We measure planet occurrence rates using the planet candidates discovered by the Q1-Q16 Kepler pipeline search .
This study examines planet occurrence rates for the Kepler GK dwarf target sample for planet radii , 0.75 \leq R _ { p } \leq 2.5 { R _ { \oplus } } , and orbital periods , 50 \leq P _ { orb } \leq 300 days , with an emphasis on a thorough exploration and identification of the most important sources of systematic uncertainties .
Integrating over this parameter space , we measure an occurrence rate of F _ { 0 } =0.77 planets per star , with an allowed range of 0.3 \leq F _ { 0 } \leq 1.9 .
The allowed range takes into account both statistical and systematic uncertainties , and values of F _ { 0 } beyond the allowed range are significantly in disagreement with our analysis .
We generally find higher planet occurrence rates and a steeper increase in planet occurrence rates towards small planets than previous studies of the Kepler GK dwarf sample .
Through extrapolation , we find that the one year orbital period terrestrial planet occurrence rate , \zeta _ { 1.0 } =0.1 , with an allowed range of 0.01 \leq \zeta _ { 1.0 } \leq 2 , where \zeta _ { 1.0 } is defined as the number of planets per star within 20 % of the R _ { p } and P _ { orb } of Earth .
For G dwarf hosts , the \zeta _ { 1.0 } parameter space is a subset of the larger \eta _ { \oplus } parameter space , thus \zeta _ { 1.0 } places a lower limit on \eta _ { \oplus } for G dwarf hosts .
From our analysis , we identify the leading sources of systematics impacting Kepler occurrence rate determinations as : reliability of the planet candidate sample , planet radii , pipeline completeness , and stellar parameters .