# UVsq-Sat NG, a New CubeSat Pathfinder for Monitoring Earth Outgoing Energy and Greenhouse Gases
## 1 Introduction
The EEI accounts for not only the GHG effect but also other climate forcings and natural variability, which also impact the amount of heat accumulated in the ocean-atmosphere system. This knowledge is valuable for formulating effective strategies to mitigate global warming and its consequences on weather patterns, ecosystems, and human societies [5]. While the greenhouse effect's mechanism and the contributions of various anthropogenic GHGs to Earth's surface warming are well established, some interactions and feedback involving clouds, polar ice ([PERSON], 2016), and oceans remain less understood. Observations and model simulations reveal that the direct warming caused by GHGs is further amplified by climate feedbacks, such as the melting of the very reflective Arctic sea ice, which exposes more ocean to the Sun and hence enhances solar radiation absorption. Overall, the simultaneous observation of multiple climate parameters, the so-called Essential Climate Variables (ECVs), is important for better characterizing all the aspects of climate change. Satellite-based observations provide a potent tool for monitoring the key ECVs simultaneously with possibly global coverage and consistency. On top of large instrumented satellites, small-sized affordable nanosatellites like CubeSats represent promising complementary platforms for monitoring GHGs levels and Earth's outgoing energy with miniaturized instruments. In addition to typically short development phases, their very low costs make it possible to deploy a large constellation of phased CubeSats in Low Earth Orbit. Such a configuration attracts increasing attention in the context of climate change observation, as it enables a global and much more continuous spatio-temporal coverage of the Earth than a single large satellite does. SmallSats are increasingly becoming indispensable tools for Earth observation ([PERSON], 2016), underscoring their vital role in enhancing our understanding of the planet. They have the potential to fundamentally revolutionize our approach for monitoring climate change from space by introducing a new paradigm, which involves coordinated plans for multiple satellites, each equipped with diverse instrument payloads. Leveraging the agility of these small satellites, characterized by their swift maneuverability, enables dynamic adjustments of viewing angles to capture swiftly evolving phenomena. This framework is tailored for real-time operations, ensuring both high spatial resolution and remarkable revisit capabilities. To study the feasibility of monitoring GHGs and the ERB with a SmallSats constellation, a new spacecraft named Uvsq-Sat NG is being specifically designed for such purposes and will be placed in Low Earth Orbit (LEO) between Q2 2025 and Q1 2026. Uvsq-Sat NG fits into the continuity of CubeSats that have already been launched by LATMOS, namely, Uvsq-Sat on 24 January 2021 ([PERSON], 2021) and Inspire-Sat 7 on 15 April 2023 ([PERSON], 2021). Both are still operating successfully in LEO. The goal is to go a step further by deploying a more complex satellite with a fully active Attitude Determination and Control System (ADCS) to address a wider range of intricate scientific needs in climate change research. Uvsq-Sat NG is a 6U CubeSat (10.0 cm \(\times\) 36.6 cm \(\times\) 22.6 cm) containing several scientific payloads. It carries Earth Radiative Sensors (ERSs) to measure outgoing solar radiation (from 100 to 3000 nm) and outgoing infrared radiation (from 3 to 100 \(\upmu\)m). These measurements must be in the continuity of those carried out with Uvsq-Sat (Uvsq-Sat, 2021) and Inspire-Sat 7, with the objective of establishing a multi-year time series of outgoing shortwave radiation (OSR) and OLR data. Uvsq-Sat NG also has a miniaturized Near-Infrared (NIR) Spectrometer (aperture of 15 mm, spectral range from 1200 to 2000 nm, spectral resolution of 6 nm, field of view of 0.15\({}^{\circ}\)) designed to map variations in the concentrations of the key GHGs, specifically CO\({}_{2}\) and CH\({}_{4}\).