Tremblin P.,University Paris Diderot |
Minier V.,University Paris Diderot |
Schneider N.,University Paris Diderot |
Durand G.A.,University Paris Diderot |
And 18 more authors.
Astronomy and Astrophysics | Year: 2011
Aims. Over the past few years a major effort has been put into the exploration of potential sites for the deployment of submillimetre astronomical facilities. Amongst the most important sites are Dome C and Dome A on the Antarctic Plateau, and the Chajnantor area in Chile. In this context, we report on measurements of the sky opacity at 200 μm over a period of three years at the French-Italian station, Concordia, at Dome C, Antarctica. We also present some solutions to the challenges of operating in the harsh polar environment. Methods. The 200-μm atmospheric opacity was measured with a tipper. The forward atmospheric model MOLIERE (Microwave Observation LIne Estimation and REtrieval) was used to calculate the atmospheric transmission and to evaluate the precipitable water vapour content (PWV) from the observed sky opacity. These results have been compared with satellite measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on Metop-A, with balloon humidity sondes and with results obtained by a ground-based microwave radiometer (HAMSTRAD). In addition, a series of experiments has been designed to study frost formation on surfaces, and the temporal and spatial evolution of thermal gradients in the low atmosphere. Results. Dome C offers exceptional conditions in terms of absolute atmospheric transmission and stability for submillimetre astronomy. Over the austral winter the PWV exhibits long periods during which it is stable and at a very low level (0.1 to 0.3 mm). Higher values (0.2 to 0.8 mm) of PWV are observed during the short summer period. Based on observations over three years, a transmission of around 50% at 350 μm is achieved for 75% of the time. The 200-μm window opens with a typical transmission of 10% to 15% for 25% of the time. Conclusions. Dome C is one of the best accessible sites on Earth for submillimetre astronomy. Observations at 350 or 450 μm are possible all year round, and the 200-μm window opens long enough and with a sufficient transparency to be useful. Although the polar environment severely constrains hardware design, a permanent observatory with appropriate technical capabilities is feasible. Because of the very good astronomical conditions, high angular resolution and time series (multi-year) observations at Dome C with a medium size single dish telescope would enable unique studies to be conducted, some of which are not otherwise feasible even from space. © 2011 ESO.
Giulieri F.,CNRS Condensed Matter Physics Laboratory |
Jeanneaux F.,Concordia Station |
Goldmann M.,University Pierre and Marie Curie |
Krafft M.P.,Charles Sadron Institute
Langmuir | Year: 2012
Langmuir monolayers of double perfluoroalkyl(alkyl) chain amphiphiles fitted with a monomorpholinophosphate polar head, [C nF 2n+1(CH 2) mO] 2P(O)[N(CH 2CH 2) 2O] (di(FnHm)MP with n = 6, 8, or 9; and m = 1 or 2), were investigated by surface pressure (π)/molecular area (A 0) compression isotherms for temperatures ranging from 15 to 50 °C, and by grazing-incidence X-ray diffraction (GIXD) at 25 °C. Ultrathin monolayers were obtained for these short surfactants. Though the hydrocarbon spacer is short, it has a remarkable impact on the monolayer's organization. At 25 °C, whereas di(F8H2)MP monolayer presents a liquid expanded (LE)/liquid condensed (LC) transition, simply replacing one CH 2 by a CF 2 in the latter compound's structure at constant chain length, i.e. shortening the spacer from 2 to 1 CH 2 (as in di(F9H1)MP), suppresses the LE phase. At 25°, GIXD established that for both di(F8H2)MP and di(F9H1)MP, the chains form an hexagonal lattice in the LC phase. The collective tilt of the two compounds is close to zero. The lattice of the dense phase can be compressed, as assessed by the continuous linear decrease of the d spacing with increasing pressure. This indicates that the azimuthal distribution of the molecular tilts is progressively reduced upon compression. The d value for di(F9H1)MP is significantly lower than that of di(F8H2)MP, providing evidence for strong condensing effect of the fluorinated chains. Molecular areas were determined directly from the compression curves and also from the X-ray data, the latter allowing reconstruction of the compression isotherms. The calculated lattice compressibilities are ∼30% and 50% of the macroscopic compressibilities for di(F9H1)MP and di(F8H2)MP, respectively. Comparison with the experimentally determined isotherms shows that the monolayer of di(F9H1)MP is more stable than that of di(F8H2)MP. The enthalpies and entropies determined for di(F9H1)MP and di(F8H2)MP, derived from the Clausius-Clapeyron equation, confirm that the observed transitions are both of the LE/LC type, although the triple point temperatures are strikingly different (27 °C vs -18 °C); this large difference further illustrates the stabilizing effect of the fluorinated chains. Disorder is hindered by the fluorinated chains and facilitated by a hydrocarbon spacer when larger than 1 CH 2. © 2012 American Chemical Society.
