MB Drift Scanning - Summary

Version 1.0 - RFM, 2000-23-06
Based on 'MB Drift Scanning'

For most azimuth angles, the drift79.sch sched file is used and the receiver rotation is given by:

If the azimuth is in the range 270 - 340 degrees, then the drift259.sch sched file is used and the receiver rotation is given by:

This should give results similar to those in the table:

Azimuth	Rotator Angle	Sched file to use
0	304.1	drift79.sch
30	274.1	drift79.sch
60	244.1	drift79.sch
90	214.1	drift79.sch
120	184.1	drift79.sch
150	154.1	drift79.sch
180	124.1	drift79.sch
210	94.1	drift79.sch
240	64.1	drift79.sch
270	214.1	drift259.sch
300	184.1	drift259.sch
330	154.1	drift259.sch

Each scan is one hour long, so it is necessary to tell it to repeat a number of times using the 'Repeats:' box on tkmulti. Check this after starting, as it seems to have a habit of reverting to '1' - which means that the drift-scan will only run for an hour.

To start drift scanning:

• Set the CAL diode and LO for multibeam. (See Switching to Multibeam)
• Ask the controller to rotate the receiver to the position calculated to match the azimuth.
• Get all the multi/tkmulti/mbcor software running. See 'Running the Multibeam Correlator' <
• Load either drift79 or drift259 schedule using the window on tkmulti.
• Enter a suitable number of repeats of the schedule (each repeat lasts an hour)
• Pull down Sched menu, and click START
• If at any time the controller has to change the telescope azimuth:
  • STOP scanning (using the 'stop' button on tkmulti).
  • Recalculate receiver rotation and get it repositioned.
  • If necessary change the sched file and re-enter the number of repeats.
  • Start scanning as above.