# Earth-based Stellar Occultation Predictions for Jupiter, Saturn, Uranus, Neptune, Titan, and Triton: 2023–2050

Richard G. French, Damya Souami

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## To cite this version:

Richard G. French, Damya Souami. Earth-based Stellar Occultation Predictions for Jupiter, Saturn, Uranus, Neptune, Titan, and Triton: 2023–2050. The Planetary Science Journal, 2023, 4, 10.3847/PSJ/aced50. obspm-04756613

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Submitted on 29 Oct 2024

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# Earth-based Stellar Occultation Predictions for Jupiter, Saturn, Uranus, Neptune, Titan, and Triton: 2023–2050

Richard G. French<fnref n="1" /> and Damya Souami<fnref n="2" />,<fnref n="3" />,<fnref n="4" />

Received 2023 March 11; revised 2023 July 16; accepted 2023 July 17; published 2023 November 2

## Abstract

In support of studies of decadal-timescale evolution of outer solar system atmospheres and ring systems, we present detailed Earth-based stellar occultation predictions for Jupiter, Saturn, Uranus, Neptune, Titan, and Triton for 2023–2050, based on the Gaia Data Release 3 star catalog and near-IR K-band photometry from the Two Micron All Sky Survey catalog. We tabulate the number of observable events by year and magnitude interval, reflecting the highly variable frequency of high-signal-to-noise ratio (S/N) events depending on the target’s path relative to the star-rich regions of the Milky Way. We identify regions on Earth where each event is potentially observable, and for atmospheric occultations we determine the latitude of the ingress and egress events. For Saturn, Uranus, and Neptune, we also compute the predicted ring occultation event times. We present representative subsets of the predicted events and highlight particularly promising events. Jupiter occultations with $K \le 7$ occur at a cadence of about one per year, with bright events at higher frequency in 2031 and 2043. Saturn occultations are much rarer, with only two predicted events with $K \le 5$ in 2032 and 2047. Ten Uranus ring occultations are predicted with $K \le 10$ for the period 2023–2050. Neptune traverses star-poor regions of the sky until 2068, resulting in only 13 predicted occultations for $K \le 12$ between 2023 and 2050. Titan has several high-S/N events between 2029 and 2031, whereas Triton is limited to a total of 22 occultations with $K \le 15$ between 2023 and 2050. Details of all predicted events are included in the Supplementary Online Material.

*Unified Astronomy Thesaurus concepts: Planetary rings (1254); Jupiter (873); Saturn (1426); Uranus (1751); Neptune (1096); Titan (2186); Triton (2187)*

## 1. Introduction

Earth-based stellar occultations have proven to be a powerful and versatile tool of solar system discovery and exploration.<fnref n="5" /> Planetary occultations have revealed the stratospheric thermal structure of Jupiter (Baum & Code 1953; Hubbard et al. 1972, 1995; Vapillon et al. 1973; Veverka et al. 1974; Raynaud et al. 2003, 2004; Christou et al. 2013), Saturn (Hubbard et al. 1997), Uranus (Sicardy et al. 1985), and Neptune (Roques et al. 1994). They serendipitously led to the discovery of the Uranian rings (Elliot et al. 1977; Millis et al. 1977), and with subsequent concerted effort they resulted in the discovery and characterization of Neptune’s ring arcs (Hubbard et al. 1986; Sicardy et al. 1986, 1991; Smith et al. 1989; De Pater et al. 2018b; Gaslac Gallardo et al. 2020), which appear to be evolving over time (Souami et al. 2022). Extensive observing campaigns of the Uranus system yielded the orbital properties of the planet’s rings and estimates of its gravitational field (Nicholson et al. 2018; French et al. 2023a, 2023b). Despite the early challenges to accurate predictions for occultations by smaller outer solar system objects, successful airborne and ground-based occultation observations provided the first

convincing detection of Pluto’s tenuous atmosphere (Elliot et al. 1989), determined the properties of its atmospheric waves (Person et al. 2008), and revealed properties of its atmospheric haze from multiwavelength observations (Person et al. 2021). Multiple occultations by Triton have added to our understanding of its atmosphere (Olkin et al. 1997). The Centaur (2060) Chiron exhibits outgassing behavior (Ruprecht et al. 2015) and possibly hosts a ring system (Sickafoose et al. 2020). Over the last decade, ambitious international observing campaigns have yielded the surprising discoveries of rings around the Centaur (10199) Chariklo (Braga-Ribas et al. 2014; Bérard et al., 2017; Morgado et al. 2021), dwarf planet (136108) Haumea (Ortiz et al. 2017), and trans-Neptunian object (TNO) (50000) Quaoar (Morgado et al. 2023; Pereira et al. 2023), and have begun to provide accurate physical properties of TNOs themselves (Souami et al. 2020; Santos-Sanz et al. 2022a; Fernández-Valenzuela et al. 2023). The availability of highly accurate star positions provided by Gaia (Gaia Collaboration et al. 2021; Gaia Collaboration 2022) has revolutionized the observing strategy for small-target occultations by enabling portable telescopes to be placed along the path of the occultation shadow. Using multiple mobile stations, Buie et al. (2020) measured the size, shape, and astrometric position of TNO (486958) Arrokoth (the flyby target of the New Horizons extended mission) from four stellar occultations. Recent densely spaced observations of occultation observations by Triton (Marques Oliveira et al. 2022) and Pluto (Young et al. 2022) captured the central flash produced by the refractive focusing by the tenuous atmospheres of these small outer solar system bodies, providing valuable information about their

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<footnote n="1">¹Department of Astronomy, Wellesley College, Wellesley, MA 02481, USA; rfrench@wellesley.edu</footnote>

<footnote n="2">²LEŚIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, F-92195 Meudon, France</footnote>

<footnote n="3">³Departments of Astronomy and of Earth and Planetary Science, 501 Campbell Hall, University of California, Berkeley, CA 94720, USA</footnote>

<footnote n="4">⁴naXys, Department of Mathematics, University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium</footnote>

<footnote n="5">⁵For somewhat dated but still useful reviews of the stellar occultation technique, including summaries of early observations, see Elliot (1979) and Elliot & Olkin (1996).</footnote>

<footnote>Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.</footnote>
possibly time-variable surface atmospheric pressure, thermal structure, and haze opacity. The shape and duplicity of the Lucy Mission prime target Polymele were similarly determined from ground-station chords separated in the sky plane by only 1.8 km (Buie et al. 2022).

Meanwhile, the detailed reconnaissance of the Saturn system by Cassini and the ongoing exploration of Jupiter with Juno, along with a wealth of Kepler and Transiting Exoplanet Survey Satellite observations of exoplanets, have prompted international interest in further exploration of ice giants in our own solar system (Hofstadter et al. 2019; Fletcher et al. 2020; Blanc et al. 2021; Cartwright et al. 2021). Indeed, the most recent National Academies planetary science decadal survey (National Academies of Sciences, Engineering, and Medicine 2022) identifies the Uranus Orbiter and Probe as the highest-priority flagship mission for the decade 2023–2032. This invites renewed attention to the possibility of future occultation observations of the rings and atmospheres of the giant planets.

In this paper, we identify scientifically useful stellar occultations that can be used to investigate the structure and decadal-timescale evolution of the atmospheres and ring systems Jupiter, Saturn, Uranus, Neptune, Titan, and Triton, complementing results from JWST and adaptive-optics ground-based imaging. We take advantage of the astrometric accuracy of the Gaia DR3 star catalog and recent improvements in the Jet Propulsion System (JPL) planetary ephemerides to identify potential occultations for the period 2023–2050. We choose this rather long time period in part to illustrate the extreme time variability of the frequency of high-S/N occultation opportunities, depending on whether the target traverses the dense star fields of the Milky Way (as was the case for Uranus and Neptune in the 1980s), or instead remains for long periods in relatively star-free regions of the sky. For each candidate occultation, we identify regions on Earth where the event is potentially observable, and for atmospheric occultations we determine the latitude of the ingress and egress events. For Saturn, Uranus, and Neptune, we also compute the predicted ring occultation event times, taking into account the known orbital characteristics of representative rings. We have included Titan and Triton, as well, since future occultation observations can provide valuable information about possible seasonal changes in their atmospheres. The uncertainties in Gaia star positions and proper motions, combined with the estimated current accuracy of the ephemerides of both moons, enable secure identification of potential future occultations worthy of closer attention and refined predictions prior to each event.

