A host of trusty old sensors on a satellite a million miles from Earth
have been producing
early warnings of dangerous solar activity
since being launched in 1997. The only problem is that satellite has already exceeded its expected
lifespan by nine years.
NASA’s Advanced Composition Explorer (ACE) satellite occupies what is called the first Lagrangian point, between the Earth and sun where the gravitational tug-of-war between the two bodies is nullified. The satellite orbits the sun from a distance of 150 million kilometers, slightly closer than Earth, always staying between the Earth and sun.
From its vantage point, ACE transmits
information about solar wind as those particles
the satellite on their
way to Earth. This gives scientists as much as an hour’s notice to prepare for the bombardment of charged particles that can disable satellites, knock out power grids and disrupt radio frequency communications.
A well-known example of the damage space weather can cause occurred March 9, 1989, when
the sun kicked out a massive plume of electrons and protons called a Coronal Mass Ejection. It reached the Earth four days later, causing a transformer failure in the HydroQuebec power network that led to a nine-hour blackout that affected 6 million people.
The ACE satellite has enough fuel to last until 2020, but it could fail at any time, and that would leave Earth extremely vulnerable, according to Thomas Bogdan, director of the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center in Boulder, Colo.
To make matters worse, there are no plans under way to put another solar wind monitor out at that position.
“Without those sensors, we are really facing a degraded space weather forecast,” Bogdan said.
Space weather prediction is more vital today than in the past, Bogdan said. The modern lifestyle relies on many more things that are affected by it. Under-developed and remote parts of the world are increasingly reliant on satellite communications because it
requires less infrastructure than terrestrial networks. In addition, airlines are flying more polar routes than ever before, in part, to save money on increasingly expensive jet fuel. Space weather affects not only the satellite communications airplanes use over most of the world but also the high-frequency communications they must use when flying over the polar regions.
Space weather warnings also have become critical for
GPS users, as satellite navigation equipment
has become nearly
being relied on for everything from precision agriculture and drilling to air traffic control functions.
Complicating things even further, the sun had been in a state of decreasing solar activity since the beginning of the decade. NOAA scientists in January saw the first evidence that the sun has started the expected
upswing in its 11-year cycle of activity. As a result they expect increasing volatility from now until 2011 or 2012. Bogdan said the world likely will be even more dependent on vulnerable technologies at the next solar maximum.
The Space Weather Prediction Center uses data from a variety of different terrestrial and space-borne sensors to issue alerts several times an hour on current and upcoming conditions. More than 6,400 customers subscribe to the free reports, including power companies, airlines and satellite operators. How the subscribers use the information depends on the industry; a power company, for example, could elect to lower the amount of power flowing through a certain part of its grid, reducing the likelihood of a blackout.
Though in Bogdan’s opinion, a follow-on solar wind monitor is the most pressing of the planet’s needs for space weather prediction, it is not the only one.
said an instrument that can measure the distribution of electrons in the ionosphere would be very helpful. Varying electron densities caused by solar activity can reduce the accuracy of GPS signals from around one meter to as many as 100 meters. If this type of sensor was on orbit, it could beam readings directly to GPS receivers which could correct themselves, he said. One such instrument, the Thermal Plasma Sensor, was scheduled to fly on NOAA’s upcoming National Polar-orbiting Operational Environmental Satellite System before it fell victim when the program had to be restructured to hold down rising costs.
Among the handful of other sensors Bogdan would like to have at his disposal, perhaps the most interesting has never been tried with any man-made satellite before. He would like to have an imaging satellite placed at the fourth Lagrangian position, directly on Earth’s orbital path but about 60 days ahead of Earth. From this position the satellite could watch solar activity as it develops on the sun, similar to a meteorologist watching the birth of a hurricane in the mid-Atlantic before it picks up speed in the Gulf of Mexico.
Placing a satellite into this type of orbit would require a tremendous amount of fuel and come with other technical difficulties, Bogdan said. But he believes funding for such projects will be available in the near future as the need for better space weather prediction capabilities is recognized.
“In the same way modern weather prediction advanced in the 20th
century, I think space weather prediction will do the same in the 21st