The main focus of this project is to create an arm that tracks satellites to receive radio signals from them. There are two Facets to this project, the Mechanical Arm that uses rotors to point an antenna at a passing satellite, and the RF area of radio reception and signal processing. Those are the requirements, and we also have to figure out a ‘why?’ and ‘how?’.
After some initial research, I believe that there are two paths this project could take. One focusing on two way radio communication, we will call this the SatComm project. And the other focusing on reception of satellite data such as weather and beacon signals, this will be called the Ground Station project. For the mechanical arm, there are numerous ways to achieve that goal. There are many plans online, with the option of designing our own.
If we went the SatComm route, programs like Orbitron would be used for rotor control and doppler shift correction. Then a dedicated ‘All Mode All Band’ Amateur radio transceiver would be connected in order to use voice modes with Linear Transponder Satellites dedicated for use by Radio Amateurs. An ‘All Mode’ Radio is important as for certain Satellites different modulation modes such as single sideband as supposed to FM is needed. There is also the option of packet radio, for data transmission over satellite to other Amateur Radio Operators. For the SatComm project we would probably use satellite tracking arms designed and intended for Amateur Radio, and Yagi antennas made for this purpose as there is not a lot of variation in RF requirements for transmit and receive from satellite to satellite.
The ‘Why’ for this route would be; through experimentation, can we figure out how to perfect and improve upon the design of our SatComm station? In the longer term of the project we can keep adding capabilities to the station, potentially that all radio communications could be done remotely for a reliable satellite contact (as has been done in the past). This would be good when there are future launches for amateur radio satellites which have a higher orbit and longer distance contacts can be achieved. The scientific aspect of this would be only about the design process. Communicating with other radio operators via satellite is done mainly for hobby and not so much for science. The next example would be much more scientifically advantageous.
The Ground Station project would consist of creating a SatNOGS station which is an open source open network of satellite ground stations. This station would receive telemetry data from a satellite (data which includes orbit information, systems information, and health of the satellite) and contribute that information to a network of ground stations across the country.
Alternatively we could also use this station to receive weather images from NOAA, METEOR, and GOES, satellites which are continuously transmitting imagery back to earth and which personal reception is encouraged and well documented. There are imagery downlinks for many NOAA satellites in the 137MHz frequency range and this would be simple to receive. However images on this frequency are usually low quality. For better images, we would need to receive data in the GHz range (Same frequency range as Wifi signals). This will require special Dish type antennas and different filters/Low noise amplifiers to receive a good signal. The advantages though would be much more data rich information as well as the ability to receive geostationary satellites. This could allow us to make an antenna that is fixed and receiving from one spot in the sky and use our satellite tracking station to receive satellites in low earth orbit.
In any case, this route would mean using a SDR (Software Defined Radio) connected to a computer as our radio to receive data. From the output of the SDR software we can use various methods to decode the data, all of which have software that has already been made for this purpose.
The ‘Why’ for this route would be much more scientific and technical; Can we create a ground station to receive signals from satellites in order to collect data about ongoing scientific experiments and satellite status, so that we can help the scientific communities who are launching the cubesats for experiments? This may mean reaching out to universities and getting information about their downlink frequencies and modulation modes so that we may receive the data that they need. In a longer term project we might see if we can transmit information to the satellites that include instructions, code, etc. from the universities or organizations that they need to get to the satellite. We could create the Pinhead Institute CubeSat Ground Station, so that anyone who needed to get data to or from the satellite could do it through us and this station.
As for the mechanical arm, a few of the considerations would be if we use an arm design that’s already out there with available plans, or if we were to create our own. We can take different aspects from different designs, as we only need servo motors or stepper motors to control Azimuth and Elevation in order to remain compatible with other designs for controlling the arm. All other mounting designs can be changed by us to fit our needs if we don’t want to use a design already made. One of the problems that need solving is how to take the data from a software and make the rotor move. This may be done with an arduino or other device that will take Serial data or other data from the computer and move the motors to the correct position.
Due to our location and mountainous region, it may be necessary that the system is self contained and portable, which means technology such as RaspberryPi computers may have to be used. There have been many builds using the RaspberryPi and much of the software is available for it. Other considerations would be power. If Amateur radio is used, 12v DC power may be needed, for a Ground Station, 5v DC may be acceptable. There is the option of Solar power and Battery Power. If a remote solar powered station exists, we may have to look at options for getting the data from it without having to get it manually (though an option) and look at circumstances where internet access is unavailable. That is a future project with no impact on what we are currently trying to achieve.
Right now, we need to start prototyping, and exploring the feasibility of our projects. The best thing we can do right now is get Satellite amateur transceivers, and SDR receivers with a variety of antennas. This will allow us to see if either route, the SatComm or Ground Station project, is worth pursuing. We also need to figure out what will work for the tracking arm; servos or stepper motors, prefab or 3d printed, etc. and start on the design process for that. Once we have the materials and a sense of direction we can go deeper into a more involved project. Until then we just need to see if this concept will work; receiving radio signals from LEO satellites using a tracking arm and a directional antenna.
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