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. 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 participation in the CHEOPS Guest Observers Programme was due to open on 9 November 2021. The AO was postponed and will now open 15 February 2022. The timetable for the AO is given below. The proposal submission tool will be made available on 15 February 2022 together with the Policies and Procedure document which captures details of the contexrt, constraints and requiremend for and relevant to the AO.

Date/duration of AO step


15 February 2022

AO-3 opens

Webpage for the AO goes “live”, including Policies and Procedures document

Phase I Proposal Handling Tool can be used

Reserved Target List is available

15 March 022. (midday GMT)

AO-3 closes

Mid-May 2022

Time Allocation Committee meets

List of proposals recommended for the award of time put forward to Director of Science

No later than  25 May 2022

Results of AO-3 announced – PIs of all submitted programmes informed of the status of their proposals

1 June 2022 (start)

Preparation of Phase II inputs.

Steps include submission of observation requests (by 14 June), ESA/SOC review (by 21 June) and update (by 24 June)

Very end of June 2022

Start of observations from AO-3 programmes

In the meantime, there are a number of documents, tools and webpages available to help you to familiarise yourselves with the capabilities of CHEOPS. Details of these can be found on the following webpage:

There is also a Frequently Asked Questions page that details answers to some commonly asked questions. This can be found at:

The Discretionary Programme remains open, with further details available at:



The results of previous Calls can be found here (AO-1: end March 2020 - March 2021; AO-2: end March 2021 - mid March 2022).

Observing time on CHEOPS is currently available through the Discretionary Programme - further details of the programme and how to apply can be found here.



Questions? Send an email to the ESA CHEOPS Project Scientist at  kate dot isaak at, replacing the " dot " and the " at " with a "." and "'@" respectiviely


Last updated: 12 January 2022