The Solar and Heliospheric Observatory—or SOHO—was a joint space probe conceived by NASA and the European Space Agency in the 1990’s for gathering a wealth of scientific information about the sun and its atmospheric emissions. In early March 1996, fourteen months after its liftoff from Cape Canaveral aboard the upper stage of an Atlas IIAS (Atlas/Centaur) launch vehicle, the satellite was injected into a counterclockwise halo orbit around the sun at what is known as the L1 Lagrangian point—named after the eighteenth-century French astronomer Joseph-Louis Lagrange, who theorized there were calculable distances at which a small object in space could remain in fixed orbital positions between two larger bodies exerting strong gravitational pulls upon it.

The mathematical formulations must be precise. Should an object in the middle of this interplanetary tug of war wander from its position by more than a few degrees, the delicate equilibrium becomes upset and its orbit will rapidly degrade.

In SOHO’s case the L1 point equaled four times the distance from our world to the moon, with any significant deviation from that point certain to result in an uncontrolled plunge toward either the earth or sun. One complication the observatory’s development team had to address, however, was that their preferred orbital position for SOHO was slightly off the L1 point, since the radio interference that would occur when it was in direct line between the two opposing spheres was bound to corrupt its data transmissions with static. A second problem was that other bodies in the solar system—distant planets, moons, asteroids—had their own weaker attractions that could jiggle SOHO’s path a little bit this way or that to ultimately disastrous effect.

The team’s solution to both these problems was to equip SOHO with an onboard propulsion system for periodic orbital adjustments, knowing this imposed an inherent limitation on its mission life. For once it exhausted the hydrazine fuel that powered its thrusters, SOHO would slip from its desired Lagrangian station and go tumbling off through space beyond recovery.

Original projections were that the billion-dollar spacecraft would be able to conduct its observations and experiments for from two to five years before the propellent reserves went dry and its mission reached an end.

Six years later and counting, it was still plugging away.

Some things are still built to last, and every so often they last longer than expected.

In March 2002, SOHO’s SWAN and MDI/SOI instruments, two of a dozen scientific devices in its payload module, sniffed the astrophysical equivalent of what American prairie farmers once would have called a locust wind.