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INSPIRE-SAT 7 is a French 2-Unit CubeSat primarily designed for Earth and Sun observations. This mission is part of the International Satellite Program in Research and Education (INSPIRE). This satellite will be deployed in Low Earth Orbit (LEO) in 2023 as the first step of the so-called ‘Terra-F’ constellation that will provide spatio-temporal resolution for Earth Energy Imbalance (EEI) measurements. This new scientific and technological pathfinder CubeSat mission (INSPIRE-SAT 7) is equipped with various channels on all sides. Among them: the Total Solar Irradiance Sensor (TSIS) payload, the Ultra-Violet Sensor (UVS) using a new generation of solar blind detectors designed to monitor the integrated Solar Spectral Irradiance (SSI) in the Hertzberg continuum, and the Earth Radiative Sensor (ERS) payload, designed to measure some Earth’s Radiative budget (ERB) components such as the outgoing short and long wave radiation at the top-of-the atmosphere for climate change studies. The Belgian Radiometry Characterization Laboratory (B.RCLab) of the Royal Belgian Institute for Space Aeronomy (BIRA-IASB) is the partner responsible for the pre-flight absolute calibration and radiometric characterization of INSPIRE-SAT7 TSIS and UVS payloads. In this work we will first describe the INSPIRE-SAT7 concept, design, scientific and operational objectives. We will then present B.RCLab facilities along with its radiometric characterization benches, including the absolute calibration capabilities and its traceability. Finally, the main results of the INSPIRE-SAT7 pre-flight calibration campaign, which took place in November 2022, will be presented. These results allowed to calculate the sensors on-orbit calibration coefficients that are crucial to perform traceable absolute EEI measurements. A radiometric comprehensive uncertainty budget will be presented along the sensors’ calibration coefficients.

The near-infrared (NIR) part of the solar spectrum is of prime importance for solar physics and climatology, directly intervening in the Earth's radiation budget. Despite its major role, available solar spectral irradiance (SSI) NIR datasets, space-borne or ground-based, present discrepancies caused by instrumental or methodological reasons. We present new results obtained from the PYR-ILIOS SSI NIR ground-based campaign, which is a replication of the previous IRSPERAD campaign which took place in 2011 at the Izaña Atmospheric Observatory (IZO). We used the same instrument and primary calibration source of spectral irradiance. A new site was chosen for PYR-ILIOS: the Mauna Loa Observatory (MLO) in Hawaii (3397 m a.s.l.), approximately 1000 m higher than IZO. Relatively to IRSPERAD, the methodology of monitoring the traceability to the primary calibration source was improved. The results as well as a detailed error budget are presented. We demonstrate that the most recent results, from PYR-ILIOS and other space-borne and ground-based experiments, show an NIR SSI lower than the previous reference spectrum, ATLAS3, for wavelengths above 1.6 µm.

The near infrared (NIR) part of the solar spectrum is of prime importance for the solar physics and climatology, directly intervening in the Earth's radiation budget. Despite its major role, available solar spectral irradiance (SSI) NIR datasets, space-borne or ground based, present discrepancies caused by instrumental or methodological reasons. We present new results obtained from the PYR-ILIOS campaign, which is a replication of the previous IRSPERAD campaign which took place in 2011 at the Izaña Observatory (IZO). We used the same instrument and primary calibration source of spectral irradiance. A new site was chosen for PYR-ILIOS: the Mauna-Loa observatory in Hawaii (3397 m asl), approximately 1000 m higher than IZO. Relatively to IRSPERAD, the methodology of monitoring the traceability to the primary calibration source was improved. The results as well as a detailed error budget are presented. We demonstrate that the most recent results, from PYR-ILIOS and other space-borne and ground-based experiments show an NIR SSI lower than ATLAS3 for wavelengths above 1.6 μm.