Titan is an object of fascination for scientists researching the solar system, as a ‘terrestrial-like’ world with active meteorology and fluvial and lacustrine formations based on methane chemistry and condensation. The Cassini-Huygens mission explored Titan extensively from 2004 to 2017, but since that time further observation of its slow seasonal cycle has been possible only via telescopes positioned on or close to the Earth. Titan’s unique characteristics led to a concerted post-Cassini observational campaign, with many of the most powerful telescopes available to astronomy. In this work we report on observations from 2022 & 2023 with three instruments on the James Webb Space Telescope (JWST), NIRCam, NIRSpec and MIRI, also in coordination with imaging from Keck II. In November 2022 and July 2023, Titan was the subject of multi-spectral filter imaging with JWST NIRCam and Keck II NIRC2, revealing tropospheric clouds at mid-northern latitudes, in line with climate modeling predictions for this season (late northern summer). In filters sensitive to the upper troposphere, we observed clouds growing and apparently ascending in altitude during a Titan day. JWST NIRSpec spectroscopy yielded for the first time a high resolution (R=2700) spectrum of Titan across the entire near-infrared (1-5 microns) unobscured by telluric absorption. This, among other things, enabled measuring the detailed structure of the CO 4.7 micron non-LTE emission, including the fundamental, the first two overtone bands and two isotopic bands. It is also the first time that CO2 emission has been resolved in the NIR and the first time it has been seen on Titan’s dayside. Finally, very sensitive spectroscopy with JWST MIRI in the mid infrared (5-28 microns) confirmed the many stratospheric gases seen by Cassini CIRS, but also added a new detection of methyl (CH3) in the middle atmosphere, a product of methane photochemistry that was expected but not previously seen. We modeled parts of the spectra to find a global mean temperature profile and profiles of minor gases. Soon we hope to extract yet more results from the NIRSpec and MIRI spectra as our understanding of the calibration and modeling progresses. In this presentation we summarize our results to date and describe planned future observations of Titan with JWST and Keck cycles.

Saturn's moon Titan undergoes a long annual cycle of 29.45 Earth years. Titan's northern winter and spring were investigated in detail by the Cassini-Huygens spacecraft (2004-2017), but the northern summer season remains sparsely studied. Here we present new observations from the James Webb Space Telescope (JWST) and Keck II telescope made in 2022 and 2023 during Titan's late northern summer. Using JWST's mid-infrared instrument, we spectroscopically detected the methyl radical, the primary product of methane break-up and key to the formation of ethane and heavier molecules. Using the near-infrared spectrograph onboard JWST, we detected several non-local thermodynamic equilibrium CO and CO2 emission bands, which allowed us to measure these species over a wide altitude range. Lastly, using the near-infrared camera onboard JWST and Keck II, we imaged northern hemisphere tropospheric clouds evolving in altitude, which provided new insights and constraints on seasonal convection patterns. These observations pave the way for new observations and modelling of Titan's climate and meteorology as it progresses through the northern fall equinox, when its atmosphere is expected to show notable seasonal changes.

