[ASA] ESO Period 117 Call for Proposals

Fri Aug 22 11:27:17 AEST 2025

ESO Period 117 Call for Proposals

The European Southern Observatory (ESO) has released the Call for Proposals for Period 117 for observations between 1 May 2026 – 30 April 2027. P117 marks the transition to a Yearly Cycle (YC), with future Calls for Proposals only being issued once per year. In addition a Fast Track Channel (FTC) with staggered deadlines throughout the year will be introduced during P117. The FTC will be offered initially one or two times per Period to be announced via ESO Science Newsletters, and will be available only for VLT/I Normal Programmes requesting less than ~20 hours of observation time.

Under the terms of the Strategic Partnership between ESO and Australia, Australian-based astronomers have access to the facilities of the La Silla and Paranal Observatories, specifically the: 

1.	3.6-m telescope (3.6 <https://url.au.m.mimecastprotect.com/s/5Ac4C3QNPBi2lgB3gcgfwsQPFNn?domain=eso.org> )
2.	New Technology Telescope (NTT <https://url.au.m.mimecastprotect.com/s/F0p2C4QOPEilO2oP2Txh8s4XYDk?domain=eso.org> )
3.	Very Large Telescope (VLT <https://url.au.m.mimecastprotect.com/s/QvtpC5QPXJi67Pv8PTyiXskt7N4?domain=eso.org> ) 
4.	Very Large Telescope Interferometer (VLTI <https://url.au.m.mimecastprotect.com/s/xqBPC6XQ4Lfyv6Dk6T5sxs5oBuv?domain=eso.org> ).

The proposal deadline is Tuesday 23 September 2025 at noon Central European Summer Time (8pm AEST, 6pm AWST). 

Complete details on how to apply can be found at the  <https://url.au.m.mimecastprotect.com/s/L7UlC71R2NTZKXqMXHqtGsoOHUe?domain=eso.org> P117 Call for Proposals web page. All applicants should consult the  <https://url.au.m.mimecastprotect.com/s/a7ZHC81V0PTY05r35cwu7syqtJw?domain=eso.org> Call for Proposals document for Period 117 and are required to have an  <https://url.au.m.mimecastprotect.com/s/dh5dC91WPRT2XW1nWc0CzsqS24C?domain=eso.org> ESO User Portal account to submit or be on proposals, as well as optimise their participation in Distributed Peer Review (if required) through the selection of appropriate keywords. Note that 21 new keywords have been added in P117, in the fields of exoplanets (11), stars (5), galaxies (3), and cosmology (2), so all PIs and Co-Is are urged to login to the User Portal and update their keywords as appropriate.

A wealth of information for Australian applicants can be found on AAL’s  <https://url.au.m.mimecastprotect.com/s/SIUlC0YKPvim5X8vXTrF1s9GL_x?domain=astronomyaustralia.org.au> Australian ESO Forum. Any questions about policies or the practical aspects of proposal preparation should be addressed to the ESO Observing Programmes Office,  <mailto:opo at eso.org> opo at eso.org. Applicants who may wish to seek advice on proposal or observing strategies, optimal choice of instrument, etc. are invited to contact AAL’s ESO Program Manager at  <mailto:Stuart.Ryder at astronomyaustralia.org.au> Stuart.Ryder at astronomyaustralia.org.au.

What's new in Period 117?

Applicants are strongly encouraged to review the expected changes in instrumentation offered and procedures for Period 117 given in Sec. 2 of the Call for Proposals. <https://url.au.m.mimecastprotect.com/s/a7ZHC81V0PTY05r35cwu7syqtJw?domain=eso.org>  Among the items likely to be of most interest to the Australian community are:

1.	Changes to Proposal Request Limits: With the start of the YC, Normal Programmes and Monitoring Programmes can now request up to 200h. Large Programmes are being accepted in P117, and now cover up to two Periods (two years) with a minimum request of 200 hours of observing time. While the number of hours that Normal or Large Programmes may request have increased, the page limits for each proposal type are unchanged, with the maximum total length of the “Scientific rationale” section for Normal and Large Programmes being 2 pages and 5 pages, respectively (including figures and references). Due to the change to the YC and the uncertainty about the number of submitted proposals, in P117 the limit on the time request to qualify for the DPR will be set after the proposal submission deadline. Therefore, the review assignment method (DPR or OPC panels) will not be known to the PI at proposal submission time.

