The Tour Analysis Tool
"Description of the Tool"
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 magnetic field is a pure dipole (M=0.21 Gauss.Rs3) aligned with the planet axis.
  • The magnetopause is a 3D surface, as determined by Maurice and Engle [JGR, vol. 100, 17143, 1995].
  • The bow shock is a 3D surface, as determined by Slavin et al [GRL, vol. 10, 9, 1983].
  • The parameters are:
  • The magnetopause stand-off distance is at 24 Rs.
  • The bow shock stand-off distance is 32.1 Rs.
  • The time-resolution of the S/C trajectory is 1hr.
  • The tilt of Saturn rotation angle over the ecliptic is set to zero.
  • 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.