Upper: LTE computations of the O₂ column density N(O₂) as a function of the temperature T for an extended homogeneous source, to yield a line intensity of 1.0 K km s^-1. For optically thin emission, intensity and column density are linearly related. 119 GHz: blue dots; 487 Ghz: black solid line; 774 GHz: red short dashes. Lower: the ratio of the 487 GHz integrated line intensity to that at 774 GHz is shown by the curve for a range of temperatures. For O1 (=O12), the error shown by the dashed line formally extends to the unplausible result of nearly 10³ K. For O4, the limit symbols are for the lower limit on the intensity ratio and the upper limit on the temperature, respectively.