SMEX (Small Explorer) is a series of low-cost (less than $120 million to develop, launch, and operate) satellites launched by NASA for solar and astronomical studies. The first six spacecraft in the series were SAMPEX (Solar Anomalous and Magnetospheric Particle Explorer) launched in July 1992, FAST (Fast Auroral Snapshot Explorer) launched in August 1996, TRACE (Transition Region and Coronal Explorer) launched in April 1998, SWAS (Submillimeter Wave Astronomy Satellite) launched in December 1998, HESSI launched in February 2002, and GALEX (Galaxy Explorer) in April 2003. The next SMEX mission will be AIM (Aeronomy of Ice in the Mesophere), which is scheduled for launch in September 2006.