UCNA Systematic Uncertainties

The UCNA experiment uses ultracold neutrons to measure the $A$ beta-decay angular correlation between electron emission direction and neutron spin. In 2007, an initial ``proof-of-principle'' statistics-limited data set was taken, providing a 4.4\% determination of $A_0$. For the higher statistics data set taken in 2008 and 2009, systematic uncertainties become increasingly important. This talk is an overview of the main systematic uncertainties (including decay-beta scattering and energy reconstruction, neutron polarization, and backgrounds) contributing to a 1.4\% determination of $A_0$ from the 2008-2009 data.