An Awesome Visit to the OCA Observatory on the Plateau de Calern

My partner and spouse Ralph Doggett and I are living the idyllic life in Grasse, France, where we enjoy exploring the region for the cultural and photographic opportunities it brings us. These opportunities are often an unexpected combination of adventures. On one recent occasion, we accepted an invitation that surprised us in a variety of ways – starting rather unexpectedly with one of those hikes that the French call a “rando” along the “Plateau de Calern” near Grasse on an unusually hot day in June.  Our hiking adventure, however, was only the beginning of several surprises – discovering a chapel inside a cave, for one, but most especially seeing for the first time a laser-driven telescope. This was, after all, an invitation to visit the famed Observatory of the Cote d’Azur (OCA) – an awesome learning experience for us in and of itself. But the visit proved to be a fabulous combination of unexpected adventures.  Here is a brief commentary with a photo collection  of the hike (“rando”) on the plateau, the cave and the observatory(plus a delightful dinner in the middle of it all).

We had been invited to visit the famed Observatory of the Cote d’Azur (OCA) by a friend, Monique Torre, who was a student in my American English class and whose partner Jean-Marie Torre had recently retired from years of working at the Observatory as a research engineer. We knew about the observatory – believing that we had seen it from a distance up in the Pre-Alpes somewhere – but had never been up in that area. Monique had warned us to dress warmly (in spite of the early summer heat) and wear comfortable shoes as we had agreed to arrive early for a walk around the terrain. We picked her up in Peymeinade, and she directed us up through St. Vallier de Thiey and past Caussols onto the Plateau de Calern where the Observatory is located.

There were multiple dome-shaped buildings scattered along the edge of the plateau, but otherwise the area was a long stretch of rocky grassland with mountains in the distance. We parked near the main observatory building and were greeted by Jean-Marie who asked us if we had any requests for what we wanted to see. He pointed in one direction across the plateau where he described we could visit an old chapel and then in the other direction to see some other geological wonder. Not knowing which direction to choose, we agreed with his suggestion that we go to the chapel first and then go off in the other direction if we still had the time.  This was not, then, simply a chance to walk around the plateau to capture glimpses of the sea. This was what the French call a “rando”.

The Randonnée on the Plateau de Calern

As we discovered, this region of the Cote d’Azur, inland into the Pre-Alpes, is very popular for the sort of “randos” that are very much a part of the local culture. That’s short for “Randonnée” or “randonner”, which translates into “hike” or “to hike”, but it actually means a long hike, usually in the countryside somewhere.  These randos are  categorized in terms of their level of difficulty – “facile, moyenne, difficile and très difficile”, based on the length but mostly the terrain. Technically, our hike was relatively short (under two hours), from the complex of OCA buildings to a cave that had been transformed into a chapel in the rocky hillside at the edge of the plateau. But for us it was relatively difficulty – classified, perhaps, as “moyenne” for those who are regular hikers. Perhaps even “facile” – but not for us older and slower folk.

 As a first outing of this sort for us this summer, I would have to say it was really quite challenging. We were much slower than our guide, and I even needed his help navigating some of the uneven terrain – especially as it overlooked a steep drop into the valley of Caussols. Ralph, on the other hand, while hiking at a slow pace (with his cameras), did hang in there for the targeted destination – a cave in the hillside that serves as a chapel at least once a year. I am grateful that our guide persisted in getting us to reach the chapel – and that Ralph was there with his camera collection. What a remarkable cultural revelation!

The Plateau de Calern is a large stretch of deserted land (no water for miles) but for the array of structures that serve as part of the Observatory of the Cote d’Azur (OCA).  The hike to the cave involved walking across large unmarked stretches of very rocky grassland, followed by steep and narrow climbs along the ridge of the plateau and up into the rocky hillside.  On my way to the cave, I had visions of that tragic figure in the story Perfume who walked (well, hiked) across the broad expanse of rocky unmarked paths from Paris to southern France back in the days before Napoleon. Could I imagine what he experienced? (Well, not the whole story, of course.)

