ArticlePDF Available

Highlighting the history of French Radio Astronomy. 5: The Nançay Large Radio Telescope

  • University of Southern Queensland (Toowoomba, Australia)

Abstract and Figures

The large radio telescope (Le Grand Radiotélescope) at the Nançay radio astronomy field station of Paris Observatory was built between 1958 and 1966 on the model of the Ohio State University radio telescope, with which a large collecting area was obtained at low cost. The Nançay radio telescope, with a surface area of 7,OOO m², is a meridian instrument which can observe equatorial sources for 30 minutes on each side of the meridian transit of the source. We describe the origin and the construction of this instrument. We also describe the evolution of the focal systems and give an outline of the first spectral and continuum observations obtained with the radio telescope in the wavelength range 6 to 32 cm.
Content may be subject to copyright.
Journal of Astronomical History and Heritage, 13(1), 29-42 (2010).
James Lequeux
LERMA, Observatoire de Paris, 61 avenue de l’Observatoire,
75014 Paris, France.
Jean-Louis Steinberg
Observatoire de Paris (Meudon), Place Jules Janssen,
92195 Meudon Cedex, France.
Wayne Orchiston
Centre for Astronomy, James Cook University, Townsville,
Queensland 4811, Australia.
Abstract: The large radio telescope (Le Grand Radiotélescope) at the Nançay radio astronomy field station of Paris
Observatory was built between 1958 and 1966 on the model of the Ohio State University radio telescope, with which
a large collecting area was obtained at low cost. The Nançay radio telescope, with a surface area of 7,000m
, is a
meridian instrument which can observe equatorial sources for 30 minutes on each side of the meridian transit of the
source. We describe the origin and the construction of this instrument. We also describe the evolution of the focal
systems and give an outline of the first spectral and continuum observations obtained with the radio telescope in the
wavelength range 6 to 32 cm.
Keywords: radio telescope, radio interferometer, Nançay, radio astronomy, incoherent scatter
Radio astronomy in France started after WWII with
small instruments, mostly solar, at the Physics Lab-
oratory of the École Normale Supérieure and at the
Institut d’Astrophysique in Paris (see Orchiston and
Steinberg, 2007). Thanks to the availability of two
7.5-m Würzburg antennas taken from the Germans, the
group at the École Normale Supérieure began galactic
radio astronomy in 1954 (Orchiston et al., 2007).
Meanwhile, the group at the Institut d’Astrophysique
built a 2-element interferometer at the Haute Provence
Observatory which was used between 1959 and 1967
to catalogue radio sources at 300 MHz (ibid.). But
radio astronomy then ceased at the Institut d’Astro-
physique, and the interferometer was dismantled.
In 1953, a field station was established at Nançay,
190 km south of Paris, by the École Normale Supér-
ieure, and the radio astronomy group moved to the
Meudon site of the Paris-Meudon Observatory the
following year. In 1955, two Würzburg dishes located
at Marcoussis, south of Paris, were transferred to
Nançay and mounted equatorially on carriages which
could be moved along a 1,480m long E-W, 6m wide,
railway track, and along a similar 380m long N-S
track. This variable-baseline interferometer became
operational in 1959, and operated in the continuum at
1,420 MHz (details are in Orchiston et al., 2007). A
169 MHz solar interferometer was put into operation at
Nançay in 1956, and a small 3cm solar interferometer
which was moved earlier from Marcoussis to Nançay
was enlarged in 1958 (see Orchiston et al., 2009).
Elsewhere in the world large single-dish radio
telescopes and interferometers were being erected for
galactic and extra-galactic studies at about this time.
For example, in England the Jodrell Bank 76-m Mark I
Radio Telescope was completed in 1957 (Lovell,
1968; 1973), and in Australia the 64-m Parkes Radio
Telescope and the Mills Cross at Hoskinstown near
Canberra were completed in 1961 and 1965 respect-
ively (see Robertson, 1992; McAdam, 2008). The
Cambridge University radio astronomy group was also
busy building interferometers (e.g. see Scheuer, 1984;
Smith, 1984). The period was favourable for large
projects in France, which was under the leadership of
General Charles de Gaulle, and it is natural that the
radio astronomers there were dreaming of a large in-
strument for non-solar work. This eventually material-
ized as the Nançay ‘Grand Radiotélescope’ (see Figure
1). In this paper we investigate the origin and devel-
opment of this instrument.
The French group at the École Normale Supérieure
and Observatoire de Paris-Meudon had considerable
experience in radio interferometry. As early as 1952
solar fringes were obtained at 3cm by Jacques Arsac
and Jean-Louis Steinberg, with the latter proudly
announcing “I think we are the first.” (Steinberg, 1952;
our translation).
Several solar radio interferometers
were subsequently installed at Marcoussis, and later at
Nançay (Pick et al., 2010). It is not surprising, there-
fore, that at the beginning of 1955 some members of
the group proposed to build a large interferometer for
non-solar studies, consisting of two 25-m diameter
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
altazimuth-mounted antennas, similar to the Dwing-
eloo Radio Telescope (see Van Woerden and Strom,
2007), but movable on E-W and N-S railway tracks.
The project was unanimously accepted by the radio
astronomy group and co-signed by its head, Jean-
François Denisse, and by Steinberg who was still at the
École Normale Supérieure (Denisse and Steinberg,
1955). The main science driver was to observe the
21cm line of interstellar atomic hydrogen, discovered
in 1951 (Ewen and Purcell, 1951; Muller and Oort,
1951), and the scientific reason for an interferometer
was as follows (Denisse and Steinberg, 1955; our
At present, the major problem is to obtain a better reso-
lution in order to solve the problems of structure [of the
radio sources] … Since 1946, interferometers have been
used in England and in Australia, with two or more
antennas on a rather long baseline. Provided that the
distance between the antennas can vary in a quasi-
continuous way, a two-antenna interferometer is in prin-
ciple equivalent in resolving power to a continuous an-
tenna with the same total length.
However, at the beginning of 1956 Denisse came up
with new ideas when he compared the interferometer
with two other options:
(1) a fully-steerable paraboloid, which was rejected on
the grounds that “… given the required surface quality
[for observing at 21 cm] and the present technical
possibilities, one can only build for a reasonable price
dishes with a surface smaller than about 900m
diameter of about 30 metres) …; and
(2) “… a [fixed] parabolic mirror illuminated by a flat
mirror movable around a horizontal axis: this is a
meridian instrument, less versatile than the other one,
but which can be built with a much larger surface area
at low cost. (quotations are cited by Darmon, 1981: 42;
our translations).
One argument against the interferometer was that
… taking into account the structure of the ground in
Nançay (sand + clay), the cost of the railway track is a
significant part of the total cost of the project which is
more than 500 million [old] francs (cited by
Darmon, 1981: 43; our translation).
This sum was equivalent to about €10 million in
This new railway track, with concrete found-
ations, was judged necessary to support the heavy 25-
m antennas on their carriages, but the argument was
rather weak because the problem of foundations was
the same for any type of radio telescope. Moreover,
the reservations expressed about steerable paraboloids
seem odd since the Jodrell Bank Radio Telescope was
almost completed and the Australians had decided to
build the Parkes Radio Telescope. A better reason—
which was difficult to acknowledge officially—was
that French industry was unable or unwilling to build
high-precision steerable paraboloids (even though this
was possible in other countries), but the radio tele-
scope simply had to be built in France given the politi-
cal climate at the time.
Meanwhile, the scientific objectives had also chang-
ed. Denisse was impressed by the results obtained on
distant galaxies with the 5-m Hale Telescope on Palo-
mar Mountain, and in particular by Baade and Min-
kowski’s (1954) identification of Cygnus A with a
faint, distant radio galaxy, and he wrote:
[Cygnus A] is at a distance of 200 million light years.
This radio source is more than 1,000 times stronger than
most of the other radio sources in which similar objects
are certainly present: so on average they must be locat-
ed 30 times further away, i.e. at 6 billion light years.
This conclusion is also confirmed by the fact that no
remarkable optical objects can be seen in the direction
of even very intense radio sources, so one must expect
that most of them are located beyond the range of large
telescopes. (Denisse, 1958: 2; our translation).
Then he went on to say that it would be of great
importance to obtain the distances of these sources,
and that the only direct method for this would be to
observe the 21-cm hydrogen line, which had recently
been discovered in absorption in Cygnus A (Lilley and
McClain, 1956). Thus, “The very large radio tele-
scope which will be constructed at Nançay field station
was conceived in order to calibrate the radio universe
Figure 1: Aerial view of Le Grand Radiotélescope at Nançay.
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
...” (Denisse, 1958: 3; our translation).
