Space Sailor

Good morning EUROAVIAns,
in today Fact Friday we talk about space navigation!

In ancient times, sailors used to navigate the seas by looking up at the night sky, not wondering about the universe and distant worlds, but to find their position in relation to known bright stars.

In today’s modern world, where every important decision is led by science and technology, such practice can almost seem like pseudoscience. Well, it is not! Navigating using stars as reference can be a useful practice, it’s main limitation is that the accuracy depends on the sailor’s experience. But, did you know that as of today, star navigation is actually one of the most employed techniques? Just… not on Earth, and not by human sailors.

Yes, you guessed it right, we are talking about satellites! Because of many (all important) different reasons, satellites need to determine and keep their attitude at a careful level, but it’s not always easy to do so if they’re rotating at high speeds, or are obscured to our signals because of their current position. Under these circumstances, the employment of the so called star trackers becomes vital to the survival of the spacecraft.

Star trackers are compact and reliable instruments for attitude determination. They are made up of an optical sensor able to detect starlight and a computational unit that determines the angles between the detected star and the sensor’s surface. With an uncertainty of estimation usually lower than 0.2 degrees, star trackers rely on immense onboard databases to compare their angle measurements to known stars and constellations, gaining all the information the satellite requires to determine its attitude in reference to planetary bodies.

Who would have thought that such an ancient and seemingly outdated technique could be so vastly employed nowadays is space exploration? This looks like a perfect example of what Newton said about standing on the shoulder of giants.