There are large patches of terrain with desert-like brush in rocky soil and a few roads made of rocks to allow vehicular access to reach the higher elevations that are reserved for observatory-related functions. Otherwise, the area is open for “randos” and the like – plus the occasional clusters of sheep or boars or what-have-you. Our guide mentioned the presence of wolves from time to time and also observed, to my distress after having walked through the brush, that there are lots of small but poisonous snakes on the plateau. Yikes! He assured us that they aren’t killer snakes, but I was relieved that I had not encountered any on the way to the cave – and that our return from the chapel was by a vehicle that fetched us along the rocky road without our having to walk back through the brush!

What an introduction to the terrain, though! As guests of the recently retired Jean-Marie, we were fascinated by the plateau, with its unique mixture of local traditions, empty spaces and scattered domelike structures  of small white observatories.

As we learned later, these scattered observatories are ,housing a wide variety of “geodesic” experiments, a mix of research and learning facilities connected with the University of Nice.  One of them, no longer functioning it seems, was the famed “Schmid” observatory. We also learned later that these structures were derived from a design by a famed architect Charles Garnier when the initial observatory was first established – way back in 1879.  Well, perhaps only the original observatory in this complex (in Nice itself) was designed by him, but we had the impression that the layout, with all its strengths and weaknesses, came from his original work – supposedly in collaboration with another well-known architect of the 19th century – Gustaf Eiffel.

A Lovely Dinner in Caussols

Anyway, the main purpose of our visit was not to tour the plateau or the scattered array of structures, but rather to visit the largest of the observatories on the plateau, housing the large refractory telescope that links the network of observatories known as the Observatoire Cote d’Azur (OCA) with a global network of similar observatories around the world. This particular structure houses the telescope – but also the laser-driven observation of data through the precise and accurate measurement of distances to the moon and to a bunch of satellites that the telescope is built to gather.

But wait, it was still only 8 pm, a good two hours before sunset.  Not yet time to visit the observatory itself. Fortunately for our tired limbs from the unusually rigorous “rando” that preceded our anticipated tour of the telescope, we were driven back to the village of Caussols, where we joined some other friends of Jean-Marie for a surprisingly elegant dinner at the Auberge de Caussols. The chef/owner of the auberge chatted cheerfully with us as we chose our three-course menus – and took the photo below of the dinner party.  Our friend Monique is on the bottom right, seated next to Ralph and me. Quite a feast it was!

The Main Event – a Refractory Marvel

Pleasantly refreshed, we returned to the OCA Observatory. The main structure has a big dome for the telescope, of course, but we started on the ground floor where one finds the main monitoring station. A non-descript but very large desk (more like a long table) held multiple computers and screens that were lit up with detailed data on display in a variety of charts and graphs. The observatory’s scientific team spends a good part of its time monitoring and analyzing the data here or in a neighboring room with multiple desks and computers, presumably connected in some way to the main monitoring station. All of this was rather non-descript for anyone not specifically acquainted with the content.  As our host Jean-Michel explained, the telescope itself is not something that they spend a lot of time looking at on its own. It is, rather, the extremely accurate data that the telescope is gathering and transmitting to these monitors that attracts their attention on a continuous basis.

The room did, however, have something that even non-scientists could appreciate. A large photo of the moon was hanging on the wall across from the monitoring station, It showed where five different Apollo and Russian lunar missions had positioned reflectors on the moon, specifically placed there for linking up with telescopes like the OCA telescope here on the Plateau de Calern.

In addition, we learned, there are satellites circling the earth with reflectors that are also capable of being linked to these points on the moon as well as to the network of the telescopes through their own reflectors. The precision of the lasers of light that are being transmitted by these telescopes and refracted back from the moon and from the satellites enables highly accurate measurements of the earth. Without going too much into the details of the science of “spatial geodesy”, one can note that there are lots of advantages to these measurements. The size, shape, distance and direction of things (like oceans or polar ice caps) on the earth’s surface, or the role of gravity and its effects, or the positioning of satellites themselves are among the things being measured. (The office on the ground floor of the observatory, by the way, also had a strangely distorted shape of the Earth that conveyed the multi-faceted nature of such things as temperature and gravity and water.) All of this means that the benefits of high-precision GPS, for example, makes it easy for everyday people like us to get around without a hard-copy map in hand. It is the precision of the data that makes all the difference. Wow! And that’s just one example of how all this sophisticated technology of laser beams is affecting our daily lives. Just imagine what all that data can do for the scientific world!

