**2. Instrumentation and Methods**

#### *2.1. CubeSat*

The experimental data used for the preparation of this paper were measured by 1U CubeSat Lucky 7 (Figures 1 and 2). Lucky 7 (catalogue no. 19038W) was launched from Vostochny Cosmodrome by the Soyuz-2.1b rocket on 27 June 2019, to a quasi-synchronous orbit of inclination of 97.5008◦ and altitude of 520 km. Regular scientific data were collected until August 2019 after successful satellite testing. Examples of the points at which the radiation was measured are shown in Figure 3.

**Figure 1.** Lucky 7 CubeSat.

**Figure 2.** Lucky 7 block diagram.

**Figure 3.** Typical points of radiation measurements.

Lucky 7 CubeSat is a private project of two people, namely Jaroslav Laifr and Pavel Kovar. Mr. Laifr developed and manufactured the satellite hardware including the power supply, radiation detector, and camera. He registered the satellite. Pavel Kovar developed the GPS receiver hardware and software and hardware and the software of the ultrahigh frequency (UHF) satellite modem, including a single-layer communication protocol capable of operating even at a high packet error rate. He is the author of the on-board computer hardware and software. He designed a ground station modem as well as ground station software.

The main component of the satellite is an onboard computer that integrates two independent computers and UHF modems that control the satellite, collect scientific data, and communicate with ground stations. The scientific module (Figure 4) is equipped with the GPS receiver piNAV 2 [32–34], the radiation detector piDOSE [35,36], a spectrometer and a low-resolution camera. The energy for satellite operation is generated by gallium arsenide solar cells that are mounted on the five satellite panels. The radiation hardening power supply is built from bipolar and silicon carbide transistors. Energy is stored in LiFe batteries with a capacity of 4 Wh.

**Figure 4.** Scientific module.

The Lucky 7 satellite can realize measurements up to 2048 min in duration. The onboard computer saves to memory the number of pulses registered by a radiation detector, position and time of the end of the measurement, and satellite statuses such as power supply voltage, current, currents from the solar cells, the temperature of the detector, and other subsystems.