Curiously, Denisse did not explicitly mention obser-
vations of the hydrogen line in emission in galaxies,
which were to become the main target of the Nançay
radio telescope; but H-line observations had been
made of only a handful of external galaxies at that
time, and presumably he thought that it would be
easier to detect the line in absorption. Then he pro-
ceeded to say that a very large collecting surface was
needed for sensitivity, and also in order to limit con-
fusion when observing faint sources. Confusion was
then considered a major topic, being the subject of
intense debate between the Cambridge group and
Mills’ team in Australia in regard to radio source
counts and their cosmological significance (e.g. see
Mills, 1984; Sullivan, 1990).
The two-element meridian radio telescope built be-
tween 1956 and 1963 by John D. Kraus (1910–2004)
and his students at the Ohio State University Radio
Observatory was taken by Denisse as a model for the
Nançay instrument, because it had a large surface area
and had been constructed for a modest cost. This
instrument (Kraus, 1986: 86-88) consisted of a fixed
curved E-W reflector 110m wide and 21m high, illum-
inated by a tiltable flat E-W reflector 104m wide
and 31m high located to the north. The two reflectors
were joined by a flat conducting ground plane, the
distance between the mirrors being 153m. Two 1,415
MHz rectangular fixed horns, for observations in the
switching-position mode, were placed at the focus of
the curved mirror, 18m from its apex. The dimensions
of these beams, defined by diffraction, were 40 N-S
and 8 E-W at this frequency, and they were separated
by 40. The Ohio radio telescope was used for a con-
tinuum survey of the whole accessible sky at 1,415
MHz, and later for a Search for Extra-Terrestrial Intel-
ligence (SETI) with a single horn feed which was able
to track a source. This novel radio telescope was
dismantled in 1998.
Denisse succeeded in convincing his colleagues to
adopt this concept rather than the interferometer.
Later interviews with several French radio astrono-
mers point to a perceived problem with interferometry
which may have played a part in this change of heart:
the need to calculate a Fourier transform in order to
obtain an image from observations with a variable-
baseline interferometer. For example, Arsac said:
For [radio] interferometry one used Fourier trans-
forms as in optics. Before computers, there was a room
at the Institut d’Optique on Boulevard Pasteur in Paris,
where ladies were computing Fourier series by hand all
Prior to 1958, it was not easy to do interferometry.
In 1959, I fought to obtain a computer for the Observa-
tory. This computer [an IBM 650] was purchased and I
headed the Computing Centre at the Paris Observatory
until 1965. On the other hand there was also a theo-
retical problem with the [mathematical validity of the]
Fourier transform. The theory of distributions outlined
by [Laurent] Schwartz at this time allowed us to solve
the problem of the Fourier transform. (cited in Darmon,
1981: 44-45).
Remember that these discussions were taking place in
1956, when these problems had yet to be solved.
The choice of a large Kraus-type French radio tele-
scope was approved by the Comité de Direction de la
Station de Nançay at a meeting on 29 June 1955.
Since the Chairman of this Committee also happened
to be the Directeur Général de l’Enseignement Supér-
ieur—who headed a large part of publically-funded
research in France—this decision was seen as an
official endorsement, and the project could begin.
It is interesting to note that the idea of a large
interferometer was not completely abandoned since
the Comité de Direction also recommended that a
large steerable antenna operating at decimetre wave-
lengths be built, which would allow very long baseline
interferometry (VLBI)
and could be used together
with the other new radio telescope at Nançay as an
interferometer in order to obtain a better resolving
power in the N-S direction. This did not materialize
because at its meeting on 14 May 1958 the Comité
recommended that
this construction should be replaced by a relatively
cheap increase in the surface area of the two [Würz-
burg] antennas … [at Nançay, which function as] an
interferometer on a railway track: [and] the sum of 4
million francs [equivalent to 65,000 Euros] is proposed
for the 1959 budget in order to carry out this trans-
formation. (Comité …, 1958; our translation).
Needless to say, this plan was never carried out.
Meanwhile, the idea of using the large Nançay Radio
Telescope and a moveable 40-m antenna was revived
by French radio astronomers in 1968 (Blum, 1968: 9),
but once again without success.
Figure 2: Principle of the Nançay large radio telescope:
elevation (top) and ground plan (bottom).
The plan was to build a French radio telescope model-
led on Kraus’ instrument (see Figure 2), but on a con-
siderably larger scale. The mirror would be a portion
of a sphere 300m wide, 35m high and of 560m radius,
while the tiltable plane mirror would be made of ten
20m × 40m elements in parallel, giving a surface
200m wide and 40m in the other direction. Both sur-
faces would be made of metallic mesh. An important
change with respect to the Ohio design was that the
tiltable mirror would be located not far from the centre
of the sphere (actually 460m from the surface) and that
the plane would be somewhat distorted on the E-W
edges, by displacing slightly the axes of the two ex-
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
Figure 3: Two 10m-wide elements of the fixed mirror, which
were assembled on the ground, are hoisted together.
treme elements on each side with respect to the axes of
the six central panels. This configuration was calcu-
lated by Arsac and François Biraud, and is similar to
that of the optical Schmidt telescope where the
spherical aberration is corrected by a deformed plate
located near the centre of curvature of the spherical
primary mirror. For the radio telescope, this would
give a diffraction-limited image on a curved focal
surface (of 280m radius) concentric with the spherical
mirror, allowing observations to be made of sources up
to 7.5º on either side of the meridian plane. By track-
ing the path of the image of a source on this focal
surface, it would then be possible to integrate its flux
for an hour for a source located at Dec. = 0°, and for
longer for sources with other declinations.
There are advantages and drawbacks to this design
when compared to that of a fully-steerable parabolic
The main advantage is the low cost per unit area.
Another one is the easy accessibility and lack of
weight limitation for focal equipment.
The main disadvantage is the fact that this is a mer-
idian telescope with an integration lime limited to
about 30 minutes on either side of the meridian cross-
Figure 4: The first section of the fixed concave mirror is com-
ing. This makes the scheduling of the telescope diffi-
cult, with a poor time-efficiency, and the limitations in
hour angle in practice forbid VLBI with other radio
telescopes. Also, the elongated lobe renders measure-
ments of linear polarization almost impossible, and
makes it difficult to compare Nançay results with
those obtained with circular antennas. Because the
focal antenna is close to the ground, some thermal
noise from the ground enters through the side lobes if
special care is not taken. Kraus solved this problem by
covering the ground with a flat reflecting surface, but
this is expensive, and runs the risk of creating ‘ghosts’
of strong sources. Similarly, the focal horn ‘sees’ in
its main lobe whatever happens to stand behind the
bottom of the plane mirror when this is inclined. At
Nançay, these significant contributions to the system
noise were only drastically reduced in the late 1990s
when appropriate measures were introduced. A final
disadvantage of the two-mirror design is that it would
be extremely expensive to replace the reflecting sur-
faces by better ones for observations at shorter wave-
lengths, whereas this is common practice with large
steerable paraboloids.
It seems that the limitations of a meridian radio tele-
scope were underestimated in the beginning, and that
the other disadvantages of the design were completely
overlooked. The low cost per unit surface area was the
decisive argument, as can be seen from the following,
somewhat naïve, statement:
The voluntary limitations on the universality of the
large Nançay mirror will render its usage secure. More-
over, it could fit in this way within the present scientific
budget of France. It is in a way a cousin of the 1.97m
[sic] Rosse [optical] reflecting telescope which was
built a century earlier than its universal brother, the
1.93m reflector at Haute Provence, because one
accepted its limitations around the meridian.
(Heidmann, 1961: 49; our translation).
It turned out to be very easy to obtain a substantial
amount of money for the new instrument: 155 million
francs (equivalent to €2.9 million in 2008) were as-
signed in the budget for 1957. Three million of this
total was used for preliminary studies including tests
in wind tunnels, and contract submissions were then
invited from French companies. Surprisingly, only
one answered positively, and this was the Compagnie
Française d’Entreprises (CFE), which was created by
Gustave Eiffel around 1880 as Entreprises Métropolit-
aines et Coloniales, and then merged with the Moisant-
Laurent-Savey Company, only to be purchased by
Usinor-Sacilor in 1959. The CFE had considerable ex-
perience in large concrete and metal constructions, and
the Director of its Industrial Department, Jean Roret
(1925–2005), was personally interested in the radio
astronomy project. A contract with CFE was signed in
December 1958 for 152 million francs (€2.5 million),
and work started in their Rouen plant and at Nançay in
May 1959.
This contract price was only sufficient to build the
first section of the radio telescope, one-fifth of the
total, consisting of a fixed 60m × 35m portion of a
spherical mirror and two tiltable flat panels covering
40m × 40m in total. This was supposed to be complet-
ed within 14 months. A further amount of 32 million
francs (€500,000) was obtained in 1960 for the build-
ings, the first focal antennas, the receivers and an
electrical generator, the local municipal power sup-
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
plies being insufficient for moving all ten panels of the
completed radio telescope at the same time.