Double ridges are sprawling features observed globally across the icy surface of Europa. They consist of two topographic highs flanking a trough. The topographic relief of the ridges is approximately 100 m, and the ridges extend up to hundreds of kilometers in length. The interior structure and dynamics of Europa's ice shell are currently poorly constrained. Therefore, accurate models for the formation of these prominent surface features can be useful for determining how the ice shell operates. We hypothesize that double ridges form as a result of incremental ice wedging. We use both analytical and numerical finite element models to quantify the deformation that occurs as an ice wedge grows incrementally within the ice shell. We show that incremental growth of the ice wedge results in surface deformation that matches the size and shape of typical Europan double ridges, including their topographic relief and surrounding troughs. We find that as the depth of the ice wedge increases, double ridges become broader and shorter. We explore the possibility of local and non-local sources for the liquid water that freezes to produce the wedge and ultimately argue in favor of local sources of liquid water within the ice shell. Europa, the second Galilean satellite, is hypothesized to have a global salt-water ocean underneath its outer icy shell. Double ridges are a common feature on Europa's icy surface. They consist of a long trough bordered on either side by uplifted hills of ice. The height of the ridges above the surface is approximately 100 m, and the ridges may extend for hundreds of kilometers over the surface of the moon. Models that show how surface features, like double ridges, may form can tell us about characteristics of the ice shell and underlying ocean that are otherwise hard to measure. We use two different techniques to model a process for how double ridges might form. In this process, water, possibly from the subsurface ocean, enters a long vertical crack in the ice shell and freezes along the sides of the crack. Over time as water continues to enter and freeze in the same place, a new wedge of ice grows inside the ice shell and pushes on material around it. The ice wedge forces ice at the surface of the shell to deform into the same size and shape of double ridges that have been observed on Europa. Numerical modeling suggests that double ridges are produced by wedges of ice that grow within Europa's ice shell Analytical and numerical models show that an ice wedge within Europa's ice shell elastically deforms the surface into double ridges Ice wedge material may be sourced from the ocean or locally from cryovolcanic dikes or water reservoirs within the shell

Saturn’s moon Titan is the only moon in the solar system with a dense atmosphere, composed largely of nitrogen (94.5–98.6%) and methane (5.5–1.4%). Due to the cold troposphere and surface (70–93 K) close to the triple point of methane, methane is a condensable substance in Titan’s lower atmosphere. It therefore plays a similar meteorological role to water on Earth, evaporating from the surface and reaching the middle troposphere, where methane clouds form and rainfall occurs, in changing seasonal patterns. In the middle and upper atmosphere, methane is processed by photochemistry and at high altitudes forms solid organic haze particles or even PAHs (polycyclic aromatic hydrocarbons). These particles are thought to be the building blocks of stratospheric aerosols as they drift downwards and grow in size to form a global haze layer in the stratosphere, which lends Titan its golden hue at visible wavelengths. In the stratosphere, slow seasonal changes in composition and haze distribution indicate the seasonal reversal of Titan’s global meridional circulation every 14.75 Earth years.Since the end of the Cassini-Huygens mission in September 2017 our ability to monitor Titan’s changing atmosphere has been curtailed, since we have lacked the ability to view Titan unimpeded by the Earth’s atmosphere across all infrared wavelengths. Nevertheless, using ground-based adaptive optics (AO) imaging from the Keck observatory on Maunakea, cloud monitoring was possible, although only in some near infrared (NIR) spectral windows. With the commissioning of the James Webb Space Telescope (JWST) in 2022 it became possible to view Titan once more at wavelengths from ∼1.0 to 28.0 μm.In this article we report results of JWST imaging and spectroscopy of Titan that occurred in November 2022 and July 2023, using three of the four observatory instruments. We also report on contemporaneous ground-based observations with the Keck NIRC2 camera that provided even higher spatial resolution imaging over a wider time range, but in a more limited set of filters. Imaging data from JWST and Keck reveals clouds at mid and high northern latitudes at different altitudes, suggestive of convection at the latitudes of the northern lakes and seas. Spectroscopy with JWST/NIRSpec enabled the detection of the CO2 4.3-μm bands and measurement of the detailed structure of the CO 4.7-μm non-LTE emission. Finally, with JWST/MIRI we made the first detection of the CH3 radical, opening new views into the photochemistry occurring in the upper atmosphere.Together, these results provide new insights into the changes in the composition and meteorology of Titan’s atmosphere that have occurred since the end of Cassini-Huygens in 2017, as Titan’s late northern summer ebbs towards the upcoming fall equinox in 2025.Figure 1: JWST (July 11th) and Keck (July 8th and 14th) observations of Titan. Upper row: RGB color composite images. JWST: blue=1.4 mm, green=1.5 mm, blue=2.0 mm (filters F140M, F150W, and F200W, respectively. Keck: blue=2.13 mm, green=2.12 red=2.06 mm (H2 1-0, Kp, and He1b, respectively). Second row: single-wavelength images taken by JWST and Keck at 2.12 mm sensitive to emission from Titan’s lower troposphere. Third row: emission at 1.64 mm (JWST) and 2.17 mm (Keck) sensitive to Titan’s upper troposphere and stratosphere. Fourth row: Titan orientation on the sky as seen on the different dates. Clouds are seen at higher altitudes on July 14th than earlier on July 8th and 11th, suggesting upward convection.

