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Lightning in the atmosphere of Venus is either ubiquitous, rare, or non-existent, depending on how one interprets diverse observations. Quantifying if, when, or where lightning occurs would provide novel information about Venus’s atmospheric dynamics and chemistry. Lightning is also a potential risk to future missions, which could float in the

Lightning in the atmosphere of Venus is either ubiquitous, rare, or non-existent, depending on how one interprets diverse observations. Quantifying if, when, or where lightning occurs would provide novel information about Venus’s atmospheric dynamics and chemistry. Lightning is also a potential risk to future missions, which could float in the cloud layers (~50–70 km above the surface) for up to an Earth-year. For decades, spacecraft and ground-based telescopes have searched for lightning at Venus, using many instruments including magnetometers, radios, and optical cameras. Two surveys (from the Akatsuki orbiter and the 61-inch telescope on Mt. Bigelow, Arizona) observed several optical flashes that are often attributed to lightning. We expect that lightning at Venus is bright near 777 nm (the unresolved triplet emission lines of excited atomic oxygen) due to the high abundance of oxygen as carbon dioxide. However, meteor fireballs at Venus are probably bright at the same wavelength for the same reason. Here we derive power laws that quantify the rate and brightness of optical flashes from meteor fireballs at Venus. We calculated that meteor fireballs are statistically likely to cause bright optical flashes at rates that are consistent with published observations. Small meteors burn up at altitudes of ~100 km, roughly twice as high above the surface as the clouds. Therefore, we conclude that there is no concrete evidence that lightning strikes would be a hazard to missions that pass through or dwell within the clouds of Venus.

ContributorsBlaske, Claire (Author) / O'Rourke, Joseph (Thesis director) / Desch, Steve (Committee member) / Barrett, The Honors College (Contributor) / School of Earth and Space Exploration (Contributor)
Created2023-05
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Many planetary science missions study thermophysical properties of surfaces using infrared spectrometers and infrared cameras. Thermal inertia is a frequently derived thermophysical property that quantifies the ability for heat to exchange through planetary surfaces.

To conceptualize thermal inertia, the diffusion equation analogies are extended using a general effusivity term: the square

Many planetary science missions study thermophysical properties of surfaces using infrared spectrometers and infrared cameras. Thermal inertia is a frequently derived thermophysical property that quantifies the ability for heat to exchange through planetary surfaces.

To conceptualize thermal inertia, the diffusion equation analogies are extended using a general effusivity term: the square root of a product of conductivity and capacity terms. A hypothetical thermal inductance was investigated for diurnal planetary heating. The hyperbolic heat diffusion equation was solved to derive an augmented thermal inertia. The hypothetical thermal inductance was modeled with negligible effect on Mars.

Extending spectral performance of infrared cameras was desired for colder bodies in the outer solar system where peak infrared emission is at longer wavelengths. The far-infrared response of an infrared microbolometer array with a retrofitted diamond window was determined using an OSIRIS-REx—OTES interferometer. An instrument response function of the diamond interferometer-microbolometer system shows extended peak performance from 15 µm out to 20 µm and 40% performance to at least 30 µm. The results are folded into E-THEMIS for the NASA flagship mission: Europa Clipper.

Infrared camera systems are desired for the expanding smallsat community that can inherit risk and relax performance requirements. The Thermal-camera for Exploration, Science, and Imaging Spacecraft (THESIS) was developed for the Prox-1 microsat mission. THESIS, incorporating 2001 Mars Odyssey—THEMIS experience, consists of an infrared camera, a visible camera, and an instrument computer. THESIS was planned to provide images for demonstrating autonomous proximity operations between two spacecraft, verifying deployment of the Planetary Society’s LightSail-B, and conducting remote sensing of Earth. Prox-1—THESIS was selected as the finalist for the competed University Nanosatellite Program-7 and was awarded a launch on the maiden commercial SpaceX Falcon Heavy. THESIS captures 8-12 µm IR images with 100 mm optics and RGB color images with 25 mm optics. The instrument computer was capable of instrument commanding, automatic data processing, image storage, and telemetry recording. The completed THESIS has a mass of 2.04 kg, a combined volume of 3U, and uses 7W of power. THESIS was designed, fabricated, integrated, and tested in ASU’s 100K clean lab.
ContributorsVeto, Michael (Author) / Christensen, Philip C (Thesis advisor) / Bell III, Jim (Committee member) / Clarke, Amanda B (Committee member) / Asphaug, Erik (Committee member) / Sariapli, Srikanth (Committee member) / Ruff, Steven (Committee member) / Arizona State University (Publisher)
Created2018