The project "TArget PrioritizAtion routineS for CHEOPS observations" (TAPAS4CHEOPS) is funded by the Austrian Research Promotion Agency (FFG) under the ASAP12 scheme and as part of the Austrian contribution to the CHEOPS mission.

Project summary

Both exoplanet missions and ground-based facilities revealed the existence of a great variety of planets, particularly of intermediate-mass (sub-Neptune, super-Earth) with masses between 2 and 14 MEarth, which present a large spread in density. These planets are the primary target of CHEOPS, the first S-class ESA mission, which aim is the detection of shallow transits of low- and intermediate-mass planets orbiting bright stars. Typical CHEOPS targets will be systems hosting planets already detected by radial velocity, for which CHEOPS will search for transits, and systems hosting planets detected with the transit method by other facilities (e.g., NGTS and TESS), but for which the measurement of the radius requires a considerable improvement. Hundreds of possible CHEOPS targets are foreseen, but the time constrained nature of CHEOPS observations will not allow to observe them all. It is therefore necessary to construct a target prioritization strategy.

The primary aim of this project is to produce the currently missign piece of information to provide a tool for a fast target prioritisation. We propose to build a method and tool capable of providing a fast rough planet characterisation, based on theoretical models, for CHEOPS targets. We recently developed a method that allows one to provide a first characterisation of the atmosphere of an intermediate-mass planet provided only its transit radius. The method allows one also to infer the minimum planetary mass, while the maximum mass can be inferred from considerations on planetary density and formation.

We are currently computing a large grid of hydrodynamic models of the upper atmosphere of planets considering a parameter space composed by: planetary mass, radius, equilibrium temperature, and stellar high-energy input flux. We will use the grid of models, together with available predictions of the atmospheric masses to compute planet atmospheric evolution tracks, taking into account a range of realistic levels for the initial high-energy stellar flux. We will use the grids to design a characterisation scheme for the planets discovered with the radial velocity method and with transits detected by CHEOPS. The scheme will be made available through a public web tool and will be used to prioritize either further CHEOPS observations or follow-up observations aiming at a full atmospheric characterisation. We will use our developed innovative method to design also a characterisation scheme for planets discovered with the transit method by other facilities, hence possible CHEOPS targets. Also these tools will be made available through a public web site. We will finally explore possible wider implications of our findings to study the feasibility of a large-scale usage of the tools developed within the project.

Project participants

Luca Fossati (PI)
Darya Kubyshkina (main project postdoc)
Helmut Lammer (support)
Monika Lendl (support)


The grid of planetary upper atmosphere models and interpolation routine presented by Kubyshkina et al. (2018) can be downloaded here here.
This is still work in progress and to properly use the data/information contained in the tar file, please, contact us at daria.kubyshkina AT or luca.fossati AT

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