RMF instructions

• The user may use a grade range 0, 0-4 or 0-12, as required, along with the corresponding RMF: sxt_pc_mat_g0.rmf, sxt_pc_mat_g0to4.rmf or sxt_pc_mat_g0to12.rmf, respectively.
• The SXT pipeline filters in grades 0-12. Additional grade filtering can be done using xselect. The user may decide, based on the scientific goal, source properties and data quality, which grade range should be used. A general suggestion is, grade 0-12 may be more suitable for harder and fainter sources, for which the highest spectral resolution is not needed, and grade 0 may be more suitable for softer and brighter sources, for which the maximum spectral resolution is required."