2:15 PM - 2:30 PM
[PCG18-09] Development of the software implemented in the onboard computer (OBC) for Kanazawa University Satellite "KOYOH"
Keywords:microsatellite, Kanazawa-SAT3, onboard computer
We have been developing a microsatellite named “KOYOH”, which aims to detect X-ray and gamma ray bursts related to gravitational waves, in Kanazawa University. In the present paper, we report the current status of the software implemented in the Onboard Computer (OBC) for KOYOH. The OBC is a main CPU equipped with a real time OS called “Toppers” and it controls all onboard components, power distribution and data communication system in the satellite. The OBC also manages uplink and downlink data communications with the ground station constructed at Kanazawa University for conducting the satellite mission.
The OBC is equipped with two kinds of interface: 24 ports of RS-422 and 32 ports of GPIO, which perform serial communication and general-purpose I/O, respectively. In addition, three sets of 16 ports analog-digital (AD) converters are connected to the OBC in order to obtain digital data from analog devices (e.g., Pt2000 temperature sensors and semiconductor temperature sensors). Using these interfaces, the OBC communicates with the onboard components in order to grasp the status of the components and control them appropriately.
For the uplink communication, we define three types of commands: OBC Commands, Direct Commands, and Timeline Commands. OBC Commands are commands that can be interpreted by the OBC, because they are implemented in the OBC software in advance, and they are related to the ground station software by ID numbers. We can execute an OBC Command by sending the corresponding ID number from the ground station software to the OBC, and the OBC software executes it referring to the ID number. The Direct Commands are amorphous commands, so that the OBC software sends the received commands directly to the corresponding component without any interpretation. Thus, Direct Commands are prohibited except in emergency. We have completed the implementation of OBC Commands and Direct Commands, and function tests are now being conducted.
For the downlink communication, we defined three types of telemetry data: House Keeping (HK) Data, Mission Data and Attitude Control System (ACS) Data. The HK Data are used to check the operation status of the satellite, such as temperature, voltage and the other parameters for health check of the onboard components. The Mission Data consists of X-ray and gamma-ray measurements data. The ACS Data indicate the detailed data on attitude control.The downlink data generated by the OBC are classified into two types: “Real data” and “Repro data”. The Real data are immediately sent to the ground during visible operation, while Repro data are once stored in the onboard Data Recorder (DR) and reproduced during the next visible operation. In the current implementation of the OBC software, two types of data can be selected for transmission, and we have confirmed that each type of data works well.
In further development, we will implement the process of Timeline Commands for the uplink and data handling functions for Mission Data and ACS Data for the downlink communication.
The OBC is equipped with two kinds of interface: 24 ports of RS-422 and 32 ports of GPIO, which perform serial communication and general-purpose I/O, respectively. In addition, three sets of 16 ports analog-digital (AD) converters are connected to the OBC in order to obtain digital data from analog devices (e.g., Pt2000 temperature sensors and semiconductor temperature sensors). Using these interfaces, the OBC communicates with the onboard components in order to grasp the status of the components and control them appropriately.
For the uplink communication, we define three types of commands: OBC Commands, Direct Commands, and Timeline Commands. OBC Commands are commands that can be interpreted by the OBC, because they are implemented in the OBC software in advance, and they are related to the ground station software by ID numbers. We can execute an OBC Command by sending the corresponding ID number from the ground station software to the OBC, and the OBC software executes it referring to the ID number. The Direct Commands are amorphous commands, so that the OBC software sends the received commands directly to the corresponding component without any interpretation. Thus, Direct Commands are prohibited except in emergency. We have completed the implementation of OBC Commands and Direct Commands, and function tests are now being conducted.
For the downlink communication, we defined three types of telemetry data: House Keeping (HK) Data, Mission Data and Attitude Control System (ACS) Data. The HK Data are used to check the operation status of the satellite, such as temperature, voltage and the other parameters for health check of the onboard components. The Mission Data consists of X-ray and gamma-ray measurements data. The ACS Data indicate the detailed data on attitude control.The downlink data generated by the OBC are classified into two types: “Real data” and “Repro data”. The Real data are immediately sent to the ground during visible operation, while Repro data are once stored in the onboard Data Recorder (DR) and reproduced during the next visible operation. In the current implementation of the OBC software, two types of data can be selected for transmission, and we have confirmed that each type of data works well.
In further development, we will implement the process of Timeline Commands for the uplink and data handling functions for Mission Data and ACS Data for the downlink communication.