2.	Joint VLT/I-ALMA proposals: ESO has a joint channel for scientific programmes requiring both VLT/I observations and ALMA observations. ESO may award a maximum of 50 hours of ALMA observing time on each of its arrays to Joint Proposals per year. Further details can be found on the Joint VLT/I-ALMA proposals page <https://url.au.m.mimecastprotect.com/s/nlEuCgZ0N1iGR1k61IyHxs4pAEi?domain=eso.org> . ESO has confirmed that ALMA would always treat an Australian-led Joint VLT/I-ALMA proposal as “ <https://url.au.m.mimecastprotect.com/s/Y5g6CjZ1N7iRX49E4uYI3smZTuP?domain=almascience.eso.org> Open Skies”, regardless of whether they get their time allocated through  <https://url.au.m.mimecastprotect.com/s/psjHCk81N9t5jyNlyIySEsGmEnn?domain=almascience.eso.org> ALMA’s own joint proposal process, or through a joint VLT/I allocation. If in doubt, users should contact the  <https://url.au.m.mimecastprotect.com/s/H7UKClx1NjiX8w7GwSDTvszayAw?domain=help.almascience.org> ALMA helpdesk.

3.	MUSE Wide Field Mode with Adaptive Optics: Astronomers are encouraged to use the MUSE Wide Field Mode with Adaptive Optics, because it is more efficient and suitable than non-AO for most science cases. While the non-AO mode is essential for programmes gathering information over the 582–597 nm wavelength which is otherwise blocked by the Na Notch filter, the benefits of AO are many-fold. Not only are the operations at the telescope routine, but importantly seeing is improved in any observing conditions (poor seeing, light cirrus, high wind speed) while proven to be more stable during long exposure times. In case no Natural Guide Star is available, the Tip-Tilt-free mode using the telescope field stabilisation still provides a significant improvement on image quality. As a result, shorter exposure times are required in AO mode to reach equivalent signal-to-noise.

4.	Instrumentation updates:

*	VISIR will be decommissioned in Period 117, and is no longer offered on UT1. However the KMOS Public Surveys <https://url.au.m.mimecastprotect.com/s/LhGlCmO5gluW3o2XocEU5sR50gi?domain=eso.org>  that will span over 3 years (with a total of 285 nights) starting in late P116 will increase pressure on UT1, due to the reduced amount of open time available.
*	MOONS, FORS-Up, and SOXS will all undergo commissioning in P117, and may be offered via the FTC prior to P118. EFOSC2 is offered in P117, with plans to be decommissioned after SOXS enters stable operations.
*	The Gravity+ AO (GPAO) system on the VLTI offers Laser Guide Star (LGS) modes for the first time in P117. NGS-VIS and LGS-VIS modes are offered for GRAVITY and MATISSE, while LGS/NGSIR is offered for GRAVITY only. The p2 tool for GRAVITY now includes an ObsPrep tab that supports the selection of a suitable Coudé guide star.
*	A fraction of the observing time with the VLTI visitor instrument suite ASGARD <https://url.au.m.mimecastprotect.com/s/SBdLCnx1jnim2Z5wZT1c6sJacab?domain=asgard-vlti.github.io>  is open to the community starting from P117, pending successful review of the observing proposals by the OPC/DPR. A preliminary coordination with the ASGARD consortium is mandatory. 

