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| High resolution image of the far side of the Sun. Image taken February 2, 2011 at 23:56 UT. Credit: NASA |
This is the Sun image released by STEREO at 10am CST on Feb. 6. While this image shows nearly the entire sun, it is not yet complete; notice the black line in the center and the blurriness near that line. There are a couple reasons for this.
1) The two spacecraft are not quite yet a perfect 180° apart in this image. As of this morning when the image was released the spacecraft are 197.7° apart. However, the spacecraft will be in perfect opposition to each other very soon. Even this perfect 180° separation would not give a full crisp far side image; for that the spacecraft would need to be at an infinite distance away. Instead you get a mostly crisp image with blurriness near the very edges of each spacecraft's view. An angle slightly less than 180 with other satellites, like SDO, filling in the slight near side gap would create a crisper image all around. That is NASAs plan and this will be possible over the next several days.
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| This drawing provides relative orbital positions of both STEREO spacecraft for each year. It is not to scale. Credit: NASA |
2) There is also a 3 day lag in downloading the high resolution data from the spacecraft and it does take the scientists some time to process this data turning it into a nice picture. You can add hours to days for that. The high resolution image released today was actually the sun on February 2, 2011 at 5:56pm CST. If this was an image from this morning, that uncovered gap (the black line) would be practically unnoticeable. The blurriness would still be there, because that is a problem of geometry and as stated above will be correctable in the next few days.
It is worth noting that NASA does have a quick data download stream from the spacecraft that is used in space weather forecasting when immediate feedback is important. It has a lag of about 5 minutes (in addition to light travel time). This quick data download unfortunately is very low resolution when compared to the full resolution feed. If these two data streams were combined to create one image the low resolution data would look blurry in comparison.
Also note, that unlike our Moon, the Sun does not have a static far side. The Sun rotates about once a month, so we can see all "sides" of it if we wait long enough. The advantage here is to see the entire Sun simultaneously. The Sun is a ball of plasma gas that is continuously changing. We cannot wait a month to see what is happening on the far side. By the time that area of the Sun is visible to the Earth the event may be long over. Scientists believe that knowing what is happening on the entire Sun at any given moment will be critical to a more complete understanding of the Sun and space weather. Additionally many earth scientists and climatologists believe that a more complete understanding of the Sun is critical to understanding our own planet and its climate.
While today's image may be neat, and is definitely worth a look, expect better images from STEREO as the month goes on.
For more information:
NASA STEREO press release: http://www.nasa.gov/mission_pages/stereo/news/entire-sun.html
STEREO YouTube Video: http://www.youtube.com/watch?v=qLB5ma2Yz1I&feature=feedu
STEREO website: http://www.nasa.gov/stereo/
STEREO website: http://www.nasa.gov/stereo/
Eyes to the skies! You'll be amazed by what you see!! AstroChick.
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