IMAGE Selected for MIDEX Program

Volume 12, Number 2, June 1996
By James L. Green

NASA has selected the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) investigation as one of two missions funded under NASA's new Medium-Class Explorer (MIDEX) program. Dr. James L. Burch from Southwest Research Institute (SWRI) is the principal investigator. The two-year IMAGE mission will provide the first-ever global images of key regions of the Earth's magnetosphere as they respond to variations in the solar wind. For over 35 years the magnetosphere has been studied almost exclusively by spacecraft making in situ or local measurements. IMAGE is a new breed of missions designed to do only remote sensing and to "see the invisible." The difference is similar to that between the brain surgeon of yesterday who opened and probed the brain directly versus the surgeon of today who can order a CAT scan to obtain a diagnosis.

The magnetosphere is the region of space controlled by the Earth's magnetic field and populated with ionized gases called plasma. The origin of the magnetospheric plasma is believed to be a mixture of both the solar wind and the ionosphere in percentages that are not well known. The magnetosphere dynamically changes its shape and internal structure because it is strongly influenced by the solar wind, which is the supersonic stream of charged particles flowing out from the Sun. The strong solar wind causes geomagnetic storms. The aurora is the most well known manifestation of the magnetosphere's interaction with the solar wind during the geomagnetic storms. Other effects of the geomagnetic storms include damaging geosynchronous spacecraft, including telecommunications spacecraft thereby disrupting communications, and destroying ground power transformers, thereby leading to electrical blackouts. It is, therefore, important to understand such geomagnetic storms and be able to predict them if possible.

IMAGE will use three different experimental techniques to carry out its mission: radio, ultraviolet, and neutral atom imaging. The radio imager will probe the boundaries of the magnetosphere and the plasmasphere (a dense region of cold ionospheric plasma surrounding the Earth in the inner magnetosphere) in minutes, while the ultraviolet imagers will image the entire auroral oval and image the structure of the plasmasphere on the time scale of five minutes or less. Three neutral atom instruments will image huge plasma regions in the inner magnetosphere every five minutes allowing scientists to study the behavior of the inner magnetosphere under both quiet and magnetic storm conditions and to learn about the sources of the magnetosphere plasmas. The neutral atom imagers detect neutral atoms created when energetic magnetospheric ions charge exchange with the Earth's neutral hydrogen cloud called the Geocorona. IMAGE is the first space science mission to employ these imaging techniques on the same spacecraft.

From its highly elliptical polar orbit IMAGE will be able to simultaneously observe changes in the magnetopause (the boundary between the magnetosphere and solar wind) in the various charged particle populations within the magnetosphere, and the size and shape of the aurora, geocorona, and the plasmasphere. To disseminate more information about IMAGE, a World Wide Web site has been set up and is at URL http://bolero.gsfc.nasa.gov/~image/IMAGE.html.

Simulated IMAGE data from RPI, FUV, NAI, and EUV.

Goddard's Space Science Data Operations Office will have overall responsibility for this data system. The National Space Science Data Center will archive the IMAGE data within days after they are acquired making them readily available to the entire scientific community. IMAGE is scheduled to be launched in early 2000. The data following into the NSSDC from IMAGE will be approximately 400 MB/day.

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Author:Miranda Beall (beall@nssdca.gsfc.nasa.gov)
Curators: Erin Gardner (gardner@gsfc.nasa.gov) and Miranda Beall (beall@g sfc.nasa.gov)
Responsible Official: Dr. Joseph H. King, Code 633
Last Revised: 21 Nov 1996 [EDG]