The authors should address the comments from both referees, providing a detailed response. From an editorial point of view, the authors should do the following:

(i) Include at the end of the Introduction a brief paragraph outlining the subsequent discussion in the paper;

(ii) Make an effort to quantify statements, such as in L. 371.

(iii) Indicate in figure captions what the end range of the colour scale signify.

The authors should address the comments below, which mainly concern that (as I understand it) the OSSE deals with TEMPO-like and IASI-3-like instruments. The authors should also specify if the OSSE is likely to be overoptimistic, for example, in the conclusions.

If the inference above is incorrect, please indicate to me why this is the case.

L. 29: As I understand it, the configuration you use is not quite that of TEMPO. Thus, I think you should say something like:”…a configuration designed to represent the best current estimate of TEMPO…”.

L. 42: Please introduce acronym for ppbv.

L. 54: As for L. 29, I think you should say something like: “…from a configuration designed to represent the best current estimate of the NASA …”.

L. 104: I suggest here you remind the reader that vis stands for visible.

L. 113: For alphabetical discrimination between the same dates, please use the order: “…Claeyman et al., 2011; Zoogman et al., 2011, 2014…”.

L. 127: Style point: I suggest you do not start a paragraph with an acronym.

L. 133: Ideally, the second model is independent, but this is not always done. Perhaps rephrase?

L. 138: I think the description of TEMPO should be modified to follow the points above for L. 29, 54.

L. 172-173: This sentence is clumsy – please reword. Also “better” than what?

L. 177-178: Please be consistent with points above for, e.g., L. 29, in the description of TEMPO.

L. 179-180: I think you should specify that the LEO instrument is not IASI-3, but is representative of it.

L. 185: I think here you mean the TEMPO instrument to be launched, so please indicate this.

L. 198: I think you should specify that the TEMPO and IASI instruments discussed here are those to be launched, not those discussed in the paper.

L. 222: For completeness, you should remind the reader that the TEMPO instrument considered is intended to represent the best current estimate of TEMPO.

L. 223, 234, 236, 309, 313, 314, 326, 328, 332, 340, 343, 363: To be consistent, I suggest using “TEMPO-like”, or something else conveying this meaning.

L. 227, 313: To be consistent, I suggest using “IASI-3-like”, or something else conveying this meaning.

L. 232: If this assumption is likely to make the OSSE over-optimistic, please indicate so here.

L. 271: Although you refer to Zoogman et al. (2011), I suggest you remind the reader why you choose 29%.

L. 282: Use “…Eq. (2)….”.

L. 289: Omit space before the full-stop “.”.

L. 315: I think you should use “…the TEMPO-like instrument for…”.

L. 344: I think you should use “The planned TEMPO instrument will provide…”.

L. 361, 366, 368, 369: “…from the TEMPO-like instrument…”.

L. 377: I think you should use “…of data from a TEMPO-like instrument using…”.

L. 389-390: I think you should use “…that the TEMPO-like geostationary…”.

L. 394-395: I think you should use “…We provide evidence that suggests that a LEO satellite instrument flying concurrently with TEMPO would provide no…”.

L. 403: I think you should use “…provided by a TEMPO-like instrument over…”. Is your OSSE likely to be overoptimistic? If so, mention here.

L. 419: In Fig. 1 caption please indicate what the ends of the colour range show: red/blue, relatively high/low values.

L. 423: “…to a TEMPO-like instrument, while…”.

L. 442, 458: “…TEMPO-like observations…”.

L. 447, 455: “…TEMPO-like…”. Heading for Fig. 5 should have “TEMPO-like”.

L. 458: Inset for Fig. 6 should have “TEMPO-like”.

L. 469: “…TEMPO-like…”. Heading for Fig. 7 should have “TEMPO-like”.

The authors have addressed the main tenor of my points. I would ask them to address the following two points before uploading the paper to ACP - the second point should definitely be adhered to:

L. 42: I would prefer it if you provided the acronym for ppbv.

L. 384: Because people often just read the abstract and conclusions of the paper, I would ask you to specify here that the configuration is TEMPO-like, thus something along the lines: “…of the TEMPO data, in a configuration designed to represent it according to the best current estimate of its future instrument characteristics, using…”.