We remind applicants of the following important policies:

1.	Distributed Peer Review: ESO uses a Distributed Peer Review (DPR) process for proposals requesting a total time including overheads below a certain threshold (TBD for P117 – see above), with the exception of proposals including at least one ToO run; proposals for Calibration Programmes; Joint proposals; and DDT proposals. All other proposals submitted for P117 will be reviewed in the usual way by the OPC and its sub-panels. PIs of proposals qualifying for DPR accept that their proposals are reviewed by ten peers who have also submitted proposals in P117, and consent to reviewing ten proposals submitted by their peers as laid out in the DPR rules and guidelines. <https://url.au.m.mimecastprotect.com/s/LtsYCoV1kpfvRV49VHrfMspf4r2?domain=eso.org>  The PI may elect to delegate the reviewer's role to one of the co-Is listed in the proposal.

2.	Visitor Mode: Requests for Visitor Mode observations may be submitted (and are encouraged for new users in particular) for P117, although any scheduled runs may need to be executed in Designated Visitor Mode <https://url.au.m.mimecastprotect.com/s/eZC8Cp81lrtAW0Dk0TphYsG6PS4?domain=eso.org>  instead for operational reasons. Direct Qantas services between Sydney and Santiago operate 4 times per week, as well as daily services on LATAM via Auckland, and direct LATAM services between Melbourne and Santiago 3 times per week. ESO will pay for the costs of one visiting observer per run, and may also cover the costs of an accompanying student.

3.	Scientific keywords: From the p1 interface <https://url.au.m.mimecastprotect.com/s/E7YzCq71mwfX3yWByS1iPsE0fcd?domain=eso.org>  users must select at least two keywords, and at most five keywords (ten for Large Programmes). The keywords must be selected in decreasing order of relevance (i.e., the first selected keyword is the most relevant).

4.	Proposal anonymisation: Under the Dual-Anonymous Peer Review (DAPR) policy applicants must formulate the scientific rationales of their proposals following these anonymisation rules and examples <https://url.au.m.mimecastprotect.com/s/r7t8Cr81nyt2YR9MRcDsDs40i8D?domain=eso.org> , which includes a detailed description of the DAPR paradigm. Failure to abide by the DAPR rules may lead to the disqualification of the proposal.

5.	If Artificial Intelligence services are used to help write a proposal, the PI remains responsible for the content of the proposal and ensuring the text is properly referenced according to normal scientific standards.

Important Data Privacy Notice for all recent and intending Australian ESO applicants

ESO supplies AAL with telescope/instrument demand and time allocation data relating to Australian astronomers only. Australian ESO applicant data is used only for statistical purposes, and will only be published or made available to other third parties such as AAL member institutions, in aggregated and anonymised form. ESO’s data collection/use provisions are  <https://url.au.m.mimecastprotect.com/s/f9cECvl1rKiA5nX1nTVtZsQVP5n?domain=astronomyaustralia.org.au> available on the AAL ESO Forum for reference. It may be necessary to use automated data matching from data provided to the  <https://url.au.m.mimecastprotect.com/s/8NoDCwV1vMfymEp6ETyuOsJQUyf?domain=lens.datacentral.org.au> Data Central Lens proposal database to confirm the identity of ESO applicants. Applicants may opt out of providing data for Australian statistical purposes (including those from P101-P116 inclusive) by contacting  <mailto:Stuart.Ryder at astronomyaustralia.org.au> Stuart.Ryder at astronomyaustralia.org.au.

______________________________

Dr. Stuart Ryder
Program Manager (Mon, Wed, Fri)
Astronomy Australia Ltd.

T: +61 (02) 9372 4843

M: +61 (0419) 970834 
E: stuart.ryder at astronomyaustralia.org.au <mailto:stuart.ryder at astronomyaustralia.org.au> 

W:  <https://url.au.m.mimecastprotect.com/s/ZUzICxngwOfxV5O85SyCksy_08A?domain=astronomyaustralia.org.au> https://url.au.m.mimecastprotect.com/s/LGTMCyojxQTLwPnDPHEFQsxsQZw?domain=astronomyaustralia.org.au 

O: c/o AAO, 105 Delhi Rd, North Ryde, NSW 2113, Australia

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