Powering a Satellite in Space: What Is Required?


Nanosatellites
We’re going to consider a “CubeSat” [1, 2]. The CubeSat programme at NASA in the United States of America enables education and research institutions to conduct experiments in space from low cost miniature platforms also known as “nanosatellites”. The satellites are built from cubes about 10 cm on each side, with a volume of 1 litre and weighing less than 1.5 Kg. Up to 6 cubes can be stacked to make a single payload for launch. After its release into orbit, a satellite can begin transmissions are received at ground stations on Earth. A typical mission might last for 120 days, after which a satellite begins a fall into the atmosphere and is burned up by the heat of re-entry.Imagine our mission is to transmit signals to a ground station on Earth. Researchers on Earth can analyse the received signals to determine the degradation due to processes taking place in the ionosphere, and thus learn about the impact of space weather on radio communications. In one such application [3] the transmissions were centred on a frequency of 450 MHz and have a bandwidth of 100 MHz. For this project, a three-unit cube satellite was chosen.The “transmit signals” sub-system contains three components, a waveform generator, a power amplifier to create a signal of sufficient strength to be reliably detected at the base station, and an antenna. A power of 0.5 W was sufficient in [3]. A battery capacity of 30 WHr was shown by modelling of the solar power generation to assure the supply of sufficient electrical power. The antenna presents a particular challenge. Like the solar panels aboard Tiangong-2, the antenna must be folded away inside the satellite at launch and then deployed in orbit. You can see examples of trials of such systems in the videos with this week’s content, including the deployment of an inflatable conical antenna from a real space flight. The transmitter would send signals twice a day to allow two receiver locations to be operational, during three orbits of the Earth.An undergraduate project out of this world!
The modelling of electrical power generation is a sophisticated task yet something that can be tackled in a research project by an undergraduate student. Such a project was undertaken by one of our students, Ade Adepegba, in 2015-16, for a 5x5x5 cm satellite.The first stage of the project was to simulate the tumbling of the satellite in orbit in order to get data for the angle of the solar panels mounted on five sides of the satellite to the sun at any instant within the orbit. This required knowledge of the orbital trajectory, a model of the rotation of a satellite around its own axes in orbit, and models of disturbances to the satellite from the friction with atmosphere, radiation from the Earth and the buffeting of the satellite by the solar wind. It was found that the mechanical disturbances to the satellite increased the rate of tumbling of the satellite around its own axes.It was found that if a polar orbit was chosen instead of an equatorial orbit, the satellite would spend less time in eclipse (in the Earth’s shadow), allowing power to be generated for a greater proportion of the orbit. The higher the orbit, the lower the atmospheric drag; this did not affect the generated power much but reduced the rate of tumbling. At higher altitude, there was again a reduction in eclipse time compared with a lower altitude.The data from the second stage was used to simulate the power produced from the five solar panels. In what is called “hardware in the loop simulation”, the simulated orbit data was used to programme a power supply to deliver the predicted power to a dummy load and an energy storage device.Each of the solar panels was expected to have a maximum power output of 25 mW. A maximum-power point tracking algorithm was implemented. In the simulations, an average output power of around 40 mW was predicted for the 50 minutes or so while the satellite was in sunlight, followed by no power generation while the satellite was in the Earth’s shadow. A complete orbit took around 100 minutes. Thus the total energy generated was of the order of 0.016 W-hours, or around 60 J.Here’s an example of some of the output from the simulations. The left-hand column shows the orbit and the total output power, which drops to zero when the satellite is in the Earth’s shadow.
References:
- CubeSat Launch Initiative
- CubeSat Deployment
- The wideband ionospheric sounder cubesat experiment
- Techkewl Cooling Vest
- M. Angling, SERENE Annual Report [University of Birmingham, 2016]
Electrical Engineering: Sensing, Powering and Controlling

Our purpose is to transform access to education.
We offer a diverse selection of courses from leading universities and cultural institutions from around the world. These are delivered one step at a time, and are accessible on mobile, tablet and desktop, so you can fit learning around your life.
We believe learning should be an enjoyable, social experience, so our courses offer the opportunity to discuss what you’re learning with others as you go, helping you make fresh discoveries and form new ideas.
You can unlock new opportunities with unlimited access to hundreds of online short courses for a year by subscribing to our Unlimited package. Build your knowledge with top universities and organisations.
Learn more about how FutureLearn is transforming access to education