Abstract. The XMM-Newton Observatory is a cornerstone mission of the European Space Agency's Horizon 2000 programme, and is the largest scientific satellite it has launched to date. This paper summarises the principal characteristics of the Observatory which are pertinent to scientific operations. The scientific results appearing in this issue have been enabled by the unprecedentedly large effective area of the three mirror modules, which are briefly described. The in-orbit performance and preliminary calibrations of the observatory are briefly summarised. The observations from the XMM-Newton calibration and performance verification phase, which are public and from which most papers in this issue have been derived, are listed. The flow of data from the spacecraft, through the ground segment, to the production of preliminary science products supplied to users is also discussed.

Abstract. The XMM-OM instrument extends the spectral coverage of the XMM-Newton observatory into the ultraviolet and optical range. It provides imaging and time-resolved data on targets simultaneously with observations in the EPIC and RGS. It also has the ability to track stars in its field of view, thus providing an improved post-facto aspect solution for the spacecraft. An overview of the XMM-OM and its operation is given, together with current information on the performance of the instrument.

We report the first high-energy survey catalog obtained with the IBIS gamma-ray imager on board INTEGRAL. The analysis has been performed on the first-year Core Program ISGRI data comprising both Galactic Plane Scan and Galactic Centre Deep Exposure pointings for a total exposure time exceeding 5 Ms. This initial survey has revealed the presence of ∼120 sources detected with the unprecedented sensitivity of ∼1 mcrab in the energy range 20-100 keV. Each source is located to an accuracy between 1Ј and 3Ј, depending on its brightness. The outstanding IBIS capability to locate soft g-ray emitters has allowed us to identify most of the detected sources with already known Galactic X-ray binary systems, while 28 of the objects are of unknown nature.

Abstract. The imaging Compton telescope COMPTEL aboard NASA's Compton Gamma-Ray Observatory has opened the MeV gamma-ray band as a new window to astronomy. COMPTEL provided the first complete all-sky survey in the energy range 0.75 to 30 MeV. The catalogue, presented here, is largely restricted to published results. It contains firm as well as marginal detections of continuum and line emitting sources and presents upper limits for various types of objects. The numbers of the most significant detections are 32 for steady sources and 31 for gammaray bursters. Among the continuum sources, detected so far, are spin-down pulsars, stellar black-hole candidates, supernova remnants, interstellar clouds, nuclei of active galaxies, gamma-ray bursters, and the Sun during solar flares. Line detections have been made in the light of the 1.809 MeV 26 Al line, the 1.157 MeV 44 Ti line, the 847 and 1238 keV 56 Co lines, and the neutron capture line at 2.223 MeV. For the identification of galactic sources, a modelling of the diffuse galactic emission is essential. Such a modelling at this time does not yet exist at the required degree of accuracy. Therefore, a second COMPTEL source catalogue will be produced after a detailed and accurate modelling of the diffuse interstellar emission has become possible.

Abstract. The JEM-X monitor provides X-ray spectra and imaging with arcminute angular resolution in the 3 to 35 keV band. The good angular resolution and the low energy response of JEM-X plays an important role in the identification of gamma ray sources and in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture instrument consisting of two identical, coaligned telescopes. Each of the detectors has a sensitive area of 500 cm 2 , and views the sky through its own coded aperture mask. The two coded masks are inverted with respect to each other and provides an angular resolution of 3 across an effective field of view of about 10• diameter.