ARES II: ARIEL School, biarritz 2021



Dates : 2 – 11 October 2021

Responsables : J.P. Beaulieu, P. Drossart

Comité d’organisation: P. Drossart, J.P. Beaulieu, Q. Changeat, J. Leconte, A. Tsiaras, O. Venot, I. Waldmann.

Sponsor: CNES, CNRS

Useful links from the 2019 edition

Ariel Space mission

ARIEL mission ESA yellow book

Planetary Spectrum generator

Chemical equilibrium calculation

Line lists from exomol

Iraclis pipeline (analysis HST data)

angelos Tsiaras thesis

Iraclis notes

ExoAI, link to TauREX code

Presentation ARIEL en français (2019)

















Ariel is a space telescope project that will measure the composition and structure of the atmospheres of 1000 extrasolar planets, from gas giants to hot and temperate rocky planets, around stars of different types. It will constrain the nature of the planets, detect the presence of clouds and study the interactions of these other worlds with their host stars. ARIEL is supported by a consortium of more than 60 institutes in 15 European countries, under British coordination, and two major partners, France (IAP, CEA, LESIA and IAS) and Italy. The project was selected in 2018 by the European Space Agency (ESA) as the fourth Mid-class mission which will launch ARIEL in 2028 from Kourou, Guyana. In preparation of the science preparation and exploitation, we are organizing regularly an ARIEL school.

This is the second edition. This school will address the central question in exoplanetary retrieval of the accuracy of the modeling. As spectroscopic observations are slowly improving from simple composition retrieval towards more accurate atmospheric structure modeling, one-dimensional models in chemistry and cloud structure, or 2D models in global circulation may reach their limits.

This school will be organized starting with curses giving a background on exoplanetary atmospheres, radiative transfer questions and chemical or meteorological models, followed by training session with direct involvement in retrieval and simulation with up-to-date models. Hands-on work is an important component of the school.


Second announcement and preliminary program

Exoplanetary atmospheres : from 1D to 3D models

Objectives : to achieve a good synthesis of the questions related to 1D-3D modeling of planet atmospheres with application to selected systems and new deeper study of 1-3 systems. We will perform blind test work, trying to retrieve the underlying systems of realistic simulated observations.

By-products : write a unique master paper including all the results reached during the school

Structure : courses + training session (with one or more senior, two juniors working together)

Preliminary program

Time frame

• Sunday Oct 3 : 9-13 (4h) – free afternoon

• Monday – Tuesday 9-13 - 14-18 (8h)

• Wednesday 9-13 (4h) - free afternoon : excursion to the ‘’château d’Abbadia ‘’

• Thursday – Friday 9-13 - 14-18 (8h)

• Saturday Oct. 9 : 9 -13 – 14-16 (6h) Closing dinner

Sunday 10, 9-11, then end of school

Total 52 hours = Courses (18h) + Training (32h=8 x 4h) + conclusions (2h) Courses 18h total –

From Saturday, Oct.2 until Wednesday, Oct 6

L = long course (2h * 6) S= short course (1h * 5) + introduction to training 1h

1. Detection of exoplanets : methods, spectral observations (Jean-Philippe Beaulieu ) -L1

2. Thermo-chemistry/ Photo-chemistry (Olivia Venot) -L2

3. Relations between Solar System and exoplanets ; planetary escape (Pierre Drossart)- S1

4. Clouds (condensation, haze, microphysics of clouds) (Pierre Drossart & TBD) – S2

5. Atmospheric structure (thermal structure, Radiative – convective models) - TBD L3

6. Atmospheric dynamics – theory (Jeremy Leconte) – L4

7. Molecular spectroscopy (TBD) – S3

8. Spectral reduction methods (Angelos Tsiaras ) S4

9. Global Circulation models (Jeremy Leconte) S5

10. Introduction to the training

11. Optimization methods, Bayesian methods, AI (Ingo Waldmann ) L5

12. Planetary spectral retrieval (Taurex et al) (Quentin Changeat) L6 Training sessions : 32 hours = 8 sessions of 4 hours (first hours devoted to starting the models and computing codes) 

Organisation of training sessions with independent groups working in parallel in competition :

• 1st part – Each group creates 3 models with GCM (3D) and chemistry (1D) – TBD

• 2d part – Each group must make retrievals from the output of the other group and find out what were the underlying initial models.

Conclusions and future plans = 2h (Saturday Oct 9) – plan of future master paper



The school is open to PhD students and post-doctoral researchers, with a total headcount of 20 participants. Teaching will be presented by researchers and professors of the field, with training session supported by young research scientists involved in the development of the models.

The 1st Ariel school in Biarritz was held in September 2019 and devoted to atmospheric retrieval studies through open source codes. It has been a great success and resulted in five academic papers published to date. These were leaded by participating students and based on work begun during the school and continued thereafter.

Support: A budget is available to support the accommodation and food for French students and a number of international applicants. Travel expenses are your responsability.

How to apply: send an email to JP Beaulieu ( and Pierre Drossart ( by May 31, 2021 with a CV describing early career, a 1-2 pages long motivation letter and a support letter from adviser and/or senior scientist.

Since there are only 20 places, it will be a competitive process. We will announce the list of selected participants and those who are on the reserve list, mid-june.

Location : It will take place at the Village de vacances VTF "Le domaine de Françon", 81 Rue de Salon, 64200 Biarritz, France. Biarritz is bordered by the Atlantic Ocean and crossed by the Pyrenees mountain range. Nestled in the extreme south-west of France, Biarritz is an elegant city, acclaimed for its beaches, surf spots, golf courses, thalassotherapy centers and gastronomy.