Far-Infrared Outgoing Radiation Understanding and Monitoring (FORUM) - System Overview and Key Technology Developments of ESA's 9th Earth Explorer. - Tibor Agócs; Felice Vanin; Paolo Laberinti; Hilke Oetjen; Damiano Serlenga; Montserrat Pinol Sole; Cedric Salenc; Daniel Lamarre; Martin Kaspers; Gonçalo Rodrigues; Asier Martinez Carou; Simon Strotmann; et al. (IGARSS, 2022)