I'm an astronaut based here at the European Space Agency in Germany, and from December 2015, to June 2016, I spent six months orbiting Earth on ... spaced out with a scale model of my own.' ...

Let’s take a look at this model ... Earth is how we measure one full day. While the Earth is spinning to give us day and night, it is also moving around the Sun. This movement is called an orbit.

The perturbation in satellite orbit is due to gravity field of the Earth, which is in turn caused by Earth’s mass distribution. As such, if we are able to measure temporal changes in gravity field of ...