Mission Status Report #38 Star Date: November 13, 2000
Caption (above left):Image of Jupiter taken with the Hubble Space Telescope. The inset boxes show the appearance of Jupiter's polar regions in ultraviolet light, and show the auroral ovals. (above right): A section of FUSE spectrum in far-ultraviolet light. This celestial "bar code" tells astronomers that the ultraviolet light arises from the molecular form of hydrogen, which is being excited by fast electrons hitting the upper atmosphere of the giant planet. (HST photo credit: John T. Clarke, U. Mich.)
(Click images above to see larger versions.)
FUSE Tests out "Moving Target" Capability!
All continues to go well on the FUSE project.
One of the highlights of the last month has been the successful observation of a so-called "moving target" (or in this case, also known as the planet Jupiter!). This is a goal that the operations team has worked toward for a number of months. Pointing at stars and galaxies is relatively simple, but pointing at an object that is moving with respect to the background stars (even moving very slowly) is a very different matter. Tests in July, August, and September allowed us to verify that the ground software and instrument computer agreed and worked together properly to control the satellite in "moving target" mode. Then in late October, we planned our first science observation, an attempt to observe the far-ultraviolet spectrum from the northern auroral oval on Jupiter.
The image above (left), taken with the Hubble Space Telescope in 1997, shows Jupiter. The inset boxes are images taken in ultraviolet light that show the auroral ovals. The aperture on FUSE was about the same size as the upper box in this picture, and observed light from the entire auroral ring in far-ultraviolet light.
A tiny piece of the resulting FUSE spectrum is shown above at right. It sort of looks like a bar code you might find on an item at the grocery store, doesn't it? Well, in effect, it is! Just like scanning a bar code provides "hidden" information, so does a spectrum contain information not obvious to the eye. In this case, the black bars across the spectrum arise from molecular hydrogen in the atmosphere of Jupiter. Jupiter's magnetic field captures free electrons and funnels them down onto the atmosphere in the shape of a ring, and it is these electrons that excite the molecular hydrogen, causing it to glow. By studying these bands in the spectrum, astronomers can learn about all sorts of things in the region surrounding Jupiter and in its atmosphere!
In other news, NASA has announced the selection of 81 groups of scientists to participate in the second year of science operations with FUSE. Those astronomers are busily preparing their inputs for submission to the project over the next week or so. FUSE begins its second full year of science operations on December 1st.
Reported by: Bill Blair, Chief of Mission Planning
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