Space Weathercamera set for launch in 2000
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"It's exciting to be in a position where you know you're going to stumble onto things you didn't suspect were there," said Dr. Dennis Gallagher at NASA's Marshall Space Flight Center.
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That's because in the 41 years that scientists have been studying the magnetosphere - the immense cloud of ionized gas formed by Earth's magnetic field - scientists have never gotten a picture of it. Somewhat like being in a massive fog, they have taken countless measurements throughout the magnetosphere, and taken pictures of its effects on the upper atmosphere. But the overall shape of the magnetosphere can only be inferred from those data.
One of the first images of the geocorona was taken in 1972 by astronaut John Young while on the Moon. The Apollo 16 mission carried a U.S. Navy ultraviolet camera that observed the stars and also produced this striking photo (far left) of hydrogen in the plasmasphere around the Earth. It was colorized (left) to show brightness variations.
Computer simulations depict how IMAGE will reveal the magnetosphere in (left to right) light emitted by neutral atoms, radio echoes, extreme ultraviolet, and far ultraviolet.
Stepping back for a better view
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Gallagher is a co-investigator for the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite scheduled for launch from Vandenberg Air Force Base, Calif., on Feb. 15, 2000. IMAGE will be the first satellite that will let scientists step back and take pictures of the magnetosphere as it changes shape.
The Earth's magnetic field acts as a buffer between the terrestrial environment and the solar wind. The two best known effects of the magnetosphere are the aurora borealis and the Van Allen radiation belts.
The aurora is caused by electrons and ions zinging back and forth along the magnetic field lines and reversing course when they hit a "mirror" point. When energized by a solar storm, these particles can punch through the mirror points and hit the outer atmosphere, causing the aurora's enchanting glow. The Van Allen belts, named for discoverer James Van Allen, can disrupt the electronics of satellites.
These solar-terrestrial effects can also disrupt communications, cause massive power outages, and even corrode long-distance pipelines. As a result, the magnetosphere has been studied closely since Van Allen's discovery in 1958. Knowing the shape of the magnetosphere and how it changes in response to the solar wind will help scientists in predicting what the effects will be here on Earth. IMAGE's objectives are:
- Identify the dominant mechanisms for injecting plasma into the magnetosphere on substorm and magnetic storm time scales,
- Determine the directly driven response of the magnetosphere to solar wind changes, and,
- Discover how and where magnetospheric plasmas are energized, transported, and subsequently lost during substorms and magnetic storms.
Right: A cutaway diagram of the magnetosphere illustrates how IMAGE will observe the magnetosphere.
Assembling an IMAGE
Among the instruments will be the Wideband Imaging Camera (WIC) provided by NASA/Marshall. Science and engineering teams at NASA/Marshall recently completed testing and calibrating the WIC and sent it to the University of California at Berkeley which integrated it into the full collection of far-ultraviolet cameras.
That assembly now is at Southwest Research Institute in San Antonio, Texas, for integration onto the instrument deck plate and more testing. Finally, the assembly will be sent to Lockheed Martin in Sunnyvale, Calif., for final assembly of the spacecraft, and then to Vandenberg Air Force Base, Calif., for launch.
"The WIC is an unusual instrument," Gallagher said. "We here at Marshall and at the University of Alabama in Huntsville have a great deal of expertise in ultraviolet optics and experience in auroral imaging."
|Imager for Magnetopause-to-Aurora Global Exploration home page has current mission status and links to technical information.
The IMAGE Far Ultraviolet home page at the University of California at Berkeley has more details about WIC and the other FUV instruments.
IMAGE POETRY - Public Outreach, Education, Teaching, and Reaching Youth - has news and activities for students.
Ultraviolet Imager aboard the Polar spacecraft gives a preview of some of the imagery that will be returned by the IMAGE Far-Ultraviolet Wideband Imaging Camera.
Southwest Research Institute, IMAGE payload builder, is active in several areas of space plasma physics.
The Space Weather Bureau (www.spaceweather.com) carries today's forecast, plus information and links about conditions in space around the Earth.
WIC builds on the team's experience with the Ultraviolet Imager (UVI) now operating aboard the Polar spacecraft. UVI provides images of the aurora borealis on both night and day sides of the northern hemisphere.
The WIC will be sensitive to light in the 140-160 nm range (visible light spans 300-700 nm). It will have a 17x17-degree field of view (about 34 times the apparent diameter of the Moon) so it can see the entire Earth.
WIC is one of three cameras in the far-ultraviolet instrument. The Spectrographic Imager will measure different types of aurora and remove the bright geocorona emissions from the images. The Geocorona Photometers will observe the distribution of the geocorona emissions to derive the magnetospheric hydrogen content responsible for neutral atom generation in the magnetosphere.
Left: The Wideband Imaging Camera shortly after it completed testing.
An open treasure chest
Unlike most other science missions, all the data from IMAGE's instruments will be made available to anyone as soon as it arrives. Traditionally, NASA has given the principal investigator exclusive use of the data for up to a year after it arrives.
The IMAGE Team
The IMAGE Principal Investigator is Dr. James L. Burch, Southwest Research Institute, San Antonio, Texas. The project is managed by NASA's Goddard Space Flight Center. At NASA/Marshall participants include Dr. Dennis Gallagher, co-investigator, and Dr. James Spann, participating scientist.
CD-ROMs containing high-resolution data (cleansed of noise and formatted for use) will be sent to the principal investigators and to the National Space Science Data Center at NASA's Goddard Space Flight Center in Greenbelt, Md. Any scientist can access IMAGE data to explore the magnetosphere.
"It's going to be an exciting time," Gallagher said. "Every time you figure out a new way to measure your environment, whether it's the universe or microscopic, you see things you didn't think would be there. You learn. That's what research is about. You learn more about the environment in new ways."
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|Author: Dave Dooling
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