Illustrative example of the upper limit derivation methodology for OCS and H₂S. Grey lines indicate the individual 2N vertical profiles of OCS retrieved according to (solid) step 3 and (dotted) step 4, for each row on the detector array. The solid blue line shows the weighted mean abundance profile, , derived fromthe individual retrievals, with the standard deviation, , shown in the shaded blue region. The solid orange line shows the profile of smoothed over altitude. The red shaded region shows the altitude range for which a 1σ detection was determined, i.e. where the value of is lower thanthe value of .