Housekeeping Data

By thresholding on the values of different housekeeping parameters using the XRTHK program the User is able exclude unwanted times in the original dataset. XRTHK outputs a list of on/off MJD times which can then be passed into XRTSORT.

A list of the all housekeeping parameters are included later in this document (Appendix 4). The most commonly used parameters (and some suggested values) are :

• MV_ACO - the master veto rate (1-170).
• XACC - the accepted X-ray rate (1-30).
• ASP_QUAL - aspect quality (0-2).

The FTOOL program fv can be used to inspect the housekeeping parameters in the evrate and aspect extensions of the ancillary fits file. fv may subsequently be used to plot one array in a file against another.

For example - the xspokes program uses the satellite roll angle to determine the position of the window support structure on the image. This system can be flawed if an observation has been performed in two sections, with the satellite at different roll angles.

To check the roll angle, start FTOOL program fv and open your _anc.fits file. Select a plot on the aspect extension and use the time and roan_cas parameters as your axis.