A portrait of the astronomer-engineer and humanist, Pierre Fedou

After reading a brief article in Science et vie (Science and life) on his idea of ‘Pulp Vision’, an amusing scroll through his personal yet professional site, and a reading of his blog where one can admire both photos of motorbikes and images of the visual display panel installed on a telescope we decided to meet the author to find out more about his scientific projects. As we ask to meet with him, he apologises for his late reply: “I’m at the top of a mountain for an observation!” We meet with Pierre Fedou, astronaut-engineer and humanist.


After reading a brief article in Science et vie on his idea of ‘Pulp Vision’, an amusing scroll through his personal and professional sites, and a reading of his blog where one can admire both photos of motorbikes and images of the visual display panel installed on a telescope we decided to meet the author to find out more about his scientific projects. As we ask to meet with him, he apologises for his late reply: “I’m at the top of a mountain for an observation!” We meet with Pierre Fedou, astronaut-engineer and humanist.


Away from the city lights, near Meudon, is a former royal chateau topped by a beautiful metal dome, 18 metres in diameter. At its foot, our host Pierre Fedou explains how, in 1876, the astronomist Jules Janssen created the Meudon Observatory on the ashes of the chateau – a building that used to belong to the great Dauphin (son of Louis XIV), and burnt to the ground during the French revolution.


We then move toward the offices in the annex of the building to see a construction that is just as surprising: the equatorial platform.

The Meudon chateau and its cupola that shelters the the world’s third largest ‘large telescope’ (‘Grande lunette’). The objectives measure 0.83m and 0.62m (aperture) and 16m (lens)*1 © Laurence Bianchini/MyScienceWork
Meudon castle

We learn that Pierre Fedou, has a number of strings to his bow apart from being trained as a level 2 guide at the Meudon Chateau. Although his business card presents him as a ‘Fringe tracker’, his activities are concentrated in four main areas. To begin with, Fedou is an astrophysics instrumentalist attached to the CNRS. His activities relate to the development of telescopes for two projects: OHANA in Hawaii and Gravity in Chili.

The first project, called OHANA*2 is a key element in the competition between Europe and the United States to construct the world’s largest telescope. The ‘size’ of a telescope refers specifically to the diameter of its primary mirror. The greater the size of this mirror, the more photons it captures. A large (and perfectly flat) telescope can thus attain a higher level of precision and make observations at a greater distance.

The United States is currently constructing the TMT (Thirty Meter Telescope), spanning thirty meters, while Europe is starting to build the E-ELT (European Extremely Large Telescope) with 42 meter span. The average diameter of a telescope is presently 10 metres, yet a telescope capable of revolutionising the observation of far off galaxies would require a diameter of 100 metres. To use such a mirror however it must be of a quasi-perfect flatness (the acceptable deviation is only 1µm/m) – a factor that severely limits the diameter of the TMT and E-ELT telescopes. In approximately 10 years, OHANA will be in direct competition with these telescopes. The Hawaiian site will have an arsenal of 8 standard size telescopes that, using interferometry, will allow the reconstruction of an image equivalent to that from an equivalent telescope whose primary mirror is one kilometre in diameter. The number of photons captured is increasing due to the growing number of telescopes and the growing size of mirrors. Thus the number of points per pixel is also increasing.

Imagine the simple case where only two telescopes are linked by interferometry. If the two are separated by a distance of 200 metres – in a direction perpendicular to that linking the two telescopes – the spatial resolution is equivalent to that obtained by a primary mirror with a diameter of 200 meters. In November 2011, the equivalent diameter obtained will be 163 meters – the distance between the Gemini North and the CFHT telescopes.


Artists conception of a black hole at the centre of our galaxy (c) Didier PRIX – Fotolia.com
Black hole picture


The second project, called Gravity (General Relativity Analysis via Vlt InTerferometrY)*3, aims to observe a supermassive black hole known as Sagittarius A* or Sgr A*, the mass of which is estimated to be 4 million times that of our sun. Since 2008, the Sgr A* black hole has been observed at the heart of our galaxy, the Milky Way [1], where its mass contributes in large part to the stability of our galaxy. The objectives of the Gravity project are two fold. The first is to observe phenomena taking place on the edge of the black hole, for example the rotation of stars around it, followed by their absorption into the black hole; and two, to probe the theory of Einstein’s general theory of relativity in a strong field.  Gravity will be installed in the VLTI laboratory. It will work by recombining beams of light from an average of four telescopes via a clever manipulation of mirrors. The beam of light measured must first be stabilised (the optical aberrations of the signal that travelled through the atmosphere must be corrected). The technique used for this is called ‘adaptive optics’ (AO). Through clever use of deformable mirrors, this technique allows the correction of wavefront distortions affecting an optical signal.

Originally developed for military ends, AO was largely used in astrophysics and, more recently, in ophthalmology. In astrophysics, the distortions of light beams coming from space are due to inhomegeneities in the atmosphere that have a different refractive index in different places. In geometrical optics, the refractive index changes the path (the distance) covered by a light beam. Schematically, the beam is slowed down by a high refractive index. Its speed, however, remains constant: it is the path travelled that increases. This accounts for the ‘twinkling’ of stars – an effect introduced by the atmosphere. In ophthalmology however, the ray of light is distorted by the vitreous humour, a mass - composed 99% of water - that keeps the retina in place against the walls of the eye. Clinical applications have been developed using AO to generate very precise images of the retina and all the elements at the back of the eye (blood vessels, rods and so on) [2].


