Efficient use of global navigation satellite system (GNSS) observations improves when applying rational satellite selection algorithms. By combining the Sherman–Morrison formula and singular value decomposition, a smaller-GDOP (geometric dilution of precision)-value method is proven for an increasing number of visible satellites. By combining this smaller-GDOP-value method with the maximum-volume-tetrahedron method, a new rapid satellite selection algorithm based on the Sherman–Morrison formula for GNSS multi-systems is proposed. The basic idea of the algorithm is as follows: First, the maximum-volume-tetrahedron method is used to obtain four initial visible satellites. Then, the other visible satellites are selected by using the smaller-GDOP-value method to reduce the GDOP value and improve the accuracy of the overall algorithm. When the number of included satellites reaches a certain value, the rate of GDOP decrease tends to approach zero. Considering the algorithm precision and the computation efficiency, reasonable thresholds and end of calculation condition equation are given, which can make the proposed algorithm autonomous. The reasonable thresholds and the end of calculation parameters are suggested by means of experiments. Under the thresholds and the end of calculation parameters, the algorithm has an adaptive functionality. Furthermore, the GDOP values of the algorithm are less than 2, indicating that this algorithm can meet one of the requirements of high-precision navigation. Moreover, compared with the computation complexity values of the optimal GDOP estimation method, which includes all visible satellites, the values of the new algorithm are about half, indicating that this algorithm has a rapid performance. These findings verify that the proposed satellite selection algorithm based on the Sherman–Morrison formula provides autonomous functionality, high-performance computing, and high-accuracy results.

The traditional space telemetry, tracking, command and communication system works in the radio frequency band. With the improvement on measurement accuracy and communication capacity in space missions, the traditional means have a certain bottleneck in dealing with the development of future space missions. The inherent lightweight, high parallel, high capacity and fine processing capabilities of Optics and microwave photonics show the potential to solve the above problems. This paper summarizes the innovative work of the Southwest China Institute of Electronic Technology in the application of laser measurement and communication integration, microwave photonic RF front-end technology in space telemetry, tracking, command and communication system. The experimental platform is established for verification, the accuracy of ranging and velocity measurement reaches millimeter level at 10Gbps single channel transmission rate with 1E-9 bit error rate under a simulation satellite-ground link. The microwave photonic RF front-end can be compatible with S to Ka band, with a sampling rate of 20Gsps and a signal bandwidth of 5GHz. It is expected to be applied to next generation of space telemetry, tracking, command and communication system or navigation and relay system.

The space-based integrated information network is composed of space-based backbone network, space-based access network and ground-based node network. It is interconnected with the ground Internet and mobile communication network to build a “ global coverage, on-demand access, on-demand service, safe and reliable ” space-based integrated information network system. As an important part of the system, the space-ground laser communication equipment is faced with many problems, such as the integration of multiple modulation systems and the location of different places. In this paper, the related problems are analyzed and verified by experiments. The results show that the system works at 1550nm wavelength, adopts coherent communication system and IM/DD communication system, coherent communication system supports BPSK, QPSK and DPSK modulation format, IM/DD communication system adopts OOK modulation format, the communication rate reaches 5Gbps under the condition of 1E-9 bit error rate.

The space TT&C system is the only means for humans to conduct life cycle tracking, telemetry, command and communication for spacecraft. Multi-function, high-precision, real-time TT&C system has always been the goal pursued by researchers in TT&C technology. These features are based on high-speed and high-precision manipulation of microwave signals, but are limited by ‘electronic bottlenecks’. The generation, control and processing of wideband signals is extremely complex and impossible to accomplish in traditional electronics. Photonic technology's inherently large bandwidth, low transmission loss, and anti-electromagnetic interference make it a key enabling technology for breaking the TT&C system bandwidth and high-precision measurement bottleneck and "illuminating the future of TT&C system." Meanwhile, the optical subsystem is light in weight, small in size, and integrable. Therefore, the introduction of photonic technology may change the system of the existing TT&C system. This paper summarizes the main research progress of optical technology in TT&C system at home and abroad, discusses the key technologies of laser and microwave photon technology in TT&C system, and forecasts its development trend.

This paper analyzes the present research status of the lunar-earth and deep space telemetry, track and command (TT&C) system, four major difficulties and challenges to establish the TT&C system are studied. Then urgent needs for antenna arraying technology, laser TT&C technology, Ka and millimeter-wave band hypothermia receiver, superconducting nanowire single photon detectors, deep space optical tracking system, narrow linewidth laser source generating technology, optical communication modulation technology and high-power low-noise amplifier were summed up. A latest cutting-edge technology for deep space TT&C system, namely the iROC (integrated radio and optical communications, iROC) system was described. Finally, with the current situation, the recommendations of future developments of the lunar-earth, deep space TT&C system have been put forward. The research results can supply references for the development of the lunar-earth, deep space TT&C system.

A novel method, which is based on the triple-frequency combination and Space-Based Telemetry, Tracking, and Command (STT&C) stations, is proposed in this paper. Considering BeiDou Navigation Satellite System (BDS) Geostationary Orbit (GEO) and Inclined Geostationary Orbit (IGSO) satellites as the STT&C facilities, firstly, we presented the BDS Medium Earth Orbit (MEO) satellites’ precise orbit determination scheme based on triple-frequency combination. Then, we gave the sufficient and necessary conditions about the visibility and the coverage rate calculation model of STT&C to BDS MEO satellite. And then we deduced the model of BDS MEO satellites precise orbit determination based on triple-frequency combination observations. At last, we designed the simulation calculation. The simulation results show that orbit determination of BDS MEO satellite based on STT&C station can be realized at all times. And most of the simulation period time, under the condition of the dm level orbit determination for GEO/IGSO satellites, the position accuracy of the relative orbit determination is better than 4 m, the horizontal accuracy of the relative orbit determination is within 2.5 m, and the vertical accuracy of the relative orbit determination is less than 3.5 m.