Figures 3, 4, 5 and 6 illustrate the erection of both
mirrors. The reflecting surface, a square wire-netting
initially foreseen as an 18mm × 18mm mesh but final-
ly realised as a 12.5mm × 12.5mm one, was fixed to
steel cables which were attached to the structure and
were adjustable. This structure was completed by the
end of 1961, with a slight delay. The surface of the
concave mirror was checked by the Division des Tra-
vaux Spéciaux of the Institut Géographique National
(IGN), headed by J. Commiot, and found to be signif-
icantly better than the contract specifications: 5-6mm
r.m.s. instead of the required 10mm. A fixed set of
parabolic antennas was installed at the focus for 21, 13
and 6cm, with small antennas and uncooled receiver
front ends, mixers and intermediate-frequency ampli-
fiers at their foci (Figure 7). On 23 January 1962 the
radio telescope was officially inaugurated, with several
speeches, including one by Denisse as head of the
Nançay field station. One can sense there was some
bitterness when he spoke about the 64-m Parkes Radio
Telescope (which had just been completed):
[When our Nançay radio telescope was decided]the
Australians were studying the present paraboloid at
Parkes which at the same time is both accurate and has
an imposing surface area: 3,000m
. At the present time
it is certainly the best radio telescope in existence, and
it is operated by a staff of exceptional quality. (Denisse,
1962: our translation).
It is true that at this time the French radio astronomy
group was still small and busy using the various solar
instruments at Nançay. Moreover, the construction of
the new radio telescope was only overseen by a single
mechanical engineer, Marcel Parise (Figure 8).
Furthermore, an unexpected problem arose: point-
ing of the tiltable panels, as measured on their axes,
was largely in error. Not only was the measuring
equipment inadequate, but there was also some distor-
tion when the panels were inclined (and there was no
computer to perform the structural analyses at this
time). The problem was completely beyond the com-
prehension of the CFE staff, and it was agreed that it
had to be solved by the radio astronomers. This was
done by attaching graduated rulers perpendicular to the
mesh along one of the edges of the panel, and ob-
serving them with a small telescope equipped with a
graduated vertical circle attached to the rotation axis.
This way the distortion was measured, and a correction
was then applied through a mechanical cam inserted
between the end of the axis and the encoder. The
encoder was supplied by Ferranti Ltd., a UK com-
During the measurements, another problem was dis-
covered: the distortion was not the same when the
inclination increased or decreased, pointing to mech-
anical hysteresis in the panels. This forced the panel
to always move in the same way, with increasing
inclination. It remained to be seen if the inclination of
the edges of the panels where the measurements were
performed was representative of the average inclina-
tion of the whole surface. This was checked by IGN
staff, who used a theodolite to measure from the
ground the positions of nine points of the panel surface
for different inclinations. The results were satisfact-
ory, but it was discovered that the surface, which was
Figure 5: One 20m-wide panel of the tiltable mirror, which was
assembled on the ground, is hoisted into place.
Figure 6: The first completed section of the tiltable flat mirror.
Each panel is driven by a pinion acting on a chain placed
along the half-circle.
Figure 7: The focal equipment of the first section of the radio
telescope. The focal diffraction spot forms on paraboloids
which concentrate the radiation on circular horns followed by
the high-frequency stages of the receivers (see, also, Figure
8). The intermediate frequency signal is sent to the focal
laboratory shown at the back of this photograph. The whole is
moveable on N-S rails for focussing. From left to right are
devices for 6, 21 and 13cm respectively. The tiltable mirror in
visible in the background.
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
Figure 8: Marcel Parise adjusting the focal system for 21cm.
approximately flat for an inclination of 45º, became
concave in the N-S direction by 8mm at the middle of
the panel for an inclination of 90º, while it became
concave by 5mm in the E-W direction. The usual rule
of thumb that the deviations of the final wave surface
should be better than
of a wavelength for good
results showed that the Nançay Radio Telescope
should be good at 21cm and 18cm, fair between 9cm
and 13cm and quite poor at 6cm.
With a few exceptions, all of the measurements,
analyses and designs of the new instrumentation were
done by Steinberg and Michel Ginat, with help from
James Lequeux and a few others (Steinberg, 2004). It
is only upon reading Ginat’s Ph.D. thesis (1966),
which is devoted to this work, that one realises just
how complex and difficult this task was.
Once the final section of the radio telescope was
operational, some continuum observations were made
of extended galactic sources at 1,430 MHz and 2,315
MHz (Bottinelli and Gouguenheim, 1964; Heidmann,
1965) and of a few large galaxies at 1,430 MHz (Heid-
mann, 1963). But since the rest of the radio telescope
was then under construction, this effectively prevented
further observations from being made.
Given the success of the first section of the radio tele-
scope it was relatively easy to raise the money for the
rest of the instrument. A new contract was set up
between the Ministry of Public Education and the CFE
and the construction proceeded without any major
problems. Figure 9 illustrates a step in the erection of
the second part of the radio telescope. The completed
instrument was officially inaugurated by the President
of the Republic himself, General de Gaulle, and the
Minister, Christian Fouchet, on 15 May 1965.
Of course it was necessary to calibrate the inclina-
tion of all of the panels in the same way as for the first
two, and this lengthy process was only finished in
1966. This work, along with other geodetic measure-
ments, was the subject of Ginat’s Ph.D. thesis (1966).
Also, in order to save money, encoders were only
installed on the axes of panels 2, 5, 6 and 9, and
the other panels were slaved to these master panels
Figure 9: The fully-tiltable mirror during construction.
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
thanks to a simple but effective electromagnetic
proximity system designed by Biraud: panels 1 and 3
to panel 2; panel 4 to panel 5; panel 7 to panel 6; and
panels 8 and 10 to panel 9. The pointing of the panels
and the necessary controls were designed by the staff,
especially by Ginat and Steinberg. Despite the pas-
sage of the years, this system is still working at
present, after only minor changes.
One also had to deal with motion of the carriage (or
rather the carriages, as two were constructed), in order
to track the displacement of the image due to diurnal
motion. This required both a vertical motion and a
motion along a curved railtrack, both depending upon
the declination of the source. Money was available to
build the mechanical and hydraulic parts of the car-
riages (the motion being secured by hydraulic motors
and jacks), but not for controlling the motions, a
problem whose difficulty had been underestimated.
There was no computer to drive real-time servos so
one needed a custom-made computer. The only Euro-
pean firm able to do this at a reasonable cost was
Ferranti Ltd., which had also supplied the encoders for
the flat mirrors as stated earlier and the control desk of
the radio telescope (Figure 10). Lequeux was in
charge of defining the needs, writing the contract and
following the construction and installation of the drive
system. The necessary funds came from a convention
(agreement) signed in 1963 between the Paris Obser-
vatory and the Centre National d’Études Spatiales
(CNES) which agreed to pay, on the basis that arti-
ficial satellites would be tracked by the radio telescope
(something which never occurred). This was arrang-
ed by Steinberg, who was in the process of setting up
a Laboratory of Space Radioastronomy at Meudon
whilst continuing his work at Nançay, and had ex-
cellent relations with the CNES. The position of the
focal antenna as a function of time was computed with
the IBM 7040 in Meudon, whose output was a punch-
ed tape. This tape was sent to Nançay and fed into the
Ferranti equipment, which was housed in several big
cabinets which filled a sizable fraction of the control
room. The total cost was 320,000 new francs
The first H-line receiver was built by Émile-Jacques
Blum, with help from Jean Delannoy, Émile Le Roux
and Leonid Nicolas Weliachew (Blum et al., 1966),
and placed on one of the carriages (Figure 11). This
was a correlation receiver, a concept invented by Blum
and derived from his studies of interferometers (Blum,
1959). The principle is as follows: if one splits the
signal from the antenna and feeds each of two identical
receivers with half of this signal, a correlation of the
outputs of these receivers will give a DC output
proportional to the power received by the antenna, the
noises in the receivers being uncorrelated. Thus, the
output is essentially unaffected by variations in the
receiver gains, which were very troublesome at this
time. For this purpose, Blum used a correlator that he
originally designed for his solar interferometer (Figure
12). Of course fluctuations in receiver noise are still
present, but it can be shown that the signal/noise ratio
of the system is comparable to or better than that of the
permutation receivers of Robert Dicke and Martin
Ryle which were largely in use at this time. A
problem with this system is that splitting the antenna
signal in a hybrid circuit like a magic T requires an-
Figure 10: The control room of the radio telescope, circa
1966. The controls on the left activated the generating set for
powering the tiltable mirrors; those in the central part
controlled the tracking of the focal carriage; and those on the
right controlled the motions of the tiltable panels. Notice the
panels in the background which housed part of the electronics
of the Ferranti equipment.