We organize our presentation as follows. Section 2 describes our procedure for identifying candidate occultations, and Section 3 summarizes the geometrical quantities determined for each potential occultation. The main body of the paper is contained in Section 4, where predicted occultations are summarized for each of the six targets. We include tabulated statistics of the frequency of occultations by stellar magnitude and year, as well as representative detailed figures and tables for a subset of our identified events. Complete figures and tables for all events are included in the Supplementary Online Material (SOM). In the final section, we compare the Gaia and Two Micron All Sky Survey (2MASS) star positions, discuss the opportunities for spacecraft occultations, identify some of the uncertainties in the predictions, especially for events far in the future, and highlight the importance of continued occultation surveillance of our chosen targets. The Appendix describes

the contents of the SOM, including documentation of the machine-readable tables.

## 2. Identification of Occultation Candidates

Previous occultation predictions for the outer planets often required dedicated astrometry and photometry of candidate stars (Klemola & Marsden 1977; Klemola et al. 1981; Mink & Klemola 1985; Nicholson et al. 1988; Klemola & Mink 1991; Mink et al. 1992). Bosh & McDonald (1992) identified stellar occultation candidates for Saturn from the Guide Star Catalog for 1991–1999, and subsequent online predictions for 2000–2009 for Jupiter, Saturn, Uranus, and Neptune by A. Bosh were posted online.<fnref n="6" /> More recently, Mink (1995) made use of the Positions and Proper Motions (PPM) catalog (Röser & Bastian 1988, 1991, 1993) to produce a statistical overview of stellar occultations between 1950 and 2050 and summary online tables of predicted events for 2000–2050 with closest-approach distances less than 30" for Jupiter,<fnref n="7" /> Saturn,<fnref n="8" /> Uranus,<fnref n="9" /> and Neptune.<fnref n="10" /> Saunders et al. (2022) identified several promising Uranus and Neptune occultations between 2025 and 2035, including S/N estimates for ground-based and space-based observations. For the present survey, we expand on these prediction lists by making use of the Gaia Data Release 3 (DR3) catalog for stellar positions, proper motions, and G and RP magnitudes (Gaia Collaboration 2022) for the period 2023–2050. Proper motions in the DR3 catalog are a factor of 2 more accurate than in the Data Release 2 catalog, significantly reducing the prediction uncertainty of the smaller targets Titan and Triton toward the end of our prediction period. We make use, also, of 2MASS (Skrutskie et al. 2006) for apparent stellar magnitudes in the K band ($\lambda \sim 2.2$ µm).

Most high-S/N Earth-based stellar occultations of the outer planets have been observed from large ground-based telescopes at IR or near-IR wavelengths, taking advantage of the strong methane absorption band near $\lambda = 2.2$ µm or the weaker methane band near $\lambda = 0.89$ µm to reduce the observed brightness of the planet relative to the occultation star. With the expectation that future high-S/N outer planet occultations are likely to be observed using IR-sensitive cameras, we used the 2MASS catalog for our initial survey, restricting the K-band magnitude to $K \le 10$ or brighter for Jupiter and Saturn, and $K \le 15$ or brighter for Uranus, Neptune, Titan, and Triton. Although scientifically useful observations are possible for stars fainter than $K = 10$ for Jupiter and Saturn, there are many much brighter stars in our prediction list that should provide ample opportunity for repeated observations of Jupiter and Saturn events in the coming decades. For Uranus (in 2023, $K = 12.76$ and $V = 5.88$; in 2050, $K = 12.36$ and $V = 5.48$) and Neptune (in 2023, $K = 12.42$ and $V = 7.79$; in 2050, $K = 12.38$ and $V = 7.75$), past observations have proven scientifically useful for stars as faint as $K \sim 12$, but there are relatively few bright events predicted for the coming decade. Given the current interest in planning for a possible ice giant mission in the relatively near future, and with the prospect of larger telescopes and improved instrumentation in the coming years, we have chosen to set a rather faint K-band limit for these two

<footnote n="6">⁶ http://www2.lowell.edu/users/amanda/occs2000/</footnote>

<footnote n="7">⁷ http://tdc-www.harvard.edu/occultations/jupiter/jupiter.ppm2000.html</footnote>

<footnote n="8">⁸ http://tdc-www.harvard.edu/occultations/saturn/saturn.ppm2000.html</footnote>

<footnote n="9">⁹ http://tdc-www.harvard.edu/occultations/uranus/uranus.ppm2000.html</footnote>

<footnote n="10">¹⁰ http://tdc-www.harvard.edu/occultations/neptune/neptune.ppm2000.html</footnote>
<table><caption>**Table 1**
Spice Kernels</caption><thead><tr><td>File Name</td><td>Contents</td></tr></thead><tbody><tr><td>naif0012.tls</td><td>Leap-seconds</td></tr><tr><td>de440.bsp</td><td>Solar system ephemeris for all but Uranus events</td></tr><tr><td>jup365.bsp</td><td>Jupiter ephemeris</td></tr><tr><td>sat4401.bsp</td><td>Saturn and Titan ephemerides</td></tr><tr><td>ura161.bsp</td><td>Uranus ephemeris for Uranus events</td></tr><tr><td>peph.ura160.bsp</td><td>Solar system ephemeris for Uranus events</td></tr><tr><td>nep097.bsp</td><td>Neptune and Triton ephemerides</td></tr><tr><td>nep101.bsp</td><td>Neptune ephemeris</td></tr><tr><td>earth_720101_070426.bpc</td><td>ITRF Earth rotation</td></tr><tr><td>earth_200101_990628Predict.bpc</td><td>ITRF Earth rotation</td></tr><tr><td>pck00010.tpc</td><td>Planetary constants</td></tr></tbody></table>

planets. We include *K*, *G*, and RP magnitudes so that observers can estimate the expected S/N based on their choice of observing wavelength. Titan and Triton (in 2023, *K* = 12.30 and *V* = 13.49; in 2050, *K* = 12.26 and *V* = 13.45) are less affected by the background brightness of their central planets, and scientifically useful occultation observations of these objects can be obtained using medium-sized telescopes at visual wavelengths. We tabulate the frequency of occultations by these targets as a function of both *K* and *G* magnitudes.

## 2.1. Geocentric Predictions

We employed our well-tested occultation code (RINGFIT) to compute the geometry of potential occultations, adopting a solar system barycenter inertial reference frame as described in French et al. (1993) and modified very slightly by French et al. (2017). We used NASA’s Navigation and Ancillary Information Facility planetary ephemerides (kernel files) and SPICE toolkit (Acton 1996) to compute the geocentric apparent positions of the six targets from 2023 to 2050. The planetary and satellite ephemerides used in this study are listed in Table 1. We used the planetary constants file *pck00010.tpc* to determine the (possibly time-variable) pole direction and the equatorial and polar radii of the targets.

Next, using a subset of the 2MASS catalog restricted to the ecliptic region, we identified all stars brighter than our chosen *K*-magnitude limits that were within 4" of each target’s path, based on the 2MASS positions at the catalog epoch of 1996.0. We chose this rather large impact parameter to account for the design specification of 0"/5 positional accuracy of the 2MASS catalog relative to ICRS, the angular extent of the planetary targets and ring systems, the Earth’s angular size as viewed from the target, estimated ephemeris uncertainties, and the effect of potentially large proper motions between the catalog epoch and the times of the predicted events.

