The languishly manned spaceflight programs of the world are attracting less and less funding, as well as a rapidly shrinking public presence. Even the most ardent supporters balk at the extravagant launch costs and fragile safety margins endemic to human endeavors in space. However, riding the coattails of these costly missions for decades have been an extensive series of unmanned missions that operate at a fraction of these costs, with vastly differentiated mission times involved. NASA and the ESA quietly landed on Titan (largely to public chagrin and apathy) in 2005, and this 13-year mission has cost a grand total of $3.2 billion, spread across NASA and its European counterparts. In contrast, each near-Earth space shuttle mission is estimated to cost $1.5 billion, and a total of $170 billion has been spent on the shuttle alone.

The STEREO mission consists of two identical probes launched simultaneously on a modified Air Force Delta II rocket in late October 2006. STEREO A and B were placed into very elliptical orbits, and NASA utilized a gravitational slingshot via the moon to place them for operations. The STEREO mission is so-termed for the orbiters’ dual observations in their final heliocentric orbit. The crux of this mission was the utilization of what astrophysics knows as La Grange points – points in space where the gravitational interaction between a two bodies is negated and an object can remain in a simple, stable orbit for long periods of time. Every pair of sun-planet interactions has five La Grange points: L1 is between the body and the sun; L2 is on the opposite side of the orbiting bodies at a precise point. Point L3 is a highly unstable region precisely 180 degrees across from Earth, in our orbital wake – an “anti-Earth” which is perpetually shrouded from our view by the sun. STEREO A and B (“Ahead” and “Behind”) were placed at La Grange points L4 and L5 – the most stable of these gravitationally-canceled regions – which lead and follow along Earth’s orbital path.

STEREO’s simplest mission descriptor is stereoscopic imagery of the Sun in ways we are obviously incapable of when stranded Earth-side. Of particular interest to researchers is the detection and study of the sun’s intermittent Coronal Mass Ejections (discussed on pages 10 and 11). For science nerds, the mission allows for some very interesting optical trickery via false-3D animated .gifs of the sun’s rotation and long, high-resolution video of our star spewing untold billions of tons of matter into the solar system. Each spacecraft carries a wealth of instruments for measuring the many parameters of the sun’s daily operations.

Among the instruments on board each spacecraft are instruments measuring the full electromagnetic spectrum, as well as heavier particles and safe distance measurement of the large plasma masses produced in the large thermonuclear reactor. This instrumentation has now come online in full, as each orbit realigns and the spacecrafts move further away from each other. In January 2009, STEREO A and B reached 90 degrees relative to each other – a landmark that scientists say will greatly improve the orbiters’ data triangulation capabilities. It is estimated that the mission will reach a full 180 degrees from each other in 2011, and this will represent the first time that the entire sun will be visible to humanity at one time. The mission has the possibility to be extended to 2015 and beyond, and like other unmanned probe missions, this would be more time than the project was optimistically budgeted. The burgeoning data emerging from STEREO, its unique mission, and its low cost at $550 million (roughly a third of a shuttle mission) will build more goodwill for NASA. Although popular culture almost exclusively cites manned space accomplishments as milestones, unmanned missions like STEREO will continue to effectively provide a provocative scientific background for decades to come.