I was born 1950 in Svalöv, a small rural village in the south of Sweden. My parents owned a shop selling stationery, newspapers, toys, and similar. My father was also a portrait photographer and I spent many hours watching him at work in the darkroom. At the age of seven my fascination with space and astronomy was sparked by the news of Sputnik 1, the first artificial satellite, being launched into space. I read everything I could find about space. With my older sister I often spent summer holidays at our grandparents’ summer house. My grandfather was a highly skilled craftsman who taught me to use various hand tools. I still enjoy working with my hands, designing and constructing things.
As a teenager my reading interests broadened and I discovered classical music, one of the great passions in my life. But I still spent many late evenings in our back yard observing the planets with a small telescope and hunting for Messier objects, or experimenting with astrophotography.
In 1969 I began studies in mathematics and physics at Lund University. My plan at that point was to become a meteorologist. However, a short optional course in astronomy, given by staff from Lund Observatory, changed my mind. From 1972 to this day I have been associated to Lund Observatory, that is the astronomy department at Lund University. I received my PhD in astronomy in 1980, became a research associate the same year, senior lecturer in 1987, and professor in 2000. Between 1998 and 2004 I was the director of Lund Observatory. I retired in 2017 but am currently employed part-time by the university.
My career in astrometry was inspired by the hundred-year-old Repsold meridian circle at Lund Observatory, which fascinated me from the moment I first saw it. I declared to my professor, Tord Elvius, that I wanted to work with astrometry for my PhD. From today’s perspective of strictly regulated postgraduate education, it seems remarkable that such a quaint choice of subject could be approved. The Lund meridian circle had not been used for decades, no-one at the department was actively working in the area, and the whole subject of (optical) astrometry was generally considered old-fashioned and unpromising. A few of my seniors did try to involve me in more fashionable projects, including ultraviolet observations of active galactic nuclei and solar spectroscopy, but none of these seemed very satisfactory to me. In my spare time I tinkered with the old meridian circle, hoping to get it in working order, or at least to better understand the beauty of its design. At this point my career might have taken a very different direction, had it not been for an unlikely coincidence in time and place. The Danish astronomer Erik Høg had just returned to his native country after 15 years at the Hamburg Observatory, where he had developed a new technique for meridian observations, photon-counting astrometry. Working at Copenhagen University Observatory, within 100 km of Lund, he was therefore a world-leading expert in precisely the field that I had just chosen for my thesis! Meetings were arranged, and Erik became my de facto PhD supervisor, colleague, and friend. In 1976 he introduced me to the Hipparcos project and the following year I joined him as a member of the space astrometry study team set up by the European Space Agency (ESA). I contributed numerous, mostly unpublished studies of different aspects of the Hipparcos mission, including the optics, scanning law, accuracy estimates, and scientific data processing. The mission was adopted by ESA in 1980, after which I became a member of the new Hipparcos Science Team. This was chaired by the newly-appointed Project Scientist, Michael Perryman.
In parallel with this I completed my PhD thesis in early 1980. It consists of a heterogeneous collection of papers dealing with meridian observations of major planets, atmospheric limitations of narrow-field astrometry, a comparison of methods for precise image location, and the detection and measurement of double stars with an astrometry satellite. The subjects reflect my reorientation towards space astrometry a few years earlier.
The appointment of Michael Perryman as the scientific leader of the pioneering space astrometry project was the beginning of an intense development phase. An increasing number of people across Europe were involved. Over a period of 16 years Michael skillfully navigated us through many difficulties right up to the triumphant conclusion of the project in 1997.
Already by 1993 it was clear that Hipparcos was going to be a great success. Proposals were submitted to ESA for more ambitious astrometry missions, taking advantage of the much more efficient CCD detectors. This eventually became the Gaia project, approved by ESA in 2000 and launched in 2013. From the very beginning of the project I took part in its development as a member of various study teams and by writing technical notes on various issues, in particular related to the astrometric data analysis and astrometric accuracy. During much of this time I collaborated closely with Michael Perryman.
It must be a great satisfaction for any scientist to be able to follow a long and complicated project from its early conception to roaring success. I have had the privilege to follow and work with two immensely successful space astrometry missions, and for this I am extremely grateful.
29 September 2022 Hong Kong
