CubeSat: Micro Satellites and Studies

The arrival of fourth year for many engineering students at my university is either loved or loathed. Senior design is a large project that all engineering students must complete to graduate. The scale of the project is one that will be larger than any previously done for academic purposes. My group and I have a rather lofty project idea. We are going to design and hopefully build a CubeSat.

What is a CubeSat? A CubeSat is like almost any other satellite simply much smaller. The size of typical satellites can be anywhere from a dog all the way up to a car or bigger. CubeSat sizes go the opposite direction. The sizes of CubeSat are referred to as 'U'. 1U is a 10x10x10 cm size satellite while a 2U would be simply two 1U stacked making 20x10x10 cm. Our target as of right now is to design a 2U CubeSat.

The potential scope of the project is enormous and since time is limited we may not be able to complete and entire CubeSat. This being said, we are going to try our best! It would be really amazing to be able to look up at the sky and know that we helped put something up there.

The design can be split up into a few subsections which I will discuss in greater detail below.

Power 

Beautiful space flower power?

Solar panels are a wonderful technology. Collecting light and convert it into electrical energy? What isn't there to love. CubeSat's typically have 3-12 months to orbit before decaying and burning up. Due to size restrictions and power requirements we won't be able to use anything like a pre-charged battery so we must power the entire mission using solar power.

What may need to happen is have the satellite orbit Earth a few times to charge an on-board battery and then have the main computer system turn on and do what is needs to. We also have to be able to power the mission equipment on-board which we are unsure of what the requirements are. This could be a tricky part of the project and is ultimately the most important.

Communication

Sadly our ground station will not be as good as commercial satellites

This is my favourite part of the entire project. Signal processing, communication systems and RF design are all things that really interest me. Fortunately this project has plenty of design work in this area to be done.

Some simple math shows that we are going to have around 130 (dB) losses on the communication channel. This is an enormous loss that we will have to try to design our antennas around. Sadly the CubeSat will have to fit into a very small containment so we will most likely need deployable antennas. I have a few ideas around what we should do with the antennas but nothing too serious until we decide what frequencies our communication channels will use.

Central Computer System

Most likely going to be an ARM based system.

Every part of the system will be controlled by the main computer system and so it is very critical that we have a good design here. Not much thought has been put into it yet but a professor involved in the project suggested that we use TCP/IP communication on the system to communicate between boards. Guess it is a good thing that I am taking a course on digital communication this semester. 

Mission

At my university we have a the pleasure of having a world renown Geodesy and Geomatics department. We also have a large number of researchers in our physics department who study Earth's upper atmosphere. There have been several missions suggested so far between the two departments and the missions all seem super cool. As I mentioned already the power for the system is most likely going to be very limited. Once we have looked more at the power systems we will have a better idea of what to expect but it seems that the physics department's mission seems easier to do from a power perspective. It would also require less equipment on the CubeSat allowing us to have a larger system in the satellite that isn't the mission.

Anybody have experience with CubeSat and/or space hardware and design?

Tips, tricks and suggestions will be very much appreciated.