The European Space Agency
AO-1 - PLATO
1st Announcement of Opportunity (AO-1)
For Participation in the PLATO Guest Observers (GO) Programme
This 1st Announcement of Opportunity (AO‑1) marks the beginning of PLATO’s Guest Observers (GO) Programme. It offers the community access to space‑based, ultra‑high‑precision photometry for scientific investigations that are complementary to the mission’s core objectives. The AO‑1 Call opens on 7 April 2026 at 12:00 noon CEST and closes on 21 May 2026 at 12:00 noon CEST. Awards of observing time are expected by the end of August 2026, enabling successful proposers to prepare timely follow‑up proposals for other space‑ and ground‑based facilities. The associated observing cycle will cover the first two years of PLATO’s nominal operations. For example, assuming a launch in January 2027, this cycle would run approximately from April 2027 to April 2029.
Milestones
| Date | Event |
|---|---|
| 7 April 2026 (12:00 noon CEST) | AO‑1 opens |
| 21 May 2026 (12:00 noon CEST) | AO‑1 closes |
| 6 – 17 July 2026 | Meetings of the Time Allocation Committee |
| By 31 August 2026 | PIs are informed of the outcome of the review |
| Launch date + 3 months | Start of AO‑1 observations |
Where to start & important notes
- Read the Policies & Procedures document carefully. It is the definitive reference for all AO Call requirements, including the PLATO science programme, available observing time, operational constraints, proposal structure, and the tools supporting proposal preparation.
- Familiarise yourself with the Mission Handbook. This document serves as the prime reference for scientists preparing PLATO observations, intorducing the spacecraft, payload, observing strategy, and data products.
- Register early for the PLATO GO system. A valid ESA Cosmos account and registration in the GO Programme are required for proposal submission.
- Consult the PLATO Input Catalogue (PIC) via the PLATO ArXiv (PAX). These tools provide essential information on available targets, contaminants, and feasibility parameters required for proposal preparation.
- Begin preparation early, consult the webpage examples and FAQ, and leverage the proposal software. Support resources are limited, and late questions may not be answered in time. Early preparation reduces the risk of missing requirements. Browse the webpages, particularly the proposal submission and FAQ sections, which provide many user-friendly illustrations of the formal material presented in the documents. Leverage the ESA Science Campaign Handling System (CHS) and built-in PLATO Call for Proposals Toolset (CfP) for target checks, noise-to-signal estimates, and much more.
- Ensure full dual-anonymity. All proposal material, including file names, must be fully anonymous. Non‑compliant proposals will be automatically rejected on formal grounds.
- Submit your proposal via the official proposal software. Proposal upload and access to selected tools require a Cosmos login and GO Programme membership, and will use the CHS & CfP software.
- Note: An award of observing time does not guarantee execution. Operational constraints, scheduling limitations, and unforeseen events may affect feasibility, even for high‑priority programmes.
- Note: Updates related to the AO Call will be posted at the bottom of this webpage.
Key Documentation
- 1st Announcement of Opportunity (AO-1) - invitation letter by ESA's Director of Science
- Policies and Procedures
- Mission Handbook
Tools and Material
- Proposal Software
- Data
Additional references
- PLATO Mission Paper
- PLATO Input Catalogue (PIC)
- LOPS2 PIC2.2.0.1 Release Notes
- LOPS2 PIC2.2.0.1 PIC Data Definition Document
- Montalto et al. (2026, preprint) - tPIC
- Nascimbeni et al. (2026, preprint) - tPIC Prime Sample
- Prisinzano et al. (2026, A&A, 706, A207) - tPIC P4 Sample
- Zwintz et al. (2026, preprint) - scvPIC
- Heller et al. (2026, preprint) - cPIC and fgPIC
PLATO Helpdesk
If you have any questions, please carefully consult the documentation referenced above. If you cannot find the information you need, our PLATO Helpdesk will be happy to help.
Updates
Dear PLATO Guest Observers,
We understand there are still questions regarding the recent CfP update. To address these efficiently, we have compiled detailed entries on our FAQ webpage.
Most importantly, please be assured that the rules have not changed and remain as defined in Section 4.8.1 of the Policies & Procedures document at the AO-1 Call opening.
The CfP update is aligned with these rules, and now helps proposers by highlighting potential violations to them before the deadline. The new features act as a safeguard, allowing issues to be identified and corrected by proposers, rather than leading to target removal during technical review, helping to maximise the chances of your proposals' success.
Best regards
Your PLATO team
Update on 13 May 2026:
Dear PLATO Guest Observers,
As we are approaching the AO-1 Call closure (21 May 2026, 12:00 noon CEST), we would like to highlight three important points regarding the PLATO proposal software and submission system:
First, the Call for Proposals (CfP) tool has been updated with new features that provide clearer indicators for the different target duplication checks outlined in the Policies & Procedures document. These enhancements are described in its updated User Manual and are intended to support your submission by offering more direct insight into aspects of the technical review step. To take full advantage of these improvements, it is essential that you re-run the CfP tool and verify that your proposed targets fulfil all respective criteria.*
Second, please note that the CfP tool and earlier versions of its User Manual contain a typo concerning some light curve cadences, which is also present in the CfPtools_input-output.csv file. The correct values are provided in the Policies & Procedures document and the Mission Handbook, and are now also reflected in the updated User Manual, together with a clarifying note. The CfPtools_input-output.csv will continue to display this typo but not have any operational impact. To recap, the correct values are: imagettes at 2.5 s (F-CAMs) or 25 s (N-CAMs); light curves at 50 s (SHORT) or 600 s (LONG).
Finally, please remember that proposals must be formally submitted via the Campaign Handling System (CHS) as saving a draft alone is not sufficient. We note that a number of proposals are still in draft status, so please ensure you complete the submission step ahead of the deadline. Submitted proposals can still be updated at any time before the deadline.
Best regards
Your PLATO team
*In short, the previous version performed duplication checks only within 120 arcsec of Prime Sample targets, leaving proposers to ensure compliance for upgraded observing modes of other PIC targets. The updated version performs duplication checks within 108 arcsec of all PIC targets, while aligning with the logic for complementary science in the Policies & Procedures. This introduces a small trade-off: targets within 108–120 arcsec of Prime Sample targets will no longer raise an error at submission, yet they remain ineligible and will be removed during technical review. We believe the improved insights outweigh this trade-off and encourage proposers to continue carefully curating their target lists using the PAX and PIC information before running the CfP tool. In particular, if your target list was not pre-curated when running the CfP tool on or before 11 May 2026, it may still include targets within 108 arcsec of other PIC targets. Some inconsistencies in the 108–120 arcsec range may also have occurred during the deployment on 12 May 2026. Re-running the CfP tool now ensures you benefit from all new features and gives a clearer view of which complementary science targets may pass technical review.
Happy proposing!