Figure 11: The focal carriage for observing the H-line. The
signal is received by a hog horn whose dimensions (2m ×
0.4m) match the diffraction spot. Notice the smaller vertical
horn which feeds the other input of the hybrid circuit (magic T)
of the correlation receiver (see the text, and Figure 13). The
cabin contains the front end, the mixer and the amplifier for
the intermediate frequency, which is sent by cables to the
focal laboratory towards the rear of the photograph.
Figure 12: Blum’s correlator. X
(t) and X
(t) are the input
signals from two antennas of an interferometer or from the two
halves of the signal of the antenna for a correlation receiver.
The voltage between A and C is proportional to [X
(t) + X
with a quadratic detecting diode, and that between B and C
proportional to [X
(t) X
, if the senses of the transform-
ers are well chosen. Hence the voltage between A and B is
the difference of these two quantities, which is proportional to
(t), the correlated product.
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
Figure 13: Principle of the 21cm line correlation receiver. For
a description see the text.
other input for balancing the impedances (Figure 13).
This input comes from a horn which is looking at the
sky, followed by a variable attenuator whose noise
must balance the noise from the antenna. Another
possibility, which has also been used in some cor-
relation receivers, was simply to insert a unidirectional
circuit between each half of the antenna signal and the
input of the corresponding receiver.
For all these receivers, the incoming signal was sent
to the mixer after amplification by a parametric ampli-
The locally-made parametric amplifiers did not
work very well and were soon replaced by commercial
ones. The first 21cm line receiver was uncooled and
had a system temperature of 350K, including 35K of
ground noise for low declination sources. It had 15
frequency channels, each 280kHz (59km/s) wide,
which were only suitable for extragalactic observa-
tions, and a continuum channel 5MHz wide. The sig-
nals were digitized and integrated, and the results were
entered on punched paper tape. This tape was sent to
Meudon and its content was transferred onto punched
cards by an IBM 1401 computer, then the reduction
was performed with the Meudon IBM 7040, with an
output on paper (Figure 14) and on punched cards.
This complicated system was replaced in 1969-1970
by a Digital Equipment PDP 8 computer located in the
control room of the radio telescope.
Another carriage (Figure 15) bore three horns for
continuum observations at 21, 11.3 and 6.2cm, and the
Figure 14: One of the first observations of an extragalactic
21cm line with the completed radio telescope. This is a listing
from the Meudon IBM 7040 computer. The 15 frequencies of
the multi-channel back end are in abscissae. The positive sig-
nal (2K of antenna temperature) is the 21cm line from the
galaxy NGC 3109, and the negative one is a residual from the
galactic line emission in this 4-hour ON-OFF observation
(after Bottinelli et al., 1966).
corresponding receivers. It seems, however, that the
21cm continuum receiver was never implemented, and
that the observers simply used the broad channel of the
line receiver instead.
In 1968 the total cost of the radio telescope with the
focal building and all of the auxiliary instrumentation
that we have just described was estimated at 15 million
francs, corresponding to €16.7 million in 2008. As
suggested by a referee, it is of interest to compare this
cost with that of contemporary large radio telescopes.
This comparison can only be approximate, because of
difficulty in obtaining the actual total costs and be-
cause of uncertainties in the exchange rates and in the
conversion into 2008 Euros. For Jodrell Bank (the
Mark I Lovell Telescope) and Parkes the estimates did
not include the first receivers and auxiliary equipment,
so we added 20% to these estimates. We do not
include the Ohio Radio Telescope because this was
essentially a home-made instrument. Our results are
presented below in Table 1.
These results must be weighted by the shortest
wavelength observable with the different radio tele-
scopes. At the time of their completion, Jodrell Bank
and Arecibo were worse than Nançay, while Parkes
was better. Also, Arecibo has a limited observing
range around the zenith, whereas Jodrell Bank and
Parkes are fully steerable. Overall, it appears that the
choice of a meridian combination for Nançay saved
money, but that the best deal was clearly Parkes, a
radio telescope which was built by German industry
(MAN-Krupp). For political and industrial reasons it
was not possible for France to obtain such an instru-
After the completion of Le Grand Radiotélescope
most of the scientists who had worked so hard on its
pointing, focal tracking and receivers partially lost
interest in the instrument, with the exception of Biraud
and Weliachew. Thus, in 1965 Le Roux left astrono-
my; during 1967-1968 Blum spent a sabbatical year at
the NRAO in Charlottesville (West Virginia) becom-
ing familiar with millimetre techniques; and in 1967
Delannoy moved to the Bordeaux Observatory in order
to build an experimental 8mm interferometer. Mean-
while, Steinberg worked full-time in his Space Radio-
astronomy Laboratory at Meudon, and in 1966 Le-
queux (with a few colleagues) founded an infrared
laboratory at Meudon, before going to Caltech in
1968-1969 in order to observe with the Owens Valley
Radio Observatory interferometer. Ginat was killed in
a mountain accident on 1 April 1968. Blum had taken
over from Denisse as Director of the Paris Observa-
tory’s Radioastronomy Department and the Nançay
field station in 1964, and he remained in charge until
1973, but he never used Le Grand Radiotélescope,
working instead on millimetre receivers. He was suc-
ceeded by Lequeux, who occasionally used the large
radio telescope but was mostly busy with other tasks,
especially (with Blum, Weliachew and Pierre Encren-
az) in setting up a large millimetre interferometer
which materialized in 1979 as one of the elements of
the German-French-Spanish Institute for Millimeter
Radio Astronomy (IRAM).
Presumably all of these scientists were exhausted by
the considerable tasks they had to achieve in order to
bring Le Grand Radiotélescope to fruition. Denisse
understood that building such a large instrument in a
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
difficult industrial climate was at the very limit of the
potential of a small group with little technical prepar-
ation, and so in 1966 he created the Institut Nation-
al d’Astronomie et de Géophysique (INAG), with a
Technical Division, in order to handle major projects.
On the other hand, some members of the staff thought
that the Nançay radio telescope would soon be super-
seded by others, like the Effelsberg 100-m steerable
parabola, which was completed in 1972. Whether they
were right or wrong will not be discussed here, but
long-standing unease was experienced by the staff,
which later resulted in a splitting of the Radioastron-
omy Department into ‘millimeter’ and ‘decimeter’
radio astronomers. In any case, the use of Le Grand
Radiotélescope was left to the younger generations.
As with any new facility, Le Grand Radiotélescope at
Nançay has been continually improved over the years.
Little has changed to the actual radio telescope itself,
but the Ferranti system to tilt the panels and move the
focal carriages was replaced by a computer in 1969-
1970. Many more changes were made to the receivers
and the focal carriages. It is difficult to track all of
them, and we will only report on some of them. We
will also briefly describe some of the early observa-
tions which were made with this radio telescope.
A 15MHz continuum channel and fifteen 60kHz
channels were first added to the H-line receiver, and
the high-frequency parts were cooled. In 1973 there
were thirty-two 60kHz channels and sixty-four 6kHz
(1.3km/s) channels, and the receiver temperature was
down to 120K in 1975. Unfortunately, the correlated
response of each pair of frequency channels turned out
to be very sensitive to the shape of the bandpass of
these channels, so that chromatism was a problem for
line observations. This, together with the cost of hav-
ing all the electronics in duplicate, led to abandoning
this type of receiver and also the parametric preampli-
fiers around 1985, and they were replaced by cooled
High Electron Mobility Transistors (HEMT) in the
front-ends. An autocorrelator was substituted for the
filter banks. However, many useful scientific results
were produced before these changes occurred, in par-
ticular the H-line detection of a large number of gal-
axies (see in ADS the many papers by R.J. Allen, C.
Balkowski, L. Botttinelli, P. Chamaraux, B.F. Darchy,
E. Gérard, L. Gouguenheim, M. Guélin, J. and N.
Heidmann, I. Kazès, R. Lauqué and N. Weliachew).
A new impetus to this major program of the Large
Nançay Radio Telescope came from the discovery of
the Tully-Fisher Relation between 21cm line width
and absolute magnitudes and diameters of galaxies
(Tully and Fisher, 1977), which offered a way of
deriving distances of galaxies independent of redshift
and allowed the Nançay observers to obtain a value of
Figure 15: The carriage for the continuum receivers. From left
to right are the hog horns for 21, 11 and 6cm respectively.
The height of the largest horn is 2m.
68 ± 8 km s
for the Hubble Constant (Fouqué
et al., 1990), which is close to the currently-adopted
figure of 71 ± 4 km s
obtained from COBE
and WMAP observations.
