Location: Slichter Hall Room 3853 

Presented By:
Marina Brozovic

Abstract:

Our knowledge of the satellite population in the solar system has grown rapidly in the past 100 years.
In the early 1900s almost every known moon was a regular satellite — the large, primordial bodies that formed with their parent planets.
The Voyager flybys fundamentally changed that picture by revealing numerous small inner satellites of the giant planets, bodies likely tied
to ring-system evolution and ongoing collisional processing near the planet. Beginning around 2000, wide-field CCD surveys (e.g. CFHT, Subaru) opened a third population regime: most new discoveries were irregular or outer satellites — dynamically distinct, highly inclined, often retrograde
objects whose origins are not native to the planet system but are best explained as captured heliocentric planetesimals from the early solar system. At JPL, we develop and maintain ephemerides for all known satellites. The orbital models range from simple precessing ellipses to full dynamical models that include tides, relativistic terms, satellite libration, and high order gravity field expansions. These models draw on data sets spanning more than a century of astrometric measurements, from early visual observations to modern spacecraft tracking. Ultimately, satellite ephemerides are not just navigation products needed to point a telescope or fly a spacecraft - they are scientific observables that encode the history and dynamics of entire planetary systems. Each orbit tells a story about its origin, its interactions, and its ongoing evolution.
We will review the current state of satellite ephemerides across the solar system and highlight some interesting dynamical puzzles.