Data Set Overview : This data set contains products acquired by radio science experiment using Ultra-Stable Oscillator (USO) onboard the Venus Climate Orbiter (VCO, also known as PLANET-C and AKATSUKI) spacecraft. This data set uses the Committee on Data Management and Computation (CODMAC) data level numbering system. The RS OCCs bending angle and temperature/pressure profiles are considered Level 5 or Derived Data. Bending angle profiles are derived from Level 3, and temperature/ pressure profiles are derived from temperature/pressure profiles. In the VCO RS numbering system, bending angle profiles are Level 3, and temperature/pressure profiles are Level 4. Parameters : The bending angle as a function of the impact parameter (VCO RS Level 3), and the temperature and the pressure as functions of the altitude (VCO RS Level 4) Processing : Atmospheric profiles are obtained from the frequency variation caused by the Venus atmosphere observed at the tracking station, termed ``atmospheric Doppler shift''. This frequency component is given in the VCO RS Level 2 data as ``RESIDUAL CALIBRATED X-BAND FREQUENCY SHIFT''. Although the atmospheric Doppler shift should be zero in the portion of the data above the height of the ionosphere, we usually observe a smoothly-varying frequency component that is attributed to the error in the trajectory data. To remove this frequency offset, we fit a linear function to this portion of the frequency time series and subtract it from the whole time series; this procedure is termed ``baseline fit''. The atmospheric Doppler shift corrected by baseline fit is combined with the trajectory data to calculate the bending angle and the impact parameter, which are given in VCO RS Level 3 data. The relationship between the bending angle and the impact parameter is converted to a refractive index profile through Abel transform. For the integration with respect to the impact parameter in Abel transformation, the bending angle needs to be a single-valued function of the impact parameter. However, the bending angle sometimes becomes a multivalued function of the impact parameter at low altitudes due to low signal-to-noise ratios. To suppress such multivalued behavior, the integration time is increased in those regions, and extreme outliers are removed by visual inspection. The deviation of the refractive index from unity is the sum of the contributions from the neutral atmosphere and the ionosphere. The neutral and ionospheric contributions are almost separated in altitude with the boundary around 100 km altitude; this enables us to retrieve the vertical profiles of the neutral atmospheric density and the electron density separately. The vertical profile of the neutral atmospheric pressure is derived from the density profile by integrating the equation of hydrostatic equilibrium. The top boundary condition for the temperature, which is needed for integration, is determined empirically. The temperature profile is calculated from the density and the pressure using the ideal gas law. In the analysis above, we adopt a refractive volume of 1.811*10**-17 m**3 that is appropriate for the composition of 96.5% CO2 and 3.5% N2, the mean molecular mass of 43.44 u, and GM of 3.24858592*10**5 km**3 s**-2. The derived temperatures and pressures constitute VCO RS Level 4. Data : Overview -------- Table data containing the temperature, the pressure and supplementary parameters as functions of the distance from Venus center. File format and structure ------------------------- The files with the extension ``.tab'' under ``data'' directory are table format, i.e., ASCII text file with fixed column length's for each line. Each column of the table for Level 3 data is as follows: No. Content --- -------------------------------- 1 SAMPLE_NUMBER 2 UTC_TIME 3 EPHEMERIS_SECONDS 4 RESIDUAL CALIBRATED X-BAND FREQUENCY SHIFT 5 RESIDUAL CALIBRATED X-BAND FREQUENCY SHIFT AFTER BASELINE FIT 6 RECONSTRUCTED_TRANSMIT_FREQUENCY 7 RADIUS 8 SIGMA_RADIUS 9 BENDING_ANGLE 10 SIGMA_BENDING_ANGLE 11 REFRACTIVE_INDEX 12 REFRACTIVITY 13 SIGMA_REFRACTIVITY 14 SIGNAL_LEVEL 15 DIFFERENTIAL_DOPPLER 16 