A Python daemon controls the antenna

The low-level antenna controller is a custom Python daemon running on the Raspberry Pi as a background service.

The daemon controls the Sequent HATs and the custom analogue module. It manages the relay sequence, reads the interlock signals and calculates the analogue commands for the azimuth and elevation drives.

The current antenna angles are measured by the original position encoders. An Arduino reads the encoder data and sends the azimuth and elevation values to the Raspberry Pi over UDP.

Separating the encoder acquisition from the main controller proved useful. The Arduino handles the timing-sensitive hardware interface, while the Raspberry Pi concentrates on control logic, safety monitoring, communication and tracking.

If valid position data is lost, the controller can stop sending movement commands and remove the drive enable. That behaviour is essential when controlling machinery of this size.

Tracking targets with NASA Horizons

A graphical tracking application was developed using Python’s Tkinter toolkit. The application can run on another computer and connect to the daemon over the network. Tkinter is Python’s standard interface to the cross-platform Tk graphical toolkit.

The application retrieves ephemeris data from the NASA/JPL Horizons API. Horizons provides calculated positions for Solar System bodies and spacecraft and is designed to support programmatic queries.

The downloaded azimuth and elevation values are stored in CSV files together with UTC timestamps. During tracking, the application selects the appropriate target position for the current time and sends it to the Raspberry Pi.

This allows the antenna to follow spacecraft, the Moon, the Sun or planets with updates accurate to the second.