The terminology other refers here to other spectral range, rather than other spectral line. SWAS "receiver 2" (92.3 GHz LO frequency) was normally tuned to observe ¹³CO at 551 GHz and H₂O at 557 GHz in the lower and upper sidebands, respectively. When it was tuned to the ortho-H₂¹⁸O 1(10)-1(01) line at 549 GHz in the lower sideband, the upper sideband was tuned to a frequency range that contains no known lines. The SWAS project distributed these other spectral range data for completeness.