Review of Huygens SSP dataset for PSA Report of the Huygens Data Review Data set: SSP Preamble As an independent reviewer of the Huygens archive, you are asked to review a PDS data set. This review must tell if the data set is ready to be release to the scientific community. Please note that the PDS compliance is checked independently by the Huygens Data Archive Team, therefore you do not have to concentrate on this aspect. This data set contains the following folders: CATALOG: list of ASCII files required by the PDS standard. DATA: contains the data products and the associated PDS labels. DOCUMENT: contains the documents and the associated labels INDEX: contains index files The following folders are optional: SOFTWARE: contains software BROWSE: contains browse images GEOMETRY: contains any data products related to geometry. CALIB: contains calibration files, tables or reports. EXTRAS: contains additional information, files, etc,, provided by the teams. We ask you to answer the following questions: First topic: The Experimenter to Archive Interface Control Document (EAICD) is part of the DOCUMENT folder. As you may know, this document is very important since it describes the content of the archive. Question #1: In your point of view, is the document clear and understandable? Do you miss some important information? It looks OK. Question #2: Is the EAICD coherent with the content/structure of the data set? The EAICD mentions calibrated data. The data set does not contain what I would consider calibrated data. Second topic: the CATALOG directory The CATALOG files are ASCII files intended to provide critical information for understanding the contents and usage of the archived data set. TARGET.CAT and SOFT.CAT are required by PDS but are not very useful for the Huygens data. Question: Are these documents clear and understandable? Do you miss some important information? Please give your opinion on the files: AAREADME.TXT | |- INST.CAT Description of the MOLA instrument. | |- INSTHOST.CAT Description of the MGS spacecraft. | |- MISSION.CAT Description of the MGS mission. Change from MOLA |- SSP_1177.LBL label for SSP_1177.ASC ans SSP_1177.PDF Change ans to and CATINFO.TXT formatting of columns in table needs improving DATASET.CAT File does not contain much information. Cutting and pasting details on each sensor and its modes of operation from other documents into this one would be helpful. PERSONNEL.CAT Called PERSON.CAT. Contents are OK INSTHOST.CAT No comments. INSTRUMENT.CAT Called INST.CAT It discusses the Huygens mission in the future tense, not past ratio of (the ratio of specific heats) Looks like a symbol for gamma wasn't converted into ASCII Formatting of citations: Geake et al (1994). GEAKEETAL1994 preferred Same for Healy See SSP_1177.PDF for details. Would this reference be better as DOCUMENT/SSP_1177.PDF? REFERENCE.CAT REFERENCES.CAT should include references to SP1177 paper even though it is included in the DOCUMENTS Add Space Science Reviews paper and Zarnecki Nature paper MISSION.CAT No comments SOFT.CAT PDS standars is missing a letter d VOLDESC.CAT has some nasty binary stuff at the end that I can't read Third topic: Review of the DATA directory. This is obviously one of the most important folders. Question #1: Is the structure (in terms of subdirectories) clear and useful? Are the filenames (explained in the EAICD document) clear enough? The structure and filenames are clear. The relationship between the filename and the file contents is very clear and logical. Question #2: Do you think that the label files are useful to understand the data files? In case of tables data products, we recommend checking the COLUMN objects: unit, exact numbers of columns etc… The descriptions of each column are very short. They need to contain more information. Example: SSP_PER_123456_0_R_ATMOS.LBL OBJECT = COLUMN COLUMN_NUMBER = 7 NAME = "CON_OUTPUT (V)" DATA_TYPE = ASCII_REAL START_BYTE = 101 BYTES = 20 DESCRIPTION = "12 bit sample" UNIT = VOLTS END_OBJECT = COLUMN Example from MGS Radio Science dataset: OBJECT = COLUMN NAME = "RAY PATH DIRECTION" COLUMN_NUMBER = 6 DATA_TYPE = ASCII_REAL START_BYTE = 82 BYTES = 6 FORMAT = "F6.1" UNIT = "DEGREE" DESCRIPTION = "The angle between local north and the direction of radio signal propagation at the point of closest approach to Mars. Angle is measured positive from local north toward local east. A signal traveling from west toward east would have a ray-path-direction of 90 degrees." END_OBJECT = COLUMN This is much more useful to the data user There are several typos where the name of a column suggests a voltage and the unit/data type suggests a number (and vice versa). Column 5 of SSP_DEN_123456_0_R_ATMOS.LBL, Columns 5,6,7 of SSP_PER_123456_0_R_ATMOS.LBL. I'm sure there are others. Question #3: You have to be sure that the data files can be read by any users. In case no software is provided, were you able to handle the files easily? Yes Question #4: In case that the data set contains raw data and calibration information: please comment the possibility to calculate calibrated data. In case that the data set contains raw, calibrated data and calibration information: comment the reproducibility of the process to obtain calibrated data. Where is the CALIBRATED data? I see only raw data. This is a major problem. I cannot derive properties of Titan from many of the list voltages or sample numbers. ACC-E. Vast quantities of information are given in SSP_CAL.ASC How does the user convert "Acc-E voltage" (column 6 of SSP_ACCE_057_1_R_IMPACT.TAB) into acceleration in ms-2? ACC-I first line of SSP_ACCI_057_1_R_IMPACT.TAB 8869.7700 4 1 1 4082 -0.0342 Column 5 = 12 bit value, Column 6 = ACC-I voltage SSP_CAL.ASC says: 0 counts minus 5V 2048 0V 4096 plus 5V I don't see how 4082 = -0.0342 volts