1 Introduction

For ESA's X-ray Multi Mirror (XMM) mission, we have developed a 6 $\times$ 6 cm² monolithic X-ray CCD array (Strüder et al. 1990) with high detection efficiency up to 15 keV, low noise level (ENC $\approx$ 5 e^-) and ultrafast readout. The detector was tailored to the requirements of the XMM telescope performance, concerning angular resolution, collecting area, energy bandwidth and field of view (FoV).

Conceptually the pn-CCD, the heart of the MPE focal plane detector, is a derivative of the silicon drift detector proposed in 1983 by Gatti & Rehak (1984). In the following years the basic concept was modified, simulated and designed in detail by Strüder et al. (1987). N-channel JFET electronics was integrated in 1992 (Pinotti et al. 1993) and the first reasonably working devices were produced in 1993.

The flight type large area detectors were fabricated in 1997 in the MPI semiconductor laboratory, with a sufficiently high yield to equip XMM and ABRIXAS, a German X-ray satellite, with defect free focal plane pn-CCDs (Strüder et al. 1997; Soltau et al. 2000).

The in-orbit commissioning of XMM's scientific payload was completed in the middle of March 2000 - three months after launch; calibration and performance verification terminated in July. Since then, the official observing programme is under way. This contribution summarizes the basic instrument features as previously planned and implemented in orbit to date, as well as their scientifically relevant measured performance in space. We have included orbit data up to September 2000.