On-the-fly Data Processing

The format of CLASS data files has been recently extended to allow the reduction of data obtained in the On-the-fly (OTF) mode by the 30-m telescope. In that mode the data is taken while the telescope beam is moving across the source to be mapped. The raw data is pre-processed (amplitude calibration) by the CAL program available at the telescope, and written in a CLASS file. Data from a scan across the source is written as a single observation, thus containing many spectra at different positions. Each spectrum is included in the observation as a `record' or `dump', labeled by time, and telescope position. This new kind of data is handled by CLASS in a way similar to the normal data, but a few commands behave differently:

• GET  has an option /RECORD n to load an individual record of an OTF scan in the R buffer. After that this data may be plotted in the usual way.
• PLOT  has an option /SCAN which displays the entire scan as a 2-dimensional image, with velocity/frequency in the X axis, record number in the Y axis, intensity being rendered as grey/color scale.
• BASE , FFT , RESAMPLE  work on all the records of an OTF scan at once.
• GRID  may be used to tabulate, grid and plot the OTF data into GILDAS data cubes that may be further processed with GILDAS tasks.