With this initial list of candidate stars, we used the astroquery.vizier Python interface to query the online VizieR catalog (Ochsenbein et al. 2000) to identify the Gaia DR3 stars that provided the closest matches to the 2MASS star positions. Given the depth of the Gaia survey, there often remained some ambiguity of the match between a given 2MASS star and its closest Gaia counterpart. We limited the Gaia candidates to those with magnitude $G \le 15$ for the Jupiter

and Saturn candidate searches, and $G \le 19$ for the fainter targets. To find a matching 2MASS catalog entry, we applied proper-motion corrections for the interval between the Gaia DR3 catalog epoch (J2016) and the 2MASS epoch (J1996), and retained events for which the closest candidate Gaia star was within an angular separation *r* = 1" of the 2MASS catalog position at epoch. We included a magnitude-dependent correction for the proper motion derived from the Gaia Early Data Release 3 (EDR3) catalog (Contat-Gaudin & Brandt 2021), but equally applicable to the DR3 proper motions as well (T. Contat-Gaudin 2023, personal communication). We also took account of propagated position error estimates, using the prescription of Butkevich & Lindegren (2014). Our final identification of the match between the 2MASS and Gaia catalog entries was based on the proximity of the 2MASS and Gaia positions and on their relative *G* and *K* magnitudes. In the detailed description of our predictions below, we note instances where the Gaia positions themselves are potentially of reduced accuracy, due to uncertainties in proper motion or in the original catalog astrometry. In Section 6, we discuss the distribution of position offsets between the two star catalogs.

As an independent check of our selection algorithm and occultation geometry calculations, we compared our results with geocentric predictions using the open-source Stellar Occultation Reduction and Analysis package (SORA; Gomes-Júnior et al. 2022) and the kernel files listed in Table 1. Both approaches returned virtually identical sets of candidate occultations. In nearly all cases, the calculated closest-approach times of the occultation chord agreed to within a few seconds, and the closest-approach sky-plane separation of the occultation chord and the target center agreed to within a few kilometers. This level of agreement is quite sufficient for our present purposes. Other occultation prediction software is available from the International Occultation Timing Association (IOTA),<fnref n="11" /> and the geometry of occultation circumstances can also be computed using the NASA/JPL Horizons software.<fnref n="12" /> Finally, Yuan et al. (2017) have developed an analytic geometry approach to predicting ground-based stellar occultations by ellipsoidal solar system bodies. All of our cross-checks indicate that our prediction method is robust at the kilometer level in the sky plane for our target objects.

## 2.2. Topocentric Predictions

The next step in our procedure was to evaluate the observability of each occultation from various locations on Earth representing six geographical regions. As a starting point, we selected a set of 13 observatories around the world, including several that have been used extensively to observe occultations in the past or for previous occultation predictions (Nicholson et al. 1988). Table 2 lists the WGS84 locations of the selected observing sites and their corresponding geographical region and region ID. (In what follows, we will refer to individual sites by their letter codes from this table.) In many cases, the listed sites are close to other major telescopes. Our current effort is complementary to Lucky Star and IOTA<fnref n="13" /> prediction efforts, which focus instead on relatively short-term

<footnote n="11">¹¹ https://occultations.org/observing/software/</footnote>

<footnote n="12">¹² https://ssd.jpl.nasa.gov/horizons/</footnote>

<footnote n="13">¹³ https://occultations.org/observing/occultation-predictions/major-planet-occultation-predictions/</footnote>
<table><caption>**Table 2**
Observing Sites</caption><thead><tr><th>Code</th><th>Name</th><th>Lat. (deg)</th><th>E lon. (deg)</th><th>Alt (m)</th><th>Region ID</th><th>Region Name</th></tr></thead><tbody><tr><td>PIC</td><td>Pic du Midi</td><td>+42.9365556</td><td>0.1423056</td><td>2890</td><td>ENA</td><td>Europe and N. Afr.</td></tr><tr><td>PAL</td><td>Palomar Mtn. (5 m)</td><td>+33.3562222</td><td>243.1360056</td><td>1706</td><td>NAM</td><td>North Am.</td></tr><tr><td>PMO</td><td>Purple Mtn. Obs. Nanking</td><td>+32.0666667</td><td>118.8208889</td><td>364</td><td>EAS</td><td>East Asia</td></tr><tr><td>KPNO</td><td>Kitt Peak Natl. Obs.</td><td>+31.9583333</td><td>248.4033333</td><td>2120</td><td>NAM</td><td>North Am.</td></tr><tr><td>MCD</td><td>McDonald Obs. 2.7 m</td><td>+30.6715833</td><td>255.9784444</td><td>2075</td><td>NAM</td><td>North Am.</td></tr><tr><td>TEN</td><td>Teide Obs./Tenerife</td><td>+28.3005000</td><td>343.4890944</td><td>2395</td><td>ENA</td><td>Europe and N. Afr.</td></tr><tr><td>IRTF</td><td>Maunakea/IRTF</td><td>+19.8262222</td><td>204.5280000</td><td>4168</td><td>NAM</td><td>North Am.</td></tr><tr><td>KAV</td><td>Kavalur Observatory</td><td>+12.5755556</td><td>78.8316667</td><td>722</td><td>EAS</td><td>East Asia</td></tr><tr><td>RIO</td><td>Rio de Janeiro</td><td>-22.8950556</td><td>316.7770833</td><td>33</td><td>SAM</td><td>South Am.</td></tr><tr><td>ESO</td><td>European Southern Obs. (3.6 m)</td><td>-29.2609722</td><td>289.2683056</td><td>2400</td><td>SAM</td><td>South Am.</td></tr><tr><td>AAT</td><td>Siding Spring (AAT)</td><td>-31.2770278</td><td>149.0660833</td><td>1164</td><td>OCN</td><td>Oceania</td></tr><tr><td>SAAO</td><td>So. Afr. Astro. Obs. (Sutherland)</td><td>-32.3795278</td><td>20.8107000</td><td>1768</td><td>SAF</td><td>Southern Africa</td></tr><tr><td>MSO</td><td>Mt. Stromlo Observatory</td><td>-35.3200000</td><td>149.0083333</td><td>770</td><td>OCN</td><td>Oceania</td></tr></tbody></table>

<table><caption>**Table 3**
Planet Event Types for All Targets</caption><thead><tr><th>Type</th><th>Description</th></tr></thead><tbody><tr><td>P</td><td>Observable from Earth, but not from geocenter or any of 13 topocentric sites</td></tr><tr><td>Pg</td><td>Observable from Earth geocenter, but not from any of 13 topocentric sites</td></tr><tr><td>Pt</td><td>Observable from at least one topocentric sites, but not from Earth geocenter</td></tr><tr><td>Pgt</td><td>Observable from Earth geocenter and at least one topocentric site</td></tr><tr><td>X</td><td>No planet limb observable from Earth</td></tr></tbody></table>

observing campaigns, most often for targets that lack accurate long-term ephemerides. We augment these efforts by providing longer-term predictions for the four giant planets, including the detailed circumstances of the ring occultations for Saturn, Uranus, and Neptune, and by presenting decadal-timescale predictions for the largest moons of Saturn and Neptune.

### 3. Occultation Geometry

We restricted our set of occultations to those with a Sun-geocenter-target (SGT) angle ≥45°, which eliminated daytime occultations from our survey. For each surviving predicted occultation, we computed the apparent sky-plane chord relative to the target center as observed from each of the 13 sites, and from the geocenter. For the topocentric observers, we also computed the elevation angle of the target object, the Sun, and the moon over the course of the occultation. We judged an occultation to be observable during any interval when the Sun was more than 5° below the horizon and the target object was more than 5° above the horizon. Throughout the paper, we refer to these as our usual altitude constraints on observability.

We assigned a *planet event type* to each candidate occultation, indicating the observability of an ingress or egress occultation by the target limb, as described in Table 3. Any potential occultation of Jupiter, Titan, or Triton of planet event type X was eliminated from further consideration.

For Saturn, Uranus, and Neptune events, we also assessed the visibility of possible ring occultations. Table 4 lists the rings, semimajor axes or boundaries *a*, and widths *W* we assumed for our predictions (French et al. 2017, 2023a; De Pater et al. 2018a). We do not make detailed predictions for possible Jupiter ring occultations, but we do include the main Jupiter ring in our sky-plane figures to show locations of the occultation chords relative to the ring system.

