Automated Satellite Receiver Project
Initial thoughts, maybe 6 students and 3 laptops (ideal..?), a pair at each for Session 1 and 2 and in Session 3 we can split into a hardware and a software team to improve the final system that will be set up for the school.
Introductions, my work and hobbies, students interests, why am I here, why are they here?
Discuss satellites, orbits (Geostationary Earth Orbit, GEO, and Low Earth Orbit, LEO, what kind of orbit do you think TV satellites use? What kind of orbit does the International Space Station use? What kind of orbits might weather satellites use?), the use of radio on spacecraft, the importance of communications and remote sensing, examples of weather satellite pictures received in Antarctica. Introduce the idea that we’re going to build our own station to receive these images direct from space to our PC...
GPredict software to show satellite orbits.
Tuning around the VHF spectrum going up from broadcast FM to civil aeronautical to NOAA satellite downlink band
Build stage 1
Goal = Get your receiver(s) up and running, listening to and looking at some signals
Expect introductions to take more time in this session so wouldn’t expect to get any further than installing the satellite tracking and radio receiver software on the PCs and having a play with them looking at various signals and satellites…
Hopefully we’ve now all got a clear picture (literally!) of the radio signals in the electromagnetic spectrum and that radio is used for many other things than just Radio 1, Solent FM, etc.
We should also understand that satellites are in different kinds of orbits depending on the job they do and that they all use radio to communicate with their controllers and customers back on Earth.
Hopefully you've now got your receivers up and running and you've had some fun tuning around and listening to some interesting stuff. If not we'll have a look at what's gone wrong and get it sorted…
What sort of signals have you looked at now? What can we see in these signals? Talk about modulation and how radio works.
Demonstrate different methods of modulation with a Morse key, microphone, analogue and digital information, compare with familiar signals like the FM broadcast stations, Radio 1 (mostly music) and Radio 4 (mostly speech)
Demonstrate a recording of a good weather satellite pass so we know what we’re aiming for.
Build stage 2
Goal = Record first weather satellite passes and decode to imagery
In this session we'll install the image decoding software and decode a sample audio file. We'll practice using the audio recording function of the radio software and look at what settings need to make to correctly receive and record a weather satellite pass. We'll have a look at the satellite pass predictions for the coming week, decide which passes we will be in a position to record and plan for that. (You will manually receive and record your satellite passes this week!). Finally cover the Wxtoimg software decode process talking about the various methods including live audio feed (which we may explore later) and importing a pre recorded audio file and the various display options.
The main thing to take from the modulation demo is that a radio signal is made up of a carrier wave that propagates and is modulated by information. There are many different ways of modulating the carrier wave from simple (On/off with Morse code) to very complex and different kinds of modulation will appear differently the spectrum display.
Hopefully we're also clear on the process we're going to use to decode images from weather satellite signals - when the satellite is passing over us, tune the radio receiver to the right frequency with the right mode selected, record the signal and when the pass is over, import the recording into our decode software and let it decode the image. In the future we might try live audio feed so the imagery can be viewed as it happens overhead.
Hopefully you’ve now managed to receive, record and decode your own weather satellite images - if so, well done!! If not, maybe it’s a quick fix and we can carry on developing the system, if it’s not obvious we’ll dive deep and look to get it sorted and draw it to a close with that achievement next session.
Analyse the signals and imagery we’ve received so far - what can the images tell us about our system? (expect horizontal lines of pager interference, horizontal lines because of raster scan method, height of image corresponds to length of time we have a good signal which is related to antenna radiation pattern…) What else can we notice about the satellite signals? (They drift from right to left during the pass… higher frequency to lower frequency… we’re observing the Doppler shift on the downlink)
How can we improve our system?
Optimise antenna pattern and polarisation to both maximise the satellite signals and reduce the terrestrial interference. Talk about antenna properties, radiation patterns and polarisation, decide on what a good antenna might be for our application.
Automate the process to save all that running around and clock-watching… talk about the structure of a simple program to take times input from a user and trigger recording commands at the given times.
(fill in the blank when I think of a good relevant demo!)
Build stage 3
Goal = Optimise antenna and automate recording
Two teams, hardware (antenna team) and software (automation team)
Check PC clock timing is accurate and talk through the importance of testing an automation process and building confidence in it before leaving it for a week only to find it drifted before the first pass…!
Check clock timing is accurate and it records when expected, have a look at imagery decoded and/or signals recorded and look for problems to fix
Probably either talking through what’s gone wrong or basking in the glory of our triumphant success...
Discuss further build ideas for improving the system. Lots of different directions this could go in (hardware, software, web publishing, Raspberry Pi, Arduino, more radio topics, etc.)