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XMM-Newton Science Analysis System


rgssources (rgssources-5.31.1) [xmmsas_20060628_1801-7.0.0]

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Attitude parameters.

The attitude is defined as the pointing direction plus the position- or roll-angle of the spacecraft. It is necessary to define the attitude for rgssources because the task must calculate values for the columns DELTA_DISP, DELTA_XDSP, FOV_PHI and FOV_R, which record the source positions with respect to the attitude.

In the case that filemode=`modify', the attitude is left by default at the value in the previous file. To alter the attitude stored in the file while in this filemode, the parameter changeattitude must be specifically set by the user to `yes'. Assuming that this is done, the attitude can then either be calculated (attstyle=`start', `mean', `median' or `expmedian') or input directly by the user (attstyle=`user', then supply attra, attdec and attapos). The four types of calculation are briefly described as follows:

• attstyle=`start': the attitude at the start of the exposure is used.

• attstyle=`mean': the mean value of the attitude (as sampled in the attitude history file) is used. This value is read from the output file from atthkgen.

• attstyle=`median': the median value of the attitude (as sampled in the attitude history file) is used.This value is read from the output file from atthkgen.

• attstyle=`expmedian': the task attfilter filters the attitude data such that only time values within the exposure duration remain. This task also calculates the usual set of means, medians etc for thsi restricted set of attitude data. With attstyle=`expmedian', rgssources reads the median value of the attitude during the exposure from the output file from attfilter.