IMPACT_PARAMETER 17 SIGMA_IMPACT_PARAMETER 18 LONGITUDE 19 LATITUDE Each column of the table for Level 4 data is as follows: No. Content --- -------------------------------- 1 SAMPLE_NUMBER 2 UTC_TIME 3 EPHEMERIS_SECONDS 4 RADIUS 5 LATITUDE 6 LONGITUDE 7 GEOPOTENTIAL 8 GEOPOTENTIAL_HEIGHT 9 PRESSURE (LOWER TEMPERATURE AT BOUNDARY) 10 SIGMA PRESSURE (LOWER TEMPERATURE AT BOUNDARY) 11 PRESSURE (MEDIUM TEMPERATURE AT BOUNDARY) 12 SIGMA PRESSURE (MEDIUM TEMPERATURE AT BOUNDARY) 13 PRESSURE (HIGHER TEMPERATURE AT BOUNDARY) 14 SIGMA PRESSURE (HIGHER TEMPERATURE AT BOUNDARY) 15 TEMPERATURE (LOWER TEMPERATURE AT BOUNDARY) 16 SIGMA TEMPERATURE (LOWER TEMPERATURE AT BOUNDARY) 17 TEMPERATURE (MEDIUM TEMPERATURE AT BOUNDARY) 18 SIGMA TEMPERATURE (MEDIUM TEMPERATURE AT BOUNDARY) 19 TEMPERATURE (HIGHER TEMPERATURE AT BOUNDARY) 20 SIGMA TEMPERATURE (HIGHER TEMPERATURE AT BOUNDARY) 21 NUMBER_DENSITY 22 SIGMA_NUMBER_DENSITY 23 SOLAR_ZENITH_ANGLE 24 LOCAL_SOLAR_TIME For further information, see PDS label file. File naming conventions ----------------------- The file naming conventions for the data files are same over the four cameras, UVI, IR1, IR2, and LIR. In addition to the four cameras, the data of LAC and RS have very similar file naming conventions. In this section, the file naming conventions for the RS data is described. The filename has the format rs_{YYYY}{MM}{DD}_{hh}{mm}{ss}_{gs}_{level}_[{type}_]v{ver}.{ext} where {YYYY}: year in four-digits {MM}: month in two-digits {DD}: day in two-digits {hh}: hour in two-digits {mm}: minute in two-digits {ss}: second in two-digits Note that {YYYY}-{MM}-{DD}T{hh}:{mm}:{ss} means the representative time of observation in UTC. {gs}: abbreviated name of ground station {level}: abbreviated name of product The values of {level} is summarized in the following table. Note that the product names, i.e., processing level definition is different with other products, such as IR1, IR2, UVI, LIR, and LAC. {level} DATA_SET_ID description ------- --------------------- -------------------------------- l1 VCO-V-RS-2-OCC-V{VER} recorded data at the ground l2 VCO-V-RS-3-OCC-V{VER} time series of signal intensity and dominant frequency l3 VCO-V-RS-5-OCC-V{VER} time series of impact parameter, refractivity, etc. l4 VCO-V-RS-5-OCC-V{VER} vertical profiles of atmospheric density, temperature, etc. where {VER} is version number of data set, e.g., 1.0. {type}: type of occultation and physical quantity {level} {type} description ------- ------ -------------------------------------------- l1 -- none, i.e., no ``type'' for this level. l2 -- none, i.e., no ``type'' for this level. l3 i data obtained during ingress. l3 e data obtained during egress. l4 ai atmospheric temperature profile obtained during ingress. l4 ae atmospheric temperature profile obtained during egress. l4 pi sulfuric acid vapor mixing ratio profile obtained during ingress. l4 pe sulfuric acid vapor mixing ratio profile obtained during egress. l4 ii electron density profile obtained during ingress. l4 ie electron density profile obtained during egress. {ver}: version string of the product in 2 digits The value is larger than or equal to 10. When the version number appeared in DATA_SET_ID is multiplied by 10, the result is equal to the value of {ver}. {ext}: extension of the file The following typical extensions are included in this data set The ``data'' directory contains only tab and lbl files. {ext} description ----- --------------------------------- lbl PDS3 label file tab table format file with ASCII text Parameters used for derivation of the data ------------------------------------------ Frequencies were calculated from raw, uncalibrated data. The effect of the antenna mispointing on the signal intensity was corrected using the antenna pattern data below. Offset angle from boresight (deg) HGA gain (dB) --------------------------------- ------------- -1.0 33.73 -0.5 35.15 0.0 35.60 0.5 35.12 1.0 33.67 In the derivation of pressure and temperature profiles, the following parameters were used. Parameter Value --------------------- ----------------------------------- GM 3.2485859200000006E+14 (m**3 s**-2) Mean