  The latest version of the HITRAN molecular spectroscopic database,
HITRAN2020, has recently been released featuring many updates, including
line-by-line broadening parameters (and their temperature dependence)
appropriate for the dominant constituents of planetary atmospheres. In this
work, line shape codes suitable for calculating microwave spectra have been
implemented within the HITRAN Application Programming Interface (HAPI). These
new additions allow for spectroscopic calculations of microwave absorbing
species pertinent to current and future studies of the atmospheres of Jupiter
and Venus, and more generally for the atmospheres of gas giants and rocky
planets. The inversion spectrum of the NH$_3$ molecule broadened by H$_2$, He
and H$_2$O dominates the microwave region of Jupiter. Whereas for Venus,
accurate spectroscopic data of SO$_2$ broadened by CO$_2$ is necessary in order
to determine its significance, if any, on the reported detection of PH$_3$ in
the Venusian upper cloud deck. Comparisons have been made to available
microwave laboratory opacities and the following results illustrate that HITRAN
data can be used in conjunction with HAPI to reproduce the existing
experimental measurements and provide reliable calculation of planetary
opacities. Users should be mindful regarding selection of appropriate
parameters in HITRAN and selecting suitable line shape functions in HAPI,
depending on the spectral region, target molecular species, as well as ambient
chemical and thermodynamic conditions.
