# INSPIRE-SAT 7, a Second CubeSat to Measure the Earth's Energy Budget and to Probe the Ionosphere
## 2 Scientific Objectives of the INSPIRE-SAT 7 Mission  
### Earth's Energy Budget Components and Earth's Energy Imbalance  
With the emergence of the NewSpace, an international project of a nanosatellite/ microsatellite constellation for the study of the Earth's global environment and climate has become possible. Climate observation is played out more than ever in space, and global warming is acknowledged as the major environmental issue of the 21 st century. Constellations of small satellites, possibly hosting different payloads, could be the best solution to characterize the spatio-temporal variability of the ERB components. Most ERB satellites have tended to only measure the total sum of radiation changes, not the individual components. The radiometric calibration uncertainties also limit the capability of the current generation of satellite-based instruments highlighting the need to have International calibration standards facilities. The current challenge is to measure at high spatio-temporal the individual ERB components that influence the atmospheric radiative transfer and heat budget. This topic represents the primary scientific objective of the INSPIRE-SAT 7 mission. Earth's energy budget describes the various types and amounts of energy that enter and leave the Earth system. ERB is composed of the incoming solar shortwave radiation, OSR (outgoing shortwave radiation reflected by the atmosphere including surface, clouds, and aerosols), and OLR (outgoing long-wave radiation emitted by the surface and atmospheric components such as greenhouse gases and clouds). The different components of ERB clearly depends on many atmospheric factors that are changing, notably greenhouse gases levels, surface albedo (linked to vegetation and land use), aerosols, and clouds. The global energy budget is also affected by external changes (incoming solar radiation) and internal climate variability. When the incoming and total outgoing energy fluxes (=OSR + OLR) are in balance, Earth is in radiative equilibrium and the climate system is relatively stable. Today, the Earth's incoming energy flux is greater than the outgoing energy flux mostly due to the increase in greenhouse gases levels which has led an enhanced greenhouse effect and hence reduction in the OLR. As a result, the planet is gaining energy and the surface is heating up which tends to increase OLR and so reestablish the Earth radiative balance [3]. One of the objectives of the INSPIRE-SAT 7 mission is to measure the ERB components and EEI. EEI represents a measure of the excess of energy that is being stored in the climate system as the result of the to anthropogenic forcing (increase in greenhouse gases levels). EEI has been identified as a crucial quantity [4] for testing climate models and for predicting the future course of global warming. Therefore, accurate EEImeasurements would certainly help to improve our understanding of climate change and the projections of future climate by climate models. Combining multiple ERB measurements in an optimal way using a small satellite constellation holds considerable promise for better estimation of EEI, and thus assessing the status of global climate change, improving climate models, and testing the effectiveness of mitigation actions. A recent study [5] demonstrates the benefits of having independent satellite TOA radiation observations and ocean heat content measurements for tracking 'long-term' changes in EEI. The vast majority of EEI ends up warming the ocean. The remainder heats the land, melts ice, and warms the atmosphere. The authors of this recent study [5] show that independent satellite and in situ observations yield statistically indistinguishable decadal increases in EEI from mid-2005 to mid-2019 of 0.50 \(\pm\) 0.47 Wm\({}^{-2}\) per decade (2\(\sigma\)). The error bar is of the order of the EEI. This estimation needs to be improved. The recommended objective is to detect any global 'long-term' trend with high accuracy (stability better than \(\pm\)0.2 Wm\({}^{-2}\) per decade).