The goal of NASA’s Europa Clipper mission is to assess the habitability of Jupiter’s moon Europa. After entering Jupiter orbit in 2030, the flight system will collect science data while flying past Europa 49 times at typical closest approach distances of 25–100 km. The mission’s objectives are to investigate Europa’s interior (ice shell and ocean), composition, and geology; the mission will also search for and characterize any current activity including possible plumes. The science objectives will be accomplished with a payload consisting of remote sensing and in-situ instruments. Remote sensing investigations cover the ultraviolet, visible, near infrared, and thermal infrared wavelength ranges of the electromagnetic spectrum, as well as an ice-penetrating radar. In-situ investigations measure the magnetic field, dust grains, neutral gas, and plasma surrounding Europa. Gravity science will be achieved using the telecommunication system, and a radiation monitoring engineering subsystem will provide complementary science data. The flight system is designed to enable all science instruments to operate and gather data simultaneously. Mission planning and operations are guided by scientific requirements and observation strategies, while appropriate updates to the plan will be made tactically as the instruments and Europa are characterized and discoveries emerge. Following collection and validation, all science data will be archived in NASA’s Planetary Data System. Communication, data sharing, and publication policies promote visibility, collaboration, and mutual interdependence across the full Europa Clipper science team, to best achieve the interdisciplinary science necessary to understand Europa.

Dragonfly, a rotorcraft lander to visit multiple locations on Saturn's largest moon, Titan, is NASA's 4th New Frontiers mission and is presently in development. Dragonfly will perform in situ exploration using aerial mobility to traverse Titan's surface to study prebiotic chemical processes and document the habitability of a carbon-rich ocean world in the outer solar system, where the key ingredients for life have been available on the surface. Dragonfly will address fundamental questions:•What makes a world habitable? Dragonfly will investigate Titan's methane hydrological cycle, geologic processing, and opportunities for organics and liquid water to mix.•What chemical processes led to the development of life? Dragonfly will inventory the diversity of complex carbon- rich materials and the chemistry at work on Titan's surface, revolutionizing our understanding of prebiotic chemistry in the Solar System.•Has life developed elsewhere in our Solar System? Dragonfly will make measurements that allow for a broad, contextualized search for potential chemical biosignatures.The Dragonfly Team passed the Mission’s Preliminary Design Review (PDR) in early March 2023, demonstrating technical readiness to proceed to final design and fabrication in Phase C. We will present the current plan for the Dragonfly Mission and its exploration of Titan.

The 27 moons of Uranus (Figure 1) are enigmatic and remain poorly understood. Voyager 2 flew by the Uranus system in 1986, collecting fascinating images of its five largest, tidally-locked ‘classical’ moons (Figure 2), while also discovering a bevy of small moons nestled in its ring system (e.g., [1]) (Figure 3). The surfaces of Uranus’ classical moons Miranda, Ariel, Umbriel, Titania, and Oberon have been modified by endogenic activity, in particular Miranda and Ariel, which exhibit substantial evidence for geologic communication between their interiors and surfaces (e.g., [1-3]) (Figure 2). The available images therefore indicate that these classical moons are candidate ocean worlds, which have, or had, liquid H2O layers beneath their icy exteriors (e.g., [3-5]). Because the Voyager 2 flyby occurred near Uranus’ southern summer solstice (subsolar latitude ~81°S), the collected images are centered near the south poles of these moons, and their northern hemispheres were largely unobservable. Furthermore, only the classical moons and the largest ring moon Puck (Figure 3) were spatially resolved by Voyager 2. The other nine ring moons Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalina, and Belinda were not resolved. Another ring moon, Perdita, was discovered via reanalysis of Voyager 2 data [6], and two more ring moons, Cupid and Mab [7,8], were discovered by space-based telescope observations. All nine known irregular satellites, Francisco, Caliban, Stephano, Trinculo, Sycorax, Margaret, Prospero, Setebos, and Ferdinand, were not detected by Voyager 2 and were discovered