Athena Onboard Computer
The on-board computer (OBC) is the “brain” of the satellite. To accomplish its tasks, An OBC needs to communicate with other subsystems and should be able to send, receive, process, and store data. It enables peripherals to communicate with each other in real-time.
Athena is an open-source on-board computer being designed to fly on Ex-Alta 2, YukonSat, AuroraSat. It is designed to be highly flexible, reliable, and connective, so that it can be used on a variety of different CubeSat applications in the future. Athena follows the Open CubeSat Platform (OCP) Stack Specification, and is made to easily integrate with other boards that follow the OCP specification, as well as many commercial off-the-shelf components.
One of the primary goals of AlbertaSat is to develop open-source hardware and software for CubeSats. The Athena Onboard Computer (OBC) is an in-house design that is powered by the TM570LC4357 Hercules Microcontroller and supports 8 GB of on-board storage. In addition to the OBC’s high computational power and low mass, it features a wide array of connectors and integrated sensors.
Athena uses the Texas Instruments TMS5704357 based on the ARM Cortex R5F as the microcontroller (MCU) on it. It was selected due to its many communication interfaces, general-purpose input/outputs and features that are ideal for satellite OBC application. The MCU compares the outputs of two identical processor cores running the same instruction set (in “lockstep”) and flags if the outputs ever differ due to a transient error. All integrated memories are able to detect and correct data corruption and bit flips due to radiation damage using error-correcting code (ECC). Athena has dedicated circuitry to detect and recover from radiation-induced failure due to latch-up.
Athena is able to use any SD card that supports an SPI interface for file storage. It also includes a 9-axis inertial measurement unit (IMU) which contains an accelerometer, a magnetometer, and a gyroscope. This allows Athena to function as an ADCS controller in certain implementations. It also provides an alternative method of obtaining the spin rate or attitude of the spacecraft in case of issues with the satellite’s attitude determination and control system. Athena accepts a 3.3 Volt power supply, a voltage that is commonly supplied by CubeSat power systems. Athena also has multiple temperature sensors placed near critical components for monitoring purposes.
The detailed characteristics of the board are given in the following table:
| Category | Specification |
| Volume Envelope | 93.35 mm x 87.63 mm x 15.48 mm |
| Mass | 50 g (TBC) |
| Supply Voltage | 3.3 V, VBATT (for burn wires) |
| Typical Power Consumption | 700 mW (TBC) |
| Microcontroller | TMS5704357 Hercules Mircocontroller |
| IMU | Hillcrest Laboratories, Inc. BNO080 |
| IMU Measurements | 9-axis: accelerometer, gyroscope, and magnetometer |
| Max Core Clock Speed | 300 MHz |
| SRAM Capacity | 512 KB |
| DRAM Capacity | 512 Mb SDRAM w/ ECC |
| Code Flash Capacity | 4 MB w/ECC (on MCU) |
| Data Flash Capacity | 128 KB (on MCU, included in Code Flash Capacity) |
| Data Interfaces | CAN (x2), UART (x4), SPI (x3), I2C (x1), GPIO (x14) |
| Operating Temperature (ambient) | -40 to +85 °C |
| Storage Temperature | -40 to +85 °C |
By Meharpreet Singh Nanda and Helena Ard
This page was last updated February 2021