QB50

QB50 is a network of CubeSats in a ‘string-of-pearls’ configuration.
The whole constellation will be launched on 2017. 

The measurements will be made for key parameters and constituents in the largely unexplored lower thermosphere and ionosphere. These multi-point measurements will allow the separation of spatial and temporal variations of several characteristics of this region. The lower thermosphere/ionosphere (90-320 km) is the least explored layer of the atmosphere.

Few atmospheric satellites and sounding rockets have provided in-situ, one-column, short-term measurements for this region. Powerful remote sensing instruments aboard Earth observation satellites in higher orbits (600–800 km) receive the backscattered signals from atmospheric constituents at various altitudes, but the signals reflected from the lower thermosphere/ionosphere are very weak to be detected. The same holds for remote sensing observations from the ground with lidars and radars. The multi-point, in-situ measurements of QB50 will be complementary to the remote sensing observations made by the instruments on Earth observation satellites and the remote sensing observations by lidars and radars on ground.

Due to the atmospheric drag, the orbits of the CubeSats will decay and progressively lower layers of the thermosphere/ionosphere will be explored without the need for on-board propulsion. The mission lifetime of an individual CubeSat is estimated to be about six months.

A single CubeSat is simply too small to carry sensors capable of significant scientific research. However, when a large number of CubeSats are launched with identical sensors, the fundamental scientific questions can be addressed. Networks of CubeSats have been under discussion in the CubeSat community for several years, but no university, institution or space agency has taken the initiative to set up and coordinate such a powerful network previously.