## 3 Results  
### Ground Tests  
The main payload instruments were tested and calibrated to verify that the experiments can provide measurements inside the defined range. For the MM, DLP and magnetometer, the testing and calibration were carried out using the facilities of Kyushu Institute of Technology in Japan. For the CPD case, which includes the CMOS and Liulin detectors, the tests were conducted at Prairie View A&M University and the Space Research and Technology Institute of the Bulgarian Academy of Sciences, respectively. Details about the Liulin detector calibration can be found in [27], while the CMOS detectors still need an extensive calibration that is currently underway at Prairie View A&M University. Double Langmuir Probe (DLP)  
Figure 9(a) shows the ground test results of the DLP plasma measurement system. The different I-V curves for each case correspond to varying numbers of samples, and hence the speed at which the applied potential was being changed. This resulted in different coupling of the circuit with the RF  
Figure 9: Magnetometer calibration tests. Offset imposed by the satellite to each axis when: no electronics are ON, and under specific subsystems operating conditions. The results will be used to remove the offset to the magnetometer measurements when the satellite is under specific operating conditions. plasma source in the chamber. For a large number of samples, the DLP generates smaller voltage steps (step size). Considering that the sheath formation varies as a function of the biasing voltage applied to the probes (VB) with respect to the floating potential Vf (zero net current or equal flow of electrons and ions), by setting the probes potential above the Vf, a net positive current due to plasma electrons flows into the plasma. If VB is set below Vf, then a net negative current of ions flows out from the plasma. By biasing the probes with negative and positive potentials, the typical I-V curve is obtained (see left of Figure 10a). After different tests performed at the LEO plasma chamber located in the facilities of the Laboratory of Spacecraft Environment INteraction Engineering (LaSEINE) in Kyutech, the \(-10\) to +10 V biasing range was deducted as optimal to obtain a full I-V curve in orbit. This range allows computing the electron density and temperature of the plasma surrounding the spacecraft according to the tests and estimated parameters from the IRI 2016 model [24] for the referred epoch. When biasing the voltage across the probes in smaller steps (more samples), the DLP system takes longer time to sweep the voltage from \(-10\) V to \(10\) V. When selecting a bigger step size (fewer samples), the DLP sweeps the voltage across the probes faster. This can be seen as a change in the frequency of the biasing voltage. Because the plasma source employed in the testing was of RF origin, the plasma potential fluctuated at the RF frequency and its harmonics. The overall effect appears as a wider I-V curve that creates a higher value of the electron temperature and shifts the floating potential to a more negative value, as described in [28]. To reduce the effect of the RF coupling with the measuring circuit, the selected step size used during the testing was between 500 and 1000, which corresponds to 65 and 131 samples. This was validated with the use of a source-meter instrument with an RF compensation stage and requesting the same number of samples. The final ground test for the DLP instrument development was the calibration of the system. The fastest way to perform calibration of the measuring unit was by the use of a relative calibration with the same SMU2400 instrument. By comparing resistance measurements from current and voltage readings, it was possible to obtain the sensitivity and linearity of the DLP system relative to the SMU2400 and the resistor value. For this purpose, a resistor of \(1\) G\(\Omega\) (\(1\times 10^{9}\) ohms), and \(1\%\) precision value, was connected between the two probes at room temperature.