We present a new analysis of the Jupiter+Saturn analog system , OGLE-2006-BLG-109Lb , c , which was the first double planet system discovered with the gravitational microlensing method .
This is the only multi-planet system discovered by any method with measured masses for the star and both planets .
In addition to the signatures of two planets , this event also exhibits a microlensing parallax signature and finite source effects that provide a direct measure of the masses of the star and planets , and the expected brightness of the host star is confirmed by Keck AO imaging , yielding masses of M _ { \ast } = 0.51 { +0.05 \atop - 0.04 } M _ { \odot } , M _ { b } = 231 \pm 19 { M _ { \oplus } } , and M _ { c } = 86 \pm 7 { M _ { \oplus } } .
The Saturn-analog planet in this system had a planetary light curve deviation that lasted for 11 days , and as a result , the effects of the orbital motion are visible in the microlensing light curve .
We find that four of the six orbital parameters are tightly constrained and that a fifth parameter , the orbital acceleration , is weakly constrained .
No orbital information is available for the Jupiter-analog planet , but its presence helps to constrain the orbital motion of the Saturn-analog planet .
Assuming co-planar orbits , we find an orbital eccentricity of \epsilon = 0.15 { +0.17 \atop - 0.10 } and an orbital inclination of i = 64 ^ { \circ } { +4 ^ { \circ } \atop - 7 ^ { \circ } } .
The 95 % confidence level lower limit on the inclination of i > 49 ^ { \circ } implies that this planetary system can be detected and studied via radial velocity measurements using a telescope of \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } 30 m aperture .