Aftermath of lightning storm

As a consequence of the lightning strike on the FIES building in March 2007 a lot of time was spent identifying and repairing damaged parts of the instrument electronics. During the work it was necessary to move the CCD controller and for no clear reason this resulted in an increase in readout noise from the detector. Repositioning the controller, switching things off, it was impossible to return to the original 3e- noise level. Eventually, after removing most of the control electronics to the front room the excess noise disappeared though the exact reason for this is not understood.

After replacing the FIES temperature monitoring system that was also destroyed by the lightning, noise was seen on all the temperature readings. The source of this noise has not been identified, though the actual temperature sensor units themselves are suspected, and has been found to have a frequency that vary with a period of 11 to 16 seconds. A preliminary solution to this has been to apply a software filter to the data before recording.

Also, shutter electronics, the electronics of the FIES camera focus mechanism, and the bottom calibration unit that were 'affected' by the lightning storm were repaired.

In the mean time, a new lightning protection was designed and is being installed. This system is separate from the lightning protection of the telescope building and has its own grounding point close to the FIES building. The damage to the FIES building was primarily caused by the relatively large distance to the telescope building which did not provide sufficient protection when lightning hit the FIES building.