Notice on SUMER Coordinates

Please note that until approx. 15.May.96 the coordinates were calculated with a step size value of 0.38 arcsec, while afterwards the more precise value 0.3763 arcsec was applied. Therefore, in the first months, the given coordinate values have to be reduced by approx. 1 %.

After SOHO was recovered and SUMER started scanning again, the step size was set to 0.3747 arcsec.

In FITS files, pointing is given in Solar coordinates, no matter if the FITS files are processed from raw telemetry or CD-ROMs, or if they are called "x-/y-coo" or "y-/z-coo": the first value gives the Solar east-west coordinate and west is positive; the second value gives the Solar north-south coordinate and north is positive.

In CD-ROM restore files (available on SUMER machines at MPAe only), pointing is given as transmitted in the SUMER science header: the first value gives the east-west coordinate and west is positive as in FITS files; the second value gives the north-south coordinate and south is positive, because SUMER is fixed "head-down" on SOHO.