The Small Explorer Program (SMEX) is a subset of NASA’s larger Explorer Program. Facing public sentiment that does not always see the value in studying the cosmos, the goal of SMEX is to operate small missions, using cheap, off-the-shelf components with price tags totaling $120 million or less. The philosophies of SMEX allow NASA to conduct dozen’s of missions for what it previously would have spent on a single mission. Every few years the people at NASA get together and determine what missions to continue to support, to end, and to start. These mission proposals tend to be submitted by academic departments of various universities and other learning institutions throughout the U.S.
SMEX has several missions that have already come to completion: The Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) was the very first SMEX mission. Launched from Vandenberg Air Force Base on July 3, 1992 and was “used to conduct studies of solar, anomalous, galactic, and magnetospheric energetic particles.” SAMPEX essentially studied the behavior of the four extra-terrestrially originating types of charged particles.
The Fast Auroral Snapshot Explorer (FAST) was the second SMEX mission and investigated the behavior of the auroral phenomenon that occurs around both of earth’s poles. The Transition Region and Coronal Explorer (TRACE) would focus its sights in the other direction, expanding our understanding of the three-dimensional magnetic structures that seem to randomly form out of the Sun’s surface, and to understand the way the superheated gases in the Sun’s upper atmosphere behave.
The Submillimeter Wave Astronomy Satellite (SWAS) was a two-year mission launched in 1998 that studied the clouds of dust and gas that exist in the vast oceans of space between stars. The SWAS mission sought to understand better how stars form by studying the chemical and energy compositions of these clouds.
As of this writing there are a number of SMEX missions currently in process. The Reuven Ramaty High Energy Solar Spectroscope Imager (RHESSI) is an ongoing attempt, started in 2002, to understand solar flares better by combining “high-resolution imaging in hard X-rays and gamma rays with high-resolution spectroscopy” to confirm or refute the commonly-held belief in the scientific community that most of “the energy released during a flare is used to accelerate, to very high energies, electrons (emitting primarily X-rays) and protons and other ions (emitting primarily gamma rays).”
The Galaxy Evolution Explorer (GALEX) is currently creating a map of galaxies in ultraviolet. This map can be thought of as a four-dimensional map in that, due to the limited speed of light, scientists will be able to study star and galaxy formation over a span of nine billion years. GALEX is a great example of the collaborative nature of the SMEX family of projects. According to the SMEX homepage “[t]he GALEX mission is a partnership between NASA’s Jet Propulsion Laboratory and the California Institute of Technology (Caltech) and includes other universities, science institutes, laboratories, and commercial technology providers from around the world.”
The Aeronomy of Ice in the Mesosphere (AIM) mission looks at the icy clouds that form in the Earth’s mesosphere at the poles. Scientists want to know why these clouds form and what effect the climate has on them, or if, rather, they have some kind of effect of the planet’s climate, by measuring these Polar Mesospheric Clouds’ temperature and chemical composition, among other properties.
The Interstellar Boundary Explorer (IBEX) focuses on the perimeter of the solar system rather than the star at the center of it, measuring what happens when the solar winds reach that depth of space and collide with the Interstellar Medium.
A few SMEX missions have been approved and are in the pipeline, like the Nuclear Spectroscopic Telescope Array (NuSTAR),which “will search for black holes, map supernova explosions, and study the most extreme active galaxies,” the Interface Region Imaging Spectrograph (IRIS), and the Gravity and Extreme Magnetism Small Explorer (GEMS), all being launched in the next couple months and years. No doubt dozens more SMEX projects that have not even been conceived of yet will be approved in the coming years and decades, the exact number of which can only be determined by the level of the American public’s interest in understanding the cosmos and our place in it.