Scalable and Configurable Electrical Interface Board for Bus System Development of Different CubeSat Platforms

Abstract

A flight-proven electrical bus system for the 1U CubeSat platform was designed in the BIRDS satellite program at the Kyushu Institute of Technology. The bus utilizes a backplane board as the mechanical and electrical interface between the subsystems and the payloads. The electrical routes on the backplane are configured by software using a complex programmable logic device (CPLD). It allows for reusability in multiple CubeSat projects while lowering costs and development time; as a result, resources can be directed toward developing the mission payloads. Lastly, it provides more time for integration and system-level verification, which are critical for a reliable and successful mission. The current trend of CubeSat launches is focused on 3U and 6U platforms due to their capability to accommodate multiple and complex payloads. Hence, a demonstration of the electrical bus system to adapt to larger platforms is necessary. This study demonstrates the configurable electrical interface board’s scalability in two cases: the capability to accommodate (1) multiple missions and (2) complex payload requirements. In the first case, a 3U-size configurable backplane prototype was designed to handle 13 mission payloads. Four CPLDs were used to manage the limited number of digital interfaces between the existing bus system and the mission payloads. The measured transmission delay was up to 20 ns, which is acceptable for simple serial communications such as UART and SPI. Furthermore, the measured energy consumption of the backplane per ISS orbit was only 28 mWh. Lastly, the designed backplane was proven to be highly reliable as no bit errors were detected throughout the functionality tests. In the second case, a configurable backplane was implemented in a 6U CubeSat with complex payload requirements compared to the 1U CubeSat platform. The CubeSat was deployed in ISS orbit, and the initial on-orbit results indicated that the designed backplane supported missions without issues.

Special Issue on Small Satellites Missions and Applications

“…This paper focuses on the calibration of a magnetometer through genetic algorithms using data observed by BIRDS-3 CubeSats. The design of the electrical interface bus for the same nanosatellites is presented in [13]. This design allows for accommodating multiple missions and different payload requirements.…”

Survey on Harness Design for CubeSats: Understanding the Constraints of CubeSats Design and Toward an Optical Wireless Bus for CubeSats

“…The pins for the PC/104 sockets increase as the number of mission devices increases installed into the satellite. Using CPLDs for interconnecting the mission devices successfully reduced the wiring among electronic circuit boards [19]. The study [19] used CPLDs for routing the data and control signals for the mission devices.…”

“…Using CPLDs for interconnecting the mission devices successfully reduced the wiring among electronic circuit boards [19]. The study [19] used CPLDs for routing the data and control signals for the mission devices. Using the CPLD approach and stackable electrical boards reduces the wire harness's mass and space.…”