Telescope oscillations

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This page has been created by CK on 9-Nov-2015.

During the NIKA2 runs since October 2015, the telescope occasionally showed strong and fast oscillations. Here, we collect all available information.

Recommendations (HU to operators on 27-Nov)

Unfortunately I do not have a solution --only-- some comments/suggestions
which may help to characterize the problem:

1. for each scan, when this occurs, can you check and report:
   -- has  there been a message "scan# loaded" ?
   -- has  there been a message "scan# started" ?
   -- have there been any messages "started" for any subscan(s),
      e.g. "subscanID onthefly started" ?
   (messages in antennaDataStream viewer and/or on,
    subscanID is something like 258.1 for scan 258 subscan 1)

2. when this occurs, try to repeat the same observing mode
   with modified parameters to see if this is related
   with position changes of a particular size.

   In particular:   

   in focusliss.pako try:

   let xAmplitude     90 instead of

   let xAmplitude     45

   for beammaps:

   try NIKA's

   instead of beammap.pako

NOTE:   I do NOT recommend to try any Lissajous with slowRate 1
        (this is likely to provoke other problems,
         because generally it is too slow to calculate a halfway smooth curve 
         of commanded positions in the Lissajous curve)

Summary of findings so far

Encoder plots

Scans showing oscillations


25th to 27th November 2015 (CK)

5th and 8th November 2015 (CM)

scan          UT start  Az/El   wind(max)    observing mode/script
              OTF parameters: x/ystart/x/yend/x/ystep/totf/notf/scan speed

20151105s152  18:53:19  110/34  3.9m/s       otf (beammap.pako 2nd part)
              -300"/-112"/300"/-112"/0"/3.5"/11s/65/54.5" per s

20151105s156  19:22:58  116/39  5.8          otf (beammap.pako 2nd part)
              -300/-112/300/-112/0/3.5/11s/65/54.5" per s

20151105s158  19:35:19  118/41  5.2          otf (beammap.pako 2nd part)
              -300/-112/300/-112/0/3.5/11s/65/54.5" per s

20151108s43   01:36:53  338/24  14.2         otf (nkotf.pako 5 5 90 0 20 40 radec)
              150/150/150/-150/-20/0/7.5s/16/40" per s 

OffProcNika2Run1TelescopeOscillations (last edited 2016-01-18 08:30:48 by CarstenKramer)