Next generation earth-to-space telecommand coding and synchronization: ground system design, optimization and software implementation

The Consultative Committee for Space Data Systems, followed by all national and international space agencies, has updated the Telecommand Coding and Synchronization sublayer to introduce new powerful low-density parity-check (LDPC) codes. Their large coding gains significantly improve the system performance and allow new Telecommand services and profiles with higher bit rates and volumes. In this paper, we focus on the Telecommand transmitter implementation in the Ground Station baseband segment. First, we discuss the most important blocks and we focus on the most critical one, i.e., the LDPC encoder. We present and analyze two techniques, one based on a Shift Register Adder Accumulator and the other on Winograd convolution both exploiting the block circulant nature of the LDPC matrix. We show that these techniques provide a significant complexity reduction with respect to the usual encoder mapping, thus allowing to obtain high uplink bit rates. We then discuss the choice of a proper hardware or software platform, and we show that a Central Processing Unit-based software solution is able to achieve the high bit rates requested by the new Telecommand applications. Finally, we present the results of a set of tests on the real-time software implementation of the new system, comparing the performance achievable with the different encoding options.

Analysis of the influence of design parameters on the agro-ecological qualities of tractor tires

Experimental studies of the impact of agricultural mobile machinery movers on the soil are seasonal in nature and require complex experimental equipment. The complexity of the physical processes occurring in the elastic wheel-ground system requires the introduction of many assumptions and limitations that reduce the accuracy of the results, according to the design of simulation models performed in the software environment. The aim of the research was to study the influence of the design parameters of the tire on the efficiency of the normal deflection along the contact spot zone X. Studies have shown that 65% to 77% of the normal deflection of the tire is used when passing the contact spot. The reinforcement parameters of the tire frame have the greatest impact on the efficiency of the normal deflection along the contact spot zone. With an increase in the number of layers of the frame cord from 2 to 8, the coefficient of usability of the normal deviation for the stroke of the contact spot decreases from 0.761 to 0.689, with an increase in the angle of inclination of the frame cords - decreases from 0.755 to 0.693.

Overview of the Flight Dynamics Subsystem for Korea Pathfinder Lunar Orbiter Mission

Korea’s first lunar mission, the Korea Pathfinder Lunar Orbiter (KPLO), aims to launch in mid-2022 via the Space-X Falcon-9 launch vehicle. For the successful flight operation of KPLO, the Korea Aerospace Research Institute (KARI) has designed and developed the Flight Dynamics Subsystem (FDS). FDS is one of the subsystems in the KPLO Deep-Space Ground System (KDGS), which is responsible for the overall flight dynamics-related operation. FDS is currently successfully implemented and meets all of the requirements derived from the critical design phases. The current work addresses the design and implementation results for the KPLO FDS. Starting from overviews on KPLO payloads, bus systems, and mission trajectory characteristics, a review on KDGS is also treated briefly. Details on the design philosophy, unique characteristics, and functionalities of all six different modules nested inside the FDS with its Graphical User Interface (GUI) design are discussed. Moreover, efforts currently devoted to the flight operation preparation of the KPLO are summarized, including many collaborative works between KARI and the National Aeronautics and Space Administration (NASA) teams.

Perancangan Antena Mikrostrip Dual Band Profil Rendah Menggunakan Teknik DGS Dan Meander Line Untuk Aplikasi GNSS

Some of the parameters that are considered to measure GNSS antenna performance are polarization, polarization, bandwidth, return loss and antenna dimensions. This study aims to design a low profile dual band microstrip antenna using the Defected Ground System (DGS) and Menader Line (ML) techniques for GNSS applications. In this research, the DGS technique is used to increase the bandwidth while the ML technique is used to reduce the antenna dimensions. This antenna design uses a FR4 Epoxy substrate with a thickness of 1.6 mm. To design and analyze the antenna, the CST Studio Suite 2016 simulator is used. The simulator is equipped with an optimizer feature that can optimize antenna parameters. Based on the design results, an antenna with a size of 183.6 x 183.6 x 1.6 mm3 has been produced. The antenna works in dual band, namely in the band 1247 - 1294 MHz (bandwidth - 3.70% BW) for radio navigation satellite services Glonass (G2) and Galileo (E6). And in the band 1539-1606 MHz (4.26% BW) for the Galileo (E1) flight radio navigation service, Compass and GPS (L1). Keywords: Global Navigation Satellite System (GNSS), low-profile dual-band microstrip antenna, Defected Ground System (DGS) dan Meander Line (ML).

Intense dB/dt variations driven by near-Earth Bursty Bulk Flows (BBFs): A case study

<p>During geomagnetically disturbed times the surface geomagnetic field often changes abruptly, producing geomagnetically induced currents (GICs) in a number of ground based systems. There are, however, few studies reporting GIC effects which are driven directly by bursty bulk flows (BBFs) in the inner magnetosphere. In this study, we investigate the characteristics and responses of the magnetosphere-ionosphere-ground system during the 7 January 2015 storm by using a multi-point approach which combines space-borne measurements and ground magnetic observations. During the event, multiple BBFs are detected in the inner magnetosphere while the magnetic footprints of both magnetospheric and ionospheric satellites map to the same conjugate region surrounded by a group of magnetometer ground stations. It is suggested that the observed, localized substorm currents are caused by the observed magnetospheric BBFs, giving rise to intense geomagnetic perturbations. Our results provide direct evidence that the wide-range of intense dB/dt<strong> </strong>(and dH/dt) variations are associated with a large-scale, substorm current system, driven by multiple BBFs.</p>