Despite his passion for astronomy, Pierre Fedou also has his feet firmly on the ground. He has a project in the pipeline for a publishing house that aims to publish a paper version of scientific theses. He also does coaching, and gives advice on strategies for how to succeed. For three years now, his activities outside of the scientific field are open towards all who show an interest. In contrast with a number of supervisors of conventional theses, he is as concerned by the state of their mental health as he is by the progress of the thesis writing. According to Pierre Fedou it is important to ensure the happiness of individuals before demanding anything of them. Fedou has been asked by universities to write a text on the theory of the ‘desperation of the thesis writer’. We just had to make the parallel with Jorge Cham, creator of the famous comics Piled Higher and Deeper also known as PHD Comics. This comic relates the (mis)adventures of doctoral candidates and their chaotic relationship with their thesis directors, the incomprehension of the family and the precarious nature of the doctoral candidate.


© jorge cham http://www.phdcomics.com/comics/archive.php?comicid=124
PhD Comics


Since 2003, Pierre Fedou has also explored ‘Pulp Vision’ with his colleague Olivier Lai, astro-physicist living in Hawaii and specialist in adaptive optics and interferometry. ‘Pulp Vision’*4 is part of ‘augmented reality’ and would allow the projection, first of an image, then a film, directly onto the human retina. If it one day emerges in the industry, pulp vision would allow the projection of an image in the corner of one’s field of vision and maybe watch a film in a bar without disturbing one’s neighbours. The proof that Pulp Vision is feasible already exists. Pierre Fedou and his colleagues have, by placing their eyes in front of a weak laser, been able see an image not projected onto a screen. The principal of Pulp Vision is based on the technique of adaptive optics - the specialisation of the two astrophysicists who came up with the idea. In this case however, the path of the light beam will only be inversed than that in the case of the retina optic previously introduced. Delayed, the Pulp Vision project will take off again with a series of tests anticipated from the end of the year in collaboration with a team from Limoges.


The adaptive optic now has a number of clinical applications allowing high-definition imagery of the retina. © nyul –Fotolia.com


This is how a new experience came into being - originating from a technique used in astronomy, and quickly noted down within the LESIA (Laboratory for Spatial study and Instrumentation in Astrophysics) research groups. We can trace the trajectory of technologies by looking at Pierre Fadou’s career and the birth of the idea of Pulp Vision worthy of science fiction. These technologies could be implemented in the military domain, research, in daily life and in medicine to modify our habits and our pastimes. To note that a number of objects that we use in daily life have a similar, forgotten history including the microwave, the World Wide Web, even Velcro!

*1 The concept of the refracting (astronomical) telescope is very different from the reflecting telescope *2 People working on OHANA: Guy Perrin, Astronomist, LESIA-Observatoire de Paris (Paris Observatory) Olivier Lai, Astronomist, Canada France Hawaii Telescope, Hawaii Julien Woillez, Astronomist, Keck Observatory, Hawai’i François Reynaud, University Professor, Université de Limoges. Pierre Fedou, Engineer, LESIA-Observatoire de Paris (Paris Observatory) *3 People working on the GRAVITY project: Guy Perrin, Astronomist, LESIA-Observatoire de Paris (Paris Observatory) Thibaut Paumard, Astronomist, LESIA-Observatoire de Paris (Paris Observatory) Sylvestre Lacour, Astronomist, LESIA-Observatoire de Paris (Paris Observatory) Pierre Fedou, Engineer, LESIA-Observatoire de Paris (Paris Observatory) *4Pulp Vision used to be called the ‘Retina projection through Fourier transformation’.  


Find out more:

1) Interferometric connection of large ground-based telescopes, J.-M. Mariotti, V.  Coudé du  Foresto, G. Perrin, Peiqian Zhao, P.Léna, Astron. Astrophys. Suppl. Ser. 116, 381-393 (1996)

2) A Fibered Large Interferometer On Top of Mauna Kea : OHANA, the OPTICAL HAWAIIAN ARRAY FOR NANO-RADIAN ASTRONOMY, Guy Perrin, Olivier Lai, Pierre Léna, Vincent Coudé du Foresto, Proc. SPIE 4006, 708 (2000), https://www.cfht.hawaii.edu/~lai/OHANA/ohana_spie.pdf

3) Interferometric Coupling of the Keck Telescopes with Single-Mode Fibers, G. Perrin et al., Science 13, 311 (2006), https://science.sciencemag.org/content/311/5758/194.abstract

4) Event-horizon scale structure in the supermassive black hole candidate at the Galactic Centre, Nature 455, 78-80 (2008) 

5) GRAVITY: The AO-Assisted, Two-Object Beam-Combiner Instrument for the VLTI, F. Eisenhauer, G. Perrin, S. Rabien, A. Eckart, P. Léna, R. Genzel, R. Abuter, T. Paumard, and W. Brandner, https://arxiv.org/abs/astro-ph/0508607

6) Adaptive Optics Retinal Imaging: Emerging Clinical Applications, P. Godara, A. M. Dubis, A. Roorda, J. L. Duncan, and J. Carroll, OPTOMETRY AND VISION SCIENCE, vol. 87, PP. 930–941, (2010), http://chung.vision.berkeley.edu/Pubs/Carroll%20review%20Dec2010OVS.pdf