A detailed description of the techniques used and results obtained for the
interplanetary navigation of the Mars Pathfinder spacecraft is presented. M
ars Pathfinder was launched on Dec. 4, 1996, and landed on Mars on July 4,
1997. To ensure a successful landing, the navigation team was required to g
uide the vehicle such that the flight-path angle error was less than 1.0 de
g at atmospheric entry. This relatively tight requirement was achieved thro
ugh the use of a ground-based orbit determination system ming Doppler and r
ange measurements obtained from Earth stations. The resulting orbit solutio
ns were used to design and execute four trajectory correction maneuvers nee
ded to ensure the vehicle would make a correct atmospheric entry. More freq
uent orbit solutions were performed during the final two days to predict th
e exact time of entry and preset the onboard entry, descent, and landing se
quence to deploy the parachute at the correct moment. The overall result wa
s a successful landing less than 30 km from the intended target, well withi
n the 100 x 200 km requirement ellipse.