Kaguya Mission Ends with a Flash

Low on fuel and its highly successful mission over, Japan's Kaguya orbiter struck the Moon on June 10th. And astronomers in Australia successfully captured the intentional crash landing.

The impact occurred within a couple seconds of 18:25:10 Universal Time, which meant the just-past-full Moon was visible in predawn darkness from Japan, Australia, and the far western Pacific. Unfortunately, it was already daylight for the mammoth telescopes atop Mauna Kea in Hawaii.

The target point occurred at 80.4°E, and 65.5°S, a location on the near side right along the darkened southeast limb. Those coordinates correspond to the inner wall of a small crater near the much larger crater Gill.

Kaguya's impact flash
A brief flash in this series of near-infrared images shows where Japan's Kaguya spacecraft crashed into the Moon on June 10, 2009. The frames were taken 1.6 seconds apart with the 3.9-meter Anglo-Australian Telescope.
Univ. of New South Wales / Anglo-Australian Obs. / J. Bailey & S. Lee
Poor weather hampered many of the observatories positioned to witness the crash. The only known success comes from the Anglo-Australian Observatory in southeastern Australia, where Jeremy Bailey (University of New South Wales) and Steve Lee (AAO) used the 3.9-meter Anglo-Australian Telescope to capture a series of images at the near-infrared wavelength of 2.3 microns.

"The observed flash was within a few seconds of the final predicted impact time [18:25:07 UT]," Bailey told me. "The biggest uncertainty for us was the weather which has been poor at Siding Spring for the previous few nights. However, the clouds cleared enough for us to get the observation." The two observers posted their images soon after acquiring them.

"It was seen on the monitor so we knew straight away we had it," Lee adds. "It was one of the few times in observing where there is some sense of immediacy, followed by instant gratification when the event was seen."

Amateurs attempted to witness the crash but came up empty-handed. From Hong Kong, the astrophotographer Wah writes, “I was using Meade 8-inch SCT and ToUCam SC3 to capture video. I could not see any flash during the period.” In Canberra, Australia, David Herald used video on a small scope but found no evidence of a flash in his recording.

Kaguya in lunar orbit
Launched in 2007, Japan's Kaguya spacecraft released a pair of smaller probes to aid in its scientific mission from lunar orbit.
JAXA
NASA scientists are keeping close tabs on all these observing reports, because Kaguya's flashy finale serves as a dry run for the forthcoming LCROSS mission. If the craft's launch takes place as planned on June 17th, ground controllers will direct a 2½-ton Centaur rocket, closely followed by LCROSS itself, into a permanently shadowed polar region between October 7th and 11th. Mission managers hope the crashes will create a towering splash of water-rich dust and vapor observable from Earth.

However, Kaguya was no lightweight — its mass was nearly 3 tons — and further analysis of the AAT images may show that only very large telescopes will have a chance to capture LCROSS's demise.