The AO-3 Call is closed.
You can find all approved programmes here.


THIRD Announcement of Opportunity (AO-3) for participation in the CHEOPS Guest Observers Programme


This announcement solicits proposals for observations to be carried out as part of the CHEOPS Guest Observers Programme in the period from 1 July 2022 to 24 September 2023 (inclusive)


Release of AO-3: call for Phase I observing proposals          15 February 2022

Deadline for submission of Phase I observing proposals       15 March 2022 (13:00 CET/12:00 GMT)

Meeting of the CHEOPS Time Allocation Committee              11 - 13 May 2022

Announcement of award of observing time on CHEOPS         By 25 May 2022

Preparation of Phase II inputs                                            1- 24 June 2022

Start of observations of AO-3 Programmes                         1 July 2022*


* it may be possible to start observations a few days earlier, however this cannot be guaranteed


Important Notes:

Prospective observers are requested to take note of the following points:

  • The Policies and Procedures document is the definitive document for the AO. As the name suggests, this details all the policies and procedures relevant to the AO. It contains details of the observing constraints applicable to CHEOPS, as well as a detailed description of the required contents of observing proposals. Information about the tools and documents available to support observers in their proposal preparation and submission are also provided. You are very strongly advised to read through the document carefully before starting proposal preparation. The document can be found in the Key Documentation section of this webpage.
  • All proposals must be submitted via the Phase I Proposal Handling Tool which is accessed via the link given in the Tools and Supporting Manuals section of this webpage. Submission requires the use of a Cosmos Website ID together with membership of the CHEOPS Guest Observers Programme Group. This is also required to download the software for the Scheduling Feasibility Checker, which is one of the tools needed to prepare proposals (see below) and also to download simulated CHEOPS data. To request credentials and group membership please follow the instructions at the following link:

         We recommend that you get an ID/register as soon as possible.

  • A Frequently Asked Questions (FAQ) page will be maintained throughout the period covered by the call. This may be consulted at this link
  • Notifications of any issues/updates to Call material will be published on the page at this link - you are recommended to check this page regularly during the period that the AO is open
  • It is important to appreciate that, due to the nature of the science that CHEOPS will address, the majority of CHEOPS observations will be time critical. These can be difficult to schedule, and in some cases it may not be possible even if a target/proposal is awarded observing time and is considered to be high priority science.
  • CHEOPS is a small mission, with a correspondingly small team to support Guest Observers. You are advised not to leave proposal preparation to the very last moment, as it may take a couple of days to answer your questions.

Last updated:  7 March 2022 - An important update to the Scheduling Feasibility Checker input files is detailed on the AO-3 updates webpage as well as on the dedicated webpage for the tool; 9 March 2022 - clarification on the rseerved status of Alpha Cen A/B is detailed on the AO-3 updates webpage.

Key Documentation:


Is CHEOPS for you?

  • Two presentations introducing the CHEOPS mission and its capabilities are avallable at this link


Tools and supporting manuals:

A number of tools and documents are available to help you with your proposal preparation.


useful reference data and links    


User-contributed tools/aids:

Below are links to tools that have been developed by members of the CHEOPS Science Team and the CHEOPS Consortium. These are shared for use at the user's own risk, with caveats and warnings that are detailed in the individual documents.



Please check the Frequently Asked Questions page for common questions as well as details of who to contact in case your question is not answered on the page.