<table><caption>**Table 4**
Planetary Ring Characteristics</caption><thead><tr><th>Planet</th><th>Ring</th><th>a (km)</th><th>W (km)</th></tr></thead><tbody><tr><td>Jupiter</td><td>Main ring</td><td>129,000</td><td></td></tr><tr><td rowspan="7">Saturn</td><td>C inner edge</td><td>74,490</td><td></td></tr><tr><td>B inner edge</td><td>91,983</td><td></td></tr><tr><td>A inner edge</td><td>122,052</td><td></td></tr><tr><td>Encke Div inner edge</td><td>133,424</td><td></td></tr><tr><td>Encke Div outer edge</td><td>133,745</td><td></td></tr><tr><td>A outer edge</td><td>136,774</td><td></td></tr><tr><td>F</td><td>140,461</td><td></td></tr><tr><td rowspan="10">Uranus</td><td>6</td><td>41,837.6</td><td>1.5</td></tr><tr><td>5</td><td>42,235.3</td><td>2.3</td></tr><tr><td>4</td><td>42,571.5</td><td>2.3</td></tr><tr><td>α</td><td>44,719.0</td><td>8.5</td></tr><tr><td>β</td><td>45,661.4</td><td>9.5</td></tr><tr><td>η</td><td>47,176.3</td><td>1.6</td></tr><tr><td>γ</td><td>47,626.8</td><td>2.2</td></tr><tr><td>δ</td><td>48,300.6</td><td>4.6</td></tr><tr><td>λ</td><td>50,024.9</td><td>2.3</td></tr><tr><td>ε</td><td>51,149.6</td><td>58.1</td></tr><tr><td rowspan="6">Neptune</td><td>Galle</td><td>42,000</td><td>2000</td></tr><tr><td>LeVerrier</td><td>53,200</td><td>100</td></tr><tr><td>Lassell</td><td>55,200</td><td>4000</td></tr><tr><td>Arago</td><td>57,200</td><td></td></tr><tr><td>Galatea</td><td>61,953</td><td></td></tr><tr><td>Adams</td><td>62,933</td><td>15</td></tr></tbody></table>

For Saturn, Uranus and Neptune, the planetary event type is appended with a *ring event type* as defined as in Table 5, depending on the observability of at least one ingress or egress ring occultation event. Any occultation with a combined planetary and ring event type of XX was eliminated from further consideration.
<table><caption>**Table 5**
Ring Event Types for Saturn, Uranus, and Neptune</caption><thead><tr><td>Type</td><td>Description</td></tr></thead><tbody><tr><td>R</td><td>Observable from Earth, but not from geocenter or any of 13 topocentric sites</td></tr><tr><td>Rg</td><td>Observable from Earth geocenter, but not from any of 13 topocentric sites</td></tr><tr><td>Rt</td><td>Observable from at least one topocentric sites, but not from Earth geocenter</td></tr><tr><td>Rgt</td><td>Observable from Earth geocenter and at least one topocentric site</td></tr><tr><td>X</td><td>No ring occultation observable from Earth</td></tr></tbody></table>

**4. Example Predictions**

For each surviving occultation on our prediction list, we produced several figures to provide visual overviews of the occultation circumstances. We illustrate these using a predicted Uranus occultation for 2028 December 29 (K = 10.98, G13.75, event type *PtRgt*). Figure 1 (top) shows a shaded view of Earth and the continents as seen from Uranus at the time of the closest approach (C/A) of the geocentric occultation chord to the target center, including the labeled observing sites and the antisolar point as an open circle. In this instance, the geocentric C/A occurred at 2028 December 29 17:37:23 UTC. Additional details of the event are shown in the figure labels: the *K* and *G* magnitudes, the apparent geocentric coordinates of the target star in J2000 coordinates, the closest-approach separation in arcsec, the position angle on the sky of the closest-approach point (PA), measured north through east, the apparent sky-plane velocity (*v*<sub>sky</sub>) of the target relative to the star at the C/A time, and *D*, the target distance from Earth in astronomical units. The gray shading marks the region for which the Sun is below the horizon. (For the small targets Titan and Triton, we show where the occultation shadow falls on Earth, rather than a sky-plane Earth view of the target.)

For Jupiter, Saturn, Uranus, and Neptune occultations, we provide a figure showing the Earth view of the target and its ring system in the sky plane, along with occultation chords for any sites during the interval when the target and Sun meet the altitude requirements enumerated above. (For the Titan and Triton occultations, we include the projected path of the shadow across the Earth.) Figure 1 (bottom) shows the Uranus sky plane for the sample event. Each occultation chord is coded by the color of the observing site label. The solid dot on each chord marks the earliest point at which the occultation star is within the window of the figure and meets the Sun and target altitude observability requirements. The geocentric chord (marked as Earth) is shown as a black dashed line, bounded by the dotted lines showing the Earth's diameter. In this example, the SAAO chord intersects the outer rings only during egress because the planet was too low in the sky for earlier observations. Only the northernmost PIC chord has a planet occultation.

Additionally, for each occultation we include a figure showing the altitude (elevation angle) of the target and Sun above/below the horizon over the course of the event, as viewed from each topocentric site that satisfies the event observability constraints at some point within the plotted vicinity of the closest-approach time, as illustrated in Figure 2 for the 2028 December 29 Uranus occultation. For each labeled site, the altitude of Uranus is shown as a solid line and the altitude of the Sun is shown as a dashed line. The time interval during which the planet itself occults the star is shown as a thick solid line, and the times of individual ring occultation events are shown as dots. The lines are restricted to the times

that meet the simultaneous requirements that the target be at least 5° above the horizon and the Sun be at least 5° below the horizon. The color-coding of the observing sites matches that of the corresponding sky-plane figure (Figure 1, bottom). For this occultation, KAV and PMO are well situated to observe the ingress and egress ring events at high elevation angle. The northernmost site, PIC, barely misses an atmosphere occultation, shortly after sunset. From SAAO, the planet is low in the sky and the egress ring events are observable shortly after sunset. No ring or atmosphere events are observable from AAT or MSO, where Uranus sinks to below 5° elevation before the ingress ring events, or from TEN, where the Sun is finally 5° below the horizon about an hour after the closest-approach time, well after the egress ring event times.

**5. Predicted Occultations**

We now describe the predicted occultations for each of our six targets. Given the large number of events, we include in the main body of the paper a representative subset of the brightest events for most targets, along with summary statistics of the number of occultations by year and stellar magnitude for each target. Complete details for each occultation are included in the summary PDF and text files on the SOM, along with typeset tables of all occultations and machine-readable files for occultations by each target. The organization and contents of the SOM are described in the Appendix.

For convenient reference, Table 6 defines the tabulated results included selectively for each target below, along with additional variables included in the machine-readable prediction files on the SOM. The tabulated entries are largely self-explanatory, with the following exceptions:

1. $\sigma(\alpha_*)$ and $\sigma(\delta_*)$ are estimated star position errors (expressed in kilometers in the sky plane) propagated from the Gaia DR3 catalog epoch to the time of each occultation, from the method of Butkevich & Lindegren (2014) as implemented in SORA (using the method *Star.error_at*), for the appropriate parameters and covariance matrix from the Gaia EDR3 catalog. These position errors are typically quite small and result from uncertainties in the proper motion of the star, but not from intrinsic uncertainties in the position of the star at the catalog epoch. The latter are reflected in the renormalized unit weight error (RUWE) values available for each occultation star in the SOM and flagged in the tables below for stars with large positional uncertainties. RUWE values above 1.4 are indicative of less accurate Gaia positions.

2. $D_*$ is the estimated projected diameter of the star at the target distance. This quantity affects the measured sharpness of transitions in brightness of ring edges and airless target limbs, as well as the scintillation amplitude of planetary atmosphere occultations. The projected star
<figure><img src="image_5.png" /><figcaption>**Figure 1.** Top: view of Earth from Uranus at the closest-approach time of the 2028 December 29 occultation. Bottom: the view of Uranus and its rings from Earth at the midtime of the occultation, showing the sky-plane chords for the labeled observatories. The geocenter path is shown dashed, and the dotted lines on either side demarcate the Earth's projected diameter.</figcaption></figure>

size can be estimated from the color, spectral type, and
spectral class of the star, although these estimates can be
systematically in error if they do not account for

interstellar reddening, which is often significant for
occultation stars that lie in the crowded star fields of
the Milky Way. For this work, we utilized the *Star*.
<figure><img src="image_6.png" /><figcaption>**Figure 2.** Altitude of Uranus (solid lines) and the Sun (dashed lines) relative to the horizon during the 2028 December 29 Uranus occultation for the labeled observing sites (Table 2). See text for details.</figcaption></figure>

apparent_diameter method of the SORA software package (Gomes-Júnior et al. 2022), which successively interrogates online star catalogs to find the necessary auxiliary apparent magnitudes of the star to estimate the projected star size. In instances where there was ambiguity about whether the candidate catalog stars matched the Gaia star in question, we omitted the calculated star diameter from our tables.