molecular weight 43.44 (u) Planetary radius 6051.8 (km) Refractive volume 1.811E-29 (m**3) Summary of results ------------------ The radio occultation experiments conducted so far are summarized in the table below. The columns are: - the orbit number, - the antenna (ground station), - the UTC time when the tangential point of the straight line between the spacecraft and the ground station was occulted by the 70-km-altitude surface of Venus, - the east longitude in degrees at the tangential point, - the north latitude in degrees at the tangential point, and - the local solar time in hours. Orbit Antenna Time (UTC) longitude latitude local time ----- ------- ---------------- --------- -------- ---------- 9 UDSC64 2016-03-03T22:42 356.49 -39.56 15.71 9 UDSC64 2016-03-03T23:22 175.34 -66.94 3.79 11 UDSC64 2016-03-24T21:43 53.13 0.17 16.21 11 UDSC64 2016-03-24T22:19 232.83 -36.11 4.24 13 UDSC64 2016-04-15T03:24 110.79 5.67 16.71 13 UDSC64 2016-04-15T03:53 290.72 -24.95 4.72 14 UDSC64 2016-04-26T00:34 140.33 6.53 16.96 14 UDSC64 2016-04-26T01:03 320.36 -19.94 4.97 15 UDSC64 2016-05-07T00:02 170.15 9.70 17.23 15 UDSC64 2016-05-07T00:33 350.22 -14.03 5.23 16 UDSC64 2016-05-18T01:55 200.28 15.29 17.49 16 UDSC64 2016-05-18T02:28 20.28 -7.26 5.50 21 UDSC64 2016-07-12T07:11 351.25 45.33 18.83 22 UDSC64 2016-07-23T02:42 20.70 49.65 19.11 22 UDSC64 2016-07-23T03:11 199.06 7.54 7.22 40 UDSC64 2017-02-06T01:48 178.97 -25.01 1.21 40 UDSC64 2017-02-06T02:09 13.82 -73.10 12.22 48 UDSC64 2017-05-04T19:48 309.98 -50.05 10.58 48 UDSC64 2017-05-04T20:02 238.28 -77.21 15.37 49 UDSC64 2017-05-15T21:34 336.20 -19.28 11.10 49 UDSC64 2017-05-15T22:00 157.25 -61.55 23.04 50 UDSC64 2017-05-26T21:05 1.87 -0.65 11.63 50 UDSC64 2017-05-26T21:32 181.19 -47.46 23.68 51 UDSC64 2017-06-06T18:22 27.95 14.71 12.12 51 UDSC64 2017-06-06T18:47 207.32 -38.92 0.16 54 IDSN32 2017-07-09T06:20 109.60 34.23 13.32 55 UDSC64 2017-07-20T05:06 137.96 41.56 13.67 55 UDSC64 2017-07-20T05:35 319.11 -1.57 1.59 56 IDSN32 2017-07-31T06:17 166.23 56.78 14.05 56 IDSN32 2017-07-31T06:47 348.42 15.48 1.90 57 IDSN32 2017-08-11T09:22 167.59 78.28 16.24 57 IDSN32 2017-08-11T09:44 18.09 39.03 2.21 Ancillary Data : Position of the ground stations ------------------------------- Here is the list of the ground stations used for radio science experiment. Name Abbr Longitude Latitude ------------------------- ------ -------------- ------------- Usuda Deep Space Center UDSC64 (138, 21, 54)E (36, 07, 44)N Indian Deep Space Network IDSN32 ( 77, 22, 08)E (12, 54, 11)N DLR Weilheim site WHM30 ( 47, 52, 52)E (11, 04, 42)N The triplets (a, b, c) appeared in the longitude and the latitude columns mean ``a  b  c '' and the last character ``E'' and ``N'' means ``East longitude'' and ``North latitude'', respectively. The ground station used for acquiring data can be found in ``VCO:GROUND_STATION'' keyword of the PDS label. Geometry information -------------------- The data on geometry were calculated using the VCO SPICE kernels data set, VCO-V-SPICE-6-V1.0. This data set is available at DARTS in ISAS/JAXA and the PDS SPICE Archives in JPL/NASA. Coordinate System : In Space -------- Some geometric quantities appearing in the labels and the header of FITS files are in J2000 coordinates. In this coordinate, the +Z-axis points northward along the Earth's J2000 rotation axis and the +X-axis points toward the first point of aries. On Venus -------- For Venusian geometry, IAU VENUS that is defined as the planetocentric coordinate system for Venus is used. Software : No software is included in this data set. However, the data products, being ASCII text files, can be readily accessed by means of a variety of text editors.

