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The GPS satellites use the Sun as a primary reference for orienting themselves throughout their orbit. When a satellite enters eclipse, this reference point is lost and an automated response commences to reaquire the Sun. This response causes the satellite to slew (rotate), called yawing, in a predictable manner as it searches for the Sun. Once the satellite reaquires the Sun, it reorients itself quickly but the period in which yawing occurred can introduce a measurable error in the position of the phase center of the satellite antenna. A similar effect can occur when the satellites are between the Earth and the Sun, and very close to the line connecting them. The satellite must rotate at this time to maintain the proper orientation to the Earth and Sun. During this "noon turn", a yaw bias can be introduced before the satellite properly aligns itself again.
The yaw file file contains information on times and yaw rates for the satellites being processed. The name of the yaw file is created from the g_file name with the first character replaced by a "y". A trucated yaw file and explanation follow.
The first two lines are descriptive. The first line contains column headings for the table which follows. The second gives the number of entries. (This line also references the explanation in the read_yaw.f file which, unfortunately is not part of this code.)
The subsequent lines contain:
Example
PRN YAW_RAT BIAS YR M 55 NOMINAL yaw rates - explanation of file in read_yaw.f 1 0.123 P 96 10 14 16 6 2 0.113 P 96 10 14 16 6 3 0.123 P 96 10 14 16 6 4 0.119 P 96 10 14 16 6 5 0.119 P 96 10 14 16 6 6 0.127 P 96 10 14 16 6 7 0.128 P 96 10 14 16 6 9 0.128 P 96 10 14 16 6 9 0.128 P 96 10 14 22 3 E 9 0.128 P 96 10 15 4 3 9 0.128 P 96 10 15 9 58 E 9 0.128 P 96 10 15 15 58 9 0.128 P 96 10 15 21 55 E 9 0.128 P 96 10 16 3 55 10 0.123 P 96 10 14 16 6 14 0.087 P 96 10 14 16 6 15 0.119 P 96 10 14 16 6 16 0.087 P 96 10 14 16 6 17 0.119 P 96 10 14 16 6 18 0.103 P 96 10 14 16 6 19 0.098 P 96 10 14 16 6 19 0.098 P 96 10 14 17 28 E 19 0.098 P 96 10 14 23 28 19 0.098 P 96 10 15 5 22 E 19 0.098 P 96 10 15 11 22 19 0.098 P 96 10 15 17 22 E 19 0.098 P 96 10 15 23 22 19 0.098 P 96 10 16 5 19 E 19 0.098 P 96 10 16 11 19 21 0.113 P 96 10 14 16 6 22 0.119 P 96 10 14 16 6 23 0.119 P 96 10 14 16 6 24 0.119 P 96 10 14 16 6 25 0.101 P 96 10 14 16 6 25 0.101 P 96 10 14 19 20 25 0.101 P 96 10 15 1 20 E 25 0.101 P 96 10 15 7 20 25 0.101 P 96 10 15 13 20 E 25 0.101 P 96 10 15 19 20 25 0.101 P 96 10 16 1 14 E 25 0.101 P 96 10 16 7 14 26 0.123 P 96 10 14 16 6 27 0.120 P 96 10 14 16 6 27 0.120 P 96 10 14 18 29 E 27 0.120 P 96 10 15 0 29 27 0.120 P 96 10 15 6 27 E 27 0.120 P 96 10 15 12 27 27 0.120 P 96 10 15 18 27 E 27 0.120 P 96 10 16 0 27 27 0.120 P 96 10 16 6 24 E 27 0.120 P 96 10 16 12 24 28 0.126 P 96 10 14 16 6 29 0.127 P 96 10 14 16 6 30 0.123 P 96 10 14 16 6 31 0.097 P 96 10 14 16 6
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