Description and In-Flight Assessment of the POSEIDON-3C Altimeter of the SWOT Mission
, Nicolas Cuvillon 1, Alexandre Homerin 3, Sophie Le Gac 1, Claire Maraldi 1, François Bignalet-Cazalet 1, Marta Alves 2 and Laurent Rey 4
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsComments, recommendations and suggestions include:
1. As there are lots of technical terms, it could be better to place a table for the terms and abbreviations for reference.
2. Explanation of legends should be firstly shown under Figure 5 not Figure 6.
3. In the paragraph from Ln 529 to Ln 537, the authors should explain the reason for higher percentage of SWOT over sea-ice, coastal area than that of Jason 3.
4. In the first paragraph, detail information or reference should be given for the pre-defined desert zones shown in Figure 15.
5. For the ‘thermal drop from September 2023’ mentioned in the last sentence from Ln 613 to Ln 614, we can notice similar pattern before September 2023. Does this affect current conclusion?
6. Figure 21 and Figure 22, figures are not completely shown. Also, the explanation of the drop between July and September 2023 in Figure 22(a) should appear immediately after these figures, not in a place far from them.
7. In Figure 30, ‘Normalized Power’ is depicted. For easier understanding, the method for normalization should be mentioned to keep it with the context.
Comments on the Quality of English Language
Grammar and spelling should be check thoroughly. For example, following spellings and sentences should be corrected or improved.
1) Ln 174, add a come before “AGC” in the parentheses
2) L184, change ‘§2.1’ to subsection 2.a1 or section 2.1 for consistency
3) Ln 189, change POSEIDON-3 in the parentheses to POSEIDON-3C
4) Ln 203-204, grammar mistake
5) Ln 214, delete the first sentence which seems redundant, giving no practical meaning
6) Ln 215, change ‘correspond’ to ‘corresponds’
7) Ln 224, ‘set point’ should be ‘setpoint’? Delete ‘this’ before ‘a priori’
8) Ln 228, change ‘M3 to M4bis’ to ‘M3 and M4bis’ or ‘M3 & M4bis’
9) Ln 229, change ‘on the nadir altimeter onboard memory’ to ‘on its onboard memory’
10) Ln 236-237, delete ‘ provided that the onboard DEM information is correctly set’
11) Ln 258, change ‘echoe’ to ‘echoes’
12) Ln 266, change ‘characterized’ to ‘characterize’
13) Ln 270, ‘by passed’ should be ‘bypassed’
14) Ln 278 & 641, ‘ageing’ should be ‘aging’
15) Ln 324, ‘change ‘in’ behind ‘command’ to ‘is’
16) Ln 358, change ‘a sufficient amount of data’ to ‘sufficient data’
17) Ln 368, ‘subsections 2.3.2
18) Ln 425, ‘Poseidon3C’ should be ‘POSEIDON-3C’
19) Ln 466. the first ‘more’ should be deleted
20) Ln 544, abbreviation ‘DPU’ should be with its full name at first appearance
21) Ln 548, ‘RFU and PCU’ conflicts with ‘RFU and DPU’ in the first sentence of this paragraph
22) Figure 16 and its title, ‘LTM, THR, LTM,…’ should be mentioned or explained before their first appearance
23) Ln 580, ’10-days’ should be ’10-day’
24) Figure 19 and Figure 20, axis title should be added for the second y-axis
25) Ln 611, change ‘not linear decays, that is’ to ‘do not linearly decay, which is…’
26) Ln 613, change ‘from’ to ‘since’
27) Ln 618, change ‘the secondary band’ to ‘C-band’, change ‘showed’ to ‘shown’
28) Ln 644, change ‘which is why’ to ‘and therefore’
29) Ln 680, change ‘gains values’ to ‘gain values’
30) Ln 686, place ‘in’ before ‘Figure 26’
31) Ln 691, ‘turn on’ should be ‘turned on’
32) Ln 711, delete ‘altimeter’ in ‘altimeter drift’
33) Ln 729, change ‘on the one hand’ to ‘on one hand’
34) Ln 740, delete ‘in the reception’
35) Ln 742, change ‘temperatures’ to ‘temperature’
36) Ln 743, change ‘in April 2023, from 10th to 15th’ to ‘from April 10th to 15th, 2023’
37) Ln 746, delete the sentence starting with ‘Figure 3 2 focuses…’
38) Ln 747, change ‘while having different’ to ‘among’
39) Ln 757, add ‘as its predecessor’ after ‘the same calibration and tracking modes’
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsPlease see the attached set of points to consider.
