Log-log plot of the HO/HO absorption line area ratio as a function of production rate for 7 different terminal expansion velocities (0.4–1 km s^-1). For each velocity, as the production rate is increased, the ratio between the two absorption lines decreases from about 500 to approximately 1. The measured ratio and expansion velocity from the MIRO dataset can be used to derive estimates for the production rate from these curves.