Briot D.,Observatoire de Paris Meudon |
Arnold L.,Observatoire de Haute Provence |
Jacquemoud S.,CNRS Paris Institute of Global Physics |
Schneider J.,Observatoire de Paris Meudon |
And 8 more authors.
EAS Publications Series | Year: 2010
So as to prepare future observations of terrestrial extrasolar planets liable to shelter life, we attempt to detect the life on the Earth seen as a dot. We use the Moon Earthshine, in which any place reflects the totality of the enlightened part of Earth facing the Moon. Observing from OHP and from ESO, we detected terrestrial chlorophyll in the near infrared, the so-called Vegetation Red Edge, and this detection is larger when forests are present than when an ocean is mainly visible from the Moon. Only if observations are made from a high latitude location, and at some moments in the year, Earthshine can be observed during a large part of the day. During these long observing windows, different 'landscapes' are facing the Moon. So the Earthshine corresponding to various parts of our Earth could be studied. Preliminary testing observations have been made at Concordia since the first winterover campaign and the LUCAS experiment has been set up. © 2010 EAS, EDP Sciences.
News Article | March 21, 2016
One thousand kilometres from the Antarctic coast, a 12-strong crew is overwintering at one of the most remote places on Earth. The Concordia Station, a French-Italian research base on the Antarctic Ice Sheet, is truly in the middle of nowhere; the next nearest station is 560km away, and all the crew can see if they look around is flat whiteness. The last plane left for the winter in February, leaving the base completely isolated. It won’t see the Sun for four months and temperatures will drop to below -60 Celsius. Oh, and because it’s 3,200 metres above sea level, inhabitants have to make do with about a third less oxygen than at sea level. It’s not a normal environment for humans, which is exactly why Floris van den Berg is there. A medical doctor sponsored by the European Space Agency, Van den Berg is running a series of research projects at Concordia to explore the physical and psychological effects of living in such surroundings—and the results could give an insight into how we’ll cope with long-distance space travel. “ESA is interested in this place because it’s one of the only places that you have, like, true isolation,” Van den Berg said in an interview over Skype. We spoke after his colleagues were asleep, as he conceded that the 512kbps satellite connection at the base was “quite shitty” if multiple people tried to Skype at the same time. A family doctor from the Netherlands, Van den Berg said it was the remote location that attracted him to the unusual job posting in the first place. Having served as a doctor on expeditions around the world, deepest Antarctica seemed like an impressive location to add to the list. “Working for the European Space Agency is also quite cool in my opinion,” he added. Concordia has several rather unique parallels with space, which makes it ideal for ESA’s research. As we venture further afield—to Mars, for example—astronauts will be spending more time in close quarters and completely isolated from the rest of the world. With current technology, it takes around eight months to send a robotic mission to the Red Planet. Given its total isolation for months at a time, Concordia is sometimes nicknamed “White Mars.” Van den Berg is responsible for collecting a varied slate of samples and data to help give insight into how this environment could affect humans’ physical and psychological wellbeing. One particularly interesting study involves teaching his crewmates to drive a flight simulator of the Soyuz spacecraft, which is currently used to transport astronauts to the International Space Station. It’s a stripped-down simulator with one seat and two joysticks, which users can practice piloting and docking. Van den Berg explained that it’s installed in the Concordia laundry room because it wouldn’t fit in his lab. After initial instruction, he will split his team into two groups; one will receive training on the simulator every month and the other every three months, and he’ll monitor their performance to see how quickly their abilities fade in the environment. “The idea is, if you send people to Mars and they’re going to be in a spaceship for six to nine months they’ll probably get a bit bored, but when they arrive at Mars they have to be quite focused on how to land the Mars lander,” he explained. The 'Simskill' Soyuz simulator. Image: Institute of Space Systems, University of Stuttgart–Andreas Fink Another Antarctic base, British Halley VI, is also conducting the simulator training. As Halley is at a lower altitude, this should help distinguish the impact of the isolation factor from that of the hypoxic conditions. A control is also being run in Stuttgart, Germany. Unsurprisingly, the flight simulator is the most popular of Van den Berg’s experiments, and he admitted he sometimes does it in his free time too. Aside from the simulator, Van den Berg runs regular tests on himself and the rest of the team, which consists of technical staff and researchers working in fields such as climate and astronomy. Using a CT scanner (the first one in Antarctica, installed in the video room) he looks at people’s bone density, which is a major health issue in space travel. He also takes blood samples and analyses them using flow cytometry—which sorts the different cells in the sample—to see how the conditions affect the immune system; NASA astronauts on the ISS are also doing this, which will offer an interesting comparison. “You see a lot of changes, especially in the beginning when people arrive,” Van den Berg said. “Because of the lack of oxygen, you see stress hormones go up quite a bit, which sort of suppresses the immunological response.” Psychological factors are naturally as pressing as physiological ones when it comes to being cooped up for so long, and Van den Berg regularly asks people to fill in questionnaires about their mood and sleep habits. Participants