There was also an extensive program involving
galactic 21cm absorption (Lazareff, 1975; Crovisier et
al., 1978), during which many observations of continu-
um sources were also made. Although more subject to
contamination by residual line emission than obser-
vations with interferometers, these results were quite
useful as a means of measuring distances to contin-
uum sources. One of the original programs was to
observe 21cm absorption in front of pulsars whose
distances were unknown at the time (Guélin et al.,
1969). In this case, the difference between the line
seen during the pulse and between the pulses gives a
pure absorption profile, hence a relatively good esti-
mate of the distance. This was the beginning of an
interest in pulsars, which developed considerably later
for the purpose of timing their pulses, and is at present
a major program of the radio telescope.
The 21cm line receiver was also used in 1975 and
later for observations of radio recombination lines, in
particular the 166α lines of carbon and sulphur
(Cesarsky et al., 1976). The receiver was used in total
power detection instead of the usual correlation mode.
Table 1: Cost comparisons for major early radio telescopes.
Date of cost
(original currency)
(2008 €)
Cost per unit
area (2008 €/m
Nançay 1968 1.5 × 10
Francs 1.67 × 10
7000 2400
Jodrell Bank 1957 8.4 × 10
£ 1.58 × 10
4500 3500
Parkes 1963 1.5 × 10
US$ 9.7 × 10
3200 3000
Arecibo 1963 9 × 10
US$ 5.8 × 10
70700 800
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
Figure 16: The focal carriage bearing the 21, 18 and 9cm hog
horns in the 1980s.
Figure 17: Principle of a correlation-receiver set-up for meas-
uring polarization. The four outputs give the power in the verti-
cal linear polarization component v
, that in the horizontal one
, the product hv, and the product hv
with a
/2 phase shift.
The fraction of circular polarization in the signal is 2hv
Figure 18: Principle of the incoherent scattering ionospheric
sounder. An emitting antenna in Saint Santin near Decazeville
sends out a monochromatic wave vertically. The scattered
radiation is received in Nançay, and in two other receiving
stations equipped with 25m diameter paraboloids near Mende
and Montpazier, which were added in 1973.
An interesting event was the arrival at Nançay in
1971 of an 18cm line receiver built in the Soviet
Union at the Sternberg Institute and the Space Re-
search Institute in Moscow. This was made possible
through cooperation between Intercosmos (the Soviet
Space Agency) and the French CNES. The receiver
(Paschenko et al., 1971) operated in the frequency-
switching mode, and had in its front end an uncooled
parametric amplifier on loan from the Max Planck In-
stitut für Radioastronomie in Bonn. The back end had
16 × 20kHz channels 3.6km/s wide. The system tem-
perature was initially 250K, but in 1972 it dropped to
150K thanks to cooling. In 1974 three channel banks
were added, each with 32 filters of respective widths
10, 6 and 6kHz. This receiver was used until 1986
when the front-end was replaced by a cooled HEMT
one (and the receiver temperature was 40K after this
change), and the filters were replaced by an auto-
correlator in common with the 21cm receiver. The
main program with this equipment was to observe OH-
IR stars, OH lines in the Galaxy and OH in comets.
These progressively became major programs for the
radio telescope, especially the cometary part following
the detection of OH in Comet Kohoutek (Biraud et al.,
1974; and for a bibliography see Crovisier et al.,
2002). Later the radio telescope was turned to external
galaxies and several OH megamasers were discovered
(Bottinelli et al., 1986).
A 9cm cooled HEMT receiver for observation of the
CH lines was constructed in the 1980s for galactic and
cometary studies, and these lines were also detected in
external galaxies (Bottinelli et al., 1991). For this, a
new carriage was built with three focal hog horns
working at 21, 18 and 9 cm (Figure 16).
While most of the research conducted with the radio
telescope related to line observations, there were also
some continuum observations. An early observing
program with the continuum channel of the 21cm line
receiver was devoted to normal galaxies (de la Beau-
jardière et al., 1968). The 11cm correlation receiver
was used to detect emission from Saturn and Uranus
and to obtain an upper limit for that from Neptune
(Gérard, 1969). Jupiter and Saturn were observed in
1972-1973 at 21, 11.1 and 6.2cm, with respective sys-
tem temperatures of about 100, 200 and 300K (Gérard
and Kazès, 1973). Biraud made an heroic attempt to
measure the polarization of quasars at 11.1cm using a
correlation receiver set-up suggested by Blum and
represented in Figure 17. The linear polarization could
not be observed with any accuracy, but circular polari-
zation was detected in PKS 1127-14 (Biraud, 1969).
One original early program in the continuum was
the observation of radio source scintillations due to the
heliospheric plasma at 11cm and other wavelengths
(Bourgois, 1969, and follow-up papers).
It should be noted the Le Grand Radiotélescope was
also used for a substantial fraction of the time for
observing incoherent scattering in the ionosphere, just
like the Arecibo Radio Telescope (see Cohen, 2009).
This resulted from an agreement between INAG and
the Centre National d’Études des Télécommunications
(CNET). As shown in Figure 18, a powerful mono-
chromatic beam at 32cm was sent vertically by an
antenna located 300km south of Nançay, and the
scattered radiation was received by the Nançay Radio
Telescope with a hog horn followed by a line receiver
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
(Figure 19). The two beams of the emitting and re-
ceiving antennas defined a volume in which the den-
sity and temperature of ions and electrons were meas-
ured, as well as the velocity and direction of the wind
(thanks to the Doppler effect). The range of elevations
explored by changing the inclination of the plane mir-
ror was 95 to 700km.
Between 1995 and 2000 a complete remodelling of
the focal installations of the Nançay Large Radio Tele-
scope took place, the so-called FORT Project (for
Foyer Optimisé pour le Radio Télescope décimétrique
de Nançay). A new carriage (Figure 20) was built on
a new railtrack, and the hog horns were replaced by
an ensemble of two eccentered concave mirrors feed-
ing one or the other of two corrugated horns accord-
ing to the wavelength. This system (Figure 21), de-
signed by staff from the CSIRO in Australia (Granet
et al., 1997; 1999), completely covers the frequency
range 1.0 to 3.5GHz and has low sidelobes. An effic-
ient system of metallic mesh in front of the focal
system and behind the tiltable mirror drastically re-
duces the effects of the ground and the trees behind
the tiltable mirror. New front ends were installed in
enclosures at 20K and the system temperature is now
~35K over the whole range of received frequencies. A
new focal laboratory was built outside the radio
beams. All this gave a new life to what is now a ven-
erable radio telescope.
The construction of Le Grand Radiotélescope at Nan-
çay took place in a favourable economic and political
climate. But the context was not as favourable when
techniques were concerned, because French industry
was not prepared to manufacture large metallic struc-
tures with any accuracy, and because on-line comput-
ers were not yet available. Moreover, the Paris Obser-
vatory radio astronomy group only had one mechan-
ical engineer, so this forced the radio astronomers to
do work for which they had little training or prepar-
ation. To their credit, they succeeded, but they were
exhausted by these efforts and the instrument was
delayed for two years: although the structure was com-
pleted and inaugurated in May 1965, the radio tele-
scope only began working properly at the end of 1967.
With its surface area of 7,000m
, comparable to that of
the Effelsberg and Greenbank 100-m diameter para-
boloids, it was one of the largest radio telescopes in
the world, Arecibo excepted. But unlike its competi-
tors, the Nançay Radio Telescope could not operate
below 9cm.
The Nançay site was relatively free of man-made
radio interference at the beginning, but like any other,
it now suffers badly from this plague. Today, sophisti-
cated techniques are required to allow any sensitive
observations, especially at decimetre and meter wave-
lengths. These techniques are in force at Nançay, but
just how long observations will be possible there at
these wavelengths is a major question. The Square
Kilometer Array (SKA) project, for which the direc-
tion of observation will be changed instantaneously as
a function of interference, is clearly the way to go for
decimetre radio astronomy.
1. This project was initiated under the auspices of the
Figure 19: A focal carriage with two radio astronomy hog
horns for 18 and 21cm (left) and a hog horn for receiving the
signal of the incoherent ionospheric scattering project at 32cm
(right), in the late 1970s.
Figure 20: New focal carriage of the radio telescope, circa
2000. The old focal laboratory was still in operation at this
time, but has since been replaced by a new one located
outside the radio beam.
Figure 21: One-tenth scale model of the quasi-optics for the
new carriage shown in Figure 20, built and tested by staff from
the CSIRO in Sydney, Australia. There are two corrugated
circular receiving horns, each one covering approximately half
of the total frequency range. One is in position, and the other
is lying on the floor.
IAU Historic Radio Astronomy Working Group in
2006, and four papers have been published to date.
The first deals with Nordmann’s attempt to detect
solar radio emission in 1901 (Débarbat et al., 2007);
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
the second with early solar eclipse observations
(Orchiston and Steinberg, 2007); the third with the
Würzburg antennas that were at Marcoussis,
Meudon and Nançay (Orchiston et al., 2007); and
the fourth with early solar research till the mid-
1950s (Orchiston et al., 2009). A sixth paper, on
post-1956 solar research at Nançay (Pick et al.,
2010) will be published later this year and a seventh
paper, on the birth of the IRAM project, is currently
in preparation.
