Saturday, March 8, 2014

NASA Van Allen Probes observations helping to improve space weather models

NASA's Van Allen Probes orbit through two giant radiation belts that surround Earth. 

Their observations help improve computer simulations of events in the belts that can affect technology in space. 

Credit: John Hopkins University Applied Physics Laboratory /NASA

Using data from NASA's Van Allen Probes, researchers have tested and improved a model to help forecast what's happening in the radiation environment of near-Earth space, a place seething with fast-moving particles and a space weather system that varies in response to incoming energy and particles from the sun.

When events in the two giant doughnuts of radiation around Earth, called the Van Allen radiation belts, cause the belts to swell and electrons to accelerate to 99 percent the speed of light, nearby satellites can feel the effects.

Scientists ultimately want to be able to predict these changes, which requires understanding of what causes them.

Now, two sets of related research published in the Geophysical Research Letters improve on these goals.

By combining new data from the Van Allen Probes with a high-powered computer model, the new research provides a robust way to simulate events in the Van Allen radiation belts.

Geoff Reeves
"The Van Allen Probes are gathering great measurements, but they can't tell you what is happening everywhere at the same time," said Geoff Reeves, a space scientist at Los Alamos National Laboratory (LANL), in Los Alamos, N.M., a co-author on both of the recent papers.

"We need models to provide a context, to describe the whole system, based on the Van Allen Probe observations."

Prior to the launch of the Van Allen Probes in August 2012, there were no operating spacecraft designed to collect real-time information in the radiation belts.

Understanding of what might be happening in any locale was forced to rely mainly on interpreting historical data, particularly those from the early 1990s gathered by the Combined Release and Radiation Effects Satellite (CRRES).

Imagine if meteorologists wanted to predict the temperature on March 5, 2014, in Washington, D.C. but the only information available was from a handful of measurements made in March over the last seven years up and down the East Coast.

That's not exactly enough information to decide whether or not you need to wear your hat and gloves on any given day in the nation's capital.

Artist's rendition of the Van Allen Probes in orbit. Credit: NASA

Thankfully, we have much more historical information, models that help us predict the weather and, of course, innumerable thermometers in any given city to measure temperature in real time.

The Van Allen Probes are one step toward gathering more information about space weather in the radiation belts, but they do not have the ability to observe events everywhere at once.

So scientists use the data they now have available to build computer simulations that fill in the gaps.

The recent work centers around using Van Allen Probes data to improve a three-dimensional model created by scientists at LANL.

The project was called DREAM3D, the Dynamic Radiation Environment Assimilation Model in 3 Dimensions. Until now the model relied heavily on the averaged data from the CRRES mission.

The Dynamic Radiation Environment Assimilation Model (DREAM) was developed at LANL to understand and to predict hazards from the natural space environment and artificial radiation belts produced by high altitude nuclear explosions.

DREAM was initially developed as a basic research activity to understand and predict the dynamics of the Earth's radiation belts. 

It uses Kalman filter mathematical techniques to assimilate data from space environment instruments with a physics-based model of the radiation belts.

DREAM can assimilate data from a variety of types of instruments and data with various levels of resolution and fidelity by assigning appropriate uncertainties to the observations.

Data from any spacecraft orbit can be assimilated but DREAM was originally designed to work with input from the LANL space environment instruments on geosynchronous and GPS platforms.

With those inputs, DREAM can be used to specify the energetic electron environment at any satellite in the outer electron belt whether space environment data are available in those orbits or not.

Even with very limited data input and relatively simple physics models, DREAM specifies the space environment in the radiation belts to a high level of accuracy.

DREAM is currently being tested and evaluated as we transition from research to operations.

No comments:

Post a Comment