All modes require an input image which is used to extract the position angle of the observation, e.g., for ESAS processing and MOS1 the file mos1S001-fovimt.fits, produced by cheese, can be used.
Mode=1 – a modified FITS region file is used to input the region information. The region file should have the following columns: SHAPE(16A), X(4E), Y(4E), R(4E), ROTANG(4E), COMPONENT (iJ, typically=1). For SHAPE=CIRCLE values, the R is the radius, but for SHAPE=ELLIPSE, the RADIUS is the semimajor and semiminor axes in the 2 elements of that column. Editing of the file can be done with the FITS file viewer fv. The values for the R column should be in arc minutes while the values for the ROTANG column should be in decimal degrees. Deriving these parameters can be done through ds9 and creating the desired regions and then looking at the region information. Currently only circular and elliptical regions are supported. These files are created by cheese and other SAS tasks and if they are created by cheese have the default name form: mos1S002-bkgregtsky.fits.
Mode=2 – an ASCII region file is used to input the region information. The input are in free format with the order of [shape RA Dec Radius] for circular regions and [shape RA Dec Semimajor Semiminor Rotang] for elliptical regions. While these ASCII files contain some of the same information as their FITS mode=1 counterparts, they must not have 'placeholder' extra values as an analog to the 4E vector columns in the FITS versions.
Mode=3 – Input is all on the command line and output is to the screen. Like the mode=2 values, for circular regions enter shape RA Dec Radius as parameters, and for elliptical regions enter shape RA Dec Semimajor Semiminor Rotang.
c.f. XMM ESAS cookbook for examples of each.