But I am slow to get to the main purpose of the visit – getting to see the telescope itself.  We were, at last, escorted upstairs to the telescope.  It was in the shape of a big cannon in the middle of the large room. There were multiple gadgets along the walls, but our focus was directed to the inside of this cannon. It had a large opening – all dark inside. But, with a flashlight shining into the darkness, one could see the mirrored backing of something that looked like a large camera lens at the far end of the cannon.

After we scrutinized the interior of the telescope, we were then urged to look up. Our host turned on a switch that opened up a large part of the domed ceiling – sort of like a piece of cake or a portion of a melon cutting into the ceiling. And he even showed how that open slice of the ceiling could be moved around to be positioned anywhere around the full circle of the structure’s ceiling. We understand that this enables the telescope to link its laser transmissions to and from the moon but also to the various satellites in the network – all of which, of course, are movable parts.  We walked around the room a bit and looked again into the cannon and up at the opening in the ceiling.

Then we went back downstairs to a very curious room that had a large staging area in the middle – like a table for a railroad set – but with clear plastic curtain sections all around it (for dust control, we were told). Instead of a train set, though, the raised table had a collection of metal boxes, cables, circular lenses and tubes.

Our host turned on a switch that lit everything up, and the things on the table started flashing away! This was the LASER! Incredible! The light was being transmitted through different objects with bursts of light here and there. It was operating to increase the strength and focus of the laser beams that would be transmitted up to and then by that telescope upstairs to the refractors on the moon and on the satellites . And, as he showed us with a slip of paper along the beams of light that were flashing from gizmo to gizmo, it was very powerful stuff (and increasingly so as it heated up)  – burning the paper just as it could easily burn off his finger if he accidentally put it in the wrong place. How interesting it was to realize that this wasn’t just someone turning on the lights to get a better look around the place but rather a matter of powering up a laser, to transmit and bounce back powerful flows of light to and from the moon and all these other distant objects.

Our next step in the tour was to go outside in the dark. The telescope was “turned on”, as it were, and suddenly there was a shimmering flow of light from the cannon shape of the telescope off into the distance, somewhere near the Big Dipper in the sky. It was a continuous shimmer of light that was connecting the telescope to a satellite. As we watched this phenomenon, we realized that the flow of light was gradually moving across the sky to stay connected to that satellite. It was fascinating to realize that this glow of light was actually transmitting powerful light rays to an invisible satellite in the sky. Then the telescope was moved for its flow of light to be transmitted in another direction. The flow of light was even moving in waves to bounce up and around the earth and on up to the moon.

As the flow of light waved in the darkness of the sky, it was also a lesson in how important it is to make sure there are no airplanes or other objects in the sky where the laser light is going. Following this illustration of its power, the flow of light was shifted back to the satellite. Later in the evening, we understand, the laser was connecting the telescope to one of the reflectors on the moon itself. But regrettably, we were exhausted and did not wait for the moonrise – well after midnight on this occasion. It was awesome, nonetheless, to see the power of that river of light in spite of its not being well suited for Ralph’s cameras to capture its magic.

In addition to this impressive light show, though, we were introduced to some of the other more traditional astronomical benefits of the observatory and its network of telescopes. Star-gazing is clearly one of these benefits – as we saw through a small but fixed telescope that first showed how a distant star in the sky was in fact two stars quite far apart. Our host also showed us a “dying” star through the telescope. And, of course, we do know that this OCA complex played an important role years ago in identifying new stars in the universe. What we didn’t get to see, but would love to know a bit more about, is what kinds of experiments are being conducted in all the smaller observatory buildings on the plateau. We do understand that this is a teaching observatory – where courses are taught with on-site observatory experiences as part of the curriculum with the University of Nice.

Thanks are due here to my long-time partner and the photographer of this display, Ralph Doggett (pictured here on the left) and to the gracious host of the outing Jean-Marie Torre, research engineer (retired) at the OCA Observatory (pictured here on the right). Thanks also to Jean-Marie’s partner and spouse Monique who arranged for us to participate and accompanied us on this awesome adventure.


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