Astrometry correction due to a thermoelastic drift

Rationale

Observations performed at the end of the Solar Aspect Angle (SAA) range (the so-called 'warm' attitude range, SAA in the 110 to 119.2 interval) could present a degradation of the pointing performance due to thermo-elastic effects. These would include a larger APE and a pointing drift.

We have performed a study on this effect by calculating the Z-axis offset for a set calibration observations. While fot STR2 temperatures below -15C the median offset presents a certain scatter around zero, for higher temperatures the behaviour of the Z-axis offset diverges. We have derived a linear correlation between the STR2 temperature and the Z-axis that aims at correcting the effect of such a thermoelastic drift.

STR2temp_vs_offset.png

We have created an script

warmbetaAPE.png

Please note that Avoiding observations performed in STR switch-over periods, those indicated in http://herschel.esac.esa.int/twiki/bin/view/Public/StrSwitchOversAndSvvResets

In order to

-- Pilar Esquej - 2016-12-01

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Topic revision: r2 - 2016-12-02 - PilarEsquej
 
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