CHEOPS Guest Observers Programme

20% of science observing time on CHEOPS is made available to the scientific community to conduct investigations of their choice in the form of an ESA-run Guest Observers’ (GO) Programme. Proposals for GO Programme observing time will be solicited through a series of annual Announcements of Opportunity (AOs). In order to allow new targets to also be included in the GO programme at any time during the mission, up to 25% of the open time will be allocated as Discretionary Time (DT), as part of the Discretionary Programme (DP). This will be overseen by ESA, in consultation with the chair of the TAC and the CHEOPS PI.

On this website we provide the links to key information relevant to prospective users of CHEOPS.


The Third Annual Announcement of Opportunity (AO-3) for observing time on CHEOPS has now closed. The Time Allocatoin Committee met on 11-13 May 2022, with their recommendations put forward to the Director of Science for consideration. A list of the programmes awarded observing time on CHEOPS can be found at:

An overview of all observing time awarded through ESA's Guest Observers Programme can be found on the webpages detailing the results of individual calls (AO-1: end March 2020 - March 2021; AO-2: end March 2021 - end March 2022; AO-3: July 2022- end September 2023), as well as that for proposals awarded time via the Discretionary Programme which has been running since June 2020.

AO-3 was the final call in the nominal mission of CHEOPS, with any further call contingent on the mission being extended. Meanwhile, scientists interested in using CHEOPS  should consider applying for observing time through the Discretionary Programme, details of which are available on a dedicated webpage at:



Questions on the Guest Observers Programme? Please send an email to the ESA CHEOPS Project Scientist at  cheops-ps at cosmos dot esa dot int, replacing the "at " with "@" and "dot" with "'." respectively, or cheops-support at cosmos dot esa dot int, with the same substitutions as noted previously.


Last updated:  27 May 2022