Using the first version of satNOGS hardware we figured out that some times due to various reasons (software, mechanical or power malfunctions) the rotator might end up in an unknown position.
At that point, the only way to resolve that situation was to manually reset the rotator to home position (pointing at the north with zero altitude). Therefore, since we wanted the rotator to operate without human supervision, we decided that an automatic homing system was crucial.
At first thought we tried an IMU, which turned out to be too noisy and affected by the rest of the systems so we ended up with a pair of opto-swithes which are manually set at the first run.
The mounts and activators of the switches are designed in a way that they remain modular and independent of the rest of the tracking hardware so that they can be fitted in previous or future versions.
Our intention is to write two homing functions in the arduino code
The first one, which is already written, is called when the arduino boots for the first time or after power loss. In this function, the rotator scans around the current location until it finds home position. Below you can see a video in action:
The second one runs after every tracking job or on demand through the serial interface and just moves the tracker to the home position. This way, whenever a new traking job begins the user knows that the job starts from zero position.
It was always our intention to have SatNOGS ground station as unattended as possible in terms of operation. We are now much closer to it!