The science data obtained by Radio Science experiments (RS) using Ultra-Stable Oscillator (USO)
onboard the AKATSUKI (also known as Venus Climate Orbiter and PLANET-C) spacecraft
are provided on this page.
RS aims to determine the vertical structure of the Venusian atmosphere
using radio occultation technique, which is achieved by using Ultra-Stable Oscillator (USO).
received signal from the spacecraft is multiplied by sinusoidal signal with similar frequency
emitted from the spacecraft, obtained beat signal with low-frequency and record it with high sampling frequency.
Level 2 (l2)
received frequency and intensity of signal, and frequency variation caused by only Venusian atmosphere:
received frequency and intensity of signal are obtained by using spectral analysis technique.
These signals include both of contribution from orbital motion of the spacecraft and Venusian atmosphere.
Frequency variation caused by only Venusian atmosphere will be obtained by subtracting contribution
from orbital motion of the spacecraft.
Level 3 (l3)
vertical profile of refraction angle and vertical density profile of neutral atmosphere:
orbital motion calculated from SPK, emission angle of radio waves, refraction angle,
and impact parameter are calculated from Level 2 data.
Using knowledge of composition of Venusian atmosphere,
density profile of neutral atmosphere is also calculated.
Level 4 (l4)
vertical profile of atmospheric temperature, pressure, and mixing ratio of H2SO4 vapor:
assuming hydrostatic balance, vertical profile of pressure is calculated from density profile,
and also calculated atmosphric temperature profile using equation of state.
From intensity of received signal, absorption rate of radio waves
by CO2 and H2SO4 are calculated.
Using knowledge of temperature dependence of absorption rate by CO2,
verical profile of mixing ratio of H2SO4 is calculated.
File Naming Convention
Filename is in "RS_DATE_TIME_LEVEL(_KIND)_VER.EXT" format.
date in UTC when image taken at in "YYYYMMDD" format, where YYYY is four-digit year (2010 -- 20??), MM is two-digit month (01 -- 12), and DD is two-digit day (01 -- 31): e.g., 20160313 for 2016-03-13.
time in UTC when image taken at in "hhmmss" format, where hh is two-digit hour (00 -- 23), mm is two-digit minutes (00 -- 59), and ss is two-digit seconds (00 -- 59): e.g., 003152 for 00:31:52.
level of product: l1, l2, l3, l4.
kind of data type: i and e for data taken during ingress and during egress, respectively; ai and ei for atmospheric temperature profile during ingress and during egress, respectively; pi and pe for H2SO4 vapor mixing ratio profile during ingress and egress, respectively; ii and ie for electron density profile during ingress and egress, respectively.
level of product: l1, l2, l3, l4.
version string: v10 for "version 1.0".
extension that represents file type: tab for table-type format text file, csv for CSV file, jpg for JPEG file, png for PNG file, and lbl for PDS3 label file.
When you publish your own work based on the AKATSUKI RS data, please refer to the following paper(s):
Imamura, T., T. Toda, A. Tomiki, D. Hirahara, T. Hayashiyama, N. Mochizuki,
Z. Yamamoto, T. Abe, T. Iwata, H. Noda, Y. Futaana, H. Ando, B. Häusler,
M. Pätzold, A. Nabatov,
Radio occultation experiment of the Venus atmosphere and ionosphere with the Venus orbiter Akatsuki,
Earth Planets Space, 63, 493-501, doi:10.5047/eps.2011.03.009, 2011.