3. $G_*$ is the velocity-corrected apparent $G$ magnitude of the occultation star, according to the prescription

$$G_* = G + 2.5 \log_{10}(v_{sky}/20), \quad (1)$$

where $v_{sky}$ is the sky-plane velocity in kilometers per second (Gomes-Júnior et al. 2022). This function increases the predicted S/N of slow occultations and downgrades the S/N of rapid occultations.

4. 2MASS DUPFLAG is set to 1 if another nearby event occurring within one day has the same 2MASS ID, indicating an ambiguity in the estimated $K$ magnitude for such events. This occurs primarily when there are crowded star fields, resulting in uncertain matching between the Gaia star and the corresponding 2MASS star. Such events are flagged in the typeset prediction tables, and this variable is included in the machine-readable event tables.

5. XXX_N_TARGETOCCS and XXX_NRINGOCCS are contained in the machine-readable tables for each target. They provide an indication of which of the seven global regions listed in Table 2 are best suited to observe a given occultation. Here, XXX is the region code, and the tabulated value indicates how many of the individual sites in Table 2 are predicted to have an observable target occultation (planet or satellite limb) or an individual ring occultation, subject to the standard altitude constraints. An additional region code, GEO, is included to denote

geocentric predictions, which are not subject to altitude constraints.

### 5.1. Jupiter

Five stellar occultations by Jupiter have been recorded photometrically in the modern era, beginning with the 1952 November 20 occultation of the $V=5.5$ star $\sigma$ Arietis (Baum & Code 1953), followed by the 1971 May 13 occultation of $\beta$ Scorpii ($V=2.63, 4.92$; Hubbard et al. 1972; Vapillon et al. 1973; Veverka et al. 1974; Raynaud et al. 2004), the 1989 December 13 occultation of SAO 78505 ($V=8.7, K=7$; Hubbard et al. 1995), the 1999 October 10 occultation of HIP 9369 ($V=7.6$; Raynaud et al. 2003), and the 2009 August 3/4 occultation of HIP 107302 (45 Cap, $V=5.5$; Christou et al. 2013).

We identified a total of 1844 Jupiter occultations between 2023 and 2050 for stars brighter than $K \le 10$. Table 7 lists the number of predicted Jupiter occultations per year. The frequency of occultations varies substantially in time, depending on the density of the star fields traversed by Jupiter. It is quite high for 2031 and 2043, with the interval reflecting Jupiter's orbital period of just under 12 yr, as Jupiter crosses a dense region of the Milky Way. The transits of the Milky Way in 2024/25, 2036/37, and 2048/49 show much more modest increases in the frequency of events. Similar variations are seen in the prediction list of Mink (1995), which includes 57 geocentric Jupiter atmospheric occultations. Our search identified only a handful of Jupiter occultations by stars brighter than $K=7$ before 2031, and only five for $K \le 4$ between 2023 and 2050, but there are many events with $K \le 9$.

To illustrate the range of event geometries and the varying aspect of Jupiter over this time interval, we include here the brightest ($K$-magnitude) 24 Jupiter occultations between 2023 and 2050 with planetary event types Pt or Pgt. Figure 3 shows
<table><caption>**Table 6**
Definitions of Tabulated Results</caption><thead><tr><th>Quantity<sup>a</sup></th><th>Units</th><th>Description</th></tr></thead><tbody><tr><td>Event ID</td><td></td><td>Unique occultation identifier; see text for details</td></tr><tr><td>C/A epoch</td><td>UTC</td><td>Predicted time of geocentric sky-plane chord closest approach to target center</td></tr><tr><td>ICRS Star Coord<br>at C/A epoch</td><td>hh mm ss dd mm ss</td><td>J2000 apparent geocentric star position at C/A epoch</td></tr><tr><td>σ(α<sub>*</sub>)</td><td>km</td><td>Estimated E-W sky-plane star position error; see text for details</td></tr><tr><td>σ(δ<sub>*</sub>)</td><td>km</td><td>Estimated N-S sky-plane star position error; see text for details</td></tr><tr><td>f<sub>0</sub></td><td>km</td><td>Planetary ephemeris offset in the sky plane (east is positive)</td></tr><tr><td>g<sub>0</sub></td><td>km</td><td>Planetary ephemeris offset in the sky plane (north is positive)</td></tr><tr><td>C/A</td><td>arcsec or mas or 1000 km</td><td>Closest approach separation of geocentric sky-plane chord and target center</td></tr><tr><td>C/A<sub>p</sub></td><td>arcsec or 1000 km</td><td>Sky-plane separation of central planet and occultation star at C/A (Triton/Titan only)</td></tr><tr><td>PA</td><td>deg</td><td>Position angle (counterclockwise, CCW, from north) of C/A point on geocentric sky-plane chord</td></tr><tr><td>ν<sub>sky</sub></td><td>km s<sup>-1</sup></td><td>Geocentric sky-plane velocity of target relative to star at C/A</td></tr><tr><td>Dist</td><td>au</td><td>Geocentric distance to target at C/A</td></tr><tr><td>Lat I</td><td>deg</td><td>Planetodetic target latitude at ingress intersection of geocentric sky-plane chord<br>and possibly oblate target limb</td></tr><tr><td>Lat E</td><td>deg</td><td>Planetodetic target latitude at egress intersection of geocentric sky-plane chord<br>and possibly oblate target limb</td></tr><tr><td>K</td><td>mag</td><td>Apparent K magnitude of occultation star, from 2MASS catalog</td></tr><tr><td>G</td><td>mag</td><td>Apparent G magnitude of occultation star, from Gaia DR3 catalog</td></tr><tr><td>G<sub>*</sub></td><td>mag</td><td>Apparent G magnitude, corrected for sky-plane velocity; see text for details</td></tr><tr><td>RP</td><td>mag</td><td>Apparent RP magnitude of occultation star, from Gaia DR3 catalog</td></tr><tr><td>E λ</td><td>deg</td><td>East longitude of sub-Earth point at C/A</td></tr><tr><td>φ</td><td>deg</td><td>Geocentric latitude of sub-Earth point at C/A</td></tr><tr><td>S-G-T</td><td>deg</td><td>Sun-geocenter-target angle at C/A</td></tr><tr><td>M-G-T</td><td>deg</td><td>Moon-geocenter-target angle at C/A</td></tr><tr><td>Event type</td><td></td><td>Planet (P) and ring (R) event characteristics:<br>g indicates geocentric event, t indicates topocentric; see text for details</td></tr><tr><td>Source ID</td><td></td><td>Gaia DR3 catalog ID</td></tr><tr><td>DUP</td><td></td><td>Source with multiple source identifiers (Gaia catalog entry)</td></tr><tr><td>RUWE<sup>a</sup></td><td></td><td>Renormalized unit weight error (Gaia catalog entry)</td></tr><tr><td>2MASS ID<sup>a</sup></td><td></td><td>2MASS catalog ID</td></tr><tr><td>2MASS DUPFLAG<sup>a</sup></td><td></td><td>If 1, another nearby event with a different STARID shares this 2MASS catalog ID</td></tr><tr><td>Geocentric Object Pos.</td><td>hh mm ss dd mm ss</td><td>J2000 apparent geocentric target position at C/A epoch</td></tr><tr><td>B</td><td>deg</td><td>Ring/equatorial plane opening angle as viewed from Earth</td></tr><tr><td>P</td><td>deg</td><td>Position angle (CCW from north) of target pole, projected in the sky plane</td></tr><tr><td>ṙ</td><td>km s<sup>-1</sup></td><td>Ring plane radial velocity at geocentric C/A (for ringed targets)</td></tr><tr><td>D<sub>*</sub></td><td>km</td><td>Estimated projected diameter of star at target, from SORA; see text for details</td></tr><tr><td>ṙ<sup>a</sup></td><td>arcsec</td><td>Angular separation between proper-motion-corrected Gaia position and<br>2MASS star at 2MASS catalog epoch (J1996)</td></tr><tr><td>XXX_N_TARGETOCCS<sup>a</sup></td><td></td><td>Number of observable target occultations by candidate sites in XXX region</td></tr><tr><td>XXX_N RingOCCS<sup>a</sup></td><td></td><td>Number of observable ring occultations by candidate sites in XXX region</td></tr></tbody></table>