also wear watches that track their activity (especially useful for tracking sleep, which people are often bad at accurately reporting) and interact with beacons on the base to record their movements. “I was quite surprised that everyone was OK with participating with this study, because it’s really like ‘Big Brother is watching,’” said Van den Berg. Participation in all of the research is voluntary. The current Concordia crew on their arrival. Image: ESA/IPEV/PNRA-B. Healey “What’s known from previous years is that in the winter everyone gets a little bit down, so people isolate themselves a bit more [and] spend more time in their bedroom and less in the living room,” he added. “This is something you can measure in detail, to see what the group dynamics are, who is visiting which areas, and how much time people spend alone or with each other.” This is all correlated with people’s questionnaire responses. Of course, Van den Berg is not immune to the psychological effects that he’s collecting data on, and he said that part of his attraction to the job was the “personal experiment” of living at the base. He said the biggest challenges, after adapting to the low oxygen, were coping with the isolation and also having to constantly bug his cohabitants to take part in his studies on top of their own work. There is another doctor at the research base to act as a clinician if people get sick or injured (the base is equipped for surgery as it’s impossible to get people to a hospital for a large chunk of the year, though the team is naturally as careful as possible not to need it). Van den Berg heads up the rescue team if there’s an incident outside the base—“with the cold here it’s really just what we call ‘scoop and run’: get them on a plank and get them inside,” he said. There is the occasional unexpected setback. When his CT machine arrived at the base in a shipping box, it had a hole in the side that looked suspiciously like a forklift had run into it. Without a repair service for thousands of kilometres, Van den Berg had to figure out how to fix it himself, with help over email and Skype. “Luckily there wasn’t too much structural damage and with tape and common sense I could fix it,” he said. With most of a year left to go, Van den Berg sounded enthusiastic about his mission but a little apprehensive. “I’m always ending up with these things where you think, ‘Oh it’s really nice!’ and then you end up in the middle of nowhere and you think, ‘Why did I do this?’ This is, I think, the story of my life,” he said. “But I’m happy because it’s a really interesting place to be.” So far, he hasn’t lost his travel bug, and working for ESA has given him a taste for venturing even further afield. Now 32, he said that if ESA were to put out a call for astronauts soon, he’d apply. With the White Mars experience under his belt, he has more of an idea than most about what he’d be letting himself in for. Correction: This story originally put the base's altitude at 2,300 m above sea level; it's actually 3,200 m. We've corrected the typo.
Crouzet N.,US Space Telescope Science Institute |
Guillot T.,French National Center for Scientific Research |
Mekarnia D.,French National Center for Scientific Research |
Szulagyi J.,French National Center for Scientific Research |
And 19 more authors.
Proceedings of the International Astronomical Union | Year: 2012
The ASTEP project aims at detecting and characterizing transiting planets from Dome C, Antarctica, and qualifying this site for photometry in the visible. The first phase of the project, ASTEP South, is a fixed 10 cm diameter instrument pointing continuously towards the celestial South Pole. Observations were made almost continuously during 4 winters, from 2008 to 2011. The point-to-point RMS of 1-day photometric lightcurves can be explained by a combination of expected statistical noises, dominated by the photon noise up to magnitude 14. This RMS is large, from 2.5 mmag at R = 8 to 6% at R = 14, because of the small size of ASTEP South and the short exposure time (30 s). Statistical noises should be considerably reduced using the large amount of collected data. A 9.9-day period eclipsing binary is detected, with a magnitude R = 9.85. The 2-season lightcurve folded in phase and binned into 1,000 points has a RMS of 1.09 mmag, for an expected photon noise of 0.29 mmag. The use of the 4 seasons of data with a better detrending algorithm should yield a sub-millimagnitude precision for this folded lightcurve. Radial velocity follow-up observations reveal a F-M binary system. The detection of this 9.9-day period system with a small instrument such as ASTEP South and the precision of the folded lightcurve show the quality of Dome C for continuous photometric observations, and its potential for the detection of planets with orbital periods longer than those usually detected from the ground. Copyright © 2013 International Astronomical Union.
News Article | January 4, 2016
In the sky above eastern Antarctica, airborne ice crystals sculpt the sun’s rays into a ring. This phenomenon, called a 22-degree halo, is the result of sunlight passing through tiny, six-sided ice cylinders in high-altitude clouds. The crystals act like prisms, bending incoming light 22 degrees off course. Millions of crystals at various orientations can cast a full circle of light around the sun. While dramatic over polar regions, these halos can occur worldwide, even at the equator. Some halos are decorated with bright spots known as sun dogs or mock suns. Italian photographer Enrico Sacchetti captured this halo in 2013 over Concordia Station, a joint Italian-French research base on the Antarctic Plateau, one of the coldest places on Earth. While ice in the air puts on a light show, the ice surrounding the station provides researchers an opportunity to study the planet’s history: Accumulating layers of snow trap bubbles of atmospheric gases and, over time, build up an archive of past climates. Ice cores from near Concordia provide the oldest records of atmospheric carbon dioxide, dating back at least 800,000 years.