Abstract: Exoplanetary atmospheres are 3D objects and various physical processes make them inhomogeneous over different parts of the planet. In particular, several studies have demonstrated that different thermal structures and wind patterns over the morning and evening terminator can produce an inhomogeneous cloud coverage over the atmosphere. However, a common assumption made while performing transmission spectroscopy of exoplanets is of a homogeneous atmosphere. Considering such an inhomogeneous atmosphere as a homogeneous one can lead to biases in retrieved atmospheric properties. Inhomogeneities in the atmosphere also leave an impact on broadband photometry. In this program, we aim to detect this effect directly on the transit lightcurve of three planets. The magnitude of this effect could be as large as 1000 ppm for suitable targets, which CHEOPS should be able to detect comfortably. While inhomogeneity can be in chemical structure or aerosol properties, we mainly aim to put constraints on asymmetric cloud coverage with CHEOPS observations. We have identified WASP-54 b, HAT-P-30 b and WASP-131 b, as being the best candidates for detection due to their atmospheric transmission signal, transit duration and temperature. Our observations would pave a way for future observations with spectroscopic capabilities to constrain the inhomogeneous atmospheres of these planets.
Temporal Coverage
2024-04-15T15:21:52Z / 2024-04-16T04:33:00Z
Version
3.0
Mission Description
CHEOPS (Benz et al., https://doi.org/10.1007/s10686-020-09679-4) is a European Space Agency (ESA) mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden and the United Kingdom.
The satellite has a single payload comprising an ultra-high precision photometer covering the 330 - 1100 nm wavelength range in a single photometric band. Observations are made as part of the Guaranteed Time Observing Programme that is formulated by the CHEOPS Science Team, and the Guest Observers Programme through which the Community at large can apply for CHEOPS time.
