Kelsi Singer

Kelsi Singer
Southwest Research Institute · Planetary Science Directorate

PhD

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203
Publications
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Publications

Publications (203)
Article
The Venetia Burney Student Dust Counter (SDC) on board the New Horizons spacecraft measures the spatial and size distributions of dust along its trajectory. Models based on early SDC measurements predicted a peak dust number density at a heliocentric distance of ∼40 au, followed by a rapid decline. Instead, SDC observed dust fluxes 2–3 times higher...
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We present new observations of the cosmic ultraviolet background (CUVB) at high Galactic latitudes (∣ b ∣ > 40 ∘ ), made using the Alice UV spectrograph on board the New Horizons spacecraft. These observations were taken at about 57 au from the Sun, outside much of the foreground emission affecting previous missions, and allowed a new determination...
Article
The outer heliosphere is profoundly influenced by nonthermal energetic pickup ions (PUIs), which dominate the internal pressure of the solar wind beyond ~10 au, surpassing both solar wind and magnetic pressures. PUIs are formed mostly through charge exchange between interstellar neutral atoms and solar wind ions. This study examines the apparent he...
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Pluto's surface displays a wide variety of geologic units from smooth plains to extremely rugged mountainous expanses. These terrains range in age from young, actively resurfaced regions (no observable craters even in the highest‐resolution New Horizons images) to old, heavily cratered, eroded regions. Here we expand upon the crater data analysis a...
Preprint
Full-text available
We present new observations of the cosmic ultraviolet background (CUVB) at high Galactic latitudes ($|b| > 40^{\circ}$), made using the Alice UV spectrograph on board the New Horizons spacecraft. These observations were taken at about 57 AU from the Sun, outside much of the foreground emission affecting previous missions, and allowed a new determin...
Article
A couple years before Voyager 1 and Voyager 2 (V2) crossed the termination shock (TS), instruments on board both spacecraft observed high intensities of accelerated termination shock particles (TSPs) beaming in opposite directions. This phenomenon was explained by magnetic field lines connecting the spacecraft to the TS prior to the crossings. The...
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We present flux measurements of Uranus observed at phase angles of 43.°9, 44.°0, and 52.°4 by the Multispectral Visible Imaging Camera on the New Horizons spacecraft during 2023, 2010, and 2019, respectively. New Horizons imaged Uranus at a distance of about 24–70 au (2023) in four color filters, with bandpasses of 400–550 nm, 540–700 nm, 780–975 n...
Preprint
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We present flux measurements of Uranus observed at phase angles of 43.9{\deg}, 44.0{\deg}, and 52.4{\deg} by the Multispectral Visible Imaging Camera (MVIC) on the New Horizons spacecraft during 2023, 2010, and 2019, respectively. New Horizons imaged Uranus at a distance of about 24-70 AU (2023) in four color filters, with bandpasses of 400-550 nm,...
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We report the detection of 239 trans-Neptunian objects discovered through the ongoing New Horizons survey for distant minor bodies being performed with the Hyper Suprime-Cam mosaic imager on the Subaru Telescope. These objects were discovered in images acquired with either the r 2 or the recently commissioned EB- gri filter using shift and stack ro...
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We obtained New Horizons LORRI images to measure the cosmic optical background (COB) intensity integrated over 0.4 μ m ≲ λ ≲ 0.9 μ m. The survey comprises 16 high-Galactic-latitude fields selected to minimize scattered diffuse Galactic light (DGL) from the Milky Way, as well as scattered light from bright stars. This work supersedes an earlier anal...
Preprint
We report the detection of 239 trans-Neptunian Objects discovered through the on-going New Horizons survey for distant minor bodies being performed with the Hyper Suprime-Cam mosaic imager on the Subaru Telescope. These objects were discovered in images acquired with either the r2 or the recently commissioned EB-gri filter using shift and stack rou...
