Euclid launched in July 2023 as a European Space Agency (ESA) mission with involvement by the National Aeronautics and Space Administration (NASA). The primary science goals of Euclid are to better understand the composition and evolution of the dark Universe. The Euclid Space Telescope carries two instruments: the VISible instrument (VIS) and the NearInfrared Spectrometer and Photometer (NISP). The Euclid data set will include data collected with 
these space-based instruments as well as “external” (EXT) images collected by ground-based telescopes and served alongside the Euclid images.

        According to the plan, the main mission duration of the Euclid mission is about 6.5 years. The first three months after launch are for commissioning, followed by a six-year main survey phase. If Euclid is still operating normally after 6.5 years, there may be an extension for additional surveying. The Euclid mission will provide scientific data to the global scientific community through three main data releases (DR1, DR2, DR3), with the final DR3 being released one year after the end of the main survey. Before each main data release (DR), there will be a “quick release” (Q1, Q2, Q3, Q4) of data from selected areas and data products, allowing scientists to get an early look at the upcoming data and refine their data analysis tools. The Euclid Quick Data Release 1, short as Euclid Q1, is the first quick release as well as the first large-scale data release of the Euclid mission.

        The Euclid Q1 released on March 19, 2025, includes data from four fields, covering a total of approximately 60 square degrees. Although it includes three Euclid Deep Fields, the exposure depth of the Q1 data is at the level of the Euclid Wide Survey, not the deep field survey. The Euclid Q1 image data comprises raw and calibrated single-exposure data in the visible and near-infrared wavelengths, as well as merged “mosaic” large images. The “mosaic” images also incorporate data from ground-based telescopes, such as the Dark Energy Survey (DES) in the southern sky and the Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) in the northern sky. The Euclid Q1 catalog data mainly includes merged image catalogs (3 tables), photometric redshift catalogs (8 tables), and spectroscopic catalogs (13 tables). The catalog data, as well as the calibrated and merged images, are processed and generated by different processing functions (PF). Corresponding to the eight subdirectories for storing tables, spectrum, and image data, names of which are related with the pipeline Processing Functions (PF), there are eight sub-metadata at the bottom of this page. Please refer this Euclid Q1 paper for more details https://arxiv.org/abs/2503.15302 as well as this user guide: https://irsa.ipac.caltech.edu/data/Euclid/docs/euclid_archive_at_irsa_user_guide.pdf.