Comments for author File: 
Comments.pdf
The paper is very well prepared and presented. However, the paper requires further proof reading by the authors. I provide some examples and suggestions in the attached file.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsGenerally the paper is well written with good use of English, with the level of errors no more than for a native English speaker. I merely itemise them below to provide an opportunity for the authors to tidy up these points. This is a very technical paper, going into the details on instrument calibration. This may not get many people who read it n full, but for those who do it will provide answers to almost all their questions on Poseidon-3C calibration. The paper makes some useful comparisons with its predecessor on JASON-3.
Mostly I provide a list of individual minor corrections. There are a few points that require clarification or replotting, but they will not change the narrative. I thus approve this submission for publication, provided that the authors CONSIDER my points. I do not need to review this again, so it is entirely up to them and the editor as to whether they feel my changes are appropriate. Graham Quartly
----------------------------------------------------------------------------------
60-day periodicity?
I was particularly interested in session 3.3.1 on periodic fluctuations in internal temperatures and the resultant (admittedly weak) effect on instrument characteristics. On line 551 they refer to a peridicity of about 60 days, but that was the value for the TOPEX/JASON orbit. If they look at their figures, they will see that for the SWOT orbit it is about 76 days. Please correct your value, but also can you refer to Quartly (2010) and Zawadzki et al. (2018) that have shown that (for the Jason satellites) this effect can come through into disseminated products (sigma0 and mean sea level respectively). This emphasises why it needs to be monitored and understood.
Broader comparison of instrument change
I note that this paper is mainly a comparison of Pos-3B and Pos-3C, but I think it would also be useful to make some passing references to the behaviour of other altimeters. There was a nice poster at "30 Years of Altimetry" meeting that brought together the change rates of various (current?) altimeters, but that work might not be published yet. There are similar plots to many of yours for S3A and S3B in Quartly et al. (2020) that cover SRAL's PTR, CAL1 and CAL2 modes and various changes in performance.
[12:116]
I am familiar with the removal of first 12 and last 12 gates from Poseidon waveforms. However I would NOT describe those remaining as "[12:116]". I understand that this is C/python terminology, but for may readers "13-116" (use of "13" and of hyphen) would be clearer.
4bis
The term "4bis" is not one I am familiar with in English. For an alternative to "4" I would use "4B"; however maybe "4bis" is the term in the official documentation, so should be left unchanged.
KaRIn acquisition
This paper covers the different acquisition and tracking modes for Pos-3C. It would be useful to have a clear statement of "Range acquisition for the swath instrument, KaRIn, is totally independent of that for Pos-3C." OR "Pos-3C is used to set the correct trackiing window for the swath instrument, KaRIn." OR "The swath instrument, KaRIn, operates in such a different manner that it doesn't need a DEM or a recption window."
Improvements to Figures
Some of the labelling in Fig. 11 is too small for all to read easily
Caption for Fig. 4b needs to specify that the purple points are the flagged ones rather than the cream coloured ones. Text above figure 14b is misleading suggesting that only 0.13e-03% of ocean are flagged, when one can see large areas of sea-ice. Either remove text above or adjust it to specify in non-sea-ice non-coastal areas.
The HK temperatures on Figs 19, 20 & 29 are useful but need to be in a darker grey to show up better. It would also be useful to have them on left-hand side of Fig. 25; if it cannot be fitted on the axes already present then maybe add as an extra left-hand panel just so that reader can see the close agreement.
Fig. 23b is missing (there are two copies of position, not one of position and one of power)
Nouns used as adjectives
A peculiarity of English is that when a noun is used as part of an adjectival phrase, it is never in the plural. Thus it should be "128-point FFT" (l.95), "16-bit coding" (l.435) , "CAL2 parameter variations" (l. 672) & "gain values" (l. 680)
Quartly, G.D. (2010) Jason-1/Jason-2 Metocean Comparisons and Monitoring, Marine Geodesy, 33: 1, 256 -271 doi: 10.1080/01490419.2010.487794
Quartly, G.D. et al. (2020) The Roles of the S3MPC: Monitoring, Validation and Evolution of Sentinel-3 Altimetry Observations. Remote Sens. 12, 1763 doi:10.3390/rs12111763
Zawadzki et al. (2018) Investigating the 59-Day Error Signal in the Mean Sea Level Derived From TOPEX/Poseidon, Jason-1, and Jason-2 Data With FES and GOT Ocean Tide Models. IEEE Transactions on Geoscience and Remote Sensing. doi: 10.1109/TGRS.2018.2796630
----------------------------------------------
l. 66, 703, 704, 713 "special" is a more appropriate word than "exceptional".
