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Smooth sailing

Posted for David Cyranoski

On 9 June, 20 days after being launched, Japan’s Ikaros spacecraft unfurled its ultrathin (0.0075 mm) sail and started its journey through deep space.

Scientists at the Japan Aerospace Exploration Agency (JAXA), who had been worried about a slight deviation between the craft’s actual spin rate and that given in pre-flight simulated models had to wait a long 46 seconds to get data confirming that the craft, some 7.4 million kilometers from Earth, was following its command signals.

Yesterday, with the craft 7.7 million kilometers away, they were able to see that the 200-meter-squared sail had unfolded, and the thin film solar cells embedded in the membrane were functioning.They celebrated with an Ikaros-shaped cake (below, which looks much less impressive than the craft itself).


Let’s hope they can soon prove that with some better photos of the sail than the first ones back.

Ikaros will be propelled by photons from the Sun hitting the sail. The idea is decades old, but this will be the first experimental verification. JAXA scientists will now be trying to steer the craft and measuring its slow but steady acceleration. Based on what they learn, JAXA hopes later this decade to power missions to Jupiter and the Trojan asteroids with a “medium-size” sail some 1250 meters squared in area, combined with ion-propulsion engines.


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