Preprint
Full-text available
We obtained New Horizons LORRI images to measure the cosmic optical background (COB) intensity integrated over $0.4\lesssim\lambda\lesssim0.9{~\rm\mu m}.$ The survey comprises 16 high Galactic-latitude fields selected to minimize scattered diffuse Galactic light (DGL) from the Milky Way galaxy, as well as scattered light from bright stars. This wor...
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The NASA New Horizons Venetia Burney Student Dust Counter (SDC) measures dust particle impacts along the spacecraft’s flight path for grains with mass ≥10 ⁻¹² g, mapping out their spatial density distribution. We present the latest SDC dust density, size distribution, and flux measurements through 55 au and compare them to numerical model predictio...
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Craters are probes of planetary surface and interior properties. Here we measure depths, widths, and spacing of circumferential ring‐graben surrounding the two largest multiring impact structures on Europa, Tyre and Callanish. We estimate formation conditions including the ice shell structure. The radial extension necessary to form these graben is...
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Impact craters, with their well‐defined initial shapes, have proven useful as heat flow probes of a number of icy bodies, provided characteristics of viscous relaxation can be identified. For Pluto's numerous craters, such identifications are hampered/complicated by infilling and erosion by mobile volatile ices, but not in every case. Large craters...
Article
We examine the 2.21-μm band from 19 disk-integrated Charon spectra measured by New Horizons/LEISA in the week leading up to its closest encounter with the Pluto system. These observations cover one Charon rotation period. Additionally, we analyze Charon’s 2.21-μm band from 22 Earth-based spectra obtained over the last two decades. We measure the eq...
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This study reports the first high-time-resolution observations of interstellar pickup ions (PUIs) in the outer heliosphere, including the first high-resolution observations of PUIs mediating shocks collected anywhere. These new data were enabled by a clever flight software reprogramming of the Solar Wind Around Pluto (SWAP) instrument on New Horizo...
Preprint
Full-text available
The New Horizons spacecraft returned images and compositional data showing that terrains on Pluto span a variety of ages, ranging from relatively ancient, heavily cratered areas to very young surfaces with few-to-no impact craters. One of the regions with very few impact craters is dominated by enormous rises with hummocky flanks. Similar features...
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Plain Language Summary It has become apparent over the last few years that small asteroids and comets are very underdense compared with the materials they are made of. This means that their total porosities are likely quite high, in excess of 70%, both as tiny voids within particles (so‐called microscopic porosity) and spaces between particles (mac...
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NASA's New Horizons mission performed the first flyby of a small Kuiper Belt Object (KBO), (486958) Arrokoth on 1 January 2019. The fast flyby revealed a fascinating, flattened, contact binary replete with a variety of unexpected geologic terrains. However, the irregular shape and constraints imposed by the fast flyby makes it a challenge to unders...
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The New Horizons spacecraft encountered the Kuiper Belt object (KBO) Arrokoth (486958), originally designated as 2014 MU 69 and formerly called “Ultima Thule,” on 2019 January 01. At 43.3 au from the Sun and 44.4 au from Earth, this was the most distant spacecraft reconnaissance of a solar system body to date. The Radio Science Experiment (REX) on...
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During the New Horizons flyby of Kuiper Belt object (486958) Arrokoth on 2019 January 1, a search was made for escaping volatiles. Using the Alice spectrograph, appulse observations of both the Sun and the star HD42954 were performed to look for signatures of far-ultraviolet absorption by various species. No escaping volatiles were detected, and in...
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A near-surface thermal model for Arrokoth is developed based on the recently released 10 ⁵ facet model of the body. This thermal solution takes into account Arrokoth’s surface reradiation back onto itself. The solution method exploits Arrokoth’s periodic orbital character to develop a thermal response using a time-asymptotic solution method, which...
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Observing dwarf planets and other large Kuiper Belt objects (KBOs) from vantage points between 8 and 47 au from the Sun, NASA’s New Horizons spacecraft has found diversity in the shapes of their solar phase curves. Here we extend solar phase angle coverage of dwarf planets (136199) Eris, (136472) Makemake, and (136108) Haumea; large KBOs (28978) Ix...