l.76 I think it is more correct to write "reduce peak emitted power"
l. 82-90 "td" looks like the product of two terms; clearer would be t sub d (use of subscript). However I also note Fig. 1 contains "t=2D/c" and features Delta t. Please make sure that nomenclature in Fig. 1 and in lines 82-90 are consistent, with the relevant variables clearly defined.
l. 100 Please add "add control" for PCU.
l. 105 should be "corrected for in ..."
l. 109-110 Refers to biases affecting range but then includes atmospheric attenuation in the list (which affects sigma0).
l. 116 "heritage from POSEIDON"
l. 121 "This step is the so-called retracking."
l. 131 replace "dynamic" with "range of attenuation values".
l. 140 "An example of ... is shwon ..." ("is" to agree with singular subject.)
l. 143 "raw" is better than "rough"
l. 148 Use "redundant" or "duplicated" rather than "redounded".
l. 164, 232, 321, The term "Mo" is not widely known; it is better to use "Mb".
l. 175-176 The authors refer to a "a single rception chain" -- was this the same for JASON2 and JASON3 or new for Pos-3C? Please clarify in text whether this was different from that on predecessors.
l. 178 Beamwidth of 1.28 degs given. Please add "for Ku-band" and also supply value for C-band.
l. 243 "The user has the possibility to authorize transitions ..." Please add a line explaining why a user might wish to do so i.e. what are the potential gains?
l. 261 Instead of "make use of" write "allow for" or "compensate for".
l. 270 "bypassed" should be one word.
l. 274 & l. 280 The authors write "regularly" and "periodically" but I wanted to know how often e.g. daily or once every 3 months. This is detailed much later in the paper, but it could be helpful to spell out here that it's "three times a day".
l. 287 "presence of an analog ..."
l. 333 "started" not "stated".
l. 357 specifies "2 weeks in each tracking mode", but then Table 2 shows only 1 week each for M2 and M3. Please clarify.
l. 369 "entered into"
l. 382 "always greater than"
l.383, 385, 392 "repeat" is better than "repetitive".
l. 396 delete "we detected"
l. 397 should this be "increased data loss" rather than "reduced data loss"?
l. 417 "extracted from"
l. 427 I think this should be "quantization" not "quantification"
l. 436-438 Comment on different trailing edge was very useful.
l. 442 I suggest caption should start "Typical waveform echoes shown by104 useful gates ..."
l. 455 Delete "in" to leave "expected hydrological target".
l. 479 Change "accounts for" to "indicates"
l. 486, 765 It should be "closed" rather than "close" (you normally have this correct in this paper).
l. 519 Specify "one full 21-day cycle".
l. 525 "It also contains ..."
l. 526 Delete the word "purposes", as it is superfluous.
l. 527-529 Give dates of cycle 6, as reader may wish to know what season this corresponds to. Also please comment on the much greater percentage of SWOT data flagged as saturated over sea-ice. Is this simply because it surveys further poleward than Jason-3 or is there some other reason?
l. 543 Change subheading to "Instrument temperature". You have not yet defined HK and "Housekeeping temperatures" doesn't mean much until you explain what that is.
l. 546 I would write "house-keeping telemetry".
l. 553 change "less important for" to "smaller than".
l. 560 In Fig. 16 you use "THR", "LTM" and "DC/DC". Either define clearly or simply remove those terms from final versions of figures 16 & 17.
l. 613 Probably should read "thermal drop in September 2023", but what is the cause of this transient feature? An SEU? A necessary switch off?
l. 617 You cannot write "Both sides are stable in time" without addressing the step features in Fig. 22a.
l. 645 Delete "whole"; it is superfluous when you also write "lifespan".
l. 650 Possibly "inferred measurements" is better than "scientific variables"
l. 682 "0" should be superscript.
l. 683 refers to AGC calibration "every 3 months in routine", but Fig. 27 shows them every 2 weeks. Please clarify -- is it just that "routine" starts in 21-day phase?
l. 705 "These activities are aimed ..."
l. 709 "over dedicated areas"
l. 719 Change "considered" to "applied".
l. 732 What is "dBW"?
l. 733 "similarly stable as"
l. 736 "sequence is aimed ..."
l. 740, 749 "spurious" is an adjective, not a noun, so you need "spurious points".
l. 744 I think a better word than "answers" is "analyses" or "records".
l. 767 "better performances than its ..."
Comments on the Quality of English LanguageGood
Author Response
Please see the attachment.
Author Response File: Author Response.docx
