Reading and watching the news I understand that shooting the USA193 is a final decision. Then I wonder where would most part of debris hit or almost hit the earth. Does anyone have an answer for this question? Another question, just in case the satellite won't be shot, approximately over where will it re-enter? Luis Hermida lat 34.9S Long 56.1W ----- Original Message ----- From: "Ted Molczan" <ssl2molcz@rogers.com> To: <seesat-l@satobs.org> Sent: Friday, February 15, 2008 6:38 AM Subject: RE: shoot down questions > Dale Ireland wrote: > >> If the satellite is hit wouldn't it actually reenter sooner >> as small high drag pieces would come down faster. > > Yes, it would. Prior to the fragmentation of 79017A / 11278 (aka P78-1 or > Solwind) by an ASAT, it had been estimated to remain in orbit for 40 years > (source: The RAE Table of Earth Satellites, 1957-1980). Of the 284 debris > fragments catalogued after the ASAT test, 90 percent decayed within 4 > years: > > http://www.satobs.org/seesat_ref/06057A/Solwind_Debris_Decay_History.pdf > > >> It wouldn't launch many fragments into higher orbits would it? > > Many fragments will have a somewhat greater apogee than prior to the > impact, but > in most cases, their perigee will also have decreased, which will tend to > hasten > decay, especially for the fragments with the highest ballistic > coefficients, > i.e. area to mass ratio. A few fragments may have apogee far greater than > that > of the original orbit. > > At the time Solwind was destroyed, its orbit was 513 X 543 km. One of its > fragments, 79017Z / 16071, entered a 510 x 1765 km orbit. Its orbital > history is > available here: > > http://www.planet4589.org/space/elements/16000/S16071 > > Note that despite its boost in apogee, it decayed within 1.83 years of the > attack, due to its very high ballistic coefficient. If that fragment had > been > generated at the altitude at which the U.S. DoD intends to destroy USA > 193, > reportedly about 130 n.m. = 241 km, then it would have decayed far more > quickly, > due to the vastly greater atmospheric density at 241 km, compared with 510 > km. > At the present typical solar flux and geomagnetic activity, the MSIS-E-90 > Atmosphere Model reveals about a 400 times greater atmospheric density at > 240 km > than at 510 km, which would reduce the time to decay from 1.8 years to > several > days. > > Of course, objects having a much lower ballistic coefficient might remain > in > orbit for weeks, even a few months, but they would likely be few in > number; > therefore, not considered to have materially increased the existing risk > of > debris collision to operational spacecraft. > > The remainder of Dale's post strayed off topic for this list. > > Ted Molczan > > ------------------------------------------------------------------------- > Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: > http://www.satobs.org/seesat/seesatindex.html > > > __________ NOD32 2877 (20080215) Information __________ > > This message was checked by NOD32 antivirus system. > http://www.eset.com > > ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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