On 20201202 we updated our ACSIS software. In the past all receptors would be written our to raw files on a per-observation basis. For the Nāmakanui insert `Ū`ū this meant that for each observation a minimum of two files would be produced, one for LSB and one for USB, each containing 4 receptors: NU0L, NU0U, NU1L, NU1U. This led to writing out blank data. Below is a quick reminder of Nāmakanui receptor naming convention:
- N= Instrument: Nāmakanui
- U = Insert: `Ū`ū
- 0/1 = Polarization: 0/1
- L/U = Side-band: LSB/USB
The ACSIS software update now keeps track of working receptors per-subsystem (spectral window) instead of per-observation, and thus does not write blank data to the .sdf output files for non-contributing receptors. This is mostly for the sake of Nāmakanui, but will also affect HARP regarding the order the receptors appear in the output files. Thus if you look at raw `Ū`ū data files taken before the change you will see blank data.
More information regarding the fits-headers that track receptors used can be found here.