Endeavour is preparing to launch for its last mission of 16 days in which it will deliver CERNs Alpha Magnetic Spectrometer to the International Space Station. This experiment will measure cosmic ray fluxes and should be able to tell us if there is any antimatter at all in space. Within the Earth’s atmosphere we can detect only the byproducts of most cosmic ray collisions with the atmosphere or Earth itself. Only weakly interacting particles such as neutrinos can be detected directly. In space it is possible to measure directly the energy of cosmic ray particles before they collide, but you have to wait a long time to get a good sample.
The launch can be watched on NASA TV and is due soon
Update: the shuttle has launched on time.