Hybrid M-FSK/DQPSK Modulations for CubeSat Picosatellites

Conventional CubeSat radio systems typically use one of several basic modulations, such as AFSK, GMSK, BPSK, QPSK and OOK or switch between them on demand if possible. These modulations represent a bal¬anced trade-off between good energy efficiency of high order M-FSK modulation and good spectral efficiency of high order M-QAM modulation. Utilization of modulations with the best energy efficiency is not possible due to strict limits on occupied frequency bandwidth. In this paper the proposed group of hybrid modulations and proposed hybrid modulator and demodulator are presented. Novel solution offer interesting possibilities of increasing spectral efficiency as well as energy efficiency of basic M-FSK modulation by embedding DQPSK symbols between two M-FSK symbols. Such group of hybrid modulations offers suitable properties for picosatellite, e.g. simple realization onboard the picosatellite, better energy and spectral efficiency, low PAPR, wide range of adaptation by changing the order of M-FSK, suitable for easy non-coherent demodulation, good immunity to Doppler effect with DM-FSK coding

Collaborative Network of Ground Stations with a Virtual Platform to Perform Diversity Combining

SGS-2021-005A conventional ground station can establish a single downlink with only one satellite at a time through steerable high-gain antenna. In addition to the lack of tracking more than one satellite at once, such single radio communication is highly vulnerable to outages when experiencing severe degrading circumstances or even with steering engine failures. Accordingly, such problematic single radio link would leave the operator with no alternative options to overcome the consequences. This work exhibits a solution to the ground station through networking. Multiple ground stations, with omnidirectional antennas instead of the steerable directive ones, can be engaged in a collaborative network to receive multiple versions of the same transmitted data for processing and combining. The suggested receive diversity combining is performed at a virtual ground station which utilizes a combining algorithm to help detect the original data from the received versions with less errors and hence reflecting more efficient and reliable services. To exploit this aimed diversity gain, a simple combining algorithm is also developed in this article. The simulation results from the proposed scheme have indicated significant performance enhancement over the single site ground station. This cooperative scheme will not only improve the system performance but also offer to track more than one satellite at a time

Collaborative Network of Ground Stations with a Virtual Platform to Perform Diversity Combining

SGS-2021-005A conventional ground station can establish a single downlink with only one satellite at a time through steerable high-gain antenna. In addition to the lack of tracking more than one satellite at once, such single radio communication is highly vulnerable to outages when experiencing severe degrading circumstances or even with steering engine failures. Accordingly, such problematic single radio link would leave the operator with no alternative options to overcome the consequences. This work exhibits a solution to the ground station through networking. Multiple ground stations, with omnidirectional antennas instead of the steerable directive ones, can be engaged in a collaborative network to receive multiple versions of the same transmitted data for processing and combining. The suggested receive diversity combining is performed at a virtual ground station which utilizes a combining algorithm to help detect the original data from the received versions with less errors and hence reflecting more efficient and reliable services. To exploit this aimed diversity gain, a simple combining algorithm is also developed in this article. The simulation results from the proposed scheme have indicated significant performance enhancement over the single site ground station. This cooperative scheme will not only improve the system performance but also offer to track more than one satellite at a time

Timepix in LEO orbit onboard the VZLUSAT-1 nanosatellite: 1-year of space radiation dosimetry measurements

The VZLUSAT-1 satellite, the first Czech CubeSat, was successfully launched on June 23, 2017, to a 510 km Sun-synchronous low-Earth orbit. It carries several scientific payloads including a Timepix detector as focal plane imager for the X-Ray telescope onboard. The Timepix detector contributes significantly to the satellite data collection, with more than 25 000 sampling acquisitions in the first year of deployment. Despite limitations of the satellite attitude control system, necessary for capturing X-Ray images of the Sun, the Timepix detector allows measuring the space radiation environment along the satellite orbit. As of September 2018, we conducted 33 whole-Earth mappings, recording radiation doses around the planet. Further, we show data from scans of the South Atlantic Anomaly and polar radiation horns, where the location and acquisition time were tailored to minimize event pile-up and particle track overlap. Since October 2017, the optics segment of the onboard X-Ray telescope was deployed, which exposed the Timepix detector unshielded to free open space. This change produced entirely new observations namely of low energy charged particles and a significant increase of measured particle flux. We also registered the effects of exposing the sensor to direct intense sunlight. We will summarize on the actual performance of the custom readout interface, which exceeds expectations in the constrained environment of the low-cost and low-powered CubeSat nanosatellite