next up previous contents index
Next: Interferometer pointing Up: Radio Pointing Previous: Radio Pointing   Contents   Index

Full sky, single-dish radio pointing

If the radio pointing has to be determined for the first time (new antenna, new receiver, new subreflector alignment, or other major changes), a full sky radio pointing is necessary. Using the OBS OBS$\backslash$POINT command, observe 30 to 40 positions, preferably clustered at high and low elevations, but well spaced in azimuth.

Use CLASS on BURE02 to reduce the pointing measurements, working on the [OBS.SINGLE] directory. A procedure named PR:INIT_POINT can be used in CLASS to get started. Open the .BUR input file, get a list of the pointing scan, using commands FIND and LIST. Then the procedure PR:POINT can be used to process the data scan by scan. For each pointing scan, it averages separately the two azimuth and two elevation subscans, fit gaussians, with two coupled components in case of beam switching, to the averages, and at each PAUSE, the user can write the result in an output data file, named Date.BUR-POINT. This can be done while data acquisition is still going on. Once all data have been reduced, open the reduced data file in input, select all data using the LAS$\backslash$FIND command, and then use ANALYSE$\backslash$PRINT POINT/OUTPUT [-.POINTING]Date.RAD to write out the fit results.

Stop CLASS and move to [OBS.POINTING] directory to use POINT to fit the pointing parameters. The default adjustable parameters are IAZ, IEL+COV, MVE, and MVN, while COH is set to its antenna dependent value, found from file INTER_BASE:GENERAL.ANk.

In RADIO mode, POINT gives variations from the previous parameter values, except for COH where it gives the absolute value (note COV = dIEL, the variation of IEL). Refraction parameters should always be fixed to zero, since the radio refraction is computed in real time.


next up previous contents index
Next: Interferometer pointing Up: Radio Pointing Previous: Radio Pointing   Contents   Index
Gildas manager 2018-09-24