[ { "id": "authors:2jvv7-zjc89", "collection": "authors", "collection_id": "2jvv7-zjc89", "cite_using_url": "https://authors.library.caltech.edu/records/2jvv7-zjc89", "type": "monograph", "title": "The Next-Generation Ground-Based Planetary Radar", "author": [ { "family_name": "Lazio", "given_name": "Joseph", "clpid": "Lazio-J" }, { "family_name": "de Kleer", "given_name": "Katherine R.", "orcid": "0000-0002-9068-3428", "clpid": "de-Kleer-K-R" }, { "family_name": "Ravi", "given_name": "Vikram", "orcid": "0000-0002-7252-5485", "clpid": "Ravi-Vikram" } ], "abstract": "

Planetary radar observations have a laudable history of “firsts” including determining the astronomical unit with

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the precision sufficient for interplanetary navigation, water ice distribution at the Moon’s south pole, water ice

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indications in the permanently shadowed regions at Mercury’s poles, determining Venus’ rotation state, polar ice

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and anomalous surface features on Mars, indications that the asteroid (16) Psyche is an exposed metallic core of

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a planetoid, establishing the icy nature of the Jovian satellites, and the initial characterizations of Titan’s surface.

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In many cases, these discoveries made by planetary radar systems have motivated missions and mission radar

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instruments.

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This W. M. Keck Institute of Space Studies study was intended to identify the compelling science and potential

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technical developments required for a next-generation, ground-based planetary radar. As new discoveries have

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occurred since the first generation of planetary radar observations, our understanding of the Solar System has

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improved, and new questions have emerged. One of the study’s motivations was to identify what discoveries might be

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enabled or how a next-generation planetary radar might address fundamental questions.

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The study found that there are three compelling science drivers for a next-generation planetary radar—Venus,

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near-Earth asteroids, and the icy moons (“ocean worlds”) of the outer Solar System.

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For Venus (“Earth’s evil twin”), long-term measurements of surface geology obtained with a planetary radar

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would provide context within which to interpret measurements from a suite of spacecraft planned to explore that

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planet over the next decade or more.

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For near-Earth asteroids, an improved characterization of the population (or populations) would result from the

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increase in both the quantity of near-Earth asteroids that could be tracked and the quality of the data obtained. A

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planetary radar would provide precise orbit determinations for planning future spacecraft missions and assessing

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planetary defense hazards.

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For the outer Solar System, much like for Venus, observations of icy moons/“ocean worlds” over unparalleled

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durations could be obtained, even enabling investigations of seasonal changes. Multiple additional science cases

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would be enabled, including potentially the tracking of interstellar objects, thereby bridging the fields of Planetary

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Science and Astrophysics.A second motivation for this study was the two major ground-based planetary radar facilities were approaching

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their half-century anniversaries in 2023, with the Arecibo Observatory planning to celebrate its 60th anniversary of

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operations and NASA’s Deep Space Network planning to celebrate the 50th anniversary of the start of construction of

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its Deep Space Station-14 (DSS-14) antenna, which hosts the Goldstone Solar System Radar (GSSR). Notably, and

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unfortunately, between the two workshops held as part of this study, the Arecibo Observatory collapsed.

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This study found that a next-generation, ground-based planetary radar could be implemented as an antenna array,

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analogous to those already used in multiple radio astronomy facilities, which would provide greater resilience than a

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monolithic antenna.

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Much of the technology for such a planetary radar array is maturing. A planetary radar array could be implemented

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with solid-state transmitters at each antenna, leveraging considerable commercial investments in solid-state technology

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and offering the promise of (much) more reliable performance than the traditional vacuum-tube klystrons. Solid-state

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transmitters have been prototyped and, in one case, deployed for spacecraft telecommunications.

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Considerable promise exists to develop automation and new algorithms, even within existing systems, for both

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scheduling observations and processing planetary radar data.

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Following this study, two more specific concept studies were conducted: “Cross-Disciplinary Deep Space Radar

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Needs Study” and “A Ground-Based Planetary Radar Array”. Both reached similar conclusions: an array of 15-25

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m diameter antennas equipped with 50-80 kW transmitters would be technically feasible and could address all

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compelling science cases identified in this report. A planetary radar array might even be capable of undertaking a

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survey designed to find near-Earth asteroids, a capability not currently available.

