## 2 Materials and Methods: Ten-Koh Mission Description
### Payload  
The main payload consists of five individual instruments, the main characteristics of which are summarized in Table 1. One of the main payloads is the Charged Particle Detector (CPD), which was developed by Prairie View A&M University, TX, USA and the Space Research and Technology Institute--Bulgarian Academy of Sciences, Bulgaria. This system consists of eight CMOS(Complementary Metal Oxide Semiconductor) detectors mounted on five faces of a cube, and the Bulgarian Liulin-type detector [19] mounted on the top of the complete assembly. The CPD instrument contributes to all four primary mission objectives. Another payload of Ten-Koh is a set of Double Langmuir Probes (DLP). This experiment is intended to study the plasma and the sheath formation around the satellite as it is spinning along its orbit. Satellite charging, which can occur at surface and internal level, is an important subject of study because it is related to satellite anomalies and is directly impacted by the space weather conditions. Satellite charging depends on the interaction of the spacecraft materials, their thickness, and charged particles energy. Fluxes of electrons ranging from 10 to 100 keV can produce surface charging, while electrons with energy bigger than 100 keV can produce internal charging (deep dielectric charging) [20]. The plasma flow around a satellite in LEO exhibits a behavior similar to the flow of a neutral gas: there is a region of compression on the side where the plasma flow impinges upon the moving spacecraft, and a wake region behind the body of the satellite (see Figure 4a). For satellites that have no attitude control, the modeling of the plasma interaction with the satellite body becomes a complex task. Therefore, in-situ measurements provided by the described experiment would be a valuable source of information useful for the validation of the plasma models. The DLP system is composed of two spherical, 10 \(\upmu\)m gold-plated electrodes, as shown in Figure 5a, which are placed outside of the spacecraft structure. The electrodes are mounted on an isolating glass fiber reinforced polymer (GFRP) plate to avoid any electrical contact with the CFRP structure, thus keep the electrodes floating with respect to the spacecraft ground. The shafts supporting the spheres are coated with alumina to ensure that only the spheres attract plasma particles, thus making the interpretation of results easier. The DLP control circuit, housed inside the spacecraft, uses a 16-bit digital-to-analog converter (DAC) to generate the DC biasing voltage. This allows the sweep duration to be tailored such that the plasma in different locations around the spinning spacecraft can be characterized, as shown in Figures 4a,b and 5a,b. The current flowing between the probes through the plasma and the biasing voltage are measured with a AD7927 12-bit ADC. The measurement circuit is isolated from the common ground of the spacecraft, which enables the plasma parameters to be measured. The purpose of the material mission (MM) is to expose three different samples of new material for space applications developed by Okuyama laboratory of Kyutech made of carbon fiber (CF) and PEEK resin:  
* Sample 1: CF/PEEK with no coating. * Sample 2: CF/PEEK with a special coating (silsesquioxane) to protect against atomic oxygen. * Sample 3: CF/PEEK with a special coating (yttrium oxide) to protect against UV. The system measures different parameters, including temperature of and strain inside the samples in order to quantify the changes in the coefficient of thermal expansion (CTE) of the new materials. By measuring the changes in CTE, internal micromechanical modifications in the chemical composition of the samples caused by the effects of space environment can be discerned. Testing in this way allows assessment of material survivability and reliability for use in space. The temperatures are sensed with AD590 temperature transducers sampled by the AD7927 ADC.