# 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  
In January 2021, the UVSQ-SAT CubeSat was launched into orbit with a SpaceX Falcon 9 rocket from Cape Canaveral in Florida (United States). In the CubeSat's early hours post-launch, the dedicated flight control team at LATMOS operations centre in Guyancourt (78, France), took meticulous care of UVSQ-SAT in what is known as the launch and early orbit phase. 'First-light' measurements from UVSQ-SAT were obtained on February 2021, with first observations of OSR and OLR [2]. The 'routine' mode was activated on 13 March 2021. Now, months later, the CubeSat has successfully passed what is known as the 'in-orbit verification phase', where its scientific payload is switched on and the instruments' performance is checked. All satellite subsystems are working in perfect order. As of this writing, UVSQ-SAT continues to operate normally in orbit at an altitude of \(\sim\)534 km. The time series obtained with UVSQ-SAT since the beginning of its operational phase in February 2021 allow the construction of OSR and OLR flux maps from the measurements made by the sensors onboard the satellite. An example of UVSQ-SAT observations is given in Figure 7c,f for the month of August 2021. It is based on UVSQ-SAT Level-1 data products (version 1.0), and requires additional data processing to improve the measurements (particularly for OLR). These maps highlight the scientific relevance of the technological choices for the study of essential climate variables at the TOA. The map reconstruction method from UVSQ-SAT time series is described in [2]. It is based on the consideration that the flux measured by UVSQ-SAT results from the different contributions of the region observed by the satellite at a given time. Thus, to reconstruct the flux maps from the time series, we need to determine retrospectively the contribution of each point of the map at each measurement point. As detailed in [2], we consider a Gaussian distribution function that depends on the satellite field of view and associates a weight to each point of the map. The weight associated to each point represents the satellite passage density and depends, in addition to the field of view, on the orbital characteristics  
Figure 7: (**a**) TOA outgoing shortwave radiation from ERA 5 model. \(1^{\circ}\times 1^{\circ}\) latitude by longitude. Monthly averaged. (**b**) TOA outgoing shortwave radiation from ERA 5 model with UVSQ-SAT data time acquisition. (**c**) TOA outgoing shortwave radiation from UVSQ-SAT observations in August 2021. (**d**) TOA outgoing longwave radiation from ERA 5 model. \(1^{\circ}\times 1^{\circ}\) latitude by longitude. Monthly averaged. (**e**) TOA outgoing longwave radiation from ERA 5 model with UVSQ-SAT data time acquisition (eclipse period). (**f**) TOA outgoing longwave radiation from UVSQ-SAT observations in August 2021 (eclipse period). and the view angle under which the satellite is seen from the surface. This method can be applied to both UVSQ-SAT observations and the ERA-5 model. In the case of the ERA-5 model, the satellite ground-track is used and the time series are simulated by considering the contribution of each point to the measurement according to the method described just before. OSR and OLR time series are derived from the measurements made by the various sensors on board the CubeSat and from in-orbit attitude knowledge. New methods were developed to obtain UVSQ-SAT in-orbit attitude knowledge using Tri-Axial Attitude Determination (TRIAD) and Multiplicative Extended Kalman Filter (MEKF) methods [16]. The different inputs available to the algorithms are three-axis angular velocities (UVSQ-SAT gyrometer), six-axis solar direction (UVSQ-SAT photodiodes in the visible domain), and three-axis magnetic field (UVSQ-SAT magnetometer). In sunlight, the CubeSat attitude is obtained with an accuracy better than 3\({}^{\circ}\) (at one \(\sigma\)) for both methods.