The European Space Agency will launch three satellites this week from Russia's Plesetsk Cosmodrome to gather data about the Earth's magnetic field over the next few years. The planet's magnetic poles have been shifting more and more rapidly over the last couple of decades, possibly as part of their usual flip from north to south every few hundred thousand years. The so-called "Swarm" mission will tell us about that and myriad other factors affecting the magnetic field surrounding Earth.
The satellites are slated to launch this Friday after a year of delays related to the Russian "Rockot" launcher. The Rockot is a converted Soviet-era nuclear missile launcher modified for peacetime space use. Since 2011 it has failed in five launches due to problems with the Breeze KM upper stage. The ESA seems relatively confident the Rockot will deliver the goods into orbit this time.
"We are ready to get going, that's for sure," ESA Swarm mission manager Rune Floberghagen said. "Having said that, of course, we can only trust that all the work that needs to be done to give us a reliable upper stage has been carried out."
Two of the Swarm satellites will fly parallel at just 287 miles above the Earth, eventually settling in at a straightedge-shave 180 miles up. The third satellite will fly higher at 331 miles. No word on whether they're designed to run out of fuel after a few years and fall back to Earth at a random location, as was the case with the GOCE gravity-measuring satellite, or if they will be control-reentered.
The Earth's magnetic field is a rich and variegated phenomenon. Our favorite feature is that it acts as a shield from space radiation, allowing life to exist. The strongest part of the field is caused by superheated liquid iron and nickel swirling in the outer core about 1,800 miles beneath the surface. Other factors contributing to the magnetic field--and causing it to vary wildly in intensity from place to place on the globe--are the Earth's crust, the ionosphere (50-375 miles up), the magnetosphere (37,000-75,000 miles up), and even the oceans (due to the salt, which is conductive.)
The magnetic field has weakened by about 15% since c. 1850. The gap between true north and magnetic north is accelerating rapidly: In the early 1990s, the gap was believed to be widening about six miles per year. Since 2001, it is widening at 65 miles per year. Does this mean we're in for a cataclysmic pole reversal sometime in the near future? Scientists aren't sure.
"Reversals are a slow process and do not happen with any regularity," said the ESA. "Nevertheless, the last time this happened was about 780,000 years ago, so we are now overdue for a reversal."
The Swarm mission should tell us more, as long as the Rockots do their job.