CHEOPS  "Frequently Asked Questions" :  AO-2


Below is a collection of Frequently Asked Questions (FAQs), together with answers, relating to the preparation and submission of proposals for CHEOPS AO-2. The page will be updated during the call to include additional questions that come up during the period that the call is open.

If you do not find an answer to the question you have, please review the documentation provided on the AO-2 webpage. If you still cannot find the answer, then please send an email to

Please note that it may take a few days for questions to be answered, and to be put up onto this webpage.

Incase of problems with the email address noted above, please contact   kate dot isaak at esa dot int, replacing "dot" with "." and "at"  with "@".


Last updated:  24 November 2020



q1 HOw to get a cosmos user account/ID

To submit proposals for the CHEOPS Guest Observers Programe you will need to obtain a Cosmos ID. You can use the tool at this link to check whether you already have a Cosmos ID and to request one if not.  It is recommended to do this early on.


Q2   WHy do I need to register for the CHEOPS Guest Observers Programme

Selected links from the AO-1 page are restricted to members of the CHEOPS Guest Observers Programme. This has been done to prevent spamming/excessive loading of ftp sites. Membership can be easily (and quickly) requested using the tool at this link. It is recommended to do this early on.


Q3   which targets (lines of sight) are already reserved and thus blocked?

There are two ways in which you can find out which targets, or more precisely which lines of sight, are already reserved or blocked, and thus must not be included in any observing proposal: 

  1. target by target, one-by-one, using the so-called reserved target list checker tool which is available at:
  2. via the csv file which contains the target name and coorindates for all targets on the rseerved target list as of 4 November 2020. Note this list will evolve during the period that the call is open - as observations of targets in the GO programe are completed (no longer reserved) and as programmes are awarded time in the discretionary programme (become reserved)


Q4   Are CHEOPS proposals restricted to exoplanetary science? Are there any restrictions in topics/any quotas?

No. Observations can be proposed that cover any science topic, not only exoplanets. There are no quotas for time that will be allocated to different non-exoplanet science topics. All proposals will be evaluated by the Time Allocation Committee according to the following criteria:

  • The scientific excellence and relevance of the proposed observations;
  • The uniqueness and applicability of CHEOPS to achieve the proposed scientific objectives of the proposal;
  • The technical feasibility and robustness of the proposed observations and data analysis.

There are constraints on the types of observations that CHEOPS can be used to do. These are detailed in the Policies and Procedures document for the Call.