Focussing performance

This web page is dedicated to make a monitoring for focus observations (in all three directions). To check the behavior of the subreflector/hexapod and ambient temperature. The elevation is not considerate due than there are already compensation and previous analisys show a one magnitude order difference with the temperature. Data since 2008 until end of August 2010 is considered. A special case is SABOCA data because during the current year we added the map focus option for the bolometer observation, the data produced with this command also was added in this analysis. It improve the final data distribution. The form above gives the absolute focus correction selecting the variable to compare (ambient or subreflector temperature ), the FrontEnd and the three different axis. The current automatic focus correction already implemented just considerate Z for LABOCA, HET345 in the case for facility instruments.
The plots below show the relation between absolute offset and temperatures for the different receivers.


The first plot is the absolute offset distribution, where in the case for APEX 1 the values are -0.2, 0.4, 0.25 for X, Y and Z. The second plots show the relation between the absolute offset and ambient temperature, the fit is a polynomial with order 2 in all the case. The third plots show the relation between the absolute offset and the subreflector temperatures average, the fit in this case is linear.


The information for these plots group is similar than the above, but for the plot between absolute offset and subreflector temperatures only for Z, with red line show the function than Dirk already implemented in the system.


For X and Y in CHAMP690 and SABOCA there are a large data dispersion, the plot distribution in both case are not clear. In Z for both case the data distribution look much better, but there are a big different between the current model and this fit.


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Last update: September 4th, 2010