`Ū`ū (230GHz)

Current Status: Shared Risk Observing for PI and LAP programs

`Ū`ū is one of three inserts held within the Nāmakanui instrument. `Ū`ū is a Sideband Separating (2SB) instrument working around the 230GHz range.

The accessible `Ū`ū tunable LO frequency range is currently 221-264.6 GHz, so observable sky frequency range with ACSIS is 215 – 270.6 GHz with IF =6 GHz.

The current attenuation on our reference signal generator makes it difficult to tune above 264 GHz.

Currently during commissioning and Shared Risk Observing – we ask users to stick with the standard IF of 6GHz and keep to 250 and 1000MHz sideband modes. If these options are not compatible with your science  please consult with your FOP. When available users are advised to use the LSB for observations.

The full bandwidth and resolution configurations available are described on the ACSIS page. `Ū`ū can be used in Stare, Jiggle and Raster observing modes.

Anticipated instrument capabilities and overall system performance have been incorporated into the JCMT Heterodyne Integration Time Calculator. As of late February 2020 all four mixers within `Ū`ū are operational and previous (commissioning phase) amplifier issues have been fixed.

Blow is an annotated part of the Nāmakanui instrument block diagram focused on the  `Ū`ū insert.

Raw Data format

Currently the raw data are saved in two files. One (set of) file(s) will contain the information from the LSB, the other will contain the information from the USB. The total number of raw output files from an observation will depend on the number of sub-systems requested (e.g. 250MHz bandwidth only or, as is the case for standard calibrator observations 250MHz and 1000MHz bandwidths).

Within the raw data the receptors are arranged in order: NU0L, NU0U, NU1L, NU1U. As the current methodology is to provide separate files for USB and LSB there are blank pixels for the alternative sideband.

The raw files will be labeled in the following format:


where a stands for ACSIS. The UT date is 20200124. The observation is a five padded number, in this case observation 6. Currently for `Ū`ū multiples of two files will be produced numbered from 1 and in a four padded number. The tracking sideband (either LSB or USB) is provided in the first N/2 files with the image sideband provided in the last N/2 files, where N is the total number of raw files for the observation.

Within the raw files you can see they contain spectra from the mixers from both instrument polarization channels (P0 and P1).

Reduced Data

All `Ū`ū are currently reducible by the Starlink software suite and the output provides a spectra at both LSB and USB. For details on running `Ū`ū reductions visit the Heterodyne Data Reduction pages.

Please not that data can be affected by Ozone lines.

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