Developed by the University of South Florida, exclusive distribution by Ontar Corporation(Released September 10, 2009) Hitran-PC is a PC computer program that can calculate or model the high-resolution ( < 0.01 cm-1 ) optical transmission spectrum of the atmosphere and of selected gases using primarily the HITRAN Line-by-Line database. Hitran-PC has been developed over the past 30 years, with various levels of improvements and capability, starting with Version 1.0 in 1991. The latest version, Hitran-PC 5.0, incorporates updates to the internal structure of the program which enabled much faster execution times and allowed combining of line-by-line spectra in a real time format making it possible to switch between individual lines and subsequent isotope, molecule totals and composite without recalculations. Additional databases were added including line-by-line and cross-sectional GEISA, and the online EPA and the Max Plank database of UV and visible spectra for added capabilities. Various other changes and interface improvements have been implemented as well.
The overall operation of Hitran-PC 5.0 is shown in the following figure. As can be seen, the user can specify the path length, temperature, concentration, line shape (Pressure, Voigt, etc.), and other parameters pertaining to the transmission of the atmosphere. These startup parameters can also be stored in a configuration file for easy use at a later time. The startup parameters are then used along with atmospheric models of pressure/temperature/altitude to model the geometry of the optical transmission path through the gas or atmosphere. Both horizontal and slant path spectral calculations can be made.