Timebox II

Measuring an asteroid by star occultation

The principle behind observing star occultations is very simple: when an asteroid passes in front of a star, its light dims for the duration of the occultation, which usually lasts a few seconds. This decrease in the star's brightness must be observed.

The precise measurement of the occultation time by several observers at different locations makes it possible to determine the size and shape of the asteroid (see image).

An important prerequisite for a valid evaluation of the data is that the beginning and end of the occultation must be specified to within a few milliseconds. The clocks in computers are too inaccurate for this. This is where the Timebox comes in!

The TimeBox II consists of a GPS receiver, a microcontroller (RP2040 Raspberry Pi Foundation) and a USB connection for the computer. It synchronises the computer's internal clock with UTC (Coordinated Universal Time) to +/- 2 ms using GPS and also provides the exact location data. Both pieces of information are required for successful participation in scientific projects on star occultation.