Arduino Based Electronic Ground Support Equipment for CubeSats

EGSE (Electronic Ground Support Equipment)
At the CubeSat Research Center here at Seoul National University, we build a lot of our satellite components in-house. So far, for SNUSAT-1, SNUSAT-1b and SNUSAT-2, the team has been able to build On-Board Computer based on ARM Cortex-M4 processor, Imaging Payload, Battery Board, Interface Boards, PCB MTQs and so forth. While these components are flight components, there are other components which are required for ground testing. 

For instance, while we conduct vibration or shock testing, we need to be able to check whether components inside are properly functioning before and after the test. Since dissembling and assembling the satellite every single time is not feasible, tedious and time consuming, an external support equipment is required to interface directly with the system inside. 

That is where the EGSE (Electronic Ground Support Equipment) comes into play.

The EGSE:

Detailed look at the EGSE

EGSEs are quintessential component for any CubeSat project. For SNUSAT-1, the EGSE is shown in the picture above. The EGSE has a 9V power input which is directly fed to an Arduino and a buck regulator which steps down the voltage to 5V. The regulated 5V is then supplied to the satellite to charge the internal battery through the USB_5V line. The charge can be connected or disconnected by placing a shunt on the Satellite Battery Charge Jumper DIP pin headers shown above in the picture. The EGSE uses an additional cord, known as the umbilical cord to connect the satellite's external interface nano-d connector. The picture of the cord is shown below:

Umbilical cord which connects the EGSE to the satellite
As shown, the 37 D-SUB connector female end is connected to the male end of the EGSE. Besides the aforementioned 5V_USB, the EGSE has access to Satellite's UART, I2C and ARM pin. An ARM pin, when activated, will "wake" the satellite from initial "sleep" mode. In the case that satellite is "Armed," so to speak, will make the satellite aware whether the two micro switches installed on the structure on the satellite is released or not. The way this works is that when a satellite is inside a P-POD (Poly PicoSatellite Deployer as shown below), the mechanical switch is pressed because the satellite is squeezed inside the tight space. Once released, the switches are released as well and if the satellite is "Armed," then the On-Board Computer immediately initiates the initial mode, which most likely, is the de-tumbling mode. 

P-POD, the satellite goes straight in and is deployed once it reaches space
The EGSE is, on the other hand, also connected to the computer. Arduino's easy UART-USB serial interface with its Integrated Development Environment (IDE) makes it an ideal choice for conducting serial communication with the satellite. Through the computer's serial monitor, an engineer can send command to the OBC to conduct specific tasks; for instance taking a picture or running the reaction wheel. This allows the engineer to check whether the satellite is functioning as expected.

User commands the satellite through the EGSE 
Open Hardware:
Most of what we do here at CubeSat Research Center is shared to the community as we undoubtedly get so much in return. Please find the schematics for the EGSE [HERE]. Hopefully by now, you will at least have a basic idea of what an EGSE is and why it is an integral part to any CubeSat project. 

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