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Affichage des articles du 2014

Plotting a data set with two different units in Matplotlib

In my thesis, I handle polarimetric observations of Venus with Venus Express. Because of the north polar elliptical orbit of the spacecraft, when observing in nadir there is a link between the phase angle and the latitude of observation1. Though, this is not always easy to understand so I found the need to plot my polarimetric measurements as a function of phase angle, but also as a function of latitude. I was thinking of plotting the phase angle on the bottom x-axis, and the latitude on the top x-axis. Can we do that in Python/Matplotlib? 
Of course you can!
Matplotlib has brilliant functions called twinx and twiny that take an axis object and duplicate it keeping the same x or y axis that the original. Therefore only the x/y axis is editable as the other is ruled by the original axes.
This can be used to plot two independent curves with different y-axis, but also to plot one value with two units (e.g. Celsius degrees and Farenheit degrees). In the latter case, the relation is known…

What to see in EGU 2014? (According to me)

The European Geosciences Union (EGU) will hold its General Assembly in Vienna from the 28th of April to the 2nd of May. Gathering more than 10 000 scientists from all over the world, the EGU is a very interesting meeting for geophysicists.

Of course, the field is dominated by Earth sciences and planetology is not the biggest topic. Nevertheless, it is a good opportunity to meet people and colleagues in the beautiful city of Vienna.

I've been there last year and it was pretty nice, especially because there was a specific session on polarization where I had a poster. I met very important people during the poster session so it was a memorable experience. Anyway, posters are better than orals to meet people and discuss with them. Well a fresh drink and some food can also help.
This year is different as I'll have my 12 minutes in the PS2.5 session : atmospheres of terrestrial planets. The session will have talks about Venus, Mars and Titan, and I'll of course be presenting my w…

Réunion Jeunes Impec 2014-30-01

Le LATMOS est constitué de 6 départements, dont deux ont des thématiques astronomiques et astrophysiques. IMPEC porte sur les atmosphères des planètes du système solaire ainsi que sur les surfaces des planètes et des petits corps (comme les comètes par exemple). HEPPI s'intéresse plus aux exosphères, et plasmas et aux interactions avec le vent solaire.
Au sein d'IMPEC nous organisons régulièrement des réunions internes que nous appellons les réunions Jeunes Impec. Le terme jeune ne recouvre pas une zone précise, mais comme la moyenne d'age dans notre département est assez basse, la plupart des chercheurs viennent. Les réunions rassemblent ainsi les doctorants, les contractuels et les permanents. Chacun parle un peu de l'avancée de ses travaux et des problèmes qu'il peut rencontrer. Les discussions sont en général assez informelles et permettent deux choses : Cela permet de rester informé de ce qui se passe dans le reste de l'équipe, ce qui n'est pas du luxe…

Computing bits — 1

Hello World,
As it says on the tin, these posts will be about tips and tricks I'll gather this and there about computing. If they were (are) useful to me, they're likely to be helpful for someone else. So I'll put them here so everybody (including me) can find them when necessary. Be warned : I'm in team (Gnu/)Linux and I follow the Curch of Vim after having spent a few years in the Church of Emacs (so I'm happy with both). As a scientist I also use Python to read and process SPICAV data. And the cloud model I use is in FORTRAN which is a necessary pain to me. And when it comes to writing something (reports, papers, posters and slides) I'm most definitely in the team LaTeX.
Luckily enough this matches perfectly with my PhD advisor's habits. Luckily because, as to quote him : “[He] would have made [me] change”. Pfiuu!
Vim + Python = PROFIT
Vim is a great text editor, whose only decent competitor is Emacs (but Emacs is almost an OS). I already had my vim set…

Pourquoi les doctorants devraient être sur les réseaux sociaux.

Article mis à jour le 2014-02-05.

Au cas où vous ne l'avez pas encore remarqué, je suis très fan de Twitter, qui est pour moi le réseau social par excellence. Mes amis et collègues sont parfois assez perplexes face à mon usage intensif des réseaux sociaux pour ce qui est de la science.
Un exemple simple est la conférence Elbereth 2013. Je reviendrai dans un autre article sur Elbereth, tant il y a à dire. Mais lors de la conférence, j'ai utilisé Twitter et le hashtag #elbereth2013 pour relayer des informations au sujet des revues et des conférences. Le problème est le suivant : j'étais le seul à tweeter. Cela m'a permis de réaliser à quel point les doctorants sont loin d'être présents professionnellement sur les réseaux sociaux. Sans doute la plupart d'entre-eux sont sur Facebook, mais plus vraisemblablement pour un usage privé.
Globalement, quand on compare les laboratoires et les chercheurs français à leurs homologues anglo-saxons, en particulier les américain…

What's up Science? — 1

Hello to all,
this post is the first in a series of “reviews” of some things I have found, read, or heard on the web and through my scientific monitoring. If I found it interesting, you might as well, so I'll do like every good scientist does: share and enjoy!
Rosetta
The big news of this week is of course the successful awakening of ESA's comet chaser : Rosetta (fr)/(en)!
I was following intensively the event on Twitter (#WakeUpRosetta), and it was already tense. But if you want to watch the full media briefings and videos on that day to feel even more the tension, ESA has set a playlist on Youtube for you.

The LATMOS is quite involved in Rosetta with 7 instruments:
On the orbiter: ALICE : UV spectro-imagerCONSERT (Comet Nucleus Sounding Experiment by Radiowave Transmission) : Hyperfrequency souding of the comet's nucleusMIDAS : Microscope to study the dustsOSIRIS : Visible cameraROSINA : Neutral and ionized gases spectrometerOn Philae:
CONSERTCOSAC : Mass spectrometer and …

Introduction

Welcome here on my blog! I am Loïc, a PhD student currently working in LATMOS in Guyancourt, France. LATMOS stands for Laboratoire ATmosphères, Milieux et Observations Spatiales, which deals with atmospheres and surfaces of our home planet and the others. This implies that there are a lot of people studying the Earth climate, using satellites and other spatial instruments. I am on the other part: the one that studies other planets. My team (IMPEC) covers Mars, Venus, Titan, asteroïds and comets.
I myself study Venus. Less popular than Mars or Titan, Venus is still pretty cool. It is hell! Surface pressure is about 90 times the Earth's atmospheric pressure, temperature can reach 400°C on the surface, and the atmosphere is mostly made of carbon dioxide and nitrogen. The rest is sulfur, reacting with the (few) water that's left to form clouds of sulfuric acid. It is so much like hell that the spacecraft we (by “we” read “the Soviet Union”) sent lasted about an hour max. I&…