", "doi": "10.26206/2jvv7-zjc89", "publisher": "W. M. Keck Institute of Space Studies (KISS), California Institute of Technology", "publication_date": "2025-09-18" }, { "id": "authors:jf3cr-h0t92", "collection": "authors", "collection_id": "jf3cr-h0t92", "cite_using_url": "https://authors.library.caltech.edu/records/jf3cr-h0t92", "type": "monograph", "title": "ALMA Observations of Io Going into and Coming out of Eclipse", "author": [ { "family_name": "de Pater", "given_name": "Imke", "orcid": "0000-0002-4278-3168", "clpid": "de-Pater-I" }, { "family_name": "Luszcz-Cook", "given_name": "Statia", "orcid": "0000-0001-9867-9119", "clpid": "Luszcz-Cook-S" }, { "family_name": "Rojo", "given_name": "Patricio", "orcid": "0000-0002-1607-6443", "clpid": "Rojo-Patricio" }, { "family_name": "Redwing", "given_name": "Erin", "orcid": "0000-0002-5595-3808", "clpid": "Redwing-E" }, { "family_name": "de Kleer", "given_name": "Katherine", "orcid": "0000-0002-9068-3428", "clpid": "de-Kleer-K-R" }, { "family_name": "Moullet", "given_name": "Arielle", "orcid": "0000-0002-9820-1032", "clpid": "Moullet-A" } ], "abstract": "
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We present 1 mm observations constructed from Atacama Large (sub)Millimeter Array (ALMA) data of SO2, SO, and KCl when Io went from sunlight into eclipse (2018 March 20) and vice versa (2018 September 2 and 11). There is clear evidence of volcanic plumes on March 20 and September 2. The plumes distort the line profiles, causing high-velocity (\u2273500 m s−1) wings and red-/blueshifted shoulders in the line profiles. During eclipse ingress, the SO2 flux density dropped exponentially, and the atmosphere re-formed in a linear fashion when reemerging in sunlight, with a “post-eclipse brightening” after ∼10 minutes. While both the in-eclipse decrease and in-sunlight increase in SO was more gradual than for SO2, the fact that SO decreased at all is evidence that self-reactions at the surface are important and fast, and that in-sunlight photolysis of SO2 is the dominant source of SO. Disk-integrated SO2 in-sunlight flux densities are ∼2–3 times higher than in eclipse, indicative of a roughly 30%–50% contribution from volcanic sources to the atmosphere. Typical column densities and temperatures are N ≈ (1.5 ± 0.3) × 1016 cm−2 and T ≈ 220–320 K both in sunlight and in eclipse, while the fractional coverage of the gas is two to three times lower in eclipse than in sunlight. The low-level SO2 emissions present during eclipse may be sourced by stealth volcanism or be evidence of a layer of noncondensible gases preventing complete collapse of the SO2 atmosphere. The melt in magma chambers at different volcanoes must differ in composition to explain the absence of SO and SO2, but simultaneous presence of KCl over Ulgen Patera.

