IMPETUS is a Horizon Europe project which aims to enable and support citizen science initiatives. As part of that process, IMPETUS provides funding for citizen science initiatives through an open call. In this document, we set out a summary of the first open call, which ran from 10th January to 13th March 2023, with successful applicants joining the IMPETUS accelerator in June 2023. This document may be of use to individuals and organisations looking to carry out their own open call, particularly in the areas of citizen science and sustainability, as well as policy makers, researchers and citizen science initiatives and administrators, who may obtain insight about the common issues and success factors in open calls.