The analysis tool performs a computation of the gross magnetospheric
properties of the different tours proposed by the project. It uses
1hr-resolution trajectories and a series of simple models of Saturn's
magnetosphere frontiers. The scope of this tool is to give a "flavor"
of the type of science members of the MAPS working group will be able
to do once at Saturn.
Models & Parameters
Models used in the analysis tool are intentionnaly
over-simplified. According to Pioneer and Voyager measurements,
Saturn's magnetosphere is highly variable: the magnetopause sub-solar
point has been reported to vary between 16 Rs and more than 30
Rs. Therefore, it would be inconsistent to use sofisticated models
to account for the global properties of a magnetosphere, whose global
parameters are unknown.
The models are:
The parameters are:
Using 1hr-resolution trajectories does not allow us to detect "events" that last
less than this period. This restriction becomes important near Saturn where the
S/C is flying fast.
Particular regions of Saturn's Magnetosphere
- Aurorae:
Invariant Latitude > 70 deg, distance to the planet < 5 Rs.
- SKR:
Invariant Latitude > 70 deg, distance to the planet < 5 Rs, local
time between 9 and 14.
- Source region:
Region that includes the rings, icy satellites and Titan
Vertical distance to the equator < 3 Rs, distance to the planet < 25 Rs.
The Vetoes
The vetoes were defined by the MAPS working group as minimum characteristics a
tour must have to be acceptable regarding the MAPS science objectives.
- LT Coverage at Titan
Local time coverage must be > 180deg at Titan. We attribute to each
crossing of Titan orbit a ``width'' of 12deg (1hr Local time). Of course,
each of these 12deg sectors are counted only once.
- Min. Periapsis
Periapsis must be < 3Rs at its minimum.
- Max. Latitude
Maximum absolute latitude must be > 65deg inside 10Rs.
- Tail Petals
S/C must go through the region: x < -40Rs,
|z| < 10Rs and |LT| < 20deg around midnight.
