DPS # Saturday, 11 October 2008 Rate of Ejection and Velocities of Material Ejected from Comet Tempel 1 after the Deep Impact Collision Sergei I. Ipatov Catholic University of America, USA. The work was initiated at University of Maryland), and Michael F. AHearn University of Maryland, College Park, USA Seefor SeriesInstru- ment INTTIME, seconds Size, pixelsEXPIDIMPACTM, seconds min, max Ma (dif)MRI , , MbMRI , , Ha (dif)HRI0.1512 , , HbHRI , , Hc (dif)HRI0.6512 , , HdHRI , , HeHRI , , Series of DI images considered. In each series, the intergration time and the size were the same. For series Ma, Ha, and Hc, we analyzed differences in brightness between a current image and that before the impact. These series are marked by (dif). For other series, we analyzed the brightness in current images. Variation of the relative brightness Br of the brightest pixel with time t. It is considered that Br=1 at t=4 s. Besides peaks during the first second (e.g., at 0.6 s), there was an increase of brightness after 10 s. 3 (a) Coordinates x and y of the brightest pixel relative to the position of the brightest pixel in the MRI image at t=0.001 s (the place of impact) at different times after the impact. (b) The angle (in degrees) of the direction from the brightest pixel at t=0.215 s (close to the place of ejection) to the brightest pixel at a current time. The angle corresponding to the direction of the impact was about -60 o. A jump of direction of ejection at t~12-13 s and te~10 s. 4 Contours corresponding to CPSB (calibrated physical surface brightness) equal to 1, 0.3, 0.1, and 0.03, for MRI images from series Mb made (a), (b), (c), (d), (e), and s (f) after the impact. 5 Rays of ejected material The excess ejection of material to a few directions (rays of ejected material) was considerable during the first 100 s, took place during several minutes, and was still observed in images at t~ s. It shows that the outburst continued up to ~10 min. Considerable excessive ejection (the outburst triggered by the impact) began approximately at the same time t e ~10 s when the direction from the place of ejection to the brightest pixel changed, the peak brightness began to increase, and there was a local peak of the rate of ejection. The sharpest rays were caused by material ejected at t e ~20 s. The upper-right excessive ejection (perpendicular to the direction of impact ) began mainly at te~15 s (though there was some ejection at te~2 s), could reach maximum at te~25-50 s, could still be considerable at te~100 s, but then could decrease, though it still could be seen at te~400 s. The value of te~15 s is correlated with the changes of the direction to the brightest pixel at t~12-13 s. The upper bump of the outer contours is clearly seen at 66