Titan and Saturn reports
June, 2013
TOST agenda
Tour Tweak exercise: TOST
• Looked at two UVIS stellar occs affected by the
tour tweak
• Tweak moved one of the occs by about 40
minutes, but this can be accommodated
Saturn Working Group and TWT
Activity
Tour Tweak exercise: Saturn
• Looked at two UVIS PIE stellar occs affected by
the tour tweak
• Tweak moved the occs by only a few minutes
– no problem
• Discovered a bigger shift (about 30 min.) for
one of the occs from a previous tour change
that had not been recognized – need to get
approval for the time change.
Action Item for the TWTs/OSTS
• 4. Science priorities and planning priorities for
the F-ring and Proximal orbits
– Bob West raised a concern about producing prioritized
science goals for each discipline for the F ring and
Proximal orbits prior to finalizing the science planning
process for these orbits. The group also agreed that
science priorities and planning should begin in
preparation for the upcoming Senior Review. Linda
Spilker agreed to generate action items for the
Discipline Working Groups to address these
concerns. Those action items are listed below:
Saturn WG Response to Linda’s Action
Item
• Authored by Andy Ingersoll with input from
the Saturn working group
Prioritized Science Goals: Summary
• Gravity (RSS) – Planetary formation, thermo-chemical
evolution, internal structure, winds
• Magnetic field (MAG) – Nature of the dynamo, rotation
of the planetary interior
• Exosphere composition (INMS) – Interaction with the
lower atmosphere, magnetosphere, and rings
• Stratosphere (UVIS & VIMS) – Stellar occultations to
study waves, composition, aerosols, latitudinal
transport of energy and constituents
• Turbulence and small scales (RADAR, ISS, VIMS) – High
resolution views to study unexplored scales of motion
• Seasonal change – continue the campaigns to 2017
Gravity (from Luciano Iess)
• Get even zonal harmonics out to J14 and tidal
Love number k2 – determine mass of core,
heavy elements in mantle, deep winds
• Want 4 good orbits, 24 hours each - avoid
HGA to ram, avoid Madrid to Canberra pass
• Orbits 14 and 16 are the best
• Compatible with INMS and MAG
Magnetic field (MAG) and Exospheric
composition (INMS)
• The Saturn DWG strongly supports both of
these objectives, but assumes that MAPS is
taking prime responsibility
• MAG is looking for non-axisymmetric features;
needs calibration time, wants to avoid highspeed turns, but is compatible with other
instruments
• INMS requires –X to dust ram < 45° for major
species, < 3° for reactive species and ions
Triangles: already planned
or executed
Diamonds: outside 12 RS
best for UVIS
Squares: inside 12 RS
Tightly-packed squares at
the equator are
best for VIMS
Stellar Occultations (UVIS)
• Occultations outside ± 12 hours (UVIS) – T and
hydrocarbons, nbar to mbar; full latitude
coverage allows estimates of horizontal
transport of energy and chemical species;
3 dedicated orbits, 40-50 total occultations
• CIRS observes occ point, extends profile down
to 100’s of mbar; best at periapse. Study
seasonal change, 15-20 year oscillation,
overlap in vertical with UVIS.
Stellar Occultations (VIMS)
• Near periapse (VIMS) – Statistical variations of
temperature within ± 1° of equator reveal
stratospheric waves; 10-12 occs is ideal. Also
good for determining He/H2 ratio (with CIRS);
~1 hour per occ, 3-9 hours from peri, any orbit
• Distant occultations of brightest stars (VIMS) –
probe deeper (to 20 mbar) than ever before;
6-7 occs total, α-Cma on Revs 275-279, α-Ori
on Revs 271-276, ~1 hour per occ
High resolution scans and views
• 2.2 cm thermal emission (RADAR) – pole-topole scan reveals variations of ammonia
vapor, want Z axis to Saturn on one orbit
• Imaging of high-contrast regions (ISS) - can get
~0.1 km resolution with WAC; spatial power
spectrum of atmospheric turbulence
• Image polar vortex at 89° latitude (VIMS) image the hexagon at 75° latitude. Time
dependence at all scales, hours to seasons
Seasonal Change Campaigns –
Completing the solstice mission to 2017
In these cases, full temporal coverage is more
important than orbit geometry
• Equatorial oscillation of temperatures and
winds (CIRS) – like QBO of Earth but 15 years
• Aurora – response to 11-year solar cycle and
30-year seasonal cycle (VIMS, UVIS, ISS)
• Equatorial thermosphere (UVIS) – high T and
large variability (388-612 K), still a mystery