Measuring our solar system

Understanding the size of planets and where they are.

Before the development of radar, astronomers measured the distance between planets through trigonometry, a process where distance to an object is derived from measurements of angles and distances taken between two known positions. Today, radar is the predominant method of measuring distance and is allows for more accurate measurements to be attained. This process works by astronomers timing how long it takes the radar beam, which is travelling at the speed of light, to travel to an object and back. By multiplying the speed of light by time taken, then dividing that in two, scientists can derive the distance of the object.
Once distance has been derived, the mass of the object can be ascertained by monitoring the orbital periods of circling satellites. To do this astronomers measure the angular separation between the satellite and the object and then use trigonometry to convert that angular separation into distance. Astronomers can then use Kepler's third law to determine total mass.