The FORUM End-to-End Simulator project: architecture and results.

Year: 2021

Authors: Luca Sgheri; Claudio Belotti; Maya Ben-Yami; Giovanni Bianchini; Bernardo Carnicero Dominguez; Ugo Cortesi; William Cossich; Samuele Del Bianco; Gianluca Di Natale; Tombs Guardabrazo; Dulce Lajas; Tiziano Maestri; Davide Magurno; Hilke Oetjen; Piera Raspollini; and Cristina Sgattoni

Autors Affiliation: IAC – CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy; INO – CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy; ESA – ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands; IFAC – CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino (FI), Italy; Universita di Bologna – Dipartimento di Fisica e Astronomia, Viale Berti Pichat 6/2, 40126 Bologna, Italy; DEIMOS Space S.L.U., Ronda de Pte. 19, 28760 Tres Cantos – Madrid, Spain.

Abstract: FORUM (Far-infrared Outgoing Radiation Understanding and Monitoring) will flight as the 9th ESA?s Earth Explorer mission, and an End-to-End Simulator (E2ES) has been developed as a support tool for the mission selection process and the subsequent development phases. The current status of the FORUM E2ES project is presented, together with the characterization of the capabilities of a full physics retrieval code applied to FORUM data. We show how the instrument characteristics and5the observed scene conditions impact on the spectrum measured by the instrument, accounting for the main sources of error related to the entire acquisition process, and the consequences on the retrieval algorithm. Both homogeneous and heterogeneous case studies are simulated in clear and cloudy conditions, validating the E2ES against two independent codes: KLIMA (clear sky) and SACR (cloudy sky). The performed tests show that the performance of the retrieval algorithm is compliant with the project requirements both in clear and cloudy conditions. The far infrared (FIR) part of the FORUM spectrum is shown to be10sensitive to surface emissivity, in dry atmospheric conditions, and to cirrus clouds, resulting in improved performance of the retrieval algorithm in these conditions. The retrieval errors increase with increasing the scene heterogeneity, both in terms of surface characteristics and in terms of fractional cloud cover of the scene.


KeyWords: FORUM, radiative transfer, clouds