Abstract
This paper provides and overview of the GRACE-FO Electrical System and an in depth discussion of the Electrical Power System (EPS). The EPS elements are presented and their features described by their key parameters. These components are inclusive of the body-mounted Solar Array Panels for Power Generation, the Power Control Unit (PCU) and Power Distribution Unit (PDU), a Li-Ion Battery and the Thermal Control System’s Heater Control Electronics (HCE’s) acting as active current control front-ends. The latter is explained more in detail with respect to its purpose and implementation. The GRACE-FO EPS has been given the designation of “quiet” EPS due to the function of the HCE within the thermal control Subsystem.The final portion of the paper provides information about the power and energy budgeting and operational aspects of the EPS such as undervoltage and overcurrent H/W features of the PCU/PDU design, and the EPS related On-board Software and On-Board Control Procedures. Finally, the system level power analysis is provided to provide the reader with a better understanding of the expected behaviour of the electrical power parameters.
Highlights
Expected to launch in 2017, the new GRACE-FO Mission* satellite pair will continue and expand upon the measurements initiated by the pathfinder GRACE Mission, launched in 2002
The PCDU is split into two boxes for accommodation reasons, the Power Control Unit (PCU) and the PDU (Power Distribution Unit)
The PCU consists of 6 modules, which are - 3 SARM (Solar Array Regulator Module), one for each Solar Array Panel; each SARM consists of 3 independent SARs for redundancy reason; 2 out of the 3 are able to convert the full power required
Summary
The GRACE-FO Electrical Block Diagram is depicted hereafter. The main blocks are: x Electrical Power Subsystem (EPS), described hereafter. X On Board Computer (OBC), the platform data handling system (DHS). X Telemetry and Telecommand (TT&C) and Science Data Transmission (SDT) subsystem as interface between the ground station and the OBC for reception of telecommands and telemetry x The Attitude and Orbit Control System (AOCS) units ensure the S/C attitude and orbit control x Thermal Control Subsystem x The GRACE-FO instruments, namely the Laser Ranging Instrument (LRI), the Microwave Instrument (MWI) instrument and the Accelerometer (ACC)
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