Atmospheric Neutral Density Experiment (ANDE)
Here are some NASA screen shots showing today's deployment of the tiny spherical satellites.
A third small satellite was deployed from Discovery’s payload bay today at 12:23 Central. The Atmospheric Neutral Density Experiment (ANDE)
..."consists of two spherical microsatellites that will measure the density and composition of the low-Earth orbit atmosphere while being tracked from the ground. The data will be used to better predict the movement of objects in orbit. The other two satellites were deployed Wednesday night."
NASA Shuttle page