later by ground-based observations (e.g., [9-11]).Voyager 2 was not equipped with a near-infrared (NIR) mapping spectrometer, and most of what we know about the compositions of Uranus’ moons has been determined using data collected by ground and space-based telescopes. The surfaces of Uranus’ classical moons are composed of H2O ice mixed with low albedo material that could be rich in organics and silicate minerals (e.g., [12-14]). Carbon dioxide (CO2) has been detected on the classical moons, primarily on their trailing hemispheres, in particular on Ariel [15,16] (Figure 4). Spectrally red material that could be rich in organics has been detected, primarily on the leading hemispheres of these moons (e.g., [17,18]) (Figure 4). Ammonia (NH3) has possibly been detected on the classical moons and may originate from their interiors [18,19]. Although useful, these prior observations are disk-integrated, limiting our ability to constrain the distribution of surface constituents and identify links between volatile species and geologic terrains. Much less is known about the surface compositions of Uranus’ 13 ring moons and nine irregular satellites, which are mostly too faint (Vmag 19.8 - 25.8) for spectroscopic analysis using existing facilities. Spectrophotometric datasets indicate that Uranus’ ring moons have dark surfaces that show hints of H2O ice features [6]. Uranus’ irregular satellites have dark, reddish surfaces (e.g., [20]) but little else is known about their surface compositions, except for Sycorax, which shows hints of H2O ice [21].An orbiting spacecraft collecting data during close flybys of Uranus’ ring system and classical moons would reveal the surface geologies of these moons, including on their previously unobserved northern hemispheres, determine their surface compositions, and determine whether any of the classical moons are, or were, ocean worlds. Furthermore, an orbiter could spend time looking outward to characterize Uranus’ irregular satellites, providing new insight into these likely captured objects (e.g., Jewitt & Haghighipour 2007). By utilizing a Jupiter gravity assist (2030 - 2034 launch window), a mission could arrive at the Uranian system in the mid 2040’s (∼11 years flight time), using existing chemical propulsion technology [22]. This arrival time frame would allow us to observe these moons’ northern hemispheres. An orbiter making close flybys of the classical moons could search for evidence of ongoing geologic activity and characterize migration of CO2 in response to changes in subsolar heating as the Uranian system transitions into southern spring in 2050.To determine whether liquid H2O layers are present in the interiors of the classical moons, the highest priority instrument onboard an orbiter would be a magnetometer, which could detect and characterize induced magnetic fields emanating from briny subsurface oceans. Visible (VIS, 0.4 - 0.7 µm) and mid-infrared (MIR, 5 - 250 µm) cameras would also be vital to search for plume activity, hot spots, and other signs of geologic communication between the interiors and surfaces of these moons. A spectrometer (0.4 - 5 µm) would be critical for characterizing volatile species that might result from outgassing of material or recently exposed or emplaced surface deposits. The abundant evidence for geologic activity in the recent past on Ariel and Miranda likely makes them the highest priority targets for any mission that aims to characterize Uranus’ satellites.References: [1] Smith, B. A. et al. 1986, Science, 233, 43. [2] Schenk, P. M. 1991, JGR: Solid Earth, 96, 1887. [3] Beddingfield, C. B. & Cartwright, R. J. 2020, Icarus, 113687. [4] Hendrix, A. R. et al. 2019, Astrobiology, 19, 1. [5] Cartwright, R.J. et al. 2021. arXiv preprint arXiv:2105.01164. [6] Karkoschka, E. 2001, Icarus, 151, 51. [7] Showalter, M. R. & Lissauer, J. J. 2006, Science, 311, 973. [8] De Pater, I. et al. 2006, Science, 312, 92. [9] Gladman, B. J. et al. 1998, Nature, 392, 897. [10] Kavelaars, J. et al. 2004, Icarus, 169, 474. [11] Sheppard, S. S. et al. 2005, AJ, 129, 518. [12] Cruikshank, D. et al. 1977, AJ, 217, 1006. [13] Clark, R. N. & Lucey, P. G. 1984, JGR: Solid Earth, 89, 6341. [14] Brown, R. H. & Clark, R. N. 1984, Icarus, 58, 288. [15] Grundy, W. et al. 2006, Icarus, 184, 543. [16] Cartwright, R. J. et al. 2015, Icarus, 257, 428. [17] Buratti, B. J. & Mosher, J. A. 1991, Icarus, 90, 1. [18] Cartwright, R. J. et al. 2018, Icarus, 314, 210. [19] Cartwright, R. J. et al. 2020c, ApJL, 898, L22. [20] Maris, M. et al. 2007, A&A, 472, 311. [21] Romon, J. et al. 2001, A&A, 376, 310. [22] Hofstadter, M. et al. 2019, Planetary and Space Science, 177, 104680.

