Performance of a mirror shell replicated from a new flight quality mandrel for eROSITA mission

Focusing mirrors manufactured via a galvanic replication process from negative shape mandrels is the chosen solution for the eROSITA X-ray mission. Media Lario Technologies (MLT) is the industrial enabler for manufacturing (in collaboration with the Max Planck Institute (MPE) and the German Space Agency (DLR)) of the Optical Payload for eROSITA - including the flight quality mandrels. Mandrels manufacturing holds a crucial role in the process of fabrication of the optics. In fact, the shape accuracy and the roughness of the replicated mirrors are strongly affected by the starting quality of the mandrel. For the e-ROSITA mandrel production an evolution of the approach used for the manufacturing of past mission mandrels (JET-X, XMM) have been developed. The low energy angular resolution of the eROSITA mirror payload needs to be 15 arcsec HEW or better; and at 8.05keV the angular resolution needs to be 20 arcsec HEW or better. Replicated mirrors with performance in this range for the low energy radiation have been obtained in the past by using mandrels that have superior geometrical shape accuracy. A proprietary multistep surface finishing process has now been developed for reaching the aggressive performance requirements demanded by the mission. The status and the metrology of the eROSITA series mandrels manufactured so far, by using the advanced polishing process, are presented. In the paper, the x-ray performance of mirror shells (as measured at MPE PANTER facility) replicated from a flight quality eROSITA mandrel, are reported.