Emily Lakdawalla • Jan 26, 2011
IKAROS: self-portrait with Venus; primary mission complete
JAXA posted a report today stating that IKAROS "has completed its regular operations." As a part of that report, they included this tiny photo, taken from the cameras that were used to monitor the deployment of the sails. See that little crescent in the background? That's Venus. IKAROS followed Akatsuki past Venuson December 8, 2010. Akatsuki's flyby occurred on the sunward side of Venus; IKAROS passed Venus' night side, at a much larger distance of 80,000 kilometers.
If I understand the translation of this IKAROS Tweet correctly, it took two weeks from the time the photo was taken to transmit the image successfully to Earth -- IKAROS' transmitter is not very powerful, and its opportunities to communicate are increasingly rare as the distance between the spacecraft and Earth increases. That also explains the tiny size of the image -- only thumbnail versions could be transmitted at the available data rate.
Here's the full text of the press release in English:
The Small Solar Power Sail Demonstrator "IKAROS" has been in its regular operation phase for about six months to verify navigation by the world's first solar sail device and power generation by the thin-film solar battery. As its missions have been achieved, the IKAROS has completed its regular operations. The demonstrator will be in the post operational phase, which leads to the development of a successor while acquiring basic knowledge of solar power sail technology including a navigation guidance technique.
On the Japanese side of the website there is a PDF report containing much more detail. Without spending the time to run every bit of text from the PDF through Google Translate, I don't know the full extent of what's discussed in the report, but it does appear that when JAXA talks about completion of regular operations, they do not mean that the IKAROS mission is over. There are trajectory diagrams showing where the spacecraft will be through December 2012. So I think that what they are saying is that IKAROS' primary mission is complete, and that the PDF report discusses the achievement of the missions' goals: the demonstration of several new technologies, including deep-space sail deployment, thin-film solar cells, and control of the sail by liquid crystal technology, among others.
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