Next: Targets
Up: Spectral Setup
Previous: Single Continuum
Contents
Spectral Scan
It is possible to define a complicated setup involving multiple tunings that are meant to cover a contiguous range in frequency using the spectral scan interface. Given a start and stop frequency, and a correlator mode, the OT will devise a set of tunings that achieve the requested frequency range. The tunings are overlapped to ensure that bad edge channels can be flagged without leading to gaps in the combined spectrum. The overlaps are greatest for the 1875 MHz-wide spectral windows (
170 MHz) and smaller (
31 MHz) for the remainder.
- Requested start frequency (sky): Frequencies can only be entered in the sky (observed) frame. The OT will start placing its spectral windows at this frequency.
- Requested stop frequency (sky): The OT will attempt to achieve this frequency by creating up to five tunings. The OT will rarely achieve this exact frequency as there are fixed gaps between each tuning and each tuning implies a fixed amount of extra frequency coverage.
- Requested range (rest): The requested range is also shown in the rest frame of the first target defined in the Field Source editor. The OT will warn if the requested range was not achieved.
- Achieved scan range (sky): In general, the OT will not achieve the exact frequency range requested and this is displayed here.
- Bandwidth: One of four correlator modes (the four widest available) should be chosen from the drop-down menu. The displayed values of spectral resolution include Hanning smoothing and spectral averaging.
- Spectral averaging: A single spectral averaging factor can be applied to all spectral windows.
- Representative frequency (sky): The default value (centre of requested range) can be changed.
Once enough information has been added, the OT will calculate a tuning setup and display the derived spectral windows. Spectral scans are only allowed for sources with a single offset pointing and for a single 12-m configuration (no ACA).
Next: Targets
Up: Spectral Setup
Previous: Single Continuum
Contents
The ALMA OT Team, 2016 Aug 23