AO-3 Updates


​​​​1. Reserved Target List

TOI 1778b was erroneously omitted from the csv file containing the reserved target list. It is included in the online version of the RTL which is to be used to provide pdf evidence that a target is not reserved as needed for proposal submission. The target details are provided below:

TOI1778b, 136.777644, 48.67243


2. Viewing possible visits to the very end of the nominal mission

To be able to view valid visits to the very end of the nominal mission using the Scheduling Feasibility Checker it is necessary to modify the Validity_Stop date in the files used to specify an observation request to UTC=2023-09-25T00:00:00. This is necessary for both time-critical and non-time critcal observations.


3. Reserved Target List

Note on Alpha Cen A/B: Alpha Cen A and Alpha Cen B are part of the GTO reserved target list. Although they correctly appear as “reserved” when a query is made in the Reserved Target List Checker using "Alpha Cen A" or "Alpha Cen B", a query with “Alpha Cen” without specifying A or B returns a free line of sight. This is because the coordinates returned by the Simbad query “Alpha Cen” (without specifying A or B) appear to be ~80 arcsec away from the A+B pair, which themselves are separated from each other by only ~15 arcsec.


4. AO-3 Call now closed

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:


Last updated 1 Mar 2023