SPARC4: Simultaneous Polarimeter And Rapid Camera in 4 bands: a new instrument to Pico dos Dias Observatory

Abstract

SPARC4 (Simultaneous Polarimeter And Rapid Camera in 4 bands) is a new instrument for the Pico dos Dias Observatory (OPD). It acquires images with a field of view of 5.7' × 5.7' in four channels simultaneously, whose spectral responses are very similar to the g, r, i, and z bands of the SDSS photometric system. It can be used as a standard imager or as an imaging polarimeter capable of measuring linear and circular polarization. The detectors are frame-transfer electron-multiplying CCDs. SPARC4 has various detector acquisition options from low-noise to fast-reading modes, achieving dead times of around 5 ms in the photometric mode. The images have excellent optical quality, with both photometric and polarimetric modes delivering S/N primarily limited by photon and detector noises. Following its first light in November 2022 and the commissioning throughout 2023, SPARC4 is an OPD facility as of the 2024A semester. This Brazilian initiative is a joint effort of the National Institute for Space Research (INPE) and the National Laboratory for Astrophysics (LNA).