This paper uses data from several satellite instruments to determine the trend in mesospheric ozone since 1992. This task is challenging because of the limited number of instruments that made observations and the diversity of sampling and detection methods. The paper is well-written but in some cases lacks sufficient detail.

The paper mentions that ozone trends have been previously found to be related to temperature trends. Beyond that, there is no exploration of the possible factors that would lead to the trends found.

Major comments

Please indicate the ozone units used (volume mixing ratio) at the beginning of Section 2, if not before. Also, please indicate what density information was used in the conversion of GOMOS measured ozone density profiles to mixing ratio. Did this follow a similar procedure to that used for the altitude to pressure conversion? If not, are densities in the two conversion processes consistent?

Why is the seasonal cycle calculated using only a portion of the time series for some instruments (page 12)? What criterion is used to select the range? Is the resulting cycle affected by high variability such as irregular occurrence of sudden stratospheric warmings?

The MLR uses a piecewise linear term for representing trends. Can you provide some justification for this? How sensitive are the results to the precise year specified for the turnaround point? Please show or discuss the trend before 1997.

Minor comments

(Note that the line numbers are not accurate on my pdf copy (00 to 99, repeating) so text referred to in my comments will be identified by page number and line number.

(Abstract) “near the mesopause” It’s probably better to give an altitude since the mesopause location is quite variable (around 80-85 km in summer high latitudes; around 95-100 km elsewhere).

(p. 8; line 96-04) Information on SOFIE is absent.

(p. 8; line 19, and elsewhere throughout the text) “wintertime (DJF)” It is recommended that you avoid a northern hemisphere bias by only using “wintertime” when presenting and discussing NH latitudes.

(p. 13, line 97) what weighting is used?

(p. 14, line 10) Please provide more justification for why HALOE and SOFIE are treated differently than the other datasets. The idea of adjusting for an offset is particularly a concern in the case of HALOE because its timeseries is so important for the calculation of the day trend.

I recommend moving Figure S4 from the Supplement to the main paper.

In the Summary section, please indicate that the trends are calculated on pressure levels.