The measurements were taken from
(1) S. Saito, Y. Endo, and E. Hirota, 1986, J. Chem. Phys. 84, 1157; and from
(2) H. Ozeki and S. Saito, 2003, J. Mol. Spectrosc. 219, 305.
The dipole moment is from an SCF ab initio calculation cited in (1). Supposedly, there is a b dipole component of about 0.5 D, but b-type transitions still cannot be reliably predicted at present.