The COMPTEL instrument, the product of a collaboration of four institutes led by MPE Garching, and launched on NASA's CGRO in 1991, is still working extremely well and continues to yield a high level of scientific output from observations in the 1-20 MeV band. The Division's interests cover gamma-ray bursts, pulsars, black hole candidates and Active Galactic Nucleii (AGN).
SAX, the Italian/Dutch X-ray astronomy mission launch-ed in April 1996, carries the focal plane imaging gas scintillation proportional counter developed in the Division. This instrument is working extremely well and provides SAX with a unique observational capability below 1 keV, with regard to grasp and spectral imaging, important attributes for a wide range of astrophysical investigations. SAX will be operated for 2 years, with the possibility of a further two.
The investigation of superconducting tunnel junctions for application as a photon detector in X-ray astronomy, and more recently in UV and optical astronomy, has continued most successfully with the demonstration of optical single photon- counting with colour discrimination, bringing a high-speed, photon-counting camera with good, intrinsic spectroscopic properties closer to reality. The first experimental paper, published in Nature in May 1996 with an accompanying 'News & Views' article entitled 'Towards the ideal detector', sparked off a flurry of professional and popular interest, announcements of other groups embarking on similar research, and approaches for technical and scientific collaborations. A small-format, ground- based, optical camera is under development, and a proposal for an instrument based on this technology for HST is being considered.
Scientific results from the Hipparcos mission are now coming on line from the scientists participating in the project, and the PIs who submitted proposals to use Hipparcos data back in 1982. Insight into the impact that this carefully designed and coordinated mission is likely to have in astrophysics is apparent from already-published work, led by the Hipparcos project scientist in the Division, on the structure of the Hertzsprung- Russell Diagram, and on upper limits to the masses of planetary companions to the stars 47 UMa, 70 Vir and 51 Peg.
Many scientific observations were made by staff members at the STScI, at the ST-ECF and within the Division proper using HST and other space-based and ground-based telescopes. The steady stream of publications continues from the staff at the IUE Observatory, both from original observations and from archived data, the latter indicating the lasting value of preserving a unique scientific resource.
The increasing level of scientific output from the ISO-SOT in the first year of ISO operation is noteworthy, given that the opportunities and time for science had been so limited over the past years due to the concentration of all efforts on the readiness for operations. The contribution of the team to the first scientific results from ISO appearing in the ISO-dedicated issue of Astronomy & Astrophysics (November (II) 1996) is very encouraging.
The following account of the Astrophysics Division's work in 1995-96 is intended to give some perspective of the breadth and quality of the activities of the staff, both in their functional and research work. It is not aimed at completeness.
SP1211