2. Steinberg was referring to fringes at centimetre
wavelengths; all previous interferometry was at
metre and decimetre wavelengths.
3. When mentioning the prices associated with the
Grand Radiotélescope Project we have tried to
convert them into 2008 Euros, based on a
comparison of the cost of living at that epoch and in
2008. This conversion was established by the
Institut National de la Statistique et des Études
Économiques (INSEE), and is available through the
following web site:
indicateur.asp ?id =29& type = 1& page=achatfranc.
4. This is not explicitly mentioned in the recommend-
ation, but VLBI was just beginning at this time in
Canada and the USA, and the French radio astrono-
mers were certainly aware of this.
5. This was one of the few instances where French
industry could not supply the required product.
Ferranti Ltd. was based in Dalkeith, near Edinburgh,
in Scotland.
6. For the concept of parametric receivers see the
Wikipedia article on ‘Parametric oscillator’.
We wish to thank Nicole Cornilleau-Wehrlin and Ber-
trand Flouret (Paris-Meudon Observatory) for provid-
ing access to photographs of the radio telescope and
the focal equipment. The Nançay radio astronomy
field station holds the copyright to all of the photo-
graphs published in this paper.
We also thank staff at the Library of the Paris-
Meudon Observatory for their efficiency and their
kindness, and the Astrophysics Data System (ADS) for
making many historical documents freely available.
Finally, we are grateful to Professor Richard Strom
(ASTRON and James Cook University) for reading
and commenting on the manuscript.
Original documents which were consulted through ADS
( are indicated by a º sign.
°Baade, W., and Minkowski, R., 1954. Identification of the
radio sources in Cassiopeia, Cygnus A, and Puppis A.
Astrophysical Journal, 119, 206-214.
°Biraud, F., 1969. Mesures de polarisation avec le radio-
télescope de Nançay. Détection de polarisation circulaire
dans les quasars à 2695 MHz. Astronomy & Astrophysics,
1, 156-163.
°Biraud, F., Bourgois, G., Crovisier, J., Fillit, R., Gérard, E.,
and Kazès, I., 1974. OH observation of Comet Kohoutek
(1973f) at 18 cm wavelength. Astronomy & Astrophysics,
34, 163-166.
°Blum, E.-J., 1959. Sensibilité des radiotélescopes et récep-
teurs à corrélation. Annales d’Astrophysique, 22, 140-163.
Blum, E.-J., 1968. Préparation du Rapport de conjuncture
pour le Vle Plan – Radioastronomie (unsigned document).
Bibliothèque de l’Observatoire de Paris, MS 1061, I-2-A,
Carton 5, File 54.
Blum E.-J., Delannoy, J., Le Roux, E., and Weliachew, L.,
1966. Le récepteur spectral du radiotélescope de Nançay.
Comptes Rendus de l’Académie des Sciences, Série B,
262, 1640-1642.
°Bourgois, G., 1969. Scintillations interplanétaires de radio-
sources à 2695 MHz. Astronomy & Astrophysics, 2, 209-
°Bottinelli, L., and Gouguenheim, L., 1964. Étude de la
Nébuleuse Rosette à 1430 et 2315 MHz. Annales
d’Astrophysique, 27, 685-694.
Bottinelli, L., Gouguenheim, L., Heidmann, J., Heidmann,
N. and Weliachew, L., 1966. Premières observations
spectrales du radiotélescope de Nançay. Comptes Rendus
de l’Académie des Sciences, Série B, 263, 223-226.
°Bottinelli, L., Gouguenheim, L., Le Squeren, A.M., Martin,
J.M., Dennefeld, M., and Paturel, G., 1986. New extra-
galactic OH megamasers. IAU Circular 4231.
°Bottinelli, L., Gouguenheim, L., Gérard, E., Le Squeren,
A.M., Martin, J.M., and Dennefeld, M., 1991. Detection
of extragalactic CH 9-cm emission with the Nançay radio
telescope. In Combes, F., and Casoli, F. (eds.) Dynamics
of Galaxies and their Molecular Cloud Distributions.
Dordrecht, Kluwer, publisher. Pp. 201.
°Cesarsky, D.A., Encrenaz, P.J., Falgarone, E.G., Lazareff,
B., Lauqué, R., Lucas, R., and Weliachew, L., 1976. A
bright source of carbon recombination line in the Rho
Ophiuchi Complex. Astronomy & Astrophysics, 48, 167-
Cohen, M., 2009. Genesis of the 1000-foot Arecibo Dish.
Journal of Astronomical History and Heritage, 12, 141-
Comité de Direction de la Station de Nançay, 1958. Minutes
of the meeting of 14 May. Bibliothèque de l’Observatoire
de Paris, MS 1061, I-2-A, Carton 9, File Station de
Nançay 1954-59.
°Crovisier, J., Colom, P., Gérard, E., Bockelée-Morvan, D.,
and Bourgois, G., 2002. Observations at Nançay of the
OH 18-cm lines in comets; the data base. Observations
made from 1982 to 1999. Astronomy & Astrophysics, 393,
°Crovisier, J., Kazès, I., and Aubry, D., 1978. The Nançay
survey of absorption by galactic neutral hydrogen I.
Absorption towards extragalactic sources. Astronomy &
Astrophysics Supplement Series, 32, 205-82. See for
analysis °Crovisier, J., 1978. Kinematics of neutral
hydrogen clouds in the solar vicinity from the Nançay 21-
cm absorption survey. Astronomy & Astrophysics, 70, 43-
Darmon, G., 1981. Psychologie d’une Décision en Science
Lourde: L’institut Franco-Allemand de Radio-Astronomie
Millimétrique. Thèse pour le Doctorat de 3e cycle, Uni-
versité de Paris et École des Hautes Études en Sciences
Débarbat, S., Lequeux, J., and Orchiston, W., 2007. High-
lighting the history of French radio astronomy. 1: Nord-
mann’s attempt to detect solar radio emission in 1901.
Journal of Astronomical History and Heritage, 10, 3-10.
°De la Beaujardière, O., Kazès, I., Le Squeren, A.-M., and
Nguyen Quang Rieu, 1968. Étude de galaxies normales
sur 1414 MHz. I. Observations. Annales d’Astrophysique,
31, 387-99. See, also, °Nguyen Quang Rieu, 1968. Étude
de galaxies normales sur 1415 MHz. II. Structure et
évolution des galaxies normales. Annales d’Astro-
physique, 31, 401-412.
Denisse, J-F., 1958. Projet d’un grand radiotélescope à la
station de Nançay. Bibliothèque de l’Observatoire de
Paris, MS 1061, I-1-B, Carton 4, File 43.
Denisse, J.F. 1962. Discourse at the dedication of the first
section of the Nançay radiotelescope. Bibliothèque de
l’Observatoire de Paris, MS 1061, I-2-A, Carton 9, file
Station de Nançay (in French).
Denisse, J.-F. and Steinberg, J-L., 1955. Projet de construct-
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
ion d’un grand instrument astronomique. Bibliothèque de
l’Observatoire de Paris, MS 1061, I-2-A, Carton 9, file
Ewen, H.I., and Purcell, E.M., 1951. Radiation from galactic
hydrogen at 1420 MHz. Nature, 168, 356-358.
°Fouqué, P., Bottinelli, L., Gouguenheim, L., Paturel, G.,
1990. The extragalactic distance scale. II. The unbiased
distance to the Virgo cluster from the B-band Tully-Fisher
relation. Astrophysical Journal, 349, 1-21.
°Gérard, E., 1969. Observations of Saturn, Uranus and
Neptune at 11.13 cm. Astronomy & Astrophysics, 2, 246-
Gérard, E. and Kazès, I., 1973. Observations of Saturn at
wavelengths of 6.2, 11.1 and 21.2 cm. Astrophysical
Letters, 13, 181.
Ginat, M., 1966. Contribution à la Construction du
Télescope à Deux Miroirs de Nançay. Thesis, University
of Paris.
Granet, C. and James, G.L., 1997. New dual-reflector feed
system for the Nançay radio telescope. IEEE Transactions
on Antennas and Propagation, 45, 1366-1373.
Granet, C., James, G.L. and Pezzani, J., 1999. The full-size
dual-reflector feed system for the Nançay radio telescope.
Journal of Electrical and Electronic Engineering of
Australia, 19, 111-122.
Guélin, M., Guibert, J., Huchtmeier, W., and Weliachew, L.,
1969. Measurements of pulsar distances by galactic
hydrogen absorption. Nature, 221, 249-250; see also in
ADS, articles from 1970 to 1974 by P. Encrenaz, E.
Falgarone, J. Gomez-Gonzalez and M. Guélin,
°Heidmann, J., 1961. Les radiotélescopes géants et l’Univers
extragalactique. L’Astronomie, 75, 49-58.