Abstract The Europa Imaging System (EIS; Fig. 1) for NASA's Europa Clipper Mission combines a narrow-angle camera (NAC) and a wide-angle camera (WAC) to explore Europa and address high-priority geology, composition, ice shell and ocean science objectives. Both cameras have framing and pushbroom imaging capability, including broadband color filters. EIS data will be used to generate: cartographic and geologic maps; regional and high-resolution topography; GIS, color, and photometric data products; a database of plume-search observations; and control points tied to radar altimetry. Our science goals are to: * constrain the formation processes of landforms by characterizing geologic structures, units, and global cross-cutting relationships; * identify relationships between surface and sub-surface structures and potential near-surface water detected by ice-penetrating radar; * investigate compositional variability between and among landforms and correlate composition be-tween individual features and regional units; * search for evidence of recent or current activity, including potential erupting plumes; * constrain ice-shell thickness from global shape measurements via limb fits; * characterize surface clutter (off-nadir surface reflections that may appear to be subsurface interfaces) to aid interpretation of deep and shallow radar sounding; * characterize scientifically compelling landing sites and hazards by determining the nature of the surface at meter scales. Figure 1: EIS NAC (left) and WAC (right) on the spacecraft nadir deck. The NAC is mounted on a 2-axis gimbal. The DPUs are in the spacecraft vault. EIS Narrow-angle Camera (NAC) The NAC has a 2.3° x 1.2° field of view (FOV) with a 10-μrad instantaneous FOV (IFOV), and from an altitude of 50-km achieves 0.5-m pixel scale over a 2-km-wide swath. Its 2-axis gimbal, ±30° cross- and along-track, enables targeting independent of spacecraft orientation, allowing near-global (>90%) mapping of Europa at ≤100-m pixel scale (to date, only ~14% of Europa has been imaged at ≤500 m/pixel), as well as regional stereo imaging. The gimbal slew rate is designed to be able to perform very high-resolution stereo imaging from as close as 50-km altitude during high-speed (~4.5 m/s) flybys to generate digital topographic models (DTMs) with ≤4-m ground sample distance (GSD) and ≤0.5-m vertical precision. The NAC will also perform high-phase-angle observations to search for potential erupting plumes; a pixel scale of 10 km from 106 km range means that the NAC can take advantage of good illumination geometry for forward scattering by potential plumes even when the spacecraft is distant from Europa. EIS Wide-angle Camera (WAC) The WAC has a 48° x 24° FOV with a 218-µrad IFOV, and is designed to acquire 3-line pushbroom stereo and color swaths along flyby ground-tracks. From an altitude of 50 km, the WAC achieves 11-m pixel scale over a 44-km-wide swath, generating DTMs with 32-m GSD and 4-m vertical precision. These data also support characterization of surface clutter for interpretation of radar deep and shallow sounding. Detectors and Electronics The cameras have identical rapid-readout, radiation-hardened 4k x 2k CMOS detectors and can perform both pushbroom and framing imaging. Color observations are acquired by pushbroom imaging using six broadband filters (Table 1; Fig 2), allowing mapping of surface units and correlation with geologic structures, topography, and compositional units from other instruments. Radiation-hard data processing units (DPUs) take advantage of the CMOS rapid, random-access readout and use real-time processing for pushbroom imaging, including: WAC 3-line stereo, digital time delay integration (TDI) to enhance signal-to-noise ratios (SNR), and readout strategies to measure and correct jitter. Table 1: NAC and WAC broad-band, stripe filters Filter Wavelength (nm) Key Uses NAC: 350–1050 Clear Mapping, stereo, context imaging, best SNR for faint targets, e.g., plume searches WAC: 370–1050 NAC: 355–400 NUV (See Figure 2) WAC: 375–400 BLU 380–475 (See Figure 2) GRN 520–590 (See Figure 2) RED 640–700 (See Figure 2) IR1 780–920 (See Figure 2) 1µm 950–1050 (See Figure 2) Figure 2: EIS broadband filter wavelengths (top) and WAC filter layout (bottom). Summary EIS data sets and collaborative science with other investigations will provide insight into Europa’s global geology, ice shell, and the potential for recent or current activity, to fulfill the goal of exploring Europa to investigate its habitability. Updates will be provided on flight instrument performance from ground testing and expected datasets from the planned tour at Jupiter.

