Welcome to
Spheres Online

the University of New Hampshire Institute for the Study of Earth, Oceans, and Space electronic newsletter.

Subscribe to Spheres Online

Spheres Archives

www.eos.unh.edu



Summer 2012
In this Issue of Spheres

Seeing the Forest
for the Trees

Tightening the Scientific
Understanding of the Belts

Big Science in a
Pintsize Package

Rock of Ages

Geospatial Science Gets
a Space of its own

News and Notes
Faculty, Staff, and Student News
From the Director


Institute for the Study of Earth,
Oceans, and Space
(EOS)
EOS Director: Harlan Spence
Editor: David Sims
Designer: Kristi Donahue
Circulation: Laurie Pinciak

Morse Hall, 8 College Road,
Durham, NH 03824
www.eos.unh.edu
eos.director@unh.edu


 



“There can be a magnetic storm and the radiation belts will get pumped up, or nothing happens, or they’ll disappear entirely. That’s puzzling, and right now we don’t understand enough to say why it’s the case.”

 




 

 

 

 

 



“…until RBSP there has never been a comprehensive, coordinated investigation with two spacecraft simultaneously, and that’s another big piece of the mission’s story.”





 

 

 

 

 

 

 


“…this is one of the few places we can actually put spacecraft directly in the medium to get the details of what’s going on–then you try to apply that to more distant objects.”










 





 


“We’ll be right in the heart of the action measuring all the waves and particle interactions, and we’ll rewrite the textbook on the radiation belts.”








 

 


Summer 2012

Tightening the Scientific Understanding of the Belts
Poised for launch, NASA's Radiation Belt Storm Probes have UNH all over them

IN THE PREDAWN HOURS of August 24, after more than a dozen years from concept to creation, the twin Radiation Belt Storm Probes (RBSP) will rocket into the harsh environment of Earth's Van Allen radiation belts to probe their inner workings as never before. On board both spacecraft will be numerous scientific hardware and software components with a UNH Space Science Center (SSC) stamp on them.

"If you look at the instrument payload and factor in current and former Space Science Center people, UNH has a prominent role in RBSP," says Harlan Spence, EOS director and principal investigator for the Energetic Particle, Composition, and Thermal Plasma (ECT) instrument suite on board the twin spacecraft.

 rbsp artists illus
Artist's conception of the RBSP satellites.
Image courtesy of Johns Hopkins University Applied Physics Laboratory.

To wit, the ECT suite is comprised of three main instruments including one, the Magnetic Electron Ion Spectrometer, or MagEIS, which is replicated four times on each satellite. So at six sophisticated instruments per spacecraft, UNH leads a team providing more than half (12 of 20 instruments) of the scientific hardware for the historic mission. And eleven UNH team members of the ECT suite will be contributing to post-launch operations and science (see list at end of story).

Other instruments in the suite include the Helium Oxygen Proton Electron (HOPE) mass spectrometer and the Relativistic Electron Proton Telescope (REPT). The ECT instrument is a multi-institutional effort and involves the Los Alamos National Laboratory, Southwest Research Institute, The Aerospace Corporation, and the University of Colorado.

UNH scientists and engineers are also involved in the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) experiment on board the RBSP spacecraft. Roy Torbert, SSC director, is a co-investigator for EMFISIS while former SSC research associate professor Craig Kletzing of the University of Iowa is principal investigator for the EMFISIS experiment.

It is fitting that Iowa is one of the four lead institutions for the mission; the university's James Van Allen discovered the belts in 1958 during the flight of the tiny Explorer 1 satellite that initiated U.S. space exploration.

The Van Allen belts are two donut-shaped regions of high-energy particles trapped by Earth's magnetic field. At the time of their discovery the radiation belts were thought to be relatively stable structures, but subsequent observations have shown they are dynamic and mysterious.

For example, sometimes after a solar storm the number of particles (protons and electrons) that populate the belts can increase dramatically and their speeds can approach the speed of light or become "relativistic"–about 186,000 miles per second. However, at other times after similar space weather events, the particles decrease in number and speed, or conditions seem to just stay the same.

Says Spence, "There can be a magnetic storm and the radiation belts will get pumped up, or nothing happens, or they'll disappear entirely. That's puzzling, and right now we don't understand enough to say why it's the case."

 magnetosphere
Within the Earth's magnetosphere is a cavity of energetic particles trapped by the Earth's magnetic field—the Van Allen belts.
Photo courtesy of NASA Marshall Space Flight Center.

But physicists do know that what's going on is a kind of a tug of war, with various forces tugging one way to inflate the belts while others tug the other way deflating them. "But we don't know when and where those various forces can win out so we can't predict whether they'll go up, down, or stay the same," Spence notes.

So, in an effort to decipher the mysteries of this dangerous radiation environment, the unprecedented dual RBSP spacecraft will brave the storm and investigate the region for a minimum of two years. The twin satellites will chase each other in a common orbit to achieve simultaneous spatial and temporal measurements of the radiation belt environment. The two probes will measure the particles and the magnetic and electric fields and waves that fill this region of space surrounding Earth – "geospace."

