- #1
solarblast
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I've written a Python program to simulate a meteor falling into the Earth's atmosphere. It's fairly straightforward. I give it the lat/long of two observing stations, and the lat/lng where the meteor begins along with an angle from north for the direction. An initial height above the beginning lat/lng is given along with the fall angle.
To define the fall angle, think of a tangent line to the Earth at the meteor's lat/lng, and another line parallel to it at the height of the meteor. Call it the height line The fall angle is measured using the height line and the radial line from the Earth's center to the height of the meteor. The origin is the intersection of the two lines, and the path of the meteor, a line, starts at the origin and moves at an angle downward from the origin. The angle is the fall angle. Typically, a fall angle is 0 (skips off the Earth's atmosphere) or moves just a few degrees into the atmosphere.
To test the program's output, I use the the radial line to the start of the track to another point on the track several degrees away. The separation angle is determined by two radial lines separated by an arbitrary angle. The length of the first line is r+h0, where r is the Earth's radius (earth is taken as a sphere), and h0 is the height of the meteor at the start of its path. The second line has a length r+h1. h1 is generally taken as less than h0.
To compute the fall angle, take the two lines as vectors, P1 and P2. P2-P1 is the path vector. How do I find the fall angle? My first take at this is to use |P1|*|P2-P1|*cos(phi) = P1 dot (P2-P1), where phi is the angle between P1 and P2-P1. If I specify, the fall angle as 10, 15 or whatever degrees, I find phi to be 90 degrees plus the specified fall angle. I seem close, but no cigar. Perhaps I need a third vector P3 that is perpendicular to P1 to form P3-P1 and P2-P1. Comments?
To define the fall angle, think of a tangent line to the Earth at the meteor's lat/lng, and another line parallel to it at the height of the meteor. Call it the height line The fall angle is measured using the height line and the radial line from the Earth's center to the height of the meteor. The origin is the intersection of the two lines, and the path of the meteor, a line, starts at the origin and moves at an angle downward from the origin. The angle is the fall angle. Typically, a fall angle is 0 (skips off the Earth's atmosphere) or moves just a few degrees into the atmosphere.
To test the program's output, I use the the radial line to the start of the track to another point on the track several degrees away. The separation angle is determined by two radial lines separated by an arbitrary angle. The length of the first line is r+h0, where r is the Earth's radius (earth is taken as a sphere), and h0 is the height of the meteor at the start of its path. The second line has a length r+h1. h1 is generally taken as less than h0.
To compute the fall angle, take the two lines as vectors, P1 and P2. P2-P1 is the path vector. How do I find the fall angle? My first take at this is to use |P1|*|P2-P1|*cos(phi) = P1 dot (P2-P1), where phi is the angle between P1 and P2-P1. If I specify, the fall angle as 10, 15 or whatever degrees, I find phi to be 90 degrees plus the specified fall angle. I seem close, but no cigar. Perhaps I need a third vector P3 that is perpendicular to P1 to form P3-P1 and P2-P1. Comments?