The Planetary Society Blog
By Emily Lakdawalla
Akatsuki captures goodbye shots of Earth
May. 22, 2010 | 19:50 PDT | May. 23 02:50 UTC
Three of Akatsuki's six science instruments have now checked in as operating normally, producing lovely photos of the receding homeworld. They were taken at around 20:50 on May 21 (I think that is Japan time, so it would be 11:50 UT if that were true). At the time, Akatsuki was about 250,000 kilometers from Earth, which subtended about 3 degres of its field of view.
More importantly, Akatsuki is receding from Earth's night side, so the view is of a thinly lit crescent -- very pretty. Earth as seen from Akatsuki's IR1 cameraAs Akatsuki sped away from Earth, it captured "First Light" images with its optical instruments pointed at its home planet in an extreme crescent phase. This view is from the IR1 camera, which captures images at a near-infrared wavelength of 0.9 microns, and a field of view 12 degrees square Once it gets to Venus, this camera will be used to look at cloud structure. Credit: JAXA / ISAS | Earth as seen from Akatsuki's UV camera This view is from the UV camera, which captures images at a near-ultraviolet wavelength of 365 nanometers, and a field of view 12 degrees square. Once it gets to Venus, this camera will be used to observe the structure of the uppermost clouds. Credit: JAXA / ISAS
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The third instrument is a longwave IR one. It had the identical view of Earth, lit as a crescent by the Sun, but this wavelength is dominated by thermal emission from Earth's surface and clouds, so we can see the whole globe.Earth as seen from Akatsuki's LIR camera
As Akatsuki sped away from Earth, it captured "First Light" images with its optical instruments pointed at its home planet in an extreme crescent phase. This view is from the LIR or Longwave IR camera, which captures images at a wavelength of 10 microns. At this wavelength, Earth's surface as well as the cooler parts of Venus' atmosphere emit thermal radiation; even though most of Earth was in nighttime darkness at the time the photo was captured, it is glowing away with emitted heat. The cold (dark) spot at the bottom of the globe is Antarctica; Australia lies nearly at the center of the view. Credit: ISAS / JAXA |
Source: JAXA
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Doesn't explain much of why, but it might indeed involve inclination changes.
That's why it's headed away from both earth and sun right now.