Monday, June 8, 2009

Fine-tuning Kaguya's Impact

Dr. Bernard H. Foing, executive director of the European Space Agency's International Lunar Exploration Working Group (ILEWG) and project scientist for ESA's SMART-1 lunar orbiter is cautioning the larger community of astronomers and other observers that the Japanese orbiter Kaguya (SELENE 1) may come down earlier.

Others are less concerned. Jim Mosher, who has lead an online group rehearsing for the impact mission of LCROSS, now preparing for launch with the LRO, June 17, puts more faith in Kaguya flight directors at the Japanese space agency JAXA.

"The Japan lunar probe Kaguya, after a productive operational phase will conclude its scientific mission with a controlled impact on the lunar surface expected on June 10, 2009 at 18:30 GMT, on the Moon's Near Side, in a dark area at the eastern limb, lunar coordinates East 80, and South 64 degrees," Foing writes.

"The SMART-1 team has constructed mosaic maps of the Kaguya landing strip using survey images obtained by the SMART-1's AMIE camera." (Close up HERE.)

"The SMART-1 images shows the Kaguya final perilune orbits and impact site are within a very cratered ancient highland terrain. Because of the high topographic relief, will the spacecraft hit the Moon before the nominal time?"

“There is a possibility that the Kaguya impact would take place in fact about 2 or 4 hours before expected," writes Foing, "if the lunar crater rim indicated by SMART-1 is high enough to be on the way.

"Observers should be prepared for that."

“For SMART-1 we had to make a last small spacecraft maneuver just 3 days before impact”, wrote Foing, “in order to avoid a lunar crater rim and enforce the landing at the exact time we had announced, within the second."

“We have to analyze the lunar topography to determine the exact time of impact, and the slopes to determine whether the incidence will be grazing enough to have Kaguya bouncing on touchdown”, says Bernard Foing, “as was observed with SMART-1 hard landing. We hope that future data compared to SMART-1 maps will show the new elongated Kaguya crater and bouncing secondary debris.”

"You may, of course, have access to more current information than the general public," Mosher responded, but (as of this writing) the information on the Kaguya site is back to saying the impact is expected at 63°S, rather than 64°S, with an update expected at 01:00 UT on June 10.

"I believe that would put the impact on the north side of Gill D, rather than the south side that you are indicating on your attachments. (See the USGS map).

"It looks like the approach to the impact site will be from the south," Mosher wrote

(JAXA's Kaguya orbital tracker, HERE.) currently puts the spacecraft elevation at 0 km at 80.4°E/66.5°S at about 18:25 UT, and puts the spacecraft at 80.4°E/49.1°S (altitude -4 km) at 18:30 UT (the announced impact time).

"By suggesting Kaguya may hit the surface 2 or 4 hours earlier than announced, " Mosher wrote to Foing, "I presume you mean it may hit in the same general area on earlier orbits. Does this imply you think it may strike the crater or highland between Gill and Wexler U?"

See Map HERE.

"Finally, I notice the Kaguya team is soliciting observations by professional astronomers in their Jun. 5, 2009: Final operation week for KAGUYA" communication at, HERE.

"I have no idea if they have gotten any takers, nor what the expected magnitude of the flash may be, nor what the chances are that it might be hidden by terrain. As mentioned in an earlier post, there are unofficial finder charts for Earth-based observers available (HERE.)

"Perhaps JAXA will release better ones in their June 10th announcement at 01:00 UT?"

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