  Models of Galactic 1.275 MeV emission produced by the decay of the
radionuclide $^{22}$Na have been computed. Several frequency-spatial
distributions of novae have been investigated using recent results of nova
rates and spatial distributions of novae in our Galaxy. These models allow us
to estimate the lower-limit of the $^{22}$Na mass ejected per ONe nova
detectable with the future spectrometer (SPI) of the INTEGRAL observatory as a
function of the frequency-spatial distribution of ONe novae in the Galaxy.
Calculations using recent estimations of the expected $^{22}$Na mass ejected
per ONe nova show that the detection of the Galactic emission of 1.275 MeV
photons will be difficult with the future spectrometer of the INTEGRAL
observatory, whereas the cumulative emission around the Galactic center has
some chances to be detected during the deep survey of the central radian of the
Galaxy.
