Gaia/Hipparcos: project interviews


Hipparcos is the first time since Sputnik in 1957 that a major new development in space science has come from outside the United States.

Freeman Dyson (Infinite in All Directions, 1988)

Starting in 2021, I have been recording interviews with some of the people that played a part in shaping the developments of space astrometry. 

These include some of the engineers and managers from the European Space Agency and its industrial teams involved in the Hipparcos and Gaia projects, some of the leading scientists, and just a few of the individuals at the forefront of ground-based astrometry in the years leading up to the move to space. Several others are planned.


Amongst these, it is interesting to hear that two senior people, with key roles in the  development of Gaia, both initially considered that the measurement goals targeted by the mission were not achievable!


My thanks to all those who have taken part, and to Moby for the use of his unreleased track Morning Span in their introduction ( The order below follows the date of the interview.



Gaia... and beyond

Erik Høg (Lolland, Denmark, 1932) joins me for a third time. In our first conversation we talked about his early involvement in ground-based astrometry, and his part in getting the Hipparcos mission optimised and adopted by ESA in the 1970s–1980s. In the second, we talked about his involvement in Hipparcos, from its acceptance in 1980 to completion in 1997, including his ideas for the Tycho experiment. Today, we talk about his contributions to ESA's complex and successful Gaia mission [recorded 9 February].

Erik Høg

2 Jun 2022


00:00 / 51:31

Gaia's Ground Based Optical Tracking campaign

Martin Altmann (Pretoria, S. Africa, 1970) is an astronomer at the Centre for Astrophysics, University of Heidelberg. He leads the Ground Based Optical Tracking campaign (GBOT). Nightly high-accuracy measurements of the Gaia satellite itself, made with various telescopes on Earth, track Gaia's position and velocity. These measurements allow the satellite's position and velocity to be determined, at all times, to around 150m and 2.5 mm/s respectively; data necessary to reconstruct Gaia's star distances and asteroid motions.

Martin Altmann

16 May 2022


00:00 / 49:20

Solar system objects being observed by Gaia

Paolo Tanga (Saluzzo, Italy, 1966) is a senior researcher in planetary science at the Nice Observatory, France. His work on asteroids in our solar system focuses on their formation, their collisional evolution, and properties such as their sizes, shapes, and chemical composition. As the leader of the data processing task on solar system observations, we talk about the large numbers of them being observed by Gaia, and why these results will be so important for our understanding of the formation and evolution of our solar system.

Paolo Tanga

1 May 2022


00:00 / 58:11

Management of Gaia by industry

Vincent Poinsignon (Macon, France, 1958) was, between 2006 and its launch in 2013, the overall industrial Project Manager for the Gaia satellite. His company, Airbus Defence & Space (a division of Airbus), located in Toulouse, southern France, played the central role in the detailed design, manufacture, assembly, testing, and eventually the launch of the Gaia satellite. Vincent joins me to reflect on the engineering and management challenges faced by this extremely demanding space science mission.

Vincent Poinsignon

27 Apr 2022


00:00 / 1:05:53

A scientist's views of the 'Hipparcos years'

Rudolf Le Poole (Delft, The Netherlands, 1942) is an astronomer at the Sterrewacht, the Astronomy Department of Leiden University, in The Netherlands. Rudolf was active in all aspects of Hipparcos: as a member of my Hipparcos Science Team (1981–1997), of the Input Catalogue Consortium, of the FAST Data Analysis Consortium, and someone interested in, and always questioning, many aspects of the instrument design. We talk about these various activities, and his perspectives looking back on the `Hipparcos years'.

Rudolf Le Poole

19 Apr 2022


00:00 / 1:14:23

The socio-economic benefits of Gaia

Leslie Budd (Hayes, Middlesex, 1949) is professor of Regional Economy in the Faculty of Business and Law, at the Open University, Milton Keynes, UK, where he is known for his work on regional and urban economics. He has been involved in studies of the socioeconomic impacts of Brexit, of Spaceport Scotland, and of space exploration, including the benefits of the ESA Exploration Roadmap. He joins me today to talk about how economists can go about quantifying the wider benefits of space programmes like Gaia.

Leslie Budd

11 Mar 2022


00:00 / 44:35

JASMINE, the Japanese infrared astrometry mission

Naoteru Gouda (Osaka, 1960) did his early research in theoretical cosmology, on topics such as structure formation and galaxy clustering. Realising the importance of accurate astrometry in understanding the dynamics and evolution of stellar systems, he joined the National Astronomical Observatory of Japan in 1999. Since then, he has been leading the development of a mission for infrared astrometry, JASMINE. He joins me today to talk about its scientific objectives and technological progress.

Naoteru Gouda

27 Jan 2022


00:00 / 33:25

The Royal Greenwich Observatory pre-Hipparcos

Leslie Morrison (Aberdeen, 1938) was recruited to the Royal Greenwich Observatory by Astronomer Royal Richard Woolley in 1960. He worked in the Meridian Department until his retirement in 1998, contributing to studies of Earth rotation and the international time service. He was involved in the Carlsberg Automatic Meridian Circle, which used principles applied to Hipparcos as well as contributing to the Hipparcos Input Catalogue. He gives an insight into ground-based astrometry in the years before the move to space.

Leslie Morrison

23 Dec 2021


00:00 / 35:33

The Gaia data processing

Anthony Brown (Leiden, 1969) was among the early users of the Hipparcos star catalogue data in the 1990s, stimulating his interest in space astrometry. As part of the working groups preparing for the Gaia data, he became chair of the Data Processing and Analysis Consortium (DPAC) in 2012. He joins me to describe how the enormous pan-European data processing task is structured and coordinated, and about some of the practical and sociological challenges facing the creation of this revolutionary star map.

Anthony Brown

7 Dec 2021


00:00 / 1:09:05

The Hipparcos mission

Erik Høg (Lolland, Denmark, 1932) joins me for a second time. In an earlier conversation we talked about the period leading up to the adoption of Hipparcos in 1980. Today, we discuss the Hipparcos mission, from its acceptance in 1980 to its completion in 1997. We talk about his role in the mission development, and in the preparation for - and the analysis of - the data sent down from the satellite. We also talk about the addition of the Tycho experiment to the baseline mission, and his memories of the satellite launch in 1989.

Erik Høg

27 Oct 2021


00:00 / 45:31