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", "doi": "10.3847/PSJ/abb93d", "issn": "2632-3338", "publisher": "American Astronomical Society", "publication": "Planetary Science Journal", "publication_date": "2020-12", "series_number": "3", "volume": "1", "issue": "3", "pages": "60" }, { "id": "authors:r6pcn-3ep32", "collection": "authors", "collection_id": "r6pcn-3ep32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191023-151847724", "type": "monograph", "title": "Tidal Heating: Lessons from Io and the Jovian System - Final Report", "author": [ { "family_name": "de Kleer", "given_name": "Katherine", "orcid": "0000-0002-9068-3428", "clpid": "de-Kleer-K-R" }, { "family_name": "McEwen", "given_name": "Alfred S.", "clpid": "McEwen-A-S" }, { "family_name": "Park", "given_name": "Ryan S.", "clpid": "Park-Ryan-S" }, { "family_name": "Bierson", "given_name": "Carver J.", "clpid": "Bierson-C-J" }, { "family_name": "Davies", "given_name": "Ashley G.", "orcid": "0000-0003-1747-8142", "clpid": "Davies-A-G" }, { "family_name": "DellaGustina", "given_name": "Daniella N.", "clpid": "DellaGustina-D-N" }, { "family_name": "Ermakov", "given_name": "Anton I.", "clpid": "Ermakov-A-I" }, { "family_name": "Fuller", "given_name": "Jim", "orcid": "0000-0002-4544-0750", "clpid": "Fuller-J" }, { "family_name": "Hamilton", "given_name": "Christopher W.", "clpid": "Hamilton-C-W" }, { "family_name": "Harris", "given_name": "Camilla D. K.", "clpid": "Harris-C-D-K" }, { "family_name": "Hay", "given_name": "Hamish C. F. C.", "clpid": "Hay-H-C-F-C" }, { "family_name": "Jacobson", "given_name": "Robert A.", "clpid": "Jacobson-R-A" }, { "family_name": "Keane", "given_name": "James T.", "orcid": "0000-0002-4803-5793", "clpid": "Keane-J-T" }, { "family_name": "Kestay", "given_name": "Laszlo P.", "clpid": "Kestay-L-P" }, { "family_name": "Khurana", "given_name": "Krishan K.", "orcid": "0000-0002-2856-1171", "clpid": "Khurana-K-K" }, { "family_name": "Kirby", "given_name": "Karen W.", "clpid": "Kirby-K-W" }, { "family_name": "Lainey", "given_name": "Valeriy J.", "clpid": "Lainey-V-J" }, { "family_name": "Matsuyama", "given_name": "Isamu", "clpid": "Matsuyama-I" }, { "family_name": "McCarthy", "given_name": "Christine", "clpid": "McCarthy-Christine" }, { "family_name": "Nimmo", "given_name": "Francis", "orcid": "0000-0003-3573-5915", "clpid": "Nimmo-F" }, { "family_name": "Panning", "given_name": "Mark P.", "orcid": "0000-0002-2041-3190", "clpid": "Panning-M-P" }, { "family_name": "Pommier", "given_name": "Anne", "clpid": "Pommier-A" }, { "family_name": "Rathbun", "given_name": "Julian", "clpid": "Rathbun-J" }, { "family_name": "Steinbr\u00fcgge", "given_name": "Gregor", "clpid": "Steinbr\u00fcgge-G" }, { "family_name": "Stevenson", "given_name": "David J.", "orcid": "0000-0001-9432-7159", "clpid": "Stevenson-D-J" }, { "family_name": "Tsai", "given_name": "Victor C.", "orcid": "0000-0003-1809-6672", "clpid": "Tsai-V-C" }, { "family_name": "Turtle", "given_name": "Elizabeth P.", "clpid": "Turtle-E-P" }, { "family_name": "Eiler", "given_name": "John M.", "clpid": "Eiler-J-M" }, { "family_name": "Young", "given_name": "Edward D.", "clpid": "Young-E-D" }, { "family_name": "Zahnle", "given_name": "Kevin J.", "clpid": "Zahnle-K-J" }, { "family_name": "Adkins", "given_name": "Jess F.", "orcid": "0000-0002-3174-5190", "clpid": "Adkins-J-F" }, { "family_name": "Mandt", "given_name": "Kathy E.", "clpid": "Mandt-K-E" }, { "family_name": "McGrath", "given_name": "Melissa A.", "clpid": "McGrath-M-A" }, { "family_name": "Moullet", "given_name": "Arielle", "orcid": "0000-0002-9820-1032", "clpid": "Moullet-A" }, { "family_name": "Waite", "given_name": "J. Hunter", "orcid": "0000-0002-1978-1025", "clpid": "Waite-J-H" }, { "family_name": "Schneider", "given_name": "Nicholas M.", "clpid": "Schneider-N-M" } ], "abstract": "Tidal heating is key to the evolution and habitability of many worlds across our solar system and beyond. However, there remain fundamental gaps in our understanding of tidal heating and coupled orbital evolution, which motivated a Keck Institute for Space Studies (KISS) workshop on this topic. The Cassini mission has led to many recent results about ocean worlds and what may become a new paradigm for understanding orbital evolution with tidal heating, the model of resonance locking in the parent planet (Fuller et al., 2016). Resonance locking explains how subsurface oceans may persist over much of geologic time, even in tiny Enceladus. The discovery\nof the Laplace resonance of Io, Europa, and Ganymede orbiting Jupiter led to the prediction of intense tidal heating of Io (Peale et al., 1979); this system provides the greatest potential for advances in the next few decades. Europa Clipper and JUpiter ICy moons Explorer (JUICE) will provide in-depth studies of Europa and Ganymede in the 2030s. The easily observed heat flow of Io, from hundreds of continually erupting volcanoes, makes it an ideal target for further investigation, and the missing link\u2014along with missions in development\u2014to understand the Laplace system. \n\nWe identified five key questions to drive future research and exploration: (Q1) What do volcanic eruptions tell us about the interiors of tidally heated bodies (e.g., Io, Enceladus, and perhaps Europa and Triton)? (Q2) How is tidal dissipation partitioned between solid and liquid materials? (Q3) Does Io have a melt-rich layer, or \"magma ocean\", that mechanically decouples the lithosphere from the deeper interior? (Q4) Is the Jupiter/Laplace system in equilibrium (i.e., does the satellite's heat output equal the rate at which energy is generated)? (Q5) Can stable isotope measurements inform long-term evolution of tidally heated bodies? \n\nThe most promising avenues to address these questions include a new spacecraft mission making close flybys of Io, missions orbiting and landing on key worlds such as Europa and Enceladus, technology developments to enable advanced techniques, closer coupling between laboratory experiments and tidal heating theory, and advances in Earth-based telescopic observations of solar system and extrasolar planets and moons. All of these avenues would benefit from technological developments. An Io mission should: characterize volcanic processes (Q1); test interior models via a set of geophysical measurements coupled with laboratory experiments and theory (Q2 and Q3); measure the rate of Io's orbital migration (to complement similar measurements expected at Europa and Ganymede) to determine if the Laplace resonance is in equilibrium (Q4); and determine neutral compositions and measure stable isotopes in Io's atmosphere and plumes (Q5). No new technologies are required for such an Io mission following advances in radiation design and solar power realized for Europa Clipper and JUICE. Seismology is a promising avenue for future exploration, either from landers or remote laser reflectometry, and interferometric synthetic aperture radar (InSAR) could be revolutionary on these active worlds, but advanced power systems plus lower mass and power-active instruments are needed for operation in the outer solar system.", "doi": "10.26206/d4wc-6v82", "publication_date": "2019-06" }, { "id": "authors:dkqcf-z8960", "collection": "authors", "collection_id": "dkqcf-z8960", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190426-092643133", "type": "monograph", "title": "Potential for Solar System Science with the ngVLA", "author": [ { "family_name": "de Pater", "given_name": "Imke", "orcid": "0000-0002-4278-3168", "clpid": "de-Pater-I" }, { "family_name": "Butler", "given_name": "Bryan", "orcid": "0000-0002-5344-820X", "clpid": "Butler-B-J" }, { "family_name": "Sault", "given_name": "R. J.", "orcid": "0000-0001-9209-7716", "clpid": "Sault-R-J" }, { "family_name": "Moullet", "given_name": "Arielle", "orcid": "0000-0002-9820-1032", "clpid": "Moullet-A" }, { "family_name": "Moeckel", "given_name": "Chris", "clpid": "Moeckel-C" }, { "family_name": "Tollefson", "given_name": "Joshua", "clpid": "Tollefson-J" }, { "family_name": "de Kleer", "given_name": "Katherine", "orcid": "0000-0002-9068-3428", "clpid": "de-Kleer-K-R" }, { "family_name": "Gurwell", "given_name": "Mark", "orcid": "0000-0003-0685-3621", "clpid": "Gurwell-M-A" }, { "family_name": "Milam", "given_name": "Stefanie", "clpid": "Milam-S-N" } ], "abstract": "Radio wavelength observations of solar system bodies are a powerful method of probing many characteristics of those bodies. From surface and subsurface, to atmospheres (including deep atmospheres of the giant planets), to rings, to the magnetosphere of Jupiter, these observations provide unique information on current state, and sometimes history, of the bodies. The ngVLA will enable the highest sensitivity and resolution observations of this kind, with the potential to revolutionize our understanding of some of these bodies. In this article, we present a review of state-of-the-art radio wavelength observations of a variety of bodies in our solar system, varying in size from ring particles and small near-Earth asteroids to the giant planets. Throughout the review we mention improvements for each body (or class of bodies) to be expected with the ngVLA. A simulation of a Neptune-sized object is presented in Section 6. Section 7 provides a brief summary for each type of object, together with the type of measurements needed for all objects throughout the Solar System.", "doi": "10.48550/arXiv.1810.08521", "publisher": "arXiv", "publication_date": "2018-10-19" } ]