°Heidmann, J., 1963. Étude de quelques galaxies normales
ou peu émissives à 1430 MHz. Annales d’Astrophysique,
26, 343-353.
°Heidmann, N., 1965. Résultats d’observations de la
radiosource W 22 (NGC 6357) à 1430 MHz et 2315 MHz.
Annales d’Astrophysique, 28, 521-533
Kraus, J.D., 1986. Radio Astronomy. Second Edition.
Powell, Cygnus-Quasar. See also
°Lazareff, B., 1975. Neutral hydrogen absorption spectra.
Astronomy & Astrophysics, 42, 25-35.
°Lilley, A.E., and McClain, E.F., 1956. The hydrogen-line
redshift of radio source Cygnus A. Astrophysical Journal,
123, 172-175.
Lovell, B., 1968. The Story of Jodrell Bank. Oxford, Oxford
University Press.
Lovell, B., 1973. Out of the Zenith: Jodrell Bank 1957-1970.
Oxford, Oxford University Press.
McAdam, B., 2008. Molonglo Observatory: building the
Cross and MOST. Journal of Astronomical History and
Heritage, 11, 63-70.
Mills, B.Y., 1984. Radio sources and the log N – log S
controversy. In Sullivan, 147-165.
Muller, C.A., and Oort, J., 1951. The interstellar hydrogen
line at 1,420 Mc./sec., and an estimate of galactic rotation.
Nature, 168, 357-358.
Orchiston, W., and Steinberg, J.-L., 2007. Highlighting the
history of French radio astronomy. 2: The solar eclipse
observations of 1949-1954. Journal of Astronomical Hist-
ory and Heritage, 10, 11-19.
Orchiston, W., Lequeux, J., Steinberg, J.-L., and Delannoy,
J., 2007. Highlighting the history of French radio astron-
omy. 3: The Würzburg antennas at Marcoussis, Meudon
and Nançay. Journal of Astronomical History and Heri-
tage, 10, 221-245.
Orchiston, W., Steinberg, J.-L., Kundu, M., Arsac, J., Blum,
E.-J., and Boischot, A., 2009. Highlighting the history of
French radio astronomy. 4: Early solar research at École
normale supérieure, Marcoussis and Nançay. Journal of
Astronomical History and Heritage, 12, 175-188.
°Paschenko, M., Slysh, V., Strukov, I., Fillit, R., Gheudin,
M., and Nguyen Quang Rieu, 1971. A search for OH
emission from infrared objects at 1612 MHz, Astronomy
& Astrophysics, 11, 482-484.
Pick, M., Orchiston, W., Steinberg, J.-L., and Boischot, A.,
2010. Highlighting the history of French radio astronomy.
6. The multi-element grating arrays at Nançay. Journal of
Astronomical History and Heritage, 13, forthcoming.
Robertson, P., 1992. Beyond Southern Skies. Radio Astron-
omy and the Parkes Telescope. Cambridge, Cambridge
University Press.
Scheuer, P.A.G., 1984. The development of aperture syn-
thesis at Cambridge. In Sullivan, 249-265.
Smith, F.G., 1984. Early work on radio stars at Cambridge.
In Sullivan, 237-248.
Steinberg, J.-L., 1952. Letter to J.-F. Denisse dated 4 May.
In Bibliothèque de l’Observatoire de Paris, MS 1061, I-1-
B, Carton 4, file 43.
Steinberg, J.-L., 2004. Une belle aventure: la création de la
station de Nançay. L’Astronomie, 118, 626-631.
Sullivan, W.T. III, 1984. The Early Years of Radio Astron-
omy. Reflections Fifty Years After Jansky’s Discovery.
Cambridge, Cambridge University Press.
Sullivan, W.T. III, 1990. The entry of radio astronomy into
cosmology: radio stars and Martin Ryle’s 2C survey. In
Bertotti, R., Balbinot, R., Bergia, S., and Messina, A.
(eds.). Modern Cosmology in Retrospect. Cambridge
University Press, Cambridge. Pp. 309-330.
°Tully R.B. and Fischer J.R., 1977. A new method of
determining distances to galaxies. Astronomy & Astro-
physics, 54, 661-673; this paper is reproduced in °Astron-
omy & Astrophysics, 500, 105-117 (2009), with comments
by Françoise Combes on pp. 119-120.
°Van Woerden, H., and Strom, R.G., 2007. Dwingeloo – the
golden radio telescope. Astronomische Nachrichten, 328,
Dr James Lequeux started research in radio
astronomy in 1954 as a young student, and after a
long military service obtained his Ph.D. in 1962.
He and Jean-Louis Steinberg produced the first
French text book on radio astronomy in 1960.
After a career in radio astronomy and in various
fields of astrophysics, his post-retirement interests
turned to history, and his 2005 book, L’Univers
Dévoilé, is a history of astronomy from 1910 to the
present day. He published a scientific biography of
Arago in 2008, and a biography of Le Verrier in
2009. James is affiliated with the LERMA Depart-
ment at the Paris Observatory.
Dr Jean-Louis Steinberg began working in radio
astronomy with J.-F. Denisse and E.-J. Blum at the
École Normale Supérieure after the War. On his
return from the 1952 URSI Congress in Sydney,
he began developing the Nançay radio astronomy
field station, and from 1960 through to 1965 he
and M. Parise led the design and construction at
Nançay of ‘Le Grand Radiotélescope’. In 1965, he
began developing space research at Meudon
Observatory. In 1960 Jean-Louis and J. Lequeux
wrote a text book on radio astronomy, which was
subsequently translated into English and Russian.
In 1962 he was appointed Editor-in-Chief of
Annales d’Astrophysique, which he and his wife
ran until 1969. For the next five years he was
one of the two Editors-in-Chief of Astronomy and
Astrophysics. Jean-Louis has authored or co-
authored about 80 scientific publications, and has
received several scientific prizes and awards.
Dr Wayne Orchiston is an Associate Professor of
Astronomy at James Cook University, Townsville,
Australia. His main research interests relate to
Cook voyage, Australian, French and New Zealand
James Lequeux, Jean-Louis Steinberg & Wayne Orchiston The Nançay Large Radio Telescope
astronomical history, with emphasis on the history
of radio astronomy, comets, historically-significant
telescopes, early astronomical groups and soci-
eties, and transits of Venus. He has published
extensively, and has edited the book The New
Astronomy. Opening the Electromagnetic Window
and Expanding our View of Planet Earth (Springer,
2005). He also has a book on early Australian
radio astronomy, co-authored by Woody Sullivan,
which will be published by Springer in 2010.
Wayne is the founder and Vice-Chairman of the
IAU Working Group on Historic Radio Astronomy.
... In France, radio astronomy started in 1947 at the Physics Laboratory of the École Normale Supérieure in Paris, soon after WWII (see . There was soon an interest in solar interferometry, when fringes were obtained at 3 cm wavelength by Jacques Arsac and Jean-Louis Steinberg in May 1952 (Lequeux et al., 2010). In 1954, the radio astronomy group moved to the Paris Observatory (Meudon), with an observing station at Nançay on grounds purchased by the École Normale Supérieure (see . ...
... As early as 1953, Jean-François Denisse and Jean-Louis Steinberg proposed a larger interferometer consisting of two movable 25-m antennas, for observation of the 21-cm hydrogen line and in the continuum. However, this project was abandoned the following year, only to be replaced by Le Grand Radiotelescope the construction of which began in 1956 and was completed in 1967 (Lequeux et al., 2010). This caused some frustration for several members of the staff who saw more future in interferometry, which at the times was rapidly being developed in Australia, in Great Britain at Cambridge and Jodrell Bank, and at the California Institute of Technology (CalTech) in the U.S.A. ...
... Meanwhile, millimetre radio astronomy was the domain of another Director, Peter Mezger, so that there were no strong grounds for internal competition. In France, Le Grand Radiotelescope at Nançay was much less versatile than the Effelsberg dish and in practice was only usable down to 10 cm or so (see Lequeux et al., 2010). As we have seen, these limitations were used as an argument in favour of their proposal by those promoting the millimetre interferometer. ...
Full-text available
Radio astronomy started around 1950 in France and in Germany. France was then building inter-ferometers and Germany large single dishes, so it was not unexpected that their first projects involving millimetre radio astronomy were respectively with an interferometer and a single dish. In this paper, we explain in detail how these two projects finally merged in 1979 with the formation of the Institute of Radio Astronomy at Millimetre wavelengths (IRAM), after a long process with many ups and downs. We also describe how Spain started radio astronomy by joining IRAM. Presently, IRAM is the most powerful facility worldwide for millimetre radio astronomy. Dedication: We wish to dedicate our paper to the memory of Émile-Jacques Blum (1923 –2009), who played a major role in the construction of IRAM but died before he could participate in the writing of this paper. An interview made one month before his death was very useful in the preparation of this paper.