Confidence Level Overview : Known issues of concern are described in the summary paper [IMAMURAETAL2017]. Review : This data set will be reviewed by the PDS Atmospheres Node. Data Coverage and Quality : Data Coverage in time --------------------- During the Sun orbiting phase (2010-12-07 -- 2015-12-06), solar corona observation was performed during superior-conjunction. These data will be include in other data set in future. The periods with and without Venus' atmosphere observations and the reasons are as follows: Orbit No TIME of peri (UTC) performed or not performed and reason -------- ------------------- ------------------------------------- 0 -- no chance due to geometry 1 2015-12-07T00:01:31 not performed; during VOI maneuver 2 2015-12-20T14:11:19 no chance due to geometry 3 2015-12-31T00:46:06 no chance due to geometry 4 2016-01-10T13:06:32 no chance due to geometry 5 2016-01-21T03:39:37 no chance due to geometry 6 2016-01-31T20:06:10 no chance due to geometry 7 2016-02-11T13:24:03 no chance due to geometry 8 2016-02-22T06:10:59 no chance due to geometry 9 2016-03-03T21:19:03 performed 10 2016-03-14T10:19:25 no chance due to geometry 11 2016-03-24T21:26:41 performed 12 2016-04-04T07:29:53 no chance due to geometry 13 2016-04-15T03:12:12 performed 14 2016-04-26T00:20:09 performed 15 2016-05-06T23:49:33 performed 16 2016-05-18T01:48:32 performed 17 2016-05-29T05:25:55 not performed; Superior-conjunction 18 2016-06-09T09:04:06 no chance due to geometry 19 2016-06-20T11:03:10 no chance due to geometry 20 2016-07-01T10:27:46 no chance due to geometry 21 2016-07-12T07:26:22 performed 22 2016-07-23T02:59:51 performed 23 2016-08-02T22:38:08 no chance due to geometry 24 2016-08-13T19:48:16 no chance due to geometry 25 2016-08-24T19:24:57 no chance due to geometry 26 2016-09-04T21:29:59 no chance due to geometry 27 2016-09-16T01:06:09 no chance due to geometry 28 2016-09-27T04:36:54 no chance due to geometry 29 2016-10-08T06:30:07 no chance due to geometry 30 2016-10-19T05:57:20 no chance due to geometry 31 2016-10-30T03:05:56 no chance due to geometry 32 2016-11-09T22:49:22 no chance due to geometry 33 2016-11-20T18:27:39 no chance due to geometry 34 2016-12-01T15:23:16 no chance due to geometry 35 2016-12-12T14:35:48 no chance due to geometry 36 2016-12-23T16:19:37 no chance due to geometry 37 2017-01-03T19:50:20 no chance due to geometry 38 2017-01-14T23:34:26 no chance due to geometry 39 2017-01-26T01:49:54 not performed due to spacecraft's attitude constraints 40 2017-02-06T01:34:35 performed 41 2017-02-16T22:48:42 no chance due to geometry 42 2017-02-27T18:28:11 no chance due to geometry 43 2017-03-10T14:00:55 no chance due to geometry 44 2017-03-21T10:56:13 performed 45 2017-04-01T10:14:19 no chance due to geometry 46 2017-04-12T12:04:09 no chance due to geometry 47 2017-04-23T15:34:37 no chance due to geometry 48 2017-05-04T19:11:15 performed 49 2017-05-15T21:18:38 performed 50 2017-05-26T21:02:18 performed 51 2017-06-06T18:23:50 performed 52 2017-06-17T14:12:39 no chance due to geometry 53 2017-06-28T09:46:54 no chance due to geometry 54 2017-07-09T06:29:49 performed 55 2017-07-20T05:24:28 performed 56 2017-07-31T06:51:02 performed 57 2017-08-11T10:12:01 performed 58 2017-08-22T13:58:32 no chance due to geometry 59 2017-09-02T16:27:18 no chance due to geometry 60 2017-09-13T16:29:56 no chance due to geometry 61 2017-09-24T13:59:00 no chance due to geometry 62 2017-10-05T09:44:23 no chance due to geometry 63 2017-10-16T05:11:35 no chance due to geometry 64 2017-10-27T01:51:37 no chance due to geometry 65 2017-11-07T00:50:05 no chance due to geometry 66 2017-11-18T02:22:54 no chance due to geometry 67 2017-11-29T05:45:36 no chance due to geometry 68 2017-12-10T09:26:17 no chance due to geometry 69 2017-12-21T11:46:48 no chance due to geometry Data Coverage in space ---------------------- No information is obtained below ~32 km since the curvature of the ray path exceeds that of the planetary surface. Quality ------- The signal-to-noise ratio can become unusually worse when the attitude maneuver of the spacecraft was not properly conducted. Such measurements are indicated in the 'NOTE' of the PDS3 label file. The quality of the measurement declines below ~40 km due to defocusing loss and absorption. Limitations : The upper boundary of the pressure and temperature profiles are set at 95 km. Temperatures near the upper boundary are influenced by the boundary condition of the temperature; the effect can be assessed by comparing the three profiles corresponding to the three different upper boundary conditions.