The prefixes that were approved by the IAU committee for the initial PSPC catalogs are:
| 1RXS | for the ROSAT Sky Survey |
| 1RXP | for the preliminary PSPC source catalog generated by MPE (1996). |
The RRA consortium has chosen the additional prefixes:
| 1RXH | for the 1998Jun release of the HRI/RRA detection database. |
| 2RXH | reserved for a furture release which will deal with the merging problem |
| 2RXP | for the RRA PSPC catalog; the release to follow that of the HRI. |