The task rgscombine can be used to combine two or more spectra from one or more sources
that have been produced by rgsproc for the same order
into a single spectrum and to calculate the corresponding
combined response matrix. In order for the task to run, the
component spectra must have been calculated by rgsproc on a fixed
wavelength grid (the rgsproc default). This method maintains proper
counting statistics and has replaced
earlier techniques. Refer to the SAS web pages section on individual
tasks for more information
(http://xmm.esac.esa.int/sas/current/doc/rgscombine/index.html).