I wrote: >>It may be an observing effect depending on whether >>the fireball was observed from north or south its flight path.
>>Note that the DOD satellite measured the flight path angle at 62 degrees from >>the horizontal, or 28 degrees from the vertical. That means the meteorite fall >>was more vertical than horizontal. I think this somewhat vertical flight path >>may have made judging the flight direction >>more difficult from the ground, maybe creating an optical illusion effect. It is >>already >>well-documented the difficulty in judging the distance to fireballs from a single >>location. Even if the true flight path was SW to NE as the DOD data indicates, and >>this >>would extend the strewnfield out to a larger size along the flight path direction, >>the near-vertical drop does constrain the size of the strewnfield ellipse. >>I'm very heavily inclined to believe the DOD satellite measurements are more >>accurate than >>the ground observations anyway, because the satellite was designed to accurately >>record these type of details. Bob Matson replies: > I think I can lay to rest any concerns that there was a mistake > in the DoD report -- the bolide did indeed travel from SSW to > NNE, and far from contradicting the eyewitness accounts, it is > in complete agreement with them. You see, with a trajectory > this steep coupled with the lack of range information (observers > on the ground can really only measure "apparent" bearing), it > is not possible to accurately determine the true bearing from > one observer's viewpoint. For observers south of Chicago, the > trajectory defined by the DoD report will indeed result in a > meteor that appears to be headed almost due northwest. To see > for yourselves, download the following .GIF file that I generated > with my SkyMap program: > > http://members.cox.net/mojave_meteorites/pftrack.gif > > The bottom line is that despite the > 22.5 deg (NNE) true heading, the bolide appears to be heading > toward azimuth 315, which is due northwest. Thanks for the plot! I kind of suspected it may have been an observing effect. Bob Verish pointed out to me that in another eyewitness case (not Park Forest), a fireball was observed to be travelling 'up'. This can happen with the right viewing perspective with a low-angle flight path, even though the fireball is really falling down. Again, the DOD data indicates the strewnfield is larger then originally thought, particularly along the true flight path. I think most of the obvious fragments have been recovered, but people should now be looking in the less obvious or less accessible areas (ie: private country clubs). For instance, some of the pieces may have fallen in soft ground and may be buried, or in areas where there is more vegetation. Ron Baalke ______________________________________________ Meteorite-list mailing list [EMAIL PROTECTED] http://www.pairlist.net/mailman/listinfo/meteorite-list
