16:15 〜 16:30
[PPS04-04] In-situ Instrumentation for in-depth Exploration of the Cloud Decks and Morphology/Composition of the Surface of Venus
キーワード：Venus, Aerosol Composition, Surface Imagery, Venus aerobot
Introduction: From a balloon-borne aerobot floating near the half-bar level, the potentially habitable cloud decks and inhospitable surface of Venus can be thoroughly explored via two in-situ instruments under development. To understand chemical and possibly biogenic processes within the clouds, we are developing a lightweight, low-power in-situ instrument package to measure both (1) the local gaseous environment (including noble gases and their isotopes) and (2) the microphysical properties of attendant aerosols, including their composition, number density and size distribution. To map the morphology and composition of the surface at 10-m scales on the planet's nightside, we are developing a near-infrared multi-color/stereo camera able to scan the surface at ~60 m/s from a tow-body suspended below the aerobot near the 47-km (~100oC) level in the relatively clear air found below the cloud deck.
In-Situ Aerosol Instrument Package: Mass ranges from 2 to 300 AMU at <0.02 AMU resolution are measured to determine, for example, the abundances of iron chloride (FeCl3) and potential biogenic species embedded within sulfur acid aerosols. Heterogeneous chemistry involving HCl, HF, and HBr in H2SO4 aerosols are expected to produce significant amounts of sulfonic acids and their daughter products. The sulfur polymers S8, S4 and S3 and disequilibrium gases and aerosols indicative of biogenic processes (e.g., PH3, NH3 and phosphorus acids) can also be measured.
The heart of the package is the Quadrupole Ion-Trap Mass Spectrometer (QITMS). An inlet aerosol separator preceded by an adjustable piezo-electric aperture allows the passage of a selectable size range of aerosols. The aerosol separator enriches H2SO4 relative to residual CO2 by a factor > 106. A 600 oC vaporizer then vaporizes the aerosols. Trace aerosol species with concentrations relative to the dominant H2SO4 material of 100 ppb and 2 ppb are measured to 10% precision in <6 and <300 secs, respectively.
The Light Optical Aerosol Counter (LOAC), developed at LP2CE-CNRS is also included. LOAC measures particle number densities and size distributions.
Tow-Body Surface Imaging Camera: Thermal radiation in the 0.85-1.18 um wavelength range upwelling from the hot (~740 oK) surface provides a means to characterize rock composition in geological features such as tessera and coronae, and to identify and characterize volcanic phenomena such as hot magma flows and water vapor enhancements.
Repeatedly lowered from the aerobot for 1- to 2-hour sub-cloud excursions, the phase-change-cooled tow-body platform traverses and scans the surface at the ~60 m/s speed of the 55-km-altitude winds, requiring imaging exposure times < 0.16 sec to limit the lateral smear to 10 meters. As currently conceived, the camera images at 3 near-IR surface-emission wavelengths: 1.01, 1.10, and 1.18 um providing SNR better than 130, 65, and 90, respectively, at a ~10-m/pixel scale. A 4th image (again at 1.01 um) provides stereo imagery at ∼12o angular separation. The 4 images are acquired simultaneously on a single 1280 (E/W) × 1024 (N/S) pixel array with each wavelength segment covering 3.15 km E-W and 10.24 km N-S. A 4-segment image set is acquired every 50 sec (i.e., every 3 km of travel).
We will present recent instrument progress, including review of new tests of (1) the aerosol separator’s ability to filter > 106, (2) QITMS’s tolerance for concentrated sulfuric acid, and (3) its ability to measure isotope abundances. For sub-cloud surface imagery, we will review new modeling results showing that sufficient surface emission is transmitted directly to the sensor to compete with the near-uniform background of Rayleigh-scattered and cloud-reflected radiation. That contrast level ensures spatial resolution down to the pixel scale.
Acknowledgments: This research was funded by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
In-Situ Aerosol Instrument Package: Mass ranges from 2 to 300 AMU at <0.02 AMU resolution are measured to determine, for example, the abundances of iron chloride (FeCl3) and potential biogenic species embedded within sulfur acid aerosols. Heterogeneous chemistry involving HCl, HF, and HBr in H2SO4 aerosols are expected to produce significant amounts of sulfonic acids and their daughter products. The sulfur polymers S8, S4 and S3 and disequilibrium gases and aerosols indicative of biogenic processes (e.g., PH3, NH3 and phosphorus acids) can also be measured.
The heart of the package is the Quadrupole Ion-Trap Mass Spectrometer (QITMS). An inlet aerosol separator preceded by an adjustable piezo-electric aperture allows the passage of a selectable size range of aerosols. The aerosol separator enriches H2SO4 relative to residual CO2 by a factor > 106. A 600 oC vaporizer then vaporizes the aerosols. Trace aerosol species with concentrations relative to the dominant H2SO4 material of 100 ppb and 2 ppb are measured to 10% precision in <6 and <300 secs, respectively.
The Light Optical Aerosol Counter (LOAC), developed at LP2CE-CNRS is also included. LOAC measures particle number densities and size distributions.
Tow-Body Surface Imaging Camera: Thermal radiation in the 0.85-1.18 um wavelength range upwelling from the hot (~740 oK) surface provides a means to characterize rock composition in geological features such as tessera and coronae, and to identify and characterize volcanic phenomena such as hot magma flows and water vapor enhancements.
Repeatedly lowered from the aerobot for 1- to 2-hour sub-cloud excursions, the phase-change-cooled tow-body platform traverses and scans the surface at the ~60 m/s speed of the 55-km-altitude winds, requiring imaging exposure times < 0.16 sec to limit the lateral smear to 10 meters. As currently conceived, the camera images at 3 near-IR surface-emission wavelengths: 1.01, 1.10, and 1.18 um providing SNR better than 130, 65, and 90, respectively, at a ~10-m/pixel scale. A 4th image (again at 1.01 um) provides stereo imagery at ∼12o angular separation. The 4 images are acquired simultaneously on a single 1280 (E/W) × 1024 (N/S) pixel array with each wavelength segment covering 3.15 km E-W and 10.24 km N-S. A 4-segment image set is acquired every 50 sec (i.e., every 3 km of travel).
We will present recent instrument progress, including review of new tests of (1) the aerosol separator’s ability to filter > 106, (2) QITMS’s tolerance for concentrated sulfuric acid, and (3) its ability to measure isotope abundances. For sub-cloud surface imagery, we will review new modeling results showing that sufficient surface emission is transmitted directly to the sensor to compete with the near-uniform background of Rayleigh-scattered and cloud-reflected radiation. That contrast level ensures spatial resolution down to the pixel scale.
Acknowledgments: This research was funded by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.