based on SSP_CAL.ASC SSP_CAL.ASC says: 1V 18.071g I don't know whether (A) a measured voltage of 1V corresponds to an acceleration of 1g or (B) a change in voltage of 1V corresponds to a change in acceleration of 1 g. How many ms-2 are in one g? Voltages are stated to 4 decimal places, so g=10 and g=9.8 are very different. API-S. SSP_APIS_4_0_R_PROX.LBL contains "API-S proximity sample (V)" Is this a measure of signal travel time, effective acoustic cross-section, or something else? SSP_CAL.ASC doesn't tell me how to convert volts into a physically useful measurement. Same applies to SSP_APIS_23_0_R_ATMOS.TAB API-V What is the difference between columns 6 and 7? I suspect it refers to a pulse going in one direction or the other direction, but I'm not sure. The delay time is given. What distance should be used to get the speed? SSP_CAL.ASC gives the front plate separation and the crystal separation. Should one of these be used? If so, which? SSP_CAL.ASC mentions errors at low pressures. Where are those errors described in more detail? DEN How does the user derive densities from voltages? SSP_CAL.ASC says: Therefore One Bit sensitivity at Titan is: 10.67867628 kgm^-3 What is the offset? Ie, does sample=3412 correspond to 3412*10.68 kgm-3? I doubt it. HK looks reasonable IMPACT Same issues as other subdirectories PER SSP_CAL.ASC says how temperature (PER_T) can be obtained from "PER Diode Volts" (DV) and how relative permittivity can be obtained from PER Volts (PV) using V0, which is derived from PER_T. Do DV and PV corresponds to CON_OUTPUT (V) and PER_OUTPUT (V)? If so, which is which? REF I think SSP_CAL.ASC gives sufficient information to use this dataset. THP I'm not sure whether or not SSP_CAL.ASC gives sufficient information to convert these voltages into temperatures. It definitely doesn't give enough information to convert the voltages into thermal conductivity and diffusivity. TIL SSP_CAL.ASC has two equations for TIL-X Voutput = 1.246 + (0.017395*THETA) (+2.50V) THETA=((TILXH*2.5/4.5) -1.246))/0.017395 (+4.50V) What are the units of THETA? Which equation should be used for the flight data? Are the locations of the tilt sensors and the direction of their axes stated clearly anywhere in the PSA archive? I didn't look for them, but such information is necessary. Assuming that the PSA user can get meaningful data products, like the speed of sound, from these files, the user also needs some sense of the measurement uncertainty to analyse the data. What are the measurement uncertainties? Question #5: What is your opinion on the completeness of the data? Raw data are complete. However, users need data converted into physically meaningful quantities, not just numbers and volts. Question #6: Are you able to compare the archived data with the results published in Nature? No. Fourth topic: the DOCUMENT directory. The ASCII format is required for any document needed to understand the data. Question #1: Is the set of documentation complete and sufficient for data calibration and processing, data visualization and analysis? As noted above, numbers and volts cannot be converted into properties of Titan's atmosphere and surface. Question #2: Are some documents missing? Are some documents useless? Many of the documents have been published, either as PhD theses or as journal articles. Citations to the appropriate primary sources should be included in the accompanying LABEL files. Add Zarnecki Nature paper and SSP Space Sci Rev paper to DOCUMENTS if possible. DOCINFO.TXT Lorenz is missing The text of Lorenz PhD includes references to several documents, but there is no list of those references at the end of the Lorenz PDF file. Question #3: Are the ASCII documents well formatted? SSP_1177.ASC formatting needs to be improved. SSP_EAICD.ASC Some of the tables are hard to read due to their lack of formatting I see TBC in the text a lot. Things should be confirmed by now. SSP_SUM.ASC has lots of gaps where figures used to be Question #4: Some documents do not have the ASCII companion. Do you think that some of them are important and that they should be converted into ASCII? Personally, I suspect that .PDF files will be easier to read in the future than .DOC files. Can .PDF copies of the two .DOC files be provided (in addition to the .DOC files?) I know that .ASC copies are given, but .PDF files will contain the figures and proper formatting. PSA users with Unix machines will not be able to read .DOC files. They should not be required to purchase (A) a PC and (B) Microsoft Windows to read these documents. Fifth topic: the optional directories Please comment the content of these directories: - BROWSE: - SOFTWARE: - GEOMETRY: - EXTRAS: CALIB SSP_CAL.ASC Mark Leese and RAL. Initially generated by AJB during visit with MCT to IWF Are these acronyms defined anywhere? I'm not sure how to use the information in this document. I hope it tells me how to convert measured voltages or digital numbers in physical quantities such as acceleration or speed. I would like to see something like: subsensor (eg ACC-I) Raw quantity and units (eg measured voltage in volts) Derived quantity and units (eg acceleration in ms-2) Form of calibration equation (eg third-order polynomial) Values of coefficients in above equation Units of g are mentioned. How many ms-2 are in one g? 10? 9.8? Conclusion: In your opinion, is this data set ready to be released to the scientific community? The raw data are well-organized and complete. However, they are much less useful to the scientific community than derived quantities such as acceleration in ms-2 or speed of sound in ms-1. These derived quantities should be added to this dataset. List here the minor and editorial corrections (if any): 1) 2) 3) List here the major corrections (if any): 1) 2) 3) Additional comments, if any: