Enhancement of Communication Quality in the X-Band Downlink Channel for Leo Earth Observation Satellites
DOI:
https://doi.org/10.15407/scine21.05.076Keywords:
satellite communication, remote sensing of the Earth, DVB-S2X, link marginAbstract
Introduction. Earth observation by low Earth orbit (LEO) satellites plays a critical role in supporting various sectors of the national economy. To increase the efficiency of this technology, optimizing the video data downlink —
particularly with respect to the satellite’s elevation angle relative to the ground station — is essential.
Problem Statement. The communication link margin varies depending on the selected signal waveform, while
changes in the satellite’s elevation angle alter the propagation path length and, consequently, the energy characteristics of the downlink. For small satellites such as CubeSats, which have limited onboard power, the potential to transmit high-data-rate video within a brief communication window — depending on modulation mode — has not been sufficiently studied.
Purpose. This study aims to enhance the performance of Earth remote sensing systems by improving the energy efficiency and throughput of satellite-to-ground video transmission in the X-band.
Materials and Methods. The analysis applies microwave communication theory to evaluate the energy budget of the downlink, incorporating Adaptive Coding and Modulation (ACM) techniques supported by the DVB-S2/S2X standard. The study considers various modulation and coding (MODCOD) schemes and output power levels at diff erent satellite elevation angles.
Results. The energy margin of the LEO satellite downlink has been calculated, enabling an assessment of the
feasibility of using DVB-S2X for video transmission from Earth observation satellites. The findings have shown
that at low elevation angles, a connection can be established using the most robust mode (QPSK 1/4), supporting a data rate of 38 Mbps. At elevation angles exceeding 50 degrees, higher-order modulation such as 32APSK 9/10 becomes feasible, achieving data rates up to 384 Mbps.
Conclusions. The study has demonstrated that applying the DVB-S2(X) standard to CubeSat-class Earth observation missions enables more efficient and adaptive use of the X-band downlink channel. This approach has improved flexibility and throughput of video data transmission, especially when tailored to satellite elevation angles.
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