Some contributions related to star positions, exoplanets, and recreational mathematics
My career has been as a scientist with the European Space Agency, leading the development of astrometry (the measurement of accurate star positions) from space. I was Project Scientist for the pioneering Hipparcos space astrometry mission, from its adoption by ESA in 1980 to its completion and catalogue publication in 1997, including overall responsibility for the project after launch. As one of the co-originators of the Gaia mission in 1993, I was the mission's study scientist until its acceptance by ESA in 2000, and subsequently its Project Scientist until my retirement from ESA in 2008.
Today, I am taking great pleasure in seeing the spectacular progress of the Gaia mission as it unfolds, and reading about its remarkable scientific results. Starting in 2021, I have been writing these summaries of some of the advances in astronomy flowing from it. They are a look back at what this long journey of space astrometry has achieved, and written in a form that I hope will be reasonably accessible to those not so deeply involved. And I have been interviewing some of the scientists and project leaders involved in these two space missions...
Most recent essays (weekly) [see the Gaia essays page for the article link]:
04 Dec 2023 Gaia essay 153. The solar motion
27 Nov 2023 Gaia essay 152. M dwarfs and the Jao gap
20 Nov 2023 Gaia essay 151. The Hyades main sequence
13 Nov 2023 Gaia essay 150. Convection - and the mixing length
Most recent interviews (irregular) [see the project/science interview pages for the audio link]:
02 Nov 2023 Ulrich Bastian talks about "PPM, Hipparcos-Tycho, and Gaia"
12 Jul 2023 Frédéric Faye talks about "Gaia: industrial system engineering" [in two parts]
13 Oct 2022 Lennart Lindegren talks about "The Hipparcos mission"
05 Sep 2022 Claus Fabricius talks about pre-Hipparcos astrometry, and Gaia validation [in two parts]