# INSPIRE-SAT 7, a Second CubeSat to Measure the Earth's Energy Budget and to Probe the Ionosphere
## 4 UVSQ-SAT CubeSat Observations in Orbit and Future Observations (INSPIRE-SAT 7, Terra F)
### UVSQ-SAT Real Observations and INSPIRE-SAT 7 Simulated Observations
During eclipses, the accuracy of the TRIAD method is 14\({}^{\circ}\), while it reaches 10\({}^{\circ}\) (at one \(\sigma\)) for the recursive MEKF method. A reduction in CubeSat attitude knowledge uncertainties would improve the UVSQ-SAT results (OSR and OLR). Finally, it is possible to generate flux maps at TOA for the desired time step. Figure 7 shows monthly averaged maps for OSR (a, b, c) and OLR at TOA (d, e, f) for the month of August 2021 (simulation, UVSQ-SAT, INSPIRE-SAT 7 projection). Three cases are considered:  
* Comparisons with the ERA 5 model (a, d). ERA 5 is produced by the Copernicus climate change service at the European Centre for Medium-Range Weather Forecasts (ECMWF). ERA 5 is a combination of past observations with models to generate consistent time series of multiple climate variables. It is the fifth-generation reanalysis for the global climate and weather [21]. The purpose of that new dataset was to replace the ERA-Interim, that was implemented in 2006 and was stopped in August 2019. The different objectives of that new implementation were to improve the spatio-temporal resolution, to allow uncertainty estimate, and to add new inputs to the large list. It now reaches a spatial resolution up to 0.25\({}^{\circ}\)\(\times\) 0.25\({}^{\circ}\) with hourly maps around the whole globe. The ERA 5 model is used to provide OSR and OLR at TOA for a given period (average over a month of data, for example). * Simulated maps using the ERA 5 model as seen by UVSQ-SAT along its track (b, e). These maps are obtained from the determination of the real UVSQ-SAT ground track as a function of time. This ground track is calculated from the two-line element set. Once the position (latitude, longitude) of the UVSQ-SAT CubeSat is determined from ground track, OSR and OLR at TOA time series are obtained from ERA 5 as they would be observed by the UVSQ-SAT CubeSat in orbit (field of view, altitude). OSR and OLR maps are reconstructed from these time series for a given period. * Reconstructed maps from observations made by UVSQ-SAT (c, f). The reconstructed method from observations is explained in detail in [2]. This method is used to provide UVSQ-SAT OSR and OLR at TOA for a given period. Qualitatively, we observe in the case of OSR an excellent agreement between the model and the observations that is encouraging for the future INSPIRE-SAT 7 perspective. Particularly, the radiation structures are identifiable for different geographic areas such as Europe and Northern Africa, Northern South America, Greenland, Alaska and Southeast Asia. For OLR, the reconstruction allows to obtain the main trends. However, the ground track of the UVSQ-SAT CubeSat is still visible, which can be improved by increasing data sampling. Figure 8 provides a quantitative analysis of the temporal evolution of OSR (left) and OLR (right) between February and August 2021. The curves are obtained by simply averaging (weighted by pixel size) the UVSQ-SAT observations (magenta), the ERA 5 model (blue), and the observations simulated from the ERA 5 model (black and red). The average monthly fluxes of OSR and OLR follow the same trend for the observations simulated with the ERA 5 model (black) and the UVSQ-SAT observations (magenta). There is a bias between the model and the observations of about 6 Wm\({}^{-2}\) in the case of OSR and  
around 20-25 Wm\({}^{-2}\) in the case of OLR. The biases can be explained by limits linked to the ground-based calibrations of the UVSQ-SAT instruments. However, they remain compatible with the requirements set out in Table 1 (absolute accuracy of \(\pm\)10.00 Wm\({}^{-2}\) for OSR and OLR). The absolute determination of the ERB parameters requires rigorous calibrations including pre-flight calibration compatible with international standards, and in flight-calibration to monitor aging with same process. The size of CubeSats and the use of broadband non-scanner instruments could represent a limit.