Note that there are minimum integration times for various imaging products. This is based on the processing time required to keep up with telescope observations in near real time.
For continuum imaging the threshold is 15 minutes.
For spectral line imaging the threshold is 45 minutes.
At times, spectral cube imaging may be disabled, unless specifically requested, due to logistical reasons.
Calibration reports should always be produced.
Some data products may be delayed in being transferred to the archive. If you need them urgently, please contact the helpdesk.
Accessing the pipeline products
Once you receive a notification from the Astronomer on Duty via the OPT that your observation is complete, follow the link to the archive.
Click on the downward-facing triangle to the far right of the listing to expand a drop-down menu.
Note that in the case of 32K observations, the calibration report is split into 4 sub-bands corresponding to the split across processor nodes.
Continuum data validation
The continuum validation products are:
Continuum image (no primary beam correction)
an MFS cube is available
Continuum image primary beam corrected
an MFS cube is available
Continuum primary beam corrected RMS image
Continuum primary beam corrected mean image
These are available as fits files as well as quick-look png images.
The structure of the Continuum image MFS cube fits file is not standard. A more complete description of its structure can be found in Section V Data Products of this document http://www.cv.nrao.edu/~bcotton/ObitDoc/MFImage.pdf, which describes the MFImage imager used by the SDP continuum imaging pipeline. In brief the image consists of multiple planes which are:
1) A plane in which the pixel values are the flux densities at the image reference frequency. 2) A spectral index plane of the fitted spectral index 4) A cube of of roughly constant fractional bandwidth subband images which are not equally spaced in frequency. The lower and upper edges of the frequencies of the subband images are indicated by the FRELnnn and FREHnnnn parameters in the fits header for the nnnnth subband (1 relative). The centre frequency is indicated by the FREQnnnn parameter and the NSPEC parameter gives the number of subband image planes following the spectral planes
Each spectral channel is imaged independently, with image parameters optimised for that particular frequency. Each plane can be downloaded independently.
Presentation on continuum QA metrics
Note that this was a preliminary presentation and some aspects may already be outdated see note below.
This presentation mentions that UHF and S-band primary beam corrections were not available at the time of filming. These have subsequently been implemented with:
UHF band beam corrections available from May 2021
S band beam corrections available from June 2021
Presentation on the first release of the MeerKAT QA report. Note that this is still under active development and some information may be out of date.