AO-4: Approved Programmes

Announced on 14 July 2023


The 4th Announcement of Opportunity (AO-4) for the CHEOPS Guest Observers (GO) Programme opened on 4 April 2023 and closed on 26 May 2023. The opportunity marks the start of the first extended mission and covers observing time in the period from 25 September 2023 until 30 September 2024. Notably, the available GO share of the science observing time was recently increased from 20% (in the Nominal Mission) to 30% (in the first Extended Mission).

A total of 29 proposals were received in reply to AO-4, requesting 1811.1 orbits (with each orbit circa 99 minutes in duration). The requests represented 120% of the available science observing time foreseen in the AO-4 observing cycle (circa 1505.5 orbits).

The CHEOPS Time Allocation Committee (TAC) met on 19 - 20 June 2023. Based on the TAC's recommendations, the Director of Science has awarded CHEOPS observing time to the proposals listed in the table below. In the end, 24 proposals were awarded observing time totaling 1472.1 orbits. Of these, 19 proposals were on exoplanet science, 3 on stellar science, and 2 on other science/goals. The TAC-recommended allocation of observing time represents up to 98% of the available GO science observing time foreseen in the AO-4 observing cycle (circa 1505.5 orbits). Of these, 3 pairs of programmes have duplicate targets, for which the TAC recommends sharing observing time. We will be in contact with the teams and liaise the next steps.

Succesful proposals will be implemented as GO programmes. Targets that are part of these GO programmes can generally not be included in other observing programmes unless in specific cases. All programmes have been assigned a priority from 1 (high) to 3 (low), in some cases at the level of individual targets. This priority is taken into account by the automated planning tool used in the weekly/biweekly planning, and is a strong indicator of the likelihood that observations will be scheduled. Observers are reminded that the award of observing time provides no guarantee that the observations can be executed, and that generally more observing timeis awarded than can be physically scheduled to minimise idle time.

Principal Investigators (PIs) of proposals that have been awarded time will be contacted by email, and are required to complete and submit observation requests at their earliest convenience. Guidelines on how to prepare observation requests will be posted on this webpage shortly. The TAC feedback will be provided to all PIs of proposals.

A fraction of up to 25% of the GO Programme time will remain available to the community to apply for time via the Discretionary Programme (DP), which is foreseen to continue running throughout the mission lifetime. This is in line with a possible over-allocation of up to 133% to facilitate the efficient scheduling of time critical observations. 



PI name (country)

Proposal title

Nr. of orbits (priority)


Isaak (NL)

Inspiration through space science: a CHEOPS-based education activity for high-school students

24.0 (P1)


Vach (AU)

CHEOPS transits of two 48-Myr mini-Neptunes in the Taurus-Orion II moving group

20.0 (P1)


Jiang (TW)

Investigating Sub-Saturns through CHEOPS Observations: Envelope-Rich K2-19b and Envelope-Poor K2-19c

48.0 (P3)***


Ilin (DE)

HIP 67522 b: a Hot Jupiter that triggers flares on its host

128.0 (P1/P2)*


Damasso (IT)

Escape from the `V1298 Tau e labyrinth’: following the CHEOPS’ thread to confirm the orbital period and large TTVs/TDVs of an infant planet

106.6 (P1)


Palethorpe (UK)

CHEOPS can confirm an Earth-sized planet in the habitable zone of a metal-poor M-dwarf neighbour

14.0 (P1)**


Nabbie (AU)

Confirming the Transit Timing Variations of a Neptune-Sized Inner Companion to a Hot Jupiter

36.0 (P1)


Garai (HU)

Refining parameters of grazing transiting exoplanets with CHEOPS and TESS

36.0 (P2)


Doyle (UK)

Hidden Gems - Giant Exoplanets around Main-Sequence Stars

57.0 (of which 26.0 in P2, and 31.0 in P3)


Hooton (UK)

Treating exoplanets as planets: a deep dive into the reflective properties of an ultra-hot Jupiter

77.8 (P1)


Venner (AU)

Characterising the nearest known temperate Earth-sized exoplanet with CHEOPS

18.0 (P1)**


Almenara (CH)

Determining the architecture of the K2-19 system

21.0 (P2)***


Gomes (BR)

Stellar Occultation by Minor Bodies in our Solar System with CHEOPS

14.0 (P1)


Grouffal (FR)

Hunting a second transit of the long-period Neptune exoplanet HIP41378 e in the gaps of TESS

299.0 (of which 120.0 in P2, and 179.0 in P3)


Stevens (US)

Probing the M-dwarf Radius and Temperature Discrepancies with the 72-day G-M EB TOI-2065

30.0 (P2)


Chakraborty (CH)

Accurate and precise characterisation of the HIP 67522 system in the presence of significant stellar variability

93.0 (P1/P2)*


Nicholson (AU)

Confirming the orbital parameters of a super-puff-host system to prepare for future atmospheric studies

19.4 (P3)


Stalport (BE)

Understanding stellar activity patterns by coupling absolute photometry and intense RV monitoring

46.0 (P2)


Jenkins (CL)

Constraining the Prevalence of Metallic Clouds within the Neptune Desert

180.0 (P2)


Scarsdale (US)

Period Measurement of The Brightest-Host Transiting Habitable Zone Terrestrial Exoplanet

49.0 (P1)


Vach (AU)

Confirmation of the first planet to be associated with the Pleiades cluster

8.0 (P2)


del Burgo Díaz (MX)

Constraining the orbital period of HD 114082 b, the most massive among the youngest exoplanets

86.1 (P2)


Mohr (US)

Period Confirmation for The Sub-Neptune Exoplanet with The Longest Period

20.0 (P2)


Heidari (FR)

Detection of the third transit of a sub-Neptune with the longest orbital period ever discovered

41.2 (P2)

*/**/*** These 3 pairs of programmes marked with asterixis have duplicate targets, for which the TAC recommends sharing observing time. We will be in contact with the teams and liaise the next steps.


Questions about CHEOPS or the GO Programme? Please email cheops-support at and we will be happy to help!
Last updated 14 July 2023