  The absorption spectrum of CO$_2$ in the wavelength range 120\,nm --- 160\,nm
is analyzed by means of quantum mechanical calculations performed using
vibronically coupled PESs of five singlet valence electronic states and the
coordinate dependent transition dipole moment vectors. The thermally averaged
spectrum, calculated for T=190\,K via Boltzmann averaging of optical
transitions from many initial rotational states, accurtely reproduces the
experimental spectral envelope, consisting of a low and a high energy band, the
positions of the absorption maxima, their FWHMs, peak intensities, and
frequencies of diffuse structures in each band. Contributions of the vibronic
interactions due to Renner-Teller coupling, conical intersections, and the
Herzberg-Teller effect are isolated and the calculated bands are assigned in
terms of adiabatic electronic states. Finally, diffuse structures in the
calculated bands are vibronically assigned using wave functions of the
underlying resonance states. It is demonstrated that the main progressions in
the high energy band correspond to consecutive excitations of the
pseudorotational motion along the closed loop of the CI seam, and progressions
differ in the number of nodes along the radial mode perpendicular to the closed
seam. Irregularity of the diffuse peaks in the low energy band is interpreted
as a manifestation of the carbene-type \'cyclic' OCO minimum.
