Meet the PocketQube team: $50sat
February 21 2014
We have been talking to the some of the teams on the front line of the PocketQube revolution. This blog features Stuart, Howie and Michael of the $50sat team, the first operational PocketQube project, cheapest satellite in history and one of the smallest as well. $50sat has currently been operational in orbit for over 90 days at the time of publishing.
How did you hear about PocketQube?
Early in 2012 Professor Twiggs started a project to see if small functional satellites could be built and launched at low cost by schools and colleges. These were to be the first PocketQubes. The suggestion was to use a PICAXE processor as this was already quite popular in the education sector. I had done some projects with the PICAXE and the RFM22B transceiver, this was noticed and I got an email asking if I wanted to be involved. Never having built a satellite before, I said yes.
Where did the idea come from, what is the objective?
The idea for the PocketQube (PQ) came from Professor Twiggs. The main objective of our project was to see if a small satellite made from commercial off the shelf components (in other words not using any space hardened parts) would be viable in low earth orbit. The secondary objective was that that it should return useful information on solar panel and battery performance. We also needed to have a method of controlling it from the ground, say to turn of the transmitter if requested.
Tell us a bit about your PocketQube Project
A phrase I kept thinking about was “you can't add simple”. It was more important to the $50SAT team (Howie DeFelice, Michael Kirkhart and Stuart Robinson) to ensure we proved the concept of the PQ than it was to build a technically advanced satellite. To maximise the chance of success we kept the electronics and mechanics as simple as possible, whilst still ensuring that the basic functions of the satellite operated reliably.
The biggest issues for $50SAT were what radio to use, which battery and how to maximise power from the solar panels. At the time $50SAT was being designed there was not a lot of choice for radios, given the size constraint and that it needed to be frequency programmable. We also needed to develop a miniature maximum power point tracker for the solar panels.
With no real information available on suitable long distance radios (Hope said the expected range of the RFM22B was around 1-2km) a lengthy series of simple but practical tests were carried out, over my local park and amongst the hills of South Wales. This provided test results and numbers that showed uplink and downlink to low Earth orbit with a RFM22B should work.
What do you do outside building your PocketQube?
I currently work in IT support for major UK utility companies (Stuart), although I started my career by spending several years as an electronic designer and supporting the manufacture of computer based products.
What does the future hold?
The success of $50SAT has shown that it is possible for simple to build and low cost satellites to operate in low earth orbit. Such satellites are perhaps best suited to low altitude short duration missions and with the upcoming developments of low altitude reduced cost launches the PQ concept is likely to be very popular in the future. Using the PQ concept schools and colleges will be able to design and build low cost and functional satellites as part of their curriculum's
There are some improved SPI interface based radios (in a PQ compatible size) now available, more sensitive and with higher output powers. So it may be that future PQ builders will be able to implement radios capable of higher data rates.
What are your top tips for budding PocketQube builders?
1. Above all else, do the numbers. There is little point in looking at high power radios, or power hungry experiments if you don't have the power to run them. The same applies to the uplink and downlink budgets, do the numbers to ensure you have a viable link with the equipment you will use or you will fail.
2. Test, test and test again. Build a working model of the electronics, put it in a box with some solar panels then put it outside in the sun and leave it alone. Is it still working, uplink and downlink, the next day, week or month ? If not why not ?
3. Unless you are a very large organisation, you will need help from others to listen to and submit reception reports for your satellite. Remember the less complex the requirements for the ground station operations are the more people will hear your satellite.
4. From the outset ensure you have a method of engaging with the worldwide community of satellite listeners and radio amateurs. The $50SAT team have had many reception reports from radio amateurs all over the globe and the reports have been invaluable in working out how well $50SAT and its systems are performing.
5. Help those that follow you, publish and post as much information about your mission as you can, after all you want the benefit of an information resource of previous missions, dont you ?
1. Start with a CLEAR definition of what your mission is. Just after we were offered the opportunity to build our own satellite, we spent a few days deciding WHAT we wanted to accomplish with $50SAT (beside deciding on a name for the satellite). This is important, even if you are ultimately not going to get your satellite launched. Your mission will likely have to be refined as you investigate how much of it is possible, or even practical. This is part of the normal system engineering process.
2. Monitor the downlink from any of the amateur satellites that are currently in orbit, just to get experience. There is one currently in orbit which does not require expensive equipment to monitor (hint, hint), and its developers are offering QSL cards (although there are a limited number of them available) for valid reception reports. Planning your ground station is an important part of your mission; if you cannot communicate with your satellite, it is just another piece of space junk orbiting the Earth. Unfortunately, it seems to be something that is overlooked in some of the student satellite projects. As one blogger stated, "Everyone wants to be a satellite stud, no one wants to be an antenna dork." You need to be an antenna dork, or at least plan on getting assistance from antenna dorks.
3. Get your amateur radio license. If you are actually getting your satellite launched and plan on utilizing amateur radio frequencies for your satellite uplink/downlink, this will be a REQUIREMENT.
If the numbers are not at least close for both power budget and link budget, then you are designing a guaranteed failure. Building upon the work of others is a force multiplier. Try to understand what drove the decisions of other successful projects and apply that process to your own project. Don't be afraid to ask for input, but make the questions as specific as possible.
What is your definition of success?
$50SAT, it works.
For more information on $50sat, check out www.50dollarsat.info.
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