New Satellites Will Tighten Knowledge of Earth’s Radiation Belts

Surrounding our planet like vast invisible donuts (the ones with the hole, not the jelly-filled kind) are the Van Allen radiation belts, regions where various charged subatomic particles get trapped by Earth’s magnetic fields, forming rings of plasma. We know that the particles that make up this plasma can have nasty effects on spacecraft electronics as well as human physiology, but there’s a lot that isn’t known about the belts. Two new satellites scheduled to launch on August 23 August 24 will help change that.

“Particles from the radiation belts can penetrate into spacecraft and disrupt electronics, short circuits or upset memory on computers. The particles are also dangerous to astronauts traveling through the region. We need models to help predict hazardous events in the belts and right now we are aren’t very good at that. RBSP will help solve that problem.”
– David Sibeck, RBSP project scientist, Goddard Space Flight Center

NASA’s Radiation Belt Storm Probes (RBSP) mission will put a pair of identical satellites into eccentric orbits that take them from as low as 375 miles (603 km) to as far out as 20,000 miles (32,186 km). During their orbits the satellites will pass through both the stable inner and more variable outer Van Allen belts, one trailing the other. Along the way they’ll investigate the many particles that make up the belts and identify what sort of activity occurs in isolated locations and across larger areas.

“Definitely the biggest challenge that we face is the radiation environment that the probes are going to be flying through,” said Mission Systems Engineer Jim Stratton at APL. “Most spacecraft try to avoid the radiation belts — and we’re going to be flying right through the heart of them.”

Read: The Van Allen Belts and the Great Electron Escape

Each 8-sided RBSP satellite is approximately 6 feet (1.8 meters) across and weighs 1,475 pounds (669 kg).

The goal is to find out where the particles in the belts originate from — do they come from the solar wind? Or Earth’s own ionosphere? — as well as to find out what powers the belts’ variations in size and gives the particles their extreme speed and energy. Increased knowledge about Earth’s radiation belts will also help in the understanding of the plasma environment that pervades the entire Universe.

Read: What Are The Radiation Belts?

Ultimately the information gathered by the RBSP mission will help in the design of future science and communications satellites as well as safer spacecraft for human explorers.

The satellites are slated to launch aboard a United Launch Alliance Atlas V rocket from Cape Canaveral Air Force Station no earlier than 4:08 a.m. EDT on August 24.

Find out more about the RBSP mission here.

Video/rendering: NASA/GSFC.

Pick Up Some Good Librations With This Stunning Moon Video

A waning gibbous moon. Rises after sunset, high in the sky after midnight, visible to the southwest after sunrise. (NASA/GSFC)

As the Moon orbits Earth, it rotates at such a rate as to keep the same face aiming our way… but not exactly the same face, as shown in this excellent video from NASA’s Goddard Space Flight Center (lovingly annotated by the Bad Astronomer himself, Dr. Phil Plait.)


The Moon has a slight wobble to its axial rotation, and over the course of a month its orientation shifts slightly — an effect called libration. Think of it like a top or gyroscope spinning on a table; it doesn’t spin perfectly vertically, but rather sways a bit while it spins. Libration is that sway.

In addition to that movement, the Moon also moves closer to and further from the Earth over the course of a year due to its elliptical orbit. This makes it appear to change size slightly.

Except for the Moon’s phases, such effects aren’t immediately obvious from one night to the next. But when assembled into a high-resolution video using images and laser altimetry data maps from the Lunar Reconnaissance Orbiter, the monthly motions of the Moon become incredibly clear!

This video shows all the views of the Moon for the entire year of 2012.

Thanks to Phil Plait of Discover Magazine’s Bad Astronomy blog for adding the music and descriptions to the GSFC’s amazing video. What a marvelous night for a Moon dance!

See the current Moon phase and the original video on the Goddard Space Flight Center’s “Dial-A-Moon” page here.

Video: NASA/Goddard Space Flight Center Visualization Studio. Notations by Phil Plait. Music by Kevin MacLeod/