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INTRAC-305 TECHNICAL DESCRIPTION
© 2011 Advantech Wireless INTRAC-305 MANUAL - Issue 3.2 Page 61
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negative when entering from the front panel. This only applies
to the LMO data field.
NORAD data The NORAD ephemeris data consists of a string of 166
characters. The first 160 characters are split into two “Card
Element Sets” of 80 characters each. The next two characters
(161 & 162) comprise the Minutes Interval and characters 163
& 164 comprise the Period of Validity of the ephemeris. The
final two characters (165 & 166) are the check sum.
There are ten blocks of orbital element parameters contained
in the NORAD ephemeris character string :-
Charas. Data Description
19 - 32 EPOCH format - YYDDD.DDDDDDDD
34 - 43 XNDT20 1st rate of change (rev/day/day)
45 - 52 XNDD60 2nd rate of change (rev/day/day/day)
54 - 61 BSTAR damping factor (er**-1)
89 - 96 XINCL inclination (deg)
98 - 105 XNODEO ascending node (deg)
107 - 113 EO eccentricity
115 - 122 OMEGAO argument of perigee (deg)
124 - 131 XMO mean anomaly (deg)
133 - 143 XNO mean motion (rev/day)
RAPID MODEL GENERATION The INTRAC-305 can use the IESS-412 or NORAD data to
build the satellite’s orbit model instead of having to learn the
orbit over a 24hr period.
The IESS-412 data is selected for the Rapid Model Generation
in the Models menu and ENTER pressed. The orbit model is
calculated and the INTRAC enters Tracking Mode.
For the NORAD data there are five choices of NORAD
algorithm. These are SGP, SGP4, SGP8, SDP4 & SDP8 and
each gives a slightly different Az/El pointing for the same
NORAD data.
SGP the original NORAD algorithm
SGP4 applies to Near Earth Orbits
SGP8 applies to Near Earth Orbits
SDP4 applies to Deep Space Orbits
SDP8 applies to Deep Space Orbits
Orbits are differentiated by their period. Those of less than 225
minutes are Near Earth Orbits and those of more then 225
minutes are Deep Space Orbits. Geostationary satellites are in
Deep Space Orbit.
It is assumed that the user know which algorithm applies to the
data to be used. However INTRAC will not allow a Near Earth
Orbit algorithm to be used with Deep Space Orbit data and
vice-versa.