The matrix used should depend on the date of the observation. Following current advice, the matrix DRMPSPC_036 should be used for observations made after mid 1991. The matrix DRMPSPC_06 should be used for observations before that date. These defaults is The latest response matrix. This can be overridden by use of the RESPFILE parameter.
It can also be used to attach an HRI response matrix. This is a single channel matrix, just containing effective areas at a number of different energies. To invoke this mode include the keyword HRI on the command line.