This paper introduces the satellite system running status and key events. This satellite has been observing the Earth for six years after its launch into a 645 km sun-synchronous orbit. Through the health trend analysis of the platform and subsystems, the orbit, power supply, rotating parts status, temperature, fuel consumption and so on are introduced in detail. The cameras’ status also are monitored and analyzed.

Over the next decade,Very High-Throughput Satellite (VHTS) will bring enough capacity to serve high speed internet and in-flight connectivity markets at scale, offering fiber-like services both in terms of price and speed. In this context, a generic VHTS mission utilizing Q/V-band feeder links and Ka-band user links is described. However, the rain attenuation on the feeder links becomes a limiting issue because of the higher frequencies. Toward this, an exploitation of multiple gateways (GWs) as a transmit diversity measure for overcoming severe propagation effects are being considered. Ground Application System (GAS) design of VHTS is illustrated including N+P GWs (N active and P redundant GWs) diversity, frequency plan, link budget and system capacity.

This paper introduces the structure and principle of a surface-mount high-precision temperature compensation crystal oscillator, and specifically describes the reliability design of a quartz-crystal resonator used inside the surface-mount temperature compensation crystal oscillator, the reliability design of surface-mount ceramic base and the reliability design of hybrid micro-assembly. Finally, the thermal and mechanical simulation results and the experimental verification of this surface-mount temperature compensation crystal oscillator are provided, which prove that this crystal oscillator has high reliability.

A 28 V-half-regulated power bus topology and an integrated PCDU (Power Conditioning and Distribution Unit) were adopted to meet the energy demand for the Chang’e 4 relay satellite. This paper first introduces the mission features and composition of the PSDS (Power Supply and Distribution System) for the Chang’e 4 relay satellite. Due to this satellite’s unusual orbit, operational mode and project restrictions, special analysis and design was conducted on the PSDS from the perspective of weight-reduction, power management, and reliability and so on. Extreme low temperature storage of SA (Solar Array) was considered and how the antenna affects the SA was analyzed. A new kind of high-specific-energy 45 Ah (Ampere-hour) battery cell was used for the first time. To make sure that the satellite would successfully pass the long shadow zones, a 100% DOD (Depth of Discharge) experiment was carried out on the battery. Since the sunlight is almost always available and there are very few times for the battery to charge or discharge, battery care to extend its lifetime is also discussed. PCDU is a device that integrates power conditioning and power distribution in one unit. The PCDU on Chang’e 4 relay satellite can output more power with less weight because of the adoption of a 28 V-half-regulated power bus topology which was also used for the first time and used lighter material for its mechanical framework. Experiment under low temperature on PCDU was conducted as well and a hot backup equalizing charge technique which is beneficial to keep performance of the battery is illustrated. The power distribution module, which is a module of PCDU, enhances the power utilization security by utilizing a static impedance measurement and build-in-test to avoid possible short circuits. As for EED (Electrical Explosive Device) module, a protection plug was specially designed and three switches with different functions were connected in series to prevent the EED from exploding by error. In addition, the allowable minimum EED bus voltage for each EED was evaluated in case of low battery voltage caused by the possible postponement of the launching time. Complete verification experiments on the ground were conducted to confirm the correctness of the design and on-orbit test data conformed to the expected results and theoretical calculation. The power supply and distribution system has been working normally since the day the Chang’e 4 relay satellite was launched into space.

The far side of the moon is a unique place for some scientific investigations. Chang’e 4 is a Chinese lunar far side landing exploration mission. Relay communication satellite, named as Queqiao, is an important and innovative part of Chang’e 4 mission. It can provide relay communication to the lander and the rover operating on the lunar far side to maintain their contacts with Earth. It was launched by LM-4C launch vehicle at the Xichang Satellite Launch Center on May 21, 2018. After five precise orbit controls and a journey of more than 20 days, Queqiao inserted into final halo mission orbit around Earth-moon libration point 2, located about 65,000 km beyond the moon. It is the world’s first communication satellite operating in that orbit. Up to now, Queqiao worked very well and provided reliable, continuous communication relay service for the lander and the rover to ensure the mission success of Chang’e 4 exploration mission. Via Queqiao, the lander and the rover were controlled to work by ground stations and obtained a great amount of scientific data. The mission overview, operation orbit selection, relay communication system design and flight profile were introduced in this article.

An overall bi-directional panoramic solar system exploration activity, not just looking at the solar system at a macro level and helping to build a simulation model for the solar system, but the probe will also be able to explore the Milky Way and the vast universe from a much wider perspective. By observing the characteristics of the solar system, solar wind, ionization envelope and other parameters from a bi-directional panorama on both sides of the solar ecliptic plane, it will assist the scientific community and human kind to understand the solar system in a more extensive, deeper and systematic way than before.
The exploration can be done in two steps. The first step is to launch a solar polar probe. Secondly to launch a bi-directional probe orbiting the galaxy in sync with the sun.