[Prev][Next][Index][Thread]
Re: (meteorobs) request for info -cook book approach for bolide orbital calculation
----- Original Message -----
From: <chiayk@singnet.com.sg>
Subject: (meteorobs) request for info -cook book approach for bolide orbital
calculation
> Hi:
> Is there any write up that detail how to derived the orbital elements
> of bolide? ( from eyewitness accounts, all sky patrol and satellites
> network)? What software packages are required. Is this approach any
> different from meteor streams study?
> Thanks
> rgds
> ykChia ( call me yK )
> Singapore 103.80255E, 1.445 N, +20m, +8 GMT
> http://www.geocities.com/ykchia_1999/index.html
>
Hello yK:
I don't know of any book that outlines in any detail what you are
looking for. Most, if they exist are probably located in, now out of print,
professional publications.
The professionals I work with have written their own computer programs in
computer languages like Fortran and are not at all user friendly.
The important thing is collecting accurate observational data. First,
you must have observers or photographic records on both sides of the
observed track. If they are all on one side, it is impossible to compute a
fall area. Predicting an accurate fall area is not as easy as one would
think. This is almost impossible from visual observations alone. If visual
observations are to be used, instrumentation should be used to measure the
start and end points and elevations of the fireball. A good sighting type
compass and a device for measuring elevations is required. I use a
sportsman's compass and a Santo clinometer. You must accurately know the
longitude, latitude and possibly the elevation of the observer. This can be
obtained from topographical survey maps or by using a G.P.S. Even if all
this data is collected from several observers on both sides of the track
there are still some problems to contend with. Visual observers almost
always don't measure the same points along the meteors path. This is
required for more accurate results. Also a visual observer CANNOT estimate
velocity of the meteoroid which is very important for accurate predictions.
With luck, video tapes of the fireball can be found and used for this. Even
after you have collected all this information and done the calculations this
does not insure that you will find the meteorite. This is very much a
matter of luck! The calculations simply tell you an area of where to look.
Probably the most accurate photographic fireball patrol network called the
Prairie Network run by the S.A.O. (now closed) could only predict a fall
area of around 1 km accuracy. The Prairie Network used large format aero
cameras with plate sizes of 9X9 inches, so accurate position measurements
could be made. Still, a number of factors effected fall area accuracy.
When computations are made, it is normal to say that the meteoroid is a
spherical body, (almost always, not the case). Also the density of the
object is given an estimated value. During the dark flight portion of the
path, the meteoroid can be blown off the predicted course by several
kilometres by high upper atmospheric winds. The shape and density or
whether the meteoroid broke up in flight will also effect your calculations.
Smaller fragments drop first with the larger pieces travelling further.
Also, most fireballs don't drop a meteorite!
I'm not trying to discourage your efforts, only pointing out the
problems. By all means, collect the data. If it is good, professionals
will jump in to help you with the calculations. Good luck!
Ed Majden - Amateur meteor studies
Associate member of MIAC and AMS affiliate.
http://www.amsmeteors.org/spectra/majdenobs.html
To stop getting email from the 'meteorobs' list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html
References: