CHEOPS - CHaracterising ExOPlanet Satellite -  is the first mission dedicated to the search for exoplanet transits using ultra-high-precision optical/near-infrared photometry on bright stars already known to host planets. It is the first S-(for small) class mission in the ESA science programme, and a partnership between ESA and Switzerland, with important contributions from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden and the UK. 

The 3.5 year lifetime (nominal, goal 5 year) mission will deliver the unique capability of determining accurate radii for a subset of planets in the Earth to Neptune mass range for which the mass has already been obtained from ground-based spectroscopic surveys, as well as for new, Neptune-sized and smaller planets discovered by ground-based transit surveys. The combination of accurate mass and radius provides a measure of the planet bulk density of the planet, and with it insights into the planet composition, structure and formation history. 

The CHEOPS payload comprises a single instrument - an ultra-stable, single-band photometer (350 - 1100 nm waveband) that is in the focal plane of a telescope with a clear aperature of 30cm. The CHEOPS science objectives put very stringent requirements on photometric precision: to detect Earth-sized planets orbiting G5 dwarfs with V-band magnitudes of between 6 and 9 requires a precision of 20 parts per million to be reached in 6 hours (transit duration of a planet with a 50-day orbit); in the case of characterisation of a Neptune-sized planet orbiting a K-type star with V-band magnitudes of down to 12, a precision of 85 parts per million in 3 hrs (transit duration of a planet with a 13 day orbit) needs to be achieved. 

The CHEOPS Consortium is led by the University of Bern. More details about the mission can be found at and

20% of total observing time will be available to the Community through an ESA-managed Guest Observers' Programme. Calls for proposals for time will be requested through a series of open ESA Announcements of Opportunity (AOs) foreseen to be issued on an annual basis, with the first AO to be made around 6 months before launch. Selection of successful proposals will be made by a Time Allocation Committee appointed by ESA based on scientific merit. 


With the launch foreseen towards the end 2018, now is an appropriate time to start preparing to respond to the first AO. Prospective observers are invited to attend the CHEOPS Open Time Workshop that will be held on the 26-27th July (1 day, afternoon and morning), immediately after the 5th CHEOPS Science Workshop (for further details on the Science Workshop, see link) to which you are very welcome to attend also/submit an abstract for.

The agenda for the Open Time workshop has been designed to inform the Community User about CHEOPS and the Guest Observers' Programme. Talks will provide an overview of the mission -- its capabilities, scientific objectives,  payload and specifications, observing modes and performances, schedule and data products --  as well details on how to apply for observing time on CHEOPS, to observe with CHEOPS and to access CHEOPS data. Hands-on demonstrations will provide the opportunity to see and to use tools that will be available to support the observer through all steps of the CHEOPS observing process: from proposal preparation, through observation preparation to archive access to CHEOPS data.  

A detailed agenda will be put on this website in coming months.  



The workshop will be held in Schloss Seggau, near Leibnitz, in the South of Austria, and will run from 14:00 26th July to lunchtime on the 27th. Details on the venue and how to get to it can be found at the  following link. 

The recommended place to stay is at the hotel within the castle - details on the accommodation, including how to book and pay, can be found at following link



To register for the Open Time Workshop please complete the form at the following link.
This single form covers registration for both the Open Time workshop and the 5th CHEOPS Science Workshop, and, in the case of the science workshop, abstract submission also. Update of your registration will be possible up to the appropriate closing dates.

The Open Time workshop registration fee is 45 Euros which covers the cost of dinner on the 26th and lunch on the 27th; both meals will be buffet-style. Refreshments during coffee breaks are also included in the fee, as is water with meals. Payment should be made on arrival to the hotel on arrival at the workshop.

Please contact CHEOPS-OT-workshop2017(at)  in case of questions (note: please replace (at) by the "at" symbol) 

Kate Isaak 
CHEOPS ESA Project Scientist  

on behalf of the Organising Committee