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We report on serendipitous findings of 13 faint meteors and 44 artificial space objects by SuprimeCam imaging observations during 2004 August 11–16. The meteors, at about 100 km altitude, and artificial satellites/debris in orbit, at 500 km altitude or higher, were clearly discriminated by their apparent defocused image sizes. We defined a peak video-rate magnitude by comparing the integrated photon counts from the brightest portion of the track traversed within 33 ms to those from a 0-mag star during the same time duration. The magnitudes thus defined for the meteors, including 1 Perseid, 1 Aquarid, and 11 sporadic meteors, were in the range 4.0 $< V_{\rm vr} <$6.4 and 4.1 $< I_{\rm vr} <$5.9. Although the spatial resolution is insufficient to resolve the source size of anything smaller than about 1 m, we developed a new estimate of the collisionally excited column diameter of these meteors. A diameter as small as a few mm was derived from their collisionally excited [O I] 5577 photon rates, meteor speed, and the volume density of the oxygen atoms at an altitude of 100 km. The actual column diameter of the radiating zone, however, could be as large as few 100 m because the excited oxygen atoms travel that distance before they emit forbidden lines in 0.7 s of its average lifetime.

We calculate the momentum transfer efficiency for small cratering impacts from 59 high-velocity (0.76–4.4 km/s) oblique impact experiments using nylon projectiles and targets made of basalt, aluminum, mild steel, mortar, and nylon. High-speed video frames show an initial luminous stream downrange of impact point for all the target materials. For basaltic and mortar targets there follows axi-symmetric ejection of target material around surface normal at the impact point. Our results suggest that: (1) momentum carried away by the axi-symmetric ejecta would significantly contribute to the normal component of momentum transfer efficiency; and (2) thepenetration depth of the projectile into target could determine the tangential momentum transfer efficiency. We calculated the efficiency of angular momentum transfer from the translational motion of projectiles to the rotation of ellipsoidal asteroids using the efficiencies for the linear momentum. The efficiency is more than four times that for spherical asteroid at their principal axis ratio of 2 : 1.4 : 1. If the experimental results hold for the impact that formed the largest crater on 253 Mathilde, the largest projectile estimated may have despun the asteroid to the present slow rotation by chance.

We conducted 10 shots of high-velocity oblique impact experiments (1.95–3.52 km/s) using nylon projectiles and spherical mortar targets. Large craters were formed, but these targets were not disrupted by the impacts. We then calculated the efficiencies of momentum transfer from the projectile to the post-impact target for each experiment. The efficiencies of angular momentum transfer from the translational motion of the projectiles to the rotation of the post-impact targets were also derived. A representative efficiency of angular momentum transfer was calculated to be 0.17 for random successive collisions. The efficiency was applied to an equation expressing the precession angle of asteroids. It is shown that 1989ML, target of Japan-US asteroid-sample-return-mission (MUSES-C) would be tumbling.

We conducted a series of high velocity oblique impact experiments (0.66–6.7 km/s) using polycarbonate (plastic) projectiles and targets made of mortar, aluminum alloy, and mild steel. We then calculated the efficiencies of momentum transfer for small cratering impacts. They are η = (M′Vn′)/(mvn) and ζ = (M′Vt′)/(mvt), wheremandvare the mass and velocity of a projectile, andM′ andV′ represent those of a postimpact target. Subscripts “n” and “t” denote the components normal and tangential to the target surface at the impact point, respectively. The main findings are: (1) η increases with increasing impact velocity; (2) η is larger for mortar than for ductile metallic targets; (3) ζ for mortar targets seems to increase with the impact velocity in the velocity range less than about 2 km/s and decrease with it in the higher velocity range; (4) ζ for the aluminum alloy targets correlates negatively with incident zenith angle of the projectile. In addition to these findings on the momentum transfer, we show theoretically that “ζL” can be expressed by η and ζ for small cratering impact. Here, ζLis the spin angular momentum that the target acquires at impact divided by the collisional angular momentum due to the projectile. This is an important parameter to study the collisional evolution of asteroid rotation. For a spherical target, ζLis shown to be well approximated by ζ.

We monitored Jupiter with a video movie camera attached to a 1.3 m reflector during the impact event of the K fragment of D/Shoemaker-Levy 9. The camera was sensitive to visible radiation. A plume, which was generated by the impact and prominent in infrared wavelength, was not detected. Jovian images with hypothetical plumes were synthesized to examine how luminous the plume should have been to be recognized. It has been revealed that the plume was no more than twice as bright as Io in visible wavelength.

Europa was eclipsed but not occulted when the K-nucleus of comet Shoemaker-Levy 9 collided with Jupiter. We tried to detect brightening of the satellite due to the reflection of impact flash, from 10:05 to 10:40 on July 19, 1994 (UT). We monitored Jupiter and its surrounding area by a CCD video movie camera attached to a telescope of 28 cm in aperture and 280 cm in focal length. We could not find any brightening even though we could detect a 10.0 V-magnitude star of F8 type near Jupiter.