**Notes.** As noted previously, an indication of the relative accuracy of the Gaia DR3 star positions is given by the RUWE catalog entry. Values of RUWE ≤ 1.4 indicate a reliable astrometric solution (https://doi.org/10.17876/gaia/dr2/45). The RUWE is included in the machine-readable prediction files on the SOM, but to provide an indication of events with less reliable astrometry, we add a superscript of * to the Event ID of any occultation with RUWE > 1.4, ** for RUWE > 2, and *** for RUWE > 5. In Section 6 below, we evaluate the influence of the value of the RUWE on the offsets between the Gaia and 2MASS star positions. A superscript * is appended to the Event ID when a nearby event has the same 2MASS ID, resulting in a corresponding K-magnitude ambiguity.

a gallery of views of Earth at mid-occultation, and Figure 4 shows the corresponding sky-plane views of Jupiter.

Table 8 provides detailed information about the 24 events shown in Figures 3 and 4. All of the items in the table are defined in Table 6, with the exception of the Event ID of the form *Tyynnn...*. Here, *T* is a unique target identifier (J for Jupiter, *S* for Saturn, *U* for Uranus, *N* for Neptune, *Ti* for Titan, and *Tr* for Triton); *yy* corresponds to the final two digits of the year of the event, and *nnn...* is the chronologically increasing number of predicted occultations by a given target in the

specified year. The complete table of predictions is contained in the SOM, with sequential Event IDs without gaps within any given year, although gaps in the numbering occur in the abbreviated tables included in the main body of the paper.

The path of Jupiter across the sky is shown in Figure 5 (upper left) from 2020 to 2050—an interval of ~2.5 Jovian orbital periods—resulting in multiple intermittent crossings of the dense star fields of the Milky Way, shown as a wavy line. A survey of the gallery figures reveals several promising Jupiter

<footnote><sup>a</sup> Contained in machine-readable (MR) tables only.</footnote>
<figure><img src="image_7.png" /><figcaption>**Figure 3.** Gallery of Earth views from Jupiter at mid-occultation for the 24 brightest predicted occultations between 2023 and 2050 with planetary event type *Pgt*. See text for details.</figcaption></figure>

occultations in the next few years. The very bright ($K = 4.93$) 2027 February 22 occultation samples Jupiter's south polar region and is visible from sites in Australia, Hawaii, and the southwest United States. Figures 3 and 4 include seven occultations in 2031, when Jupiter crosses the Milky Way in the direction of the Galactic center. Several of these events have multiple chords that sample a variety of latitudes on Jupiter. Relatively few occultations are predicted for 2033–2042, but there are many bright star events in 2043, when Jupiter's path lies in the direction of the Galactic center, with multiple chords and a wide range of sampled latitudes during the atmosphere occultations.

Although we have not evaluated possible Jupiter ring occultations, it is clear from the sky-plane figures that such events are rare because the orientation of the ring ansae is very nearly parallel to the sky-plane chords, resulting in few predicted ring intersections. This is a consequence of the low inclination of Jupiter's orbit relative to the ecliptic and its pole being nearly normal to its orbital plane.

The results shown here are just a small subset of the predicted events, and we encourage observers to consult the SOM for detailed information about the full set of Jupiter occultations, some of which are only marginally fainter than the restricted range of events in the figures and tables included in the main body of the paper.

<table><caption>**Table 7**
Jupiter Occultations 2023–2050</caption><thead><tr><th>Year</th><th>K &lt; 4</th><th>K 4–5</th><th>K 5–6</th><th>K 6–7</th><th>K 7–8</th><th>K 8–9</th><th>K 9–10</th></tr></thead><tbody><tr><td>2023</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1</td><td>2</td><td>6</td></tr><tr><td>2024</td><td>...</td><td>...</td><td>...</td><td>2</td><td>3</td><td>7</td><td>15</td></tr><tr><td>2025</td><td>...</td><td>...</td><td>1</td><td>...</td><td>2</td><td>7</td><td>19</td></tr><tr><td>2026</td><td>...</td><td>...</td><td>...</td><td>1</td><td>...</td><td>4</td><td>8</td></tr><tr><td>2027</td><td>...</td><td>1</td><td>...</td><td>...</td><td>1</td><td>...</td><td>2</td></tr><tr><td>2028</td><td>...</td><td>...</td><td>...</td><td>1</td><td>...</td><td>1</td><td>5</td></tr><tr><td>2029</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2</td><td>2</td></tr><tr><td>2030</td><td>...</td><td>...</td><td>...</td><td>3</td><td>2</td><td>3</td><td>6</td></tr><tr><td>2031</td><td>1</td><td>2</td><td>6</td><td>14</td><td>90</td><td>262</td><td>346</td></tr><tr><td>2032</td><td>...</td><td>1</td><td>...</td><td>1</td><td>7</td><td>10</td><td>21</td></tr><tr><td>2033</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2</td><td>3</td><td>5</td></tr><tr><td>2034</td><td>...</td><td>...</td><td>...</td><td>2</td><td>1</td><td>1</td><td>5</td></tr><tr><td>2035</td><td>...</td><td>1</td><td>...</td><td>1</td><td>2</td><td>3</td><td>5</td></tr><tr><td>2036</td><td>...</td><td>...</td><td>1</td><td>1</td><td>4</td><td>6</td><td>26</td></tr><tr><td>2037</td><td>...</td><td>...</td><td>1</td><td>3</td><td>2</td><td>11</td><td>15</td></tr><tr><td>2038</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>3</td><td>6</td></tr><tr><td>2039</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1</td><td>1</td><td>4</td></tr><tr><td>2040</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1</td><td>2</td><td>3</td></tr><tr><td>2041</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>6</td></tr><tr><td>2042</td><td>...</td><td>...</td><td>1</td><td>...</td><td>...</td><td>5</td><td>8</td></tr><tr><td>2043</td><td>1</td><td>3</td><td>8</td><td>23</td><td>99</td><td>243</td><td>332</td></tr><tr><td>2044</td><td>...</td><td>...</td><td>...</td><td>2</td><td>1</td><td>5</td><td>12</td></tr><tr><td>2045</td><td>...</td><td>...</td><td>1</td><td>2</td><td>...</td><td>...</td><td>6</td></tr><tr><td>2046</td><td>...</td><td>...</td><td>...</td><td>1</td><td>2</td><td>5</td><td>6</td></tr><tr><td>2047</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1</td><td>...</td><td>3</td></tr><tr><td>2048</td><td>1</td><td>...</td><td>...</td><td>2</td><td>5</td><td>13</td><td>26</td></tr><tr><td>2049</td><td>...</td><td>...</td><td>...</td><td>1</td><td>6</td><td>8</td><td>16</td></tr><tr><td>Totals</td><td>3</td><td>8</td><td>19</td><td>60</td><td>233</td><td>607</td><td>914</td></tr></tbody></table>
<figure><img src="image_8.png" /><figcaption>**Figure 4.** Gallery of sky-plane geocentric views of Jupiter at mid-occultation for the 24 brightest predicted occultations between 2023 and 2050 with planetary event type *Pgt*. See text for details.</figcaption></figure>

## 5.2. Saturn

The 1989 July 3 occultation of the bright star 28 Sgr ($K=1.48$) was predicted by Taylor (1987) and enabled the first detailed post-Voyager look at the structure of Saturn's rings (French et al. 1993; Nicholson et al. 2000) and stratosphere (Hubbard et al. 1997). The event also featured a central flash, when multiple stellar images were detected along the limb of Saturn near mid-occultation (Nicholson et al. 1995) and an occultation by Titan (Sicardy et al. 1999). An occultation of the star GSC 6323-01396 ($V=11.9$) by Saturn's rings was observed with the High-Speed Photometer on the Hubble Space Telescope (HST) on 1991 October 2/3 (Elliot et al. 1993), providing useful information about the pole direction and radius scale of Saturn's ring system. On 1998 November 14, Saturn and its rings occulted the star GSC 0622-00345 (Harrington et al. 2010), yielding information about gravity waves in Saturn's upper atmosphere. Subsequently, the Cassini orbital tour provided extensive observations of the Saturn's rings and the atmospheres of both Saturn and Titan, but future Earth-based stellar occultations by Saturn and its rings could still provide valuable information about spatial and temporal variations in the rings and the planet's stratosphere.