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Full-text available
The New Horizons spacecraft returned images and compositional data showing that terrains on Pluto span a variety of ages, ranging from relatively ancient, heavily cratered areas to very young surfaces with few-to-no impact craters. One of the regions with very few impact craters is dominated by enormous rises with hummocky flanks. Similar features...
Article
Full-text available
We used New Horizons LORRI images to measure the optical-band (0.4 ≲ λ ≲ 0.9 μ m) sky brightness within a high-galactic-latitude field selected to have reduced diffuse scattered light from the Milky Way galaxy (DGL), as inferred from the IRIS all-sky 100 μ m map. We also selected the field to significantly reduce the scattered light from bright sta...
Article
Full-text available
The Venetia Burney Student Dust Counter (SDC) is an in situ dust detector on board the New Horizons spacecraft measuring the interplanetary dust particle (IDP) distribution for grains with mass m > 10 ⁻¹² g. SDC provides a near-continuous measure of the interplanetary dust environment, with recent results spanning beyond 50 au. This coverage includ...
Preprint
Full-text available
A near surface thermal model for Arrokoth is developed based on the recently released $10^5$ facet model of the body. This thermal solution takes into account Arrokoth's surface re-radiation back onto itself. The solution method exploits Arrokoth's periodic orbital character to develop a thermal response using a time-asymptotic solution method, whi...
Preprint
Full-text available
We used New Horizons LORRI images to measure the optical-band ($0.4\lesssim\lambda\lesssim0.9{\rm\mu m}$) sky brightness within a high galactic-latitude field selected to have reduced diffuse scattered light from the Milky Way galaxy (DGL), as inferred from the IRIS all-sky $100~\mu$m map. We also selected the field to significantly reduce the scat...
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Full-text available
Outer solar system impact bombardment is largely unconstrained. Although recent data from the Jupiter, Saturn, and Pluto systems have produced new constraints, analysis is incomplete without inclusion of the Uranus system. We reanalyze Uranus system crater populations with recent improvements in processing of Voyager 2 imaging. No consensus in crat...
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We present high-precision orbits for 15 trans-Neptunian objects (TNOs) that have been observed by NASA’s New Horizons spacecraft at distances from 0.092 to 2.2 au. We also give predictions of 66 future opportunities to observe stellar occultations by them in late 2021–2029, eight of which are possible to observe from the United States. Observation...
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The orientation and morphology of the bilobate, cold classical Kuiper belt object (486958) Arrokoth (formerly 2014 MU69) is consistent with a slow, tidal merger of a close binary. However, the discrepancy between Arrokoth's present‐day rotation (15.9 hr) and synchronous rotation for nominal cometary densities near ∼500 kg/m³ implies reduction (up t...
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Since 2007 the Alice spectrograph on the New Horizons (NH) spacecraft has been used to periodically observe the Lyman- α (Ly α ) emissions of the interplanetary medium (IPM), which mostly result from resonant scattering of solar Ly α emissions by interstellar hydrogen atoms passing through the solar system. Three observations of IPM Ly α along a si...
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The size–frequency distribution (SFD) of objects across the solar system is influenced by their formation and dynamic evolution. Bodies in different areas of the solar system—especially the inner versus outer—have likely experienced different histories, so measuring that SFD across orders of magnitude of solar distance can elucidate those different...
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The topography of Neptune’s large icy moon Triton could reveal important clues to its internal evolution, but has been difficult to determine. New global digital color maps for Triton have been produced as well as topographic data for <40% of the surface using stereogrammetry and photoclinometry. Triton is most likely a captured Kuiper Belt dwarf p...
Preprint
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One of the clearest but unresolved questions for Europa is the thickness of its icy shell. Europa's surface is resplendent with geological features that bear on this question, and ultimately on its interior, geological history, and astrobiological potential. We characterize the size and topographic expression of circular and subcircular features cr...
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New Horizons images of the illuminated nonencounter hemisphere (far side) of Charon display geomorphic features that are consistent with features observed in the highest-resolution images of the encounter hemisphere. Scarps, ridges, craters, and one area of smooth plains are identified. These features support previous hypotheses of global expansion...
