DeepEarthScience

Imagine a spacecraft the size of your car travelling at an altitude of 600 km with a velocity of 7.6 km/s. Now try to determine where the spacecraft is and how fast it is flying, also called its dynamic state. There is no speedometer (no wheels turning) or a pitot tube like in an aircraft (no air to measure). So, we, as astrodynamicists (yes, I think that is a word), have different techniques to accurately determine the state of the spacecraft. Highly accurate measurements of distances (also called range) between the satellite and ground stations are used, as well as the changes in these distances (called range-rate). If you follow this blog a little bit, you know that we work on building a ground station at the TU Delft that measures these range-rates with respect to cubesats. With some complicated, but very elegant mathematics, these measurements are transformed into very precise orbit determinations of satellites. Some of my colleagues can tell you within one cm accurate where thei...