Our search resulted in the identification of 290 predicted occultations by Saturn and/or its rings for the period 2023–2050 for a limiting magnitude $K \le 10$. Table 9 lists the number of predicted events per year as a function of K magnitude, excluding years with no predicted events. Each entry in the table is of the form $P/R$, where P is the number of

predicted planetary atmosphere occultations with event types P, Pg, Pgt, or Pt, and R is the number of predicted ring occultations with event types that include R, Rg, Rgt, or Rt. We predict a total of 267 atmosphere events and 284 ring events for Saturn, considerably fewer than the 1844 predicted Jupiter atmosphere occultations (Table 7). In comparison, the prediction list of Mink (1995) based on the PPM catalog includes just 14 geocentric Saturn atmospheric occultations, an indication of their rarity compared to Jupiter events.

Predicted Saturn occultations for 2023–2050 are not only rare but are also unevenly spaced in time, with clusters of events occurring when Saturn crosses the denser star fields of the Milky Way. This is illustrated in Figure 5 (upper right), which shows the apparent path of Saturn as viewed from Earth between 2020 and 2050. Saturn next traverses the Milky Way in 2033, in the less dense direction opposite to the brighter Galactic center. In 2048 (half a Saturn orbital period later) Saturn's path crosses the direction of the Galactic center, resulting in abundant bright occultations.

