The terrestrial energy balance represents a measure of the excess energy stored in the climate system. A possible measurement of this variable can be made at the top of the atmosphere by quantifying the imbalance between the incoming solar flux and the outgoing reflected and infrared flux. This is the objective of the UltraViolet and infrared Sensors at high Quantum efficiency on-board a small SATellite (UVSQ-SAT) mission, validating miniaturized technologies on-board a CubeSat with 1U standards (about 11 cm x 11 cm x 11 cm). This satellite was put into orbit in January 2021 by SpaceX’s Falcon 9 launcher and is totally functional. In order to measure the various fluxes with accuracy it is necessary to know precisely the orientation of the satellite at each time. Indeed, the knowledge of this orientation makes it possible to dissociate the various fluxes and to correct them from the angle to the considered source (Earth, Sun). To do so, two methods were implemented to retrieve the satellite’s attitude based on Sun and Nadir pointing along with inertial measurement unit (IMU) data. To ensure more accurate knowledge of the attitude determination in every configuration (daylight and eclipse), neural networks were implemented based on the available sensors. A multilayer perceptron was thus trained in order to find the orientation of the satellite. Based on the attitude retrieved the different flux were computed at each time from the sensors signals. We present here the development and the outcomes of the neural network applied to in-orbit data recovered from the UVSQ-SAT mission.

Monitoring Earth Energy Imbalance (EEI) is absolutely fundamental to understand and prevent climate change as it corresponds to the Earth’s excess heat. In particular, measuring radiative forcing in an environment with a wide range of conditions entails a better understanding of its impact on the climate.The UltraViolet and infrared Sensors at high Quantum efficiency on-board a small SATellite (UVSQ-SAT) aims to improve measurements of those radiations at Top Of the Atmosphere (TOA). It becomes a pathfinder for Radiation Budget measurements on-board a CubeSat demonstrating a disruptive technology, implementing miniaturized sensors on a small satellite (twelve miniaturized thermopiles sensors and four photodiodes). This project is promoted by the University of Saint-Quentin-en-Yvelines with the support of the International Satellite Program in Research and Education (INSPIRE). The satellite will be launched and in-orbit in December 2020.One of the main purposes of the mission is to measure the Essential Climate Variables (ECV) more precisely using multi-point observation, in an effort to improve spatiotemporal coverage through future constellation. The scientific goals of the mission are first to observe incoming solar radiation and outgoing terrestrial radiations at Top Of the Atmosphere. The second purpose is to measure solar spectral irradiance in the Herzberg continuum. Finally, the third objective is to improve the technological readiness of a sensor.This session will focus on the ability to define the spatiotemporal accuracy required to monitor the variability of those Essential Climate Variables. Therefore, it will allow us to determine the number of satellites and characteristics of the future constellation meeting these specifications.