"We know we can't study the particles in the absence of the electromagnetic fields that are causing them to change," says Spence. "In the past, there have been missions that have studied particles and missions that have studied wave phenomena and magnetic and electric fields. But until RBSP there has never been a comprehensive, coordinated investigation with two spacecraft simultaneously, and that's another big piece of the mission's story."

With a single spacecraft making measurements at a single point in space and time, there's no way of knowing what's happening "over there." But with twin satellites close together, says Spence, "you can actually see how things are evolving in space as they're evolving in time. Until we have that understanding we have no idea if the phenomenon we measure is something sweeping over the spacecraft or if it's just happening right at the spacecraft. Nailing this down will help us differentiate between current, competing theories."

Particles front and center

The measurement of particles is the very heart of the RBSP mission, and the ECT suite is all about particles. The suite's science goals address the top-level mission objective to provide understanding–ideally to the point of predictability–of how populations of relativistic electrons and penetrating ions in space form or change in response to variable inputs of energy from the Sun.

 rbsp
The identical Radiation Belt Storm Probes will follow similar orbits that will take them through both the inner and outer radiation belts. The highly elliptical orbits range from a minimum altitude of approximately 373 miles (600 kilometers) to a maximum altitude of approximately 23,000 miles (37,000 kilometers).
Image courtesy of Johns Hopkins University Applied Physics Laboratory.

The ECT sensors measure not only the core radiation belt electrons and ions, but also the lower energy charged particles in the inner magnetosphere that control the processes that accelerate, transport, and lead to the loss of radiation belt particles.

"We're measuring the particles that define the radiation belts," says Spence. "And we need to make exquisitely good measurements to develop the understanding we need to predict the variability of the belts."

Those exquisite measurements will be made on both the slow and fast end of the energetic particles in order to get a full picture of how they evolve and how surrounding electric and magnetic waves and fields act upon them and/or are acted upon by the particles. Two other instrument suites aboard the RBSP spacecraft, including EMFISIS, will make the field and wave measurements.

The ECT instrument suite has the capability to differentiate and cleanly measure these energy ranges on the fly (an extremely complex technical achievement) and must do so in order to push the science forward.

Explains Spence, "We've made these measurements in the past but we've made them crudely, and that just leads to confusion. The problem is that you're trying to measure, with great accuracy, populations of one type of particle while others are slamming through the instrument and creating all sorts of spurious signals."

He adds, "In a sense, RBSP enables the next level of discovery. Van Allen made the first, simple discovery of the radiation belts, and subsequent spacecraft have sharpened our views on their behavior. Now we're really trying to understand them by doing extremely detailed physics. But we're also going to discover new things that, previously, we didn't even know how to ask questions about."

It's only been within the last two decades that the radiation belts were discovered to be more complex and dynamic than originally thought. And it is the interaction of particles, fields, and waves that drive the complexity and dynamism.

Using the analogy of a conveyor belt accelerating low-energy particles into the high-energy range, Spence says, "The ECT will measure all the particles that are participating in this conveyor belt, including the lower energy particles that do things to generate the waves that move the higher energy particles."

Particles packing a big punch

Even miniscule particles like electrons moving at nearly the speed of light can inflict serious damage to any matter they hit, and this can be extremely dangerous for satellites or astronauts working in or passing through the region where "space weather" occurs.

Having the ability to predict behaviors of the radiation belts will enable engineers and space weather forecasters to better protect astronauts and the satellites society depends on for communication, defense, shipping, air and ground navigation, and more.

That's the more practical, applied side of the RBSP mission, but getting a better understanding of the inner workings of the radiation belts will help scientists understand fundamental, universal processes–all of which can be plugged into numerical models leading to better predictive capabilities.

Says EMFISIS principal investigator Kletzing, "The processes that are building the belts up and tearing them down are, we think, universal. They occur on a whole variety of scales on other planets, and on the Sun and distant stars. But here, in geospace, this is one of the few places we can actually put spacecraft directly in the medium to get the details of what's going on–then you try to apply that to more distant objects."

Indeed, says Spence, "We'll be right in the heart of the action measuring all the waves and particle interactions, and we'll rewrite the textbook on the radiation belts."

ECT suite team members from UNH include Spence, Michael Golightly, Chia-Lin Huang, Lynn Kistler, Hiroshi Matsui, Sonya Smith, and Jichun Zhang, as well as UNH graduate students, Robert Allen, Alex Boyd, Alex Crew, and Guanwen Wang. Additional ECT team members include former UNH/SSC colleagues Vania Jordanova (research faculty) and Liz McDonald (Ph.D. student) of the Los Alamos National Laboratory, and Terry Onsager (research faculty) of NOAA.

EMFISIS team members from UNH include Torbert, Chuck Smith, Mark Chutter, Jerry Needell, and graduate students Matthew Argall and Kristoff Paulson.

by David Sims, Science Writer, Institute for the Study of Earth, Oceans, and Space.