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- All Subjects: Imager
- Creators: Garvie, Laurence
Description
Information about the elemental composition of a planetary surface can be determined using nuclear instrumentation such as gamma-ray and neutron spectrometers (GRNS). High-energy Galactic Cosmic Rays (GCRs) resulting from cosmic super novae isotropically bombard the surfaces of planetary bodies in space. When GCRs interact with a body’s surface, they can liberate neutrons in a process called spallation, resulting in neutrons and gamma rays being emitted from the planet’s surface; how GCRs and source particles (i.e. active neutron generators) interact with nearby nuclei defines the nuclear environment. In this work I describe the development of nuclear detection systems and techniques for future orbital and landed missions, as well as the implications of nuclear environments on a non-silicate (icy) planetary body. This work aids in the development of future NASA and international missions by presenting many of the capabilities and limitations of nuclear detection systems for a variety of planetary bodies (Earth, the Moon, metallic asteroids, icy moons). From bench top experiments to theoretical simulations, from geochemical hypotheses to instrument calibrations—nuclear planetary science is a challenging and rapidly expanding multidisciplinary field. In this work (1) I describe ground-truth verification of the neutron die-away method using a new type of elpasolite (Cs2YLiCl6:Ce) scintillator, (2) I explore the potential use of temporal neutron measurements on the surface of Titan through Monte-Carlo simulation models, and (3) I report on the experimental spatial efficiency and calibration details of the miniature neutron spectrometer (Mini-NS) on board the NASA LunaH-Map mission. This work presents a subset of planetary nuclear science and its many challenges in humanity's ongoing effort to explore strange new worlds.
ContributorsHeffern, Lena Elizabeth (Author) / Hardgrove, Craig (Thesis advisor) / Elkins-Tanton, Linda (Committee member) / Parsons, Ann (Committee member) / Garvie, Laurence (Committee member) / Holbert, Keith (Committee member) / Lyons, James (Committee member) / Arizona State University (Publisher)
Created2022
Description
Characterizing the surface mineralogy of asteroids is critical to constraining their formation history and provides insight into the processes of planetary formation. One method of determining the surface mineralogy of asteroids is comparison of their visible to near-infrared reflectance (VNIR) spectra with laboratory spectra from meteorites and minerals. Subsequent in-situ investigation of these asteroids by spacecraft can supplement or supersede interpretations derived from Earth-based observations.I investigated a suite of aubrites, sulfide minerals, and metal-rich chondrites in a variety of forms (hand samples, powders, and slabs) to identify similarities with ‘spectrally featureless’ asteroids. I collected VNIR spectra and powder X-ray diffraction patterns of these samples and compared their overall reflectance and spectral slope with X-complex and T-, L-, and D-type asteroid spectra.
The Psyche Mission will orbit asteroid (16) Psyche beginning in 2026. I provide a pre-flight assessment of the surface composition of Psyche by comparing spectra of Psyche to a large spectral library of possible surface analog materials (e.g., iron meteorites, mesosiderites, pallasites, sulfides, enstatite, ordinary, and metal-rich chondrites, endmember silicates, and mixtures of silicates, metal, and sulfides). Spectra of Psyche are generally consistent with iron meteorite powder, mixtures of iron meteorite powder and low-Fe, low-Ca pyroxene, sulfide minerals, and the CH/CBb chondrite Isheyevo. Next, I demonstrate some anticipated capabilities of the Psyche Multispectral Imager by comparing spectral parameters derived from Imager-convolved data to those from high resolution laboratory spectra. I offer preliminary strategies for classifying surface composition based on Imager filter ratios and overall reflectance.
Last, I present an assessment of a benchtop, commercial-off-the-shelf (COTS) version of the Psyche Imager. The COTS Imager uses the same model CCD and a similar f-number commercial camera lens. I measured the gain, full well, linearity, read noise, quantum efficiency, and modulation transfer function to compare with eventual calibration data from the flight Imager. I validate the results of a radiometric model developed for the flight Imager with signal measurements from the COTS Imager. This work demonstrates that the COTS Imager is an effective testbed for validating Imager requirements and developing software and procedures for eventual calibration of the flight instrument.
ContributorsDibb, Steven (Author) / Bell, James (Thesis advisor) / Hardgrove, Craig (Committee member) / Garvie, Laurence (Committee member) / Elkins-Tanton, Linda (Committee member) / Bose, Maitrayee (Committee member) / Arizona State University (Publisher)
Created2021