Responsible	Samuel Schoenenberger
Last Updated	10/12/2025, 12:48:54 PM
Last Author	Kai Berszin

Earth Horizon Sensor

Scope

This page describes the hardware properties of the CubeSense Earth and the mathematical description of the functionality of Eath Horizon Sensor.

CubeSense Earth

The CubeSense Earth is an infrared horizon sensor. More on this on the CubeSpace Website. The CubeSense sun is an infrared Earth Horizon sensor that provides pitch and roll determination and works both during eclipse and with sunlight.

Mathematical Description

The Earth Horizon sensor is an infrared horizon sensor that can determine the pitch and the roll of the CubeSat by measuring the orientation relative to the earth horizon (rotation and elevation angle) when detected. The earth horizon at height $h$ in $km$ and earth radius $R_E=6378km$ is at $\theta_{earth horizon} = \arcsin{\frac{R_E}{(R_E + h)}}$ Hence by measuring the angle of the earth horizon relative to the spacecrafts current attitude, the pitch an the roll angles can be calculated.

Issues

The Earth Sensor outputs faulty measurements when at start, middle and end of ecplise, causing big spikes in estimated attitude error. A naive solution is to increase the uncertainty in the Estimation Mode to 1.0, reducing its influence on the estimation.