Large linear dunes are found in great abundance across the equatorial regions of Saturn’s moon Titan. They are similar in width and spacing to the large dunes of the Saharan, Arabian and Namibian deserts, indicating atmospheric conditions, sand sizes and winds are comparable to those on Earth. An examination of their geomorphometric properties, such as length, width, spacing and distribution can reveal aspects of their relationship with wind strength and direction and controls by underlying topography. We traced long axes of about 70% of all measurable dunes, which involved over 20,000 measurements. We mapped all of the dunes in Shangri-La, Fensal, Aztlan, and half of the Belet Sand Sea. In addition, we measured 90,000 dune widths across Titan at 500 m intervals and fit a nonstationary statistical model with a Gaussian spatial process to determine correlations of dune spacings. Dune long axes are dominantly oriented E-W, a proxy for the sand flux and wind directions. Dunes range to over 400 km in length, with an average length of 40 km. The average length may reflect a rough spacing of obstacles, large-scale topographic variations, or the availability of sand. Dunes are directed slightly NE in the Belet Sand Sea, where dunes are especially abundant and wider. The longest dunes are also found here. Belet may thus represent a fully mature sand sea, where dunes are free to grow as long and large as possible. To the east is the Shangri-La sand sea, which is the location of the Dragonfly landing site. Shangri-La hosts dunes directed dramatically southward, especially near the Xanadu region margin. Dunes here are narrower and interdunes are clearly visible near the elevated rim of the Selk impact crater and other topographic obstacles. Sand collects most densely along the eastern boundary, at the margin of Xanadu, and at the downwind margins of all sand seas. This perhaps indicates that sand is transported until major boundaries are encountered that preclude sand movement. Dune width values can be divided into about 5 major (20 minor) regions globally within the sand seas, with widest groupings at the sand sea centers and isolated, narrower groupings at higher latitudes. The narrowest dunes appear to have the most obstacles or topographic control or be at the highest latitudes. However, within each cluster, dunes of any size within the 1-3 km width range can exist. These studies reveal that while local controls are impactful, dunes will ultimately grow to the extent possible under the conditions present, which on Titan are highly favorable for large linear dunes. Further examination of dune parameters can reveal details about the landscape, basement bedrock conditions, sand transport history and regional wind effects on the dunes of Titan.

In response to ESA’s “Voyage 2050” announcement of opportunity, we propose an ambitious L-class mission to explore one of the most exciting bodies in the Solar System, Saturn’s largest moon Titan. Titan, a “world with two oceans”, is an organic-rich body with interior-surface-atmosphere interactions that are comparable in complexity to the Earth. Titan is also one of the few places in the Solar System with habitability potential. Titan’s remarkable nature was only partly revealed by the Cassini-Huygens mission and still holds mysteries requiring a complete exploration using a variety of vehicles and instruments. The proposed mission concept POSEIDON (Titan POlar Scout/orbitEr and In situ lake lander DrONe explorer) would perform joint orbital and in situ investigations of Titan. It is designed to build on and exceed the scope and scientific/technological accomplishments of Cassini-Huygens, exploring Titan in ways that were not previously possible, in particular through full close-up and in situ coverage over long periods of time. In the proposed mission architecture, POSEIDON consists of two major elements: a spacecraft with a large set of instruments that would orbit Titan, preferably in a low-eccentricity polar orbit, and a suite of in situ investigation components, i.e. a lake lander, a “heavy” drone (possibly amphibious) and/or a fleet of mini-drones, dedicated to the exploration of the polar regions. The ideal arrival time at Titan would be slightly before the next northern Spring equinox (2039), as equinoxes are the most active periods to monitor still largely unknown atmospheric and surface seasonal changes. The exploration of Titan’s northern latitudes with an orbiter and in situ element(s) would be highly complementary in terms of timing (with possible mission timing overlap), locations, and science goals with the upcoming NASA New Frontiers Dragonfly mission that will provide in situ exploration of Titan’s equatorial regions, in the mid-2030s.

