Our CDHS consists of the On-Board Computer (OBC) and it is the ‘brain’ of our CubeSat. It controls all the actions taken by our satellite, manages the commands and handles the data.
OBC (On-Board Computer)
Our OBC will be definitely an ARM Coretex. It has to interface with all the other subsystems and manage all the devices, such as the EPS’ Power Management System microcontroller, payload’s camera(s) and sensors, radiocommunication system’s transceiver, structure’s deployment systems, etc.
PCB design:
Our PCBs will be designed accordingly to the PC/104 format. It defines the dimensions of the PCBs and hints on how to stack them. There are plenty PC/104 standards (PC/104, PC/104-Plus, PCI-104, EBX, EPIC) to choose from.
Electronics in space:
Even though the Low Earth Orbit (LEO) is the safest orbit to be on, because it is mostly protected by the ionosphere, the environment there can still be harsh sometimes. The two most important space conditions to beware are temperature and radiation.
Temperature
A metal plate on a LEO satellite can cycle from –170°C to 123°C depending on its Sun face and its time in sunlight. If a CubeSat is spinning, this will even out the heat distribution a bit.
It is recommended to buy electronics with a temperature range of at least -40°C to +80°C. The most common solutions to temperature problems are heat sinks for cooling down and heaters (such as coils) for warming up.
Radiation
LEO is mostly protected by the ionosphere, because of its low altitude. The ionosphere is the very thin part of the atmosphere that also coincides with much of the Earth’s magnetic field. The Earth’s magnetic field shields us from the Sun’s most fierce activity. High-energy particles, flare emissions, and CMEs (Coronal Mass Ejections) get shunted by the magnetic field before they can reach the ground. Where the magnetic field lines dip near the poles, this energy expresses itself as the aurora.
Radiation can have some unpleasant effects on electronic components. There are two main ionizing radiation problems: TID (Total Ionizing Dose) and SEEs (Single Event Effects). On LEO we should mostly protect our CubeSat from SEEs, which are caused by highly energetic particles, that can cause bit flips in digital circuits or voltage spikes in analog circuits.
It is important to shield our electronics, use rad-hard (radiation hardened) components, watchdogs, current sensing, separate power buses, high voltage tolerating capacitors, MRAM and ECC memory, etc.
Mr Fahrenheit
Mr Fahrenheit is a CubeSat satellite project entirely managed by high-school students attending IB World School 1531 from Warsaw, Poland.
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mrfahrenheit.cubesat@gmail.com