Next: Instrument use Up: Down Time Previous: General overview Contents
Below are listed those faults for which 2 or more hours were lost.
The problem was one of the ALFOSC calibration lamps that had remained switched-on while observing with FIES. This did not affect the resulting spectra with FIES as the lamp shines away for the fiber entrance, but it seriously affected the target acquisition which is done with StanCam which is positioned on the opposite side. The software has been changed to make sure that the lamps are switched-off under all normal circumstances.
On a few occasions with large intervals in between the shutter of the Filter and Shutter Unit which contains two filter wheels and is mounted between the telescope and either ALFOSC or MOSCA would closed by itself. Various solutions where tried, where the most likely cause was believe to be a loss of power to the controller of the shutter and the wiring was checked and the power supply was replaced. Unfortunately, the error would only occur after many days or weeks while thorough testing did not show a problem. The last solution that was tried was to replace the converted which regulates the incoming voltage to the correct value. Since this unit was replaced more than a month ago no more problems have been reported and the problem has likely been solved.
Apart from the first time the problem occurred, relatively little time was lost on subsequent occasions with the exception of one case where the observer tried to solve the problem himself. This actually caused more problems which is included here in the total down time.
During observations with FIES continuous problems were encountered centering targets on the fiber. This was mainly due to errors by the observers not following the precise and detailed instructions provided. However, the way the system works is not very transparent and also allows the errors to be made without any warning and we are working on making the system more fail proof.
Thomas Augusteijn 2008-11-14