Abstract The Europa Imaging System (EIS; Fig. 1) for NASA's Europa Clipper Mission combines a narrow-angle camera (NAC) and a wide-angle camera (WAC) to explore Europa and address high-priority geology, composition, ice shell and ocean science objectives. Both cameras have framing and pushbroom imaging capability, including broadband color filters. EIS data will be used to generate: cartographic and geologic maps; regional and high-resolution topography; GIS, color, and photometric data products; a database of plume-search observations; and control points tied to radar altimetry. Our science goals are to: * constrain the formation processes of landforms by characterizing geologic structures, units, and global cross-cutting relationships; * identify relationships between surface and sub-surface structures and potential near-surface water detected by ice-penetrating radar; * investigate compositional variability between and among landforms and correlate composition be-tween individual features and regional units; * search for evidence of recent or current activity, including potential erupting plumes; * constrain ice-shell thickness from global shape measurements via limb fits; * characterize surface clutter (off-nadir surface reflections that may appear to be subsurface interfaces) to aid interpretation of deep and shallow radar sounding; * characterize scientifically compelling landing sites and hazards by determining the nature of the surface at meter scales. Figure 1: EIS NAC (left) and WAC (right) on the spacecraft nadir deck. The NAC is mounted on a 2-axis gimbal. The DPUs are in the spacecraft vault. EIS Narrow-angle Camera (NAC) The NAC has a 2.3° x 1.2° field of view (FOV) with a 10-μrad instantaneous FOV (IFOV), and from an altitude of 50-km achieves 0.5-m pixel scale over a 2-km-wide swath. Its 2-axis gimbal, ±30° cross- and along-track, enables targeting independent of spacecraft orientation, allowing near-global (>90%) mapping of Europa at ≤100-m pixel scale (to date, only ~14% of Europa has been imaged at ≤500 m/pixel), as well as regional stereo imaging. The gimbal slew rate is designed to be able to perform very high-resolution stereo imaging from as close as 50-km altitude during high-speed (~4.5 m/s) flybys to generate digital topographic models (DTMs) with ≤4-m ground sample distance (GSD) and ≤0.5-m vertical precision. The NAC will also perform high-phase-angle observations to search for potential erupting plumes; a pixel scale of 10 km from 106 km range means that the NAC can take advantage of good illumination geometry for forward scattering by potential plumes even when the spacecraft is distant from Europa. EIS Wide-angle Camera (WAC) The WAC has a 48° x 24° FOV with a 218-µrad IFOV, and is designed to acquire 3-line pushbroom stereo and color swaths along flyby ground-tracks. From an altitude of 50 km, the WAC achieves 11-m pixel scale over a 44-km-wide swath, generating DTMs with 32-m GSD and 4-m vertical precision. These data also support characterization of surface clutter for interpretation of radar deep and shallow sounding. Detectors and Electronics The cameras have identical rapid-readout, radiation-hardened 4k x 2k CMOS detectors and can perform both pushbroom and framing imaging. Color observations are acquired by pushbroom imaging using six broadband filters (Table 1; Fig 2), allowing mapping of surface units and correlation with geologic structures, topography, and compositional units from other instruments. Radiation-hard data processing units (DPUs) take advantage of the CMOS rapid, random-access readout and use real-time processing for pushbroom imaging, including: WAC 3-line stereo, digital time delay integration (TDI) to enhance signal-to-noise ratios (SNR), and readout strategies to measure and correct jitter. Table 1: NAC and WAC broad-band, stripe filters Filter Wavelength (nm) Key Uses NAC: 350–1050 Clear Mapping, stereo, context imaging, best SNR for faint targets, e.g., plume searches WAC: 370–1050 NAC: 355–400 NUV (See Figure 2) WAC: 375–400 BLU 380–475 (See Figure 2) GRN 520–590 (See Figure 2) RED 640–700 (See Figure 2) IR1 780–920 (See Figure 2) 1µm 950–1050 (See Figure 2) Figure 2: EIS broadband filter wavelengths (top) and WAC filter layout (bottom). Summary EIS data sets and collaborative science with other investigations will provide insight into Europa’s global geology, ice shell, and the potential for recent or current activity, to fulfill the goal of exploring Europa to investigate its habitability. Updates will be provided on flight instrument performance from ground testing and expected datasets from the planned tour at Jupiter.

