Spherical picosatellite for monitoring of high atmosphere density

The lower thermosphere (between 100 and 250 km in height) and many of the processes developing there are still rather badly known. Active satellites are scarce in these regions as drag would cause its re-entry in a matter of days or weeks.

Two types of low mass spherical satellites are being developed to determine the density of the lower thermosphere by two methods: by directly measuring the drag by means of high-accuracy MEMS-accelerometers, and indirectly by analyzing the data of GNSS receivers. The ballistic coefficients are kept to very low values to maximize the deceleration caused by drag. The first kind of satellite will have a mass of no more than 100 grams and will be non-stabilized (V1), while the second is expected to have less than 1 kg and will be aerodynamically stabilized along 1 axis (V2). The diameter of each satellite model would be of 10 cm.

The accelerometers are the main sensor of the satellite and must be able to measure accelerations down to ~1 micro-g. A primary battery will feed all the electronic devices.

A complete mission would require a swarm of spherical satellites distributed in polar orbits along several orbital planes. While this would produce the highest scientific revenue, it would also call for dedicated launches.

As the residence time in orbit will be very limited, around one week depending on the ballistic coefficient, the satellite must be as simple and cheap as possible.