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. This RS OCCs Doppler data are considered Level 3 or Composite Data and are derived from Level 2. In the VCO RS level definition, this data set is called Level 2. Parameters : The observed frequency, the residual frequency corresponding to the effect of the Venus atmosphere, and the observed signal intensity, with the sampling interval of around 0.01 seconds. Processing : One-way downlink at X-band (8410.932 MHz) stabilized by an onboard ultra-stable oscillator (USO) is used in the experiment. In the processing of recorded data, we first subtract the Doppler shift calculated from the orbital information and a model atmosphere from the original signal by heterodyning, thereby suppressing the frequency variation and enabling narrow-band filtering. Then, approximate carrier frequencies are determined for successive time blocks by fitting a theoretical signal spectrum (sinc function) to the discrete Fourier transforms. The resultant frequency variation is subtracted from the signal by heterodyning in order to apply another narrow-band filtering. The signal frequency and intensity time series are obtained by successively fitting a sinc function to the narrow-band filtered data. Since the ray bending in the Venus atmosphere exceeds the beam width of high-gain antenna (HGA), the spacecraft performs attitude maneuvers to compensate for the changing direction of the signal path. The direction of the antenna beam is changed along a polygonal (zigzag) curve in such a way that the difference between the controlled beam direction and the ideal beam direction based on the Venus International Reference Atmosphere (VIRA) is less than 0.05. The difference sometimes exceeds this limit because of an inaccurate trajectory prediction at the time of command generation or no attitude maneuver due to limitation of spacecraft operation, leading to non-negligible decline of the signal intensity. The effect of such antenna mispointing on the measured intensity is corrected using the measured antenna pattern and the trajectory data reconstructed after the experiment provided that the antenna mispointing is less than 0.5. The accuracy of this intensity correction is estimated to be better than 1 dB in most of the cases. Before the intensity correction, the noise level was estimated from the portion of the data dominated by noise and then the estimated noise component was subtracted from the whole time series. Data : Overview -------- Table data containing the frequency, the intensity and supplementary parameters as functions of time. 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 is as follows: No. Content --- -------------------------------- 1 SAMPLE_NUMBER 2 UTC_TIME 3 DAY_OF_YEAR_WITH_FRACTIONS 4 EPHEMERIS_SECONDS 5 DISTANCE 6 TRANSMIT_FREQUENCY_RAMP_REFERENCE_TIME 7 TRANSMIT FREQUENCY - CONSTANT TERM 8 TRANSMIT FREQUENCY - LINEAR TERM 9 OBSERVED X-BAND ANTENNA FREQUENCY 10 PREDICTED X-BAND ANTENNA FREQUENCY 11 CORRECTION_OF_EARTH_ATMOSPHERE_PROPAGATION 12 RESIDUAL CALIBRATED X-BAND FREQUENCY SHIFT 13 SIGNAL LEVEL X-BAND 14 DIFFERENTIAL_DOPPLER 15 SIGMA OBSERVED X-BAND ANTENNA FREQUENCY 16 SIGNAL QUALITY X-BAND 17 SIGMA SIGNAL LEVEL X-BAND 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.