Current knowledge of the Uranian system is limited to observations from the flyby of Voyager 2 and limited remote observations. However, Uranus remains a highly compelling scientific target due to the unique properties of many aspects of the planet itself and its system. Future exploration of Uranus must focus on cross-disciplinary science that spans the range of research areas from the planet’s interior, atmosphere, and magnetosphere to the its rings and satellites, as well as the interactions between them. Detailed study of Uranus by an orbiter is crucial not only for valuable insights into the formation and evolution of our solar system but also for providing ground truths for the understanding of exoplanets. As such, exploration of Uranus will not only enhance our understanding of the ice giant planets themselves but also extend to planetary dynamics throughout our solar system and beyond. The timeliness of exploring Uranus is great, as the community hopes to return in time to image unseen portions of the satellites and magnetospheric configurations. This urgency motivates evaluation of what science can be achieved with a lower-cost, potentially faster-turnaround mission, such as a New Frontiers–class orbiter mission. This paper outlines the scientific case for and the technological and design considerations that must be addressed by future studies to enable a New Frontiers–class Uranus orbiter with balanced cross-disciplinary science objectives. In particular, studies that trade scientific scope and instrumentation and operational capabilities against simpler and cheaper options must be fundamental to the mission formulation.

NASA’s Dragonfly mission will send a rotorcraft lander to the surface of Titan in the mid-2030s. Dragonfly's science themes include investigation of Titan’s prebiotic chemistry, habitability, and potential chemical biosignatures from both water-based “life as we know it” (as might occur in the interior mantle ocean, potential cryovolcanic flows, and/or impact melt deposits) and potential “life, but not as we know it” that might use liquid hydrocarbons as a solvent (within Titan’s lakes, seas, and/or aquifers). Consideration of both of these solvents simultaneously led to our initial landing site in Titan’s equatorial dunes and interdunes to sample organic sediments and water ice, respectively. Ultimately, Dragonfly's traverse target is the 80 km diameter Selk Crater, at 7° N, where we seek previously liquid water that has mixed with surface organics. Our science goals include determining how far prebiotic chemistry has progressed on Titan and what molecules and elements might be available for such chemistry. We will also determine the role of Titan’s tropical deserts in the global methane cycle. We will investigate the processes and processing rates that modify Titan’s surface geology and constrain how and where organics and liquid water can mix on and within Titan. Importantly, we will search for chemical biosignatures indicative of past or extant biological processes. As such, Dragonfly, along with Perseverance, is the first NASA mission to explicitly incorporate the search for signs of life into its mission goals since the Viking landers in 1976.

The factors contributing to the initial selection of a dune site near the Selk impact structure on Titan as the first landing site for the Dragonfly mission are described. These include arrival geometry and aerodynamic/aerothermodynamic considerations, illumination, and Earth visibility, as well as the likely presence of exposed deposits of water-rich material, potentially including materials where molten ice has interacted with organics. Cassini observations of Selk are summarized and interpreted: near-infrared reflectance and microwave emission data indicate water-rich materials in and around the crater. Radar topography data shows the rim of Selk to have slopes on multi-km scales reaching only ∼2° degrees, an order of magnitude shallower than early photoclinometric estimates.