mixer during the 19B shared risk period means that the bandwidth and resolution configurations available are currently expected to be the same as for RxA3m. The standard heterodyne observing modes expected to be available for `Ū`ū shared risk observing are Stare, Jiggle and Raster. For more details on these observing modes, please see this page.

Anticipated instrument capabilities and overall system performance have been incorporated into the JCMT Heterodyne Integration Time Calculator. This is with the following two caveats:

  • One polarization channel has been lost and so time estimates should be doubled to compensate for the loss in expected sensitivity.
  • Only 2 sub-bands are available for use at this moment


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