Document Title:
14
User’s Manual for the GPS Orion-S/-HD Receiver
Document No.
Issue 1.0
GTN-MAN-0110
June 22, 2003
DLR/GSOCNo part of this document shall be reproduced in any form or disclosed to third parties without prior authorization.
play of the IIP allows the range safety officer to discern whether the rocket would eventually
land outside the permissible range area and thus necessitate an abort of the boosted flight or
even a destruction of the malfunctioning vehicle.
For an optimal support of sounding rockets, the Orion-HD receiver is able to predict the in-
stantaneous impact point (IIP) from its navigations solution. The instantaneous position and
velocity are expressed in the local horizontal coordinate system and a plane-Earth parabolic
trajectory model with first order corrections for surface curvature, gravity variation and Earth
rotation is used to predict the motion up to the intersection with the surface of the Earth [13].
Due to its inherent simplicity the analytical IIP model is well suited for real-time time compu-
tations but is still competitive in terms of accuracy. Comparisons have demonstrated that the
overall agreement with a full modeling of conservative forces is high enough to introduce IIP
prediction errors of less than 1.5% of the ground range for sounding rockets reaching alti-
tudes of up to 700 km and flight times of about 15 min.
In view of negligible processor requirements, the IIP prediction is always performed along
with the navigation solution. However, the F47 or $PDLRM,IIP has to be activated (using the
DR Data Rate command) to output the geodetic impact point coordinates and the time to
impact.
