Ivo Vertat

Autonomous and semi-autonomous radio commanding of VZLUSAT-1 nanosatellite from ground control station in Pilsen

Nano- and pico-satellites are currently used as low cost in-orbit-demonstrators of new technologies or for the university research. These satellites are launched to the low Earth orbits and radio commanded from the ground control stations. Most of them are equipped with narrow band transceivers working in UHF radio amateur frequency band, reaching only low data transmission rates. Low Earth orbits also limits the number and duration of satellite passing in the range of ground control station. One ground control station has approximately six satellite passes per day, each with duration only in few minutes. This strictly limits the amount of transmitted data between satellite and ground control station. In this paper the software controlled and assisted radio commanding of VZLUSAT-1 nanosatellite during the QB50 scientific mission is described. Two basic modes of satellite radio commanding are described with the aim to increase data throughput during commanding. Software controlled autonomous and software assisted semi-autonomous modes allow effective commanding of satellite while keeping the attention of satellite operator to the satellite condition and keeping the full control over the radio transmission as radio amateur regulation requires. Also the critical operational limits of satellite electronics faces to cosmic vacuum and radiation environment have to be continuously monitored for safety satellite operation.

Efficient and Reliable Solar Panels for Small CubeSat Picosatellites

CubeSat picosatellites have a limited area of walls for solar cells assembling and the available area has to be effectively shared with other parts, such as planar antennas, optical sensors, camera lens, and access port. With standard size of solar cell strings, it is not possible to construct a reliable solar panel for CubeSat with redundant strings interconnection. Typical solar panels for CubeSat consist of two solar cell strings serially wired with no redundancy in case of solar string failure. The loss of electric energy from one solar panel can cause a serious problem for most picosatellites due to minimum margin in the blueprints of the picosatellite subsystem power budget. In this paper, we propose a new architecture of solar panels for PilsenCUBE CubeSat with a high level of redundancy in the case of solar string failure or following switched power regulator failure. Our solar panels use a high efficiency triple junction GaInP2/GaAs/Ge in the form of small triangle strings from the Spectrolab Company. A suitable technology for precise solar cell assembling is also discussed, because CubeSat picosatellites are usually developed by small teams with limited access to high-end facilities.

Multidimensional Parity Check codes with short block lengths

The Multidimensional Parity Check codes (MDPC) are one of the possible FEC methods of the short information messages. Especially the MDPCs with reduced generator matrix results in codes with block length from few to tens of bits with indispensable code-gain. This paper presents two methods of generation of the MDPC and describe the algorithm for iterative decoding of these codes. The MDPC with short block length were tested and their BER were compared with BER of equivalent LDPC.

The signal splitter for laboratory GNSS signal distribution

The paper presents a design of a four way signal splitter working in L frequency band, for standard GNSS (Global Navigation Satellite Systems) signals. These splitters are used when more than one receiver has to be connected to one signal source, like an antenna, a signal distribution socket or a test signal generator. The advantage of the solution is realization by a PCB structure, without need of any expensive or hard to find special components. The splitter is also integrated with a transformation from 75 Ω to 50 Ω. Then cheaper 75 Ω cable can be used for the signal distribution system. Final results from the splitter testing are also included in the paper.