  The rovibronic structure of A$^2\Sigma^+$, B$^2\Pi$ and C$^2\Pi$ states of
nitric oxide (NO)is studied with the aim of producing comprehensive line lists
for its near ultraviolet spectrum. Empirical energy levels for the three
electronic states are determined using the a combination of the empirical
MARVEL procedure and ab initio calculations, and the available experimental
data are critically evaluated. Abinito methods which deal simultaneously with
the Rydberg-like A$^2\Sigma^+$ and C$^2\Pi$, and the valence B$^2\Pi$ state are
tested. Methods of modeling the sharp avoided crossing between the B$^2\Pi$ and
C$^2\Pi$ states are tested. A rovibronic Hamiltonian matrix is constructed
using variational nuclear motion program DUO whose eigenvalues are fitted to
the MARVEL energy levels. The matrix also includes coupling terms obtained from
the refinement of the ab initio potential energy and spin-orbit coupling
curves. Calculated and observed energy levels agree well with each other,
validating the applicability of our method and providing a useful model for
this open shell system.
