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DEFINITION OF A YUMA ALMANAC

ID: PRN of the SVN

Health: 000=usable

Eccentricity: This shows the amount of the orbit deviation from circular (orbit). It is the distance between the foci divided by the length of the semi-major axis (our orbits are very circular).

Time of Applicability (s): The almanac reference time in seconds of the GPS Week.  Kind of a time tag.  ToA is not the time the almanac was generated, rather it is ~70 hours in the future (close to the center of the 6 day fit) from the time the almanac was generated.

Orbital Inclination (rad): The angle to which the SV orbit meets the equator (GPS is at approx. 55 degrees). Roughly, the SV's orbit will not rise above approx. 55 degrees latitude. The number is part of an equation: #= pi/180 = the true inclination.

Rate of Right Ascension (r/s): Rate of change in the measurement of the angle of right ascension as defined in the Right Ascension mnemonic.

SQRT(A) (m 1/2):  Square Root of Semi-Major Axis -  This is defined as the measurement from the center of the orbit to either the point of apogee or the point of perigee.

Right Ascen at Week (rad):  The satellite almanac orbital "geographic longitude of the ascending node of the orbital plane at the weekly epoch" (OMEGA0) as defined in IS-GPS-200

Argument of Perigee (rad): An angular measurement along the orbital path measured from the ascending node to the point of perigee, measured in the direction of the SV's motion.

Mean Anom (rad): Angle (arc) traveled past the argument of perigee (value= -pi to pi radians).  If the value exceeds pi radians, subtract 2*pi radians to find the mean anomaly.  When the SV has passed perigee and heading towards apogee, the mean anomaly is positive.  After the point of apogee, the mean anomaly value will be negative to the point of perigee.  Mean Anomaly is measured from Perigee not from Ascending Node.

Af(0) (s): SV clock bias in seconds

Af(1) (s/s): SV clock Drift in seconds per seconds

Week: GPS weeks since 6 Jan 1980 modulo 1024. Current rollover basis is 22 Aug 1999.  Next rollover is 07 Apr 2019.