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One of the most striking and curious features of the small Kuiper Belt Object (KBO), Arrokoth, explored by New Horizons is the bright, annular neck it exhibits at the junction between its two lobes. Here we summarize past reported findings regarding the properties of this feature and then report new results regarding its dimensions, reflectivity an...
Article
We present a concept study for a distinctive robotic spacecraft mission that combines both the exploration of a never-before-visited class of planetary bodies and cutting-edge astrophysical investigations. The planetary targets are a class of objects called Centaurs that have relatively recently escaped from the Kuiper Belt and currently orbit clos...
Preprint
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We investigate what can be learned about a population of distant KBOs by studying the statistical properties of their light curves. Whereas others have successfully inferred the properties of individual, highly variable KBOs, we show that the fraction of KBOs with low amplitudes also provides fundamental information about a population. Each light c...
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Full-text available
In this study, we extend the prior interstellar pickup ion (PUI) observations from the Solar Wind Around Pluto (SWAP) instrument on New Horizons out to nearly 47 au—essentially halfway to the termination shock in the upwind direction. We also provide significantly improved analyses of these and prior observations, including incorporating a cooling...
Preprint
Chaos terrains are characterized by disruption of preexisting surfaces into irregularly arranged mountain blocks with a chaotic appearance. Several models for chaos formation have been proposed, but the formation and evolution of this enigmatic terrain type has not yet been fully constrained. We provide extensive mapping of the individual blocks th...
Article
One of the clearest but unresolved questions for Europa is the thickness of its icy shell. Europa's surface is resplendent with geological features that bear on this question, and ultimately on its interior, geological history, and astrobiological potential. We characterize the size and topographic expression of circular and subcircular features cr...
Article
Full-text available
Persephone is a NASA concept mission study that addresses key questions raised by New Horizons’ encounters with Kuiper Belt objects (KBOs), with arguably the most important being, “Does Pluto have a subsurface ocean?” More broadly, Persephone would answer four significant science questions: (1) What are the internal structures of Pluto and Charon?...
Preprint
Full-text available
One of the most striking and curious features of the small Kuiper Belt Object (KB), Arrokoth, explored by New Horizons, is the bright, annular neck it exhibits at the junction between its two lobes. Here we summarize past reported findings regarding the properties of this feature and report new findings regarding its dimensions, reflectivity and co...
Article
Full-text available
A strong case can be made for a flyby mission through the outer solar system in the coming decades. The census of the larger worlds of the trans-Neptunian region has shown that they display incredible diversity. Surface geology and composition, shapes, and binarity are far more varied in these distant populations than in many other regions of the s...
Preprint
Full-text available
Persephone is a NASA concept mission study that addresses key questions raised by New Horizons' encounters with Kuiper Belt objects (KBOs), with arguably the most important being "Does Pluto have a subsurface ocean?". More broadly, Persephone would answer four significant science questions: (1) What are the internal structures of Pluto and Charon?...
Article
We have compared spectroscopic data of Sputnik Planitia on Pluto, as acquired by New Horizons' Linear Etalon Imaging Spectral Array (LEISA) instrument, to the geomorphology as mapped by White et al. (2017) using visible and panchromatic imaging acquired by the LOng-Range Reconnaissance Imager (LORRI) and the Multi-spectral Visible Imaging Camera (M...
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Full-text available
We used existing data from the New Horizons Long-range Reconnaissance Imager (LORRI) to measure the optical-band (0.4 ≲ λ ≲ 0.9 μ m) sky brightness within seven high–Galactic latitude fields. The average raw level measured while New Horizons was 42–45 au from the Sun is 33.2 ± 0.5 nW m ⁻² sr ⁻¹ . This is ∼10× as dark as the darkest sky accessible t...
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We augment the heliospheric network of galactic cosmic ray (GCR) monitors using 2012–2017 penetrating radiation measurements from the New Horizons (NH) Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI), obtaining intensities of ≳75 MeV particles. The new, predominantly GCR observations provide critical links between the Sun and V...