Applying for Observing Time

Telescope time with ESO telescopes at the La Silla Paranal Observatory is allocated twice a year in periods of six months. Allocation periods run from 1 October through 31 March, and from 1 April through 30 September. Applications for observing time must be submitted using the web-based p1 interface accessible at  

The Call for Proposals describes the conditions under which observing time is offered with ESO telescopes at the La Silla, Paranal, and Chajnantor (APEX) sites of the Observatory. The document is available in electronic form via this Web page.

The deadline for Period 108 (1 October 2021 –  31 March 2022) is:

25 March, 2021

(12:00 noon, Central European Time)

Applications for observing time with ESO Telescopes have to be prepared using the p1 web system.
It is the PI's responsibility to resolve any submission problems well before the deadline. Please note that ESO cannot provide support beyond 11:00 CET on the day of the deadline.

Mandatory update of the ESO User Portal profiles for science users

Please see the announcement on the request to update user profiles on the ESO User Portal. Users failing to do so will not be able to submit a proposal as PI and/or as CoI.


Special Call for Period 107

Following the suspension of the regular Call for Proposals for ESO Period 107 due to the ongoing COVID-19 pandemic, and as previously announced, ESO is issuing a Special Call (hereafter SC107) for the submission of projects consisting of novel and urgent observations that must be executed during P107 (1 April  - 30 September 2021).

The spirit of SC107 is to offer ESO's community the opportunity to take the lead on (or to maintain its leadership) on new, important scientific cases, without having to miss out on them because of the pandemic.

SC107 will be open as of 1 April 2021.

Detailed information and guidelines related to SC107 can be found here  Users will be able to submit proposals any time and only for observations that must be carried out during P107 (1 April  - 30 September 2021).

Requests for Period 108 and subsequent semesters must be submitted through the regular channelswhereas requests for transient events must be submitted through the DDT channel.

Director's Discretionary Time Proposals

Up to 5% of the general observing time may be used for Director's Discretionary Time Proposals (DDT proposals). For detailed information about DDT proposals see the separate DDT Proposal page. Proposals must be submitted via the p1 interface (instructions can be found here).

DDT proposals for Period 107 can be submitted as of 1 April 2021

For sudden astronomical events requiring urgent or even immediate observations, detailed requests can be submitted. A detailed description of ESO's "Target of Opportunity" POLICY (ToO) is given in a separate document. Please read it carefully before submitting any ToO.


Call for Proposals for Period 108

Applications may be submitted for the usage of the telescopes, instruments and instrument modes specified in the Call for Proposals for Period 108.

  • Period 108 Call for Proposals

  • Useful links for Period 108
    Links to technical information about ESO facilities; foreseen changes in the performance of the offered instruments and useful information for the preparation of ESO proposals for the current call for proposals.

  • Late Breaking News
    Please check this page regularly. It will contain information about the Call for Proposals that becomes available after the release.

Applications for observing time on ESO telescopes must be submitted by the respective deadline (end of March and end of September) using the Web-based p1 interface accessible at

This is accessible via your User Portal credentials. The Principal Investigator and all Co-Investigators must have an ESO User Portal account. You can register at Please refer also to the instructions given in the Call for Proposals.

In case you need practical assistance from ESO to prepare your proposal, please send an email to

The above address can be used for all questions and comments related to the proposal submission (how to prepare your proposal, what error messages really mean, etc.), as well as more general questions concerning instrument performance, Observatory policy, etc.