... WAET can be seen as a fully-steerable optical variant of the Kraus-type radio telescope, notably implemented as the Big Ear at Ohio State [1] and the Nançay Radio Telescope (1965-) [8]. In contrast to WAET, Kraus-type telescopes have a non-tracking siderostat; they operate at fixed elevation, either as transit telescopes or with a moveable (15 • h −1 ) feed that can track targets briefly at the chosen elevation. ...
Full-text available
The Wide Aperture Exoplanet Telescope (WAET) is a new ground-based optical telescope layout with an extremely asymmetric aperture, which results in new exoplanet imaging reach at very low cost. We suggest that hWAET, a 100x2 telescope, can be built for $150M in the 2020s, and >300m versions merit further R&D.
... After returning to Australia at the end of 1999 I expanded the geographical scope of my research beyond New Zealand and Australia to include the early development of radio astronomy in France (see Débarbat et al. 2007;Encrenaz et al. 2011;Lequeux et al. 2010;Pick et al. 2011-see Fig. 1.19) and later Japan (see Ishiguro and Orchiston 2016; In 2000 I established a Transits of Venus Working Group of the IAU, with a view to encouraging worldwide research on historic transits of Venus in the lead-up to the 2004 and 2012 events. As well as looking at Cook's involvement in the 1769 transit I Fig. 1.19 A recent photograph of the sole surviving Würzburg antenna at the Nançay Radio Astronomy Field Station in France. ...
Full-text available
... Tritton (2011) discusses the history of radio telescopes in Great Britian, while Strom (2008) reminded us of de Voogt's contributions as both an amateur and professional astronomer. Several papers reviewing the history of radio astronomy in France have been published by ), Lequeux et al. (2009), Pick et al. (2011 and Encrenaz et al. (2011). Papers on the history of the Stockert radio telescope by Wielebinski, R. (2010) and the Effelsberg radio telescope by Wielebinski et al. (2011) Wendt et al. (2011c). ...
Full-text available
IAU Commission 40 for Radio Astronomy (hereafter C40) brought together scientists and engineers who carry out observational and theoretical research in radio astronomy and who develop and operate the ground and space-based radio astronomy facilities and instrumentation. As of June 2015, the Commission had approximately 1,100 members from 49 countries, corresponding to nearly 10 per cent of the total IAU membership.
... Papers reviewing the history of radio astronomy in France have been published by ), Lequeux et al. (2009), Pick et al. (2011) and Encrenaz et al. (2011. The early history of radio astronomy in Germany has been published by Wolfschmidt (2008). ...
... In 2012, a new edition of this book for a non science audience Making Waves: The Story of Ruby Payne-Scott, Australian Pioneer Radio Astronomer will be published by Goss as part of the Springer Astronomers' Universe popular astronomy series. Several papers reviewing the history of radio astronomy in France have been published by Orchiston et al. (2009), Lequeux et al. (2009), Pick et al. (2011), Encrenaz et al. (2011. Papers on the history the Stockert radio telescope by Wielebinski, R. (2010) and the Effelsberg radio telescope by Wielebinski et al. (2011) document the development of radio astronomy in Germany. ...
Full-text available
The IAU Working Group on Historical Radio Astronomy (WGHRA) was formed at the 2003 General Assembly of the IAU as a Joint Working Group of Commissions 40 (Radio Astronomy) and 41 (History of Astronomy), in order to: a) assemble a master list of surviving historically-significant radio telescopes and associated instrumentation found worldwide; b) document the technical specifications and scientific achievements of these instruments; c) maintain an on-going bibliography of publications on the history of radio astronomy; and d) monitor other developments relating to the history of radio astronomy (including the deaths of pioneering radio astronomers).
... 4. This project was initiated under the auspices of the IAU Working Group on Historic Radio Astronomy in 2006, and five papers have been published to date. The first dealt with Nordmann's attempt to detect solar radio emission in 1901 (Débarbat et al., 2007); the second with early solar eclipse observations ; the third with the Würzburg antennas that were at Marcoussis, Meudon and Nançay ; the fourth with early solar work conducted at the École Normale Supérieure, Marcoussis and Nançay ; and the fifth with the Nançay Large Radio Telescope (Lequeux et al., 2010). For an earlier overview see Denisse (1984). ...
Full-text available
After constructing a number of simple antennas for solar work at Nangay field station, during the second half of the 1950s and through into the 1960s radio astronomers from the Paris Observatory (Meudon) erected five different innovative multi-element arrays. Three of these operated at 169 MHz, a fourth at 408 MHz and the fifth array at 9,300 MHz. While all of these radio telescopes were used for solar research, one of the 169 MHz arrays was used mainly for galactic and extra-galactic research. In this paper we discuss these arrays and summarise the science that was achieved with them during this important period in the development of French radio astronomy.
Full-text available
During the Second World War, a number of radar scientists independently discovered powerful radio emission from the Sun. Following the cessation of hostilities, and making use of their wartime experience, scientists, mostly at Jodrell Bank and Cambridge in the UK and in Sydney, Australia, used discarded radar systems to further investigate the complex solar radio emission, discovered powerful radio emission from old supernova explosions, and even more powerful radio sources from what later became known as radio galaxies. Encouraged by their early successes with relatively primitive equipment and the potential for new discoveries, scientists in the UK, Australia, the USSR, and the Netherlands developed plans to build more powerful radio telescopes and sophisticated new instrumentation.
The Nançay radio telescope is involved in two main scientific pulsar programs. Monitoring observations of various types of pulsars provide high quality rotational parameters, full radio polarization profiles and ephemerides to support observations taking place at high energy (Fermi LAT). Dense and precise timing measurements of a set of ultra-precise millisecond pulsars is carried out within a European collaboration (EPTA) to search for the subtle effect of gravitational waves, such as emitted by super-massive binary black holes at the center of galaxies.
Full-text available
The first tentative steps in solar radio astronomy took place during the 1940s and early 1950s as physicists and engineers in a number of countries used recycled World War II equipment to investigate the flux levels and polarisation of solar bursts and emission from the quiet Sun, and sought to understand the connection between this emission and optical features in the solar photosphere and chromosphere. There was also an abiding interest in the terrestrial effects of this solar radio emission. Among these solar pioneers were French radio astronomers from the École Normale Supérieure in Paris. In this paper we review the early solar observations made by them from Paris, Marcoussis and Nançay prior to the construction of a number of innovative multi-element solar interferometers at the Nançay field station in the mid-1950s.
Full-text available
After constructing a number of simple antennas for solar work at Nangay field station, during the second half of the 1950s and through into the 1960s radio astronomers from the Paris Observatory (Meudon) erected five different innovative multi-element arrays. Three of these operated at 169 MHz, a fourth at 408 MHz and the fifth array at 9,300 MHz. While all of these radio telescopes were used for solar research, one of the 169 MHz arrays was used mainly for galactic and extra-galactic research. In this paper we discuss these arrays and summarise the science that was achieved with them during this important period in the development of French radio astronomy.
This book presents the story of the planning and construction of the Parkes telescope in New South Wales, Australia and surveys its achievements over the past thirty years. Around this central scheme the author presents a broader history of radio astronomy.
To improve both the sensitivity and bandwidth performance of the Nançay radio telescope, the existing Hoghorn feeds are to be replaced by a dual-reflector feed system originally designed and tested on a 1/20th scale model at CSIRO. The full-size system has now been completed and the authors describe the engineering required to implement it. They give an overview of the design, manufacture and results from the testing of the various components comprising two compact corrugated horns and their associated orthomode transducers and two complex-shaped reflectors forming the dual-reflector configuration.
When Bernard Mills left the GSIRO in 1960 to establish a radio astronomy group in the School of Physics, University of Sydney, he had not only invented the principle of cross-type radio telescopes but proved their great efficiency at surveying the positions, intensity and structure of radio sources. He had ambitious plans for a second generation Cross - a radio telescope with arms one mile long. This paper describes the circumstances of Mills' appointment as Professor of Astrophysics and the recruitment of an international Department that achieved his vision with the Molonglo Cross: The construction involved interaction with many colleagues - engineers in other university departments and government agencies, and with the contracting firms. Formal links were set up with the Electrical Engineering Department through The Radio Astronomy Centre in the University of Sydney and then with Arecibo Observatory through the Cornell-Sydney University Astronomy Center. When the Molonglo Cross completed its main survey in 1978 after eleven years, it was switched off and the EW arm was then converted to the Molonglo Observatory Synthesis Telescope. Many of the staff involved with the MOST are now challenged by SKAMP, testing systems for the Square Kilometre Array with cylindrical geometry in the Molonglo Prototype. These two later developments out of the original Cross telescope are described briefly.