Design and flight results of the VHF/UHF communication system of Longjiang lunar microsatellites

Abstract

As a part of China’s Chang’e-4 lunar far side mission, two lunar microsatellites for low frequency radio astronomy, amateur radio and education, Longjiang-1 and Longjiang-2, were launched as secondary payloads on 20 May 2018 together with the Queqiao L2 relay satellite. On 25 May 2018, Longjiang-2 successfully inserted itself into a lunar elliptical orbit of 357 km × 13,704 km, and became the smallest spacecraft which entered lunar orbit with its own propulsion system. The satellite carried the first amateur radio communication system operating in lunar orbit, which is a VHF/UHF software defined radio (SDR) designed for operation with small ground stations. This article describes and evaluates the design of the VHF/UHF radio and the waveforms used. Flight results of the VHF/UHF radio are also presented, including operation of the radio, performance analysis of downlink signals and the first lunar orbit UHF very-long-baseline interferometry (VLBI) experiment.

Local correlation of delta-DOR signals with low signal-to-noise ratio and severe radio frequency interference

“…S8524b and s8525b were the simultaneous interferometry observation of the spacecraft Queqiao and Longjiang 2 in the Chang'E 4 project. Longjiang 2 was launched on the same day with Queqiao (May 21 in 2018), but keeping angle separations during the whole cruise stage (Wei et al 2020). The VLBI antennas pointed to Queqiao, so that Longiang 2 was located slightly off-beam, which led to the lower SNR of DOR signals received by VLBI stations.…”

“…The troposphere delay used for calibration are measured by the global positioning system receivers equipped at the CVN stations (Song et al 2011). Zhou et al (2018, 2020 applied more Chinese stations to construct the ionospheric correction model for CVN stations. At last, the calibrated delta-DOR delay are used for the orbit and position determination of the spacecraft (Huang et al 2014).…”

A Cloud-Computing-Based Portable Networked Ground Station System for Microsatellites

“…The aim of this paper is to assist in the design of communication systems. Wei receives [14] TM signals from lunar microsatellites through an SDR-based ground station. Although this design is excellent, they did not take into account the multiple access of the network.…”