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Science Plan of Japanese Venus Orbiter, Akatsuki

Science Plan of Japanese Venus Orbiter, Akatsuki. Takeshi Imamura, Akatsuki Team Japan Aerospace Exploration Agency. LIR. LAC. UVI. IR1. IR2. USO. First light. UVI 365nm. LIR 10μm. IR1 0.9μm. Venus Climate Orbiter/Akatsuki (PLANET-C project). Scientific objectives

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Science Plan of Japanese Venus Orbiter, Akatsuki

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  1. Science Plan of Japanese Venus Orbiter, Akatsuki Takeshi Imamura, Akatsuki Team Japan Aerospace Exploration Agency

  2. LIR LAC UVI IR1 IR2 USO

  3. First light UVI 365nm LIR 10μm IR1 0.9μm

  4. Venus Climate Orbiter/Akatsuki(PLANET-C project) • Scientific objectives • Mechanism of super-rotation • Structure of meridional circulation • Meso-scale processes • Formation of H2SO4 clouds • Lightning • Active volcanism, inhomogeneity of surface material • Zodiacal light (during cruise : from next week) • Launch : May 21, 2010  Arrival: December 7, 2010 • VOI-1 on Dec 7, VOI-2 on Dec 11, VOI-3 on Dec 13 • Mission life :More than 2 Earth years

  5. Mechanism of super-rotation Stratosphere Acceleration Thermal tides Waves or Turbulence • Which is working? Any other mechanisms? • Key parameters: Planetary-scale waves, Meridional circulation, Large-scale turbulence Cloud Troposphere Gravity waves Hadley circulation Thermal tides NP Eq SP NP Eq SP NP Eq SP

  6. Cloud processes • Dynamics of cloud formation, role of meridional circulation in transporting cloud-related species • Origin of UV markings • Whether lightening occurs or not Schubert (1983)

  7. Observation from an orbiter Lightning and airglow camera PI: Y. Takahashi Longwave IR camera (cloud temperature) • 4 cameras sounding different altitudes, a high-speed lightning detector, and an ultra-stable oscillator for radio science • Constructing 3-D model of atmospheric dynamics PI: M. Taguchi Ultraviolet imager (cloud top) PI: S. Watanabe 1-mm camera (surface) PI: N. Iwagami 2-mm camera (lower atmosphere) PI: T. Satoh Radio science (vertical structure) PI: T. Imamura

  8. Onboard instruments

  9. Wavelengths for cloud-tracking 10mm, cloud top (65km), dayside & nightside 365nm, cloud top (65km), dayside 2.02mm, cloud top(65m), dayside 365 nm image taken by PVO/OCPP 8.6 um image taken by Subaru telescope, high-pass filtered Cloud altimetry by VenusExpress/VIRTIS 0.9mm, lower cloud (50km), dayside 2.3mm, lower cloud (50km), nightside Cloud top and bottom are covered both on the dayside and nightside 0.98 um image taken by Galileo/SSI 2.3 um image taken by Galileo/NIMS

  10. Resolution: 10-20 km Observations to be conducted during one orbital revolution Successive Global images of atmosphere and ground surface (~24 hours) Limb images (~0.5 hour) Orbital period: 30 hours Close-up images, Stereo viewing, Lightning/Airglow (~2 hours x 2) Temperature / H2SO4 vapor / Ionosphere by radio occultation

  11. Orbital motion partially synchronized with the super-rotation Spacecraft 60 m/s westward flow near the cloud base - Time evolution of meso-scale processes - Precise determination of wind vectors A concept similar to geostationary meteorological satellite (movie provided by M. Odaka)

  12. Perfect synchronization with super-rotation Akatsuki’s partial synchronization Coverage of global viewing Time Time ~1 day 5-7 days 0°360° 0°360° Longitude in a reference frame rotating with the super-rotation Longitude in a reference frame rotating with the super-rotation

  13. Detectable modes • Wavenmber-1 waves have been detected at the cloud top by spectral analysis of UV brightness (DelGenio & Rossow, 1990) • Equatorial mode : c-U = 16 m/s  intrinsic period = 27 days • Midlatitude mode : c-U = -32 m/s  intrinsic period = 10 days • Given the repetition period of full longitudinal coverage of 5-7 days, the Nyquist frequency is formally 10-14 days. • However, with the continuous data over up to 1 day in each orbital revolution, much faster waves will also be covered. Especially eastward fast modes are easy to be detected.

  14. Latitude and local solar time of radio occultation • 360-deg local time coverage in the tropics Thermal tides, Diurnal variation of cloud layer • Intensive observation in the sub-solar region  Origin of ‘cells’ • Locations probed by radio occultation will be imaged by cameras a short time before or after the occultation.

  15. Receiving VEX radio occultation signals using Usuda antenna in Japan • April 40, May 6, and June 16 in 2010 • The performances of the ground system and data processing software were verified. Static stability H2SO4 vapor mixing ratio

  16. 3-D sounding

  17. Dec 15, 2010 32kbps Orbital motion Disk diameter < 12° Lightening and airglow North pole visible IR1 0.9um, 0.97um, 1.01um, IR2 1.73, 2.26, 2.32um, LIR 10um Venus 12° FOV N.P. IR1 0.9um, UVI 365nm, LIR limb IR1 0.9um, IR2 2.02um, UVI 283, 365nm, LIR 10um UVI 365nm x 7 times, LIR 10um (km) Locations observed by RS are imaged by cameras night_delux, night_delux_ir1 LAC day_delux vicinity_slim_7 limb lir RS

  18. Jan 15, 2011 32kbps Orbital motion Disk diameter < 12° North pole visible Venus 12° FOV N.P. (km) night_delux, night_delux_ir1 LAC day_delux vicinity_slim_7 limb lir RS

  19. Feb 15, 2011 16kbps Orbital motion Disk diameter < 12° North pole visible Venus 12° FOV N.P. (km) LAC day_slim day_delux vicinity_slim_7 RS

  20. Telemetry rate 130 images will be acquired in each orbital revolution

  21. Data processing pipeline Level 0 : Uncompressed images • Level 2 and Level 3 data will be released to the public with PDS-like label files. Level 1 : Calibrated images with FITS header Level 2 : Calibrated images with FITS header, including geometry information Level 3 : Wind vectors and other higher-level products on longitude-latitude grids in netCDF format

  22. An example of FITS data (Earth UV image) (FITS creating software developed by Manabu Yamada)

  23. An example of netCDF data (Venus Express VMC) (netCDF creating software developed by Kazunori Ogohara)

  24. Complementary missions Coordinated observations are being planned.

  25. Summary • VCO/Akatsuki will address the unique dynamical state of the Venus atmosphere with systematic sampling of meteorological variables from equatorial orbit. • Three-dimensional structure of the atmosphere and its temporal variation will be observed by using 4 cameras, a high-speed lightning detector and radio occultation. • Data processing pipeline is under development. Wind vectors as well as image data and radio occultation data will be released to the public. See you soon at Venus !

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