The Strategic High-Altitude Radiance Code, SHARC-3, calculates atmospheric radiance and transmission over a 1 - 40 microns spectral region for arbitrary lines of sight (LOS) between 50 and 300 km altitude. It models radiation due to nonlocal thermodynamic equilibrium (NLTh) molecular emissions, the dominant sources at these altitudes. This third release of SHARC has been upgraded to model LOS's across and near the atmospheric terminator. It interpolates between several atmospheric profiles, which represent variations in species concentration through that region. In addition the spectral distribution of sunlight which has passed through the lower atmosphere is approximated by a series of optical depth functions for that part of the solar path below 50 km altitude. Auxiliary atmospheric profile generator and slit function programs enhance the capabilities of the code. Data for the previously supported major radiators have been upgraded where necessary, and CH4 and minor isotopes of H2O have been added. As before, auroral regions can be embedded in quiescent atmospheres, and industry-standard kinetics and radiation transport modules have been employed. This manual outlines the scientific basis of the code, details steps for code installation and use as supplied, and indicates how the user may modify the supplied chemistry if desired.