B-plane Evolution Under Highly Non-Keplerian Dynamics

Juno is the second of a series of New Frontiers missions and was launched in 2011.
The spacecraft was set en route to Jupiter, and its Jupiter Orbit Insertion occurred
on 2016-07-04 after a five-year cruise in deep space. The mission phase just prior
to this large maneuver is called approach. As navigation team, we were responsible
for precise orbit determination of the Juno spacecraft to ensure a successful
orbit insertion. To evaluate the navigation performance we employed the B-plane
mapping, where the incoming hyperbolic velocity defines the plane perpendicular
to it, and the time to go to hit the plane will directly map into the uncertainties of
the target point. The B-plane is a convenient tool when assessing the navigation
performance as it is not affected by non-linearities due to the gravitational pull of
the targeted body. However, as the Jupiter Orbit Insertion approached we started
to realize that the B-plane mapping uncertainties were significantly larger than expected.
We found that the B-plane mapping time had tremendous influence on the
covariance inflation in the B-plane. Because of the close approach distance during
the Jupiter Orbit Insertion and the strong interaction with J2 spherical harmonic
coefficient, the Juno dynamics were too far from a Keplerian one assumed for the
B-plane mapping. We first discuss the analytical approach of the B-plane mapping
uncertainty and perform a numerical analysis to isolate the components of the Juno
dynamics that cause the B-plane covariance inflation.