The ring opening angle of Saturn's rings varies over time, as shown in Figure 6 (top) for the period 2020–2050. The solid line shows the ring opening angle B as viewed from Earth, with an annual periodic term reflecting the relative inclinations of the orbits of Earth and Saturn. The dashed line shows the ring opening angle $B'$ as viewed from the Sun. The next Saturn ring plane crossings (RPXs) will occur near the years 2025 and 2040. Red dots mark predicted Saturn occultations for stars brighter than $K=8$. These are most frequent near 2033 and
<table><caption>Table 8
Geocentric Jupiter Occultation Predictions 2023–2050</caption><thead><tr><th>Event ID<br>Event Type</th><th>C/A Epoch<br>Source ID</th><th>ICRS Star Coord at Epoch<br>Geocentric Object Position</th><th>σ(α<sub>*</sub>) (km)<br>σ(δ<sub>*</sub>) (km)</th><th>C/A (")<br>C/A (10<sup>3</sup> km)</th><th>PA (deg)<br>P (deg)</th><th>ν<sub>sky</sub> (km s<sup>-1</sup>)<br>B (deg)</th><th>Dist (au)<br>r̄ (km s<sup>-1</sup>)</th><th>Lat I (deg)<br>Lat E (deg)</th><th>K<br>D<sub>*</sub> (km)</th><th>G<br>G<sub>*</sub></th><th>RP<br>DUP</th><th>E λ (deg)<br>φ (deg)</th><th>S-G-T<br>M-G-T</th></tr></thead><tbody><tr><td>J250025</td><td>2025-10-13 14:00:32.12</td><td>07 41 12.72000 +21 26<br>47.82082</td><td>1.0</td><td>1.093</td><td>188.48</td><td>13.98</td><td>5.144</td><td>0.4</td><td>5.132</td><td>7.526</td><td>6.792</td><td>243.2</td><td>86.7</td></tr><tr><td>Pgt</td><td>673253445252610816</td><td>07 41 12.70846 +21 26<br>46.74017</td><td>0.7</td><td>4.076</td><td>11.37</td><td>1.51</td><td></td><td>7.0</td><td>1.860</td><td>7.137</td><td>0</td><td>21.4</td><td>7.1</td></tr><tr><td>J270002*</td><td>2027-02-22 11:12:09.02</td><td>09 31 38.98066 +15 46<br>12.26555</td><td>5.6</td><td>20.375</td><td>18.85</td><td>-16.71</td><td>4.383</td><td>-66.0</td><td>4.926</td><td>7.341</td><td>6.619</td><td>183.1</td><td>166.9</td></tr><tr><td>Pgt</td><td>619023298387097856</td><td>09 31 39.43671 +15 46<br>31.54791</td><td>3.4</td><td>64.771</td><td>20.61</td><td>-0.39</td><td></td><td>-69.2</td><td>1.747</td><td>7.146</td><td>1</td><td>15.7</td><td>33.4</td></tr><tr><td>J310050</td><td>2031-02-21 15:38:06.92</td><td>17 36 05.07176 -22 46<br>56.99064</td><td>1.4</td><td>4.626</td><td>182.43</td><td>24.36</td><td>5.611</td><td>18.1</td><td>5.910</td><td>10.153</td><td>9.019</td><td>238.6</td><td>67.9</td></tr><tr><td>Pgt</td><td>4116789654396613888</td><td>17 36 05.05760 -22 47<br>01.61267</td><td>0.7</td><td>18.825</td><td>1.74</td><td>-2.66</td><td></td><td>16.5</td><td>2.181</td><td>10.367</td><td>0</td><td>-22.8</td><td>67.8</td></tr><tr><td>J310215</td><td>2031-04-05 00:30:08.82</td><td>17 52 55.94041 -22 53<br>37.68089</td><td>5.2</td><td>7.678</td><td>0.98</td><td>4.84</td><td>4.937</td><td>-24.3</td><td>4.807</td><td>11.483</td><td>9.945</td><td>68.0</td><td>106.2</td></tr><tr><td>Pgt</td><td>4070200249968817792</td><td>17 52 55.94993 -22 53<br>30.00383</td><td>3.1</td><td>27.493</td><td>-0.08</td><td>-2.61</td><td></td><td>-26.6</td><td>6.508</td><td>9.943</td><td>1</td><td>-22.9</td><td>107.3</td></tr><tr><td>J310218</td><td>2031-04-25 20:54:48.13</td><td>17 52 55.94041 -22 53<br>37.68078</td><td>4.9</td><td>14.726</td><td>179.85</td><td>-4.56</td><td>4.635</td><td>47.6</td><td>4.807</td><td>11.483</td><td>9.945</td><td>101.3</td><td>126.7</td></tr><tr><td>Pgt</td><td>4070200249968817792</td><td>17 52 55.94324 -22 53<br>52.40699</td><td>2.9</td><td>49.504</td><td>-0.08</td><td>-2.61</td><td></td><td>47.4</td><td>6.110</td><td>9.878</td><td>1</td><td>-22.9</td><td>173.5</td></tr><tr><td>J310286</td><td>2031-05-16 23:13:14.27</td><td>17 47 10.16210 -22 53<br>33.02782</td><td>2.4</td><td>4.520</td><td>0.58</td><td>-12.08</td><td>4.403</td><td>-13.3</td><td>5.739</td><td>11.042</td><td>9.679</td><td>44.5</td><td>148.4</td></tr><tr><td>Pgt</td><td>4068933410786852736</td><td>17 47 10.16540 -22 53<br>28.50815</td><td>1.4</td><td>14.432</td><td>0.55</td><td>-2.61</td><td></td><td>-13.2</td><td>2.412</td><td>10.494</td><td>0</td><td>-22.9</td><td>98.0</td></tr><tr><td>J310312</td><td>2031-05-20 15:48:24.05</td><td>17 45 38.86109 -22 53<br>28.30089</td><td>6.7</td><td>14.034</td><td>0.71</td><td>-13.08</td><td>4.372</td><td>-42.1</td><td>5.827</td><td>14.685</td><td>13.940</td><td>151.7</td><td>152.3</td></tr><tr><td>Pgt</td><td>4068857162169473792</td><td>17 45 38.87365 -22 53<br>14.26747</td><td>3.9</td><td>44.504</td><td>0.71</td><td>-2.61</td><td></td><td>-42.1</td><td></td><td>14.224</td><td>0</td><td>-22.9</td><td>145.1</td></tr><tr><td>J310320</td><td>2031-05-22 05:59:54.18</td><td>17 44 57.16658 -22 52<br>56.78582</td><td>5.5</td><td>10.008</td><td>180.78</td><td>-13.47</td><td>4.360</td><td>29.4</td><td>5.640</td><td>13.846</td><td>12.036</td><td>297.1</td><td>154.0</td></tr><tr><td>Pgt</td><td>4116890534598985728</td><td>17 44 57.15678 -22 53<br>06.79313</td><td>3.3</td><td>31.649</td><td>0.78</td><td>-2.61</td><td></td><td>29.4</td><td></td><td>13.417</td><td>0</td><td>-22.9</td><td>164.5</td></tr><tr><td>J310705</td><td>2031-11-04 02:35:13.83</td><td>17 48 17.20920 -23 18<br>07.26401</td><td>4.3</td><td>4.775</td><td>181.72</td><td>33.83</td><td>5.867</td><td>20.1</td><td>5.384</td><td>11.027</td><td>9.670</td><td>185.6</td><td>46.3</td></tr><tr><td>Pgt</td><td>4068768518408378624</td><td>17 48 17.19876 -23 18<br>12.03675</td><td>2.6</td><td>20.318</td><td>0.42</td><td>-2.20</td><td></td><td>17.2</td><td>4.082</td><td>11.598</td><td>0</td><td>-23.3</td><td>170.2</td></tr><tr><td>J320018*</td><td>2032-04-23 14:58:06.36</td><td>20 11 35.30687 -20 13<br>00.46270</td><td>3.6</td><td>0.327</td><td>349.41</td><td>11.96</td><td>5.019</td><td>3.1</td><td>4.506</td><td>7.896</td><td>6.941</td><td>226.6</td><td>92.9</td></tr><tr><td>Pgt</td><td>6866344807161369856</td><td>20 11 35.30260 -20 13<br>00.14155</td><td>2.5</td><td>1.189</td><td>-14.24</td><td>-1.13</td><td></td><td>-5.3</td><td>3.073</td><td>7.338</td><td>0</td><td>-20.1</td><td>110.8</td></tr><tr><td>J350001</td><td>2035-01-09 17:47:09.76</td><td>00 25 26.06476 +01 22<br>09.00817</td><td>2.5</td><td>16.455</td><td>334.89</td><td>19.93</td><td>5.071</td><td>-60.8</td><td>4.537</td><td>8.424</td><td>7.289</td><td>350.9</td><td>77.6</td></tr><tr><td>Pgt</td><td>2547038618688047232</td><td>00 25 25.59910 +01 22<br>23.90770</td><td>1.5</td><td>60.512</td><td>-25.24</td><td>2.32</td><td></td><td>-61.1</td><td>3.543</td><td>8.420</td><td>0</td><td>1.6</td><td>76.4</td></tr><tr><td>J360003</td><td>2036-03-15 17:47:35.37</td><td>03 01 40.65900 +16 18<br>54.99790</td><td>3.3</td><td>8.494</td><td>162.82</td><td>31.32</td><td>5.557</td><td>31.6</td><td>5.933</td><td>8.265</td><td>7.547</td><td>325.1</td><td>52.4</td></tr><tr><td>Pgt</td><td>34248069218428800</td><td>03 01 40.83331 +16 18<br>46.88312</td><td>3.0</td><td>34.231</td><td>-16.98</td><td>2.89</td><td></td><td>32.1</td><td>1.367</td><td>8.752</td><td>0</td><td>16.5</td><td>170.0</td></tr><tr><td>J370020</td><td>2037-04-11 15:44:22.59</td><td>05 21 58.59041 +22 57<br>13.24662</td><td>2.6</td><td>10.207</td><td>175.46</td><td>27.71</td><td>5.566</td><td>37.4</td><td>5.223</td><td>8.283</td><td>7.371</td><td>4.7</td><td>59.7</td></tr><tr><td>Pgt</td><td>3414783812488249088</td><td>05 21 58.64892 +22 57<br>03.07188</td><td>1.7</td><td>41.201</td><td>-3.25</td><td>2.35</td><td></td><td>40.1</td><td>2.262</td><td>8.637</td><td>0</td><td>23.0</td><td>104.0</td></tr><tr><td>J430151</td><td>2043-03-03 23:23:54.17</td><td></td><td>17.1</td><td>7.795</td><td>0.31</td><td>21.91</td><td>5.508</td><td>-27.8</td><td>5.166</td><td>14.657</td><td>12.899</td><td>117.7</td><td>73.0</td></tr></tbody></table>
<table><caption>Table 8
(Continued)</caption><thead><tr><th>Event ID<br>Event Type</th><th>C/A Epoch<br>Source ID</th><th>ICRS Star Coord at Epoch<br>Geocentric Object Position</th><th>σ(α<sub>*</sub>) (km)<br>σ(δ<sub>*</sub>) (km)</th><th>C/A (′′)<br>C/A (10<sup>3</sup> km)</th><th>PA (deg)<br>P (deg)</th><th>ν<sub>sky</sub> (km s<sup>-1</sup>)<br>B (deg)</th><th>Dist (au)<br>r (km s<sup>-1</sup>)</th><th>Lat I (deg)<br>Lat E (deg)</th><th>K<br>D<sub>*</sub> (km)</th><th>G<br>G<sub>*</sub></th><th>RP<br>DUP</th><th>E λ (deg)<br>φ (deg)</th><th>S-G-T<br>M-G-T</th></tr></thead><tbody><tr><td>Pgt</td><td>4069447879086908416</td><td>17 58 42.60177 −22 59<br>14.48648</td><td>11.4</td><td>31.140</td><td>−0.70</td><td>−2.51</td><td></td><td>−30.0</td><td>14.756</td><td>0</td><td></td><td>−23.0</td><td>18.5</td></tr><tr><td>J430157</td><td>2043-03-07 08:17:34.33</td><td>17 58 42.60478 −22 59<br>06.69112</td><td>7.0</td><td>17.902</td><td>0.13</td><td>20.44</td><td>5.455</td><td>−81.9</td><td>4.879</td><td>10.823</td><td>9.399</td><td>341.4</td><td>75.9</td></tr><tr><td>Pgt</td><td>4069438430158980864</td><td>18 00 34.94357 −22 59<br>30.34468</td><td>5.0</td><td>70.827</td><td>−0.90</td><td>−2.50</td><td></td><td>−83.7</td><td>5.284</td><td>10.846</td><td>0</td><td>−23.0</td><td>24.5</td></tr><tr><td>J430238</td><td>2043-05-23 17:33:30.24</td><td>18 05 37.49681 −23 01<br>49.83575</td><td>7.0</td><td>15.665</td><td>178.58</td><td>−12.59</td><td>4.370</td><td>47.6</td><td>5.876</td><td>12.169</td><td>10.655</td><td>127.4</td><td>150.6</td></tr><tr><td>Pgt</td><td>4069573871938648320</td><td>18 05 37.52495 −23 02<br>05.49575</td><td>4.7</td><td>49.653</td><td>−1.44</td><td>−2.43</td><td></td><td>47.7</td><td>3.097</td><td>11.667</td><td>0</td><td>−23.0</td><td>32.4</td></tr><tr><td>J430246</td><td>2043-05-25 18:18:19.03</td><td>18 04 45.87252 −23 02<br>25.38066</td><td>9.4</td><td>2.705</td><td>358.66</td><td>−13.12</td><td>4.354</td><td>−7.8</td><td>5.102</td><td>11.764</td><td>10.161</td><td>114.0</td><td>152.8</td></tr><tr><td>Pgt</td><td>4069584424693604736</td><td>18 04 45.86795 −23 02<br>22.67675</td><td>5.8</td><td>8.542</td><td>−1.35</td><td>−2.43</td><td></td><td>−7.8</td><td></td><td>11.306</td><td>0</td><td>−23.0</td><td>9.3</td></tr><tr><td>J430271*</td><td>2043-06-12 00:30:09.82</td><td>17 56 11.96283 −23 04<br>28.69795</td><td>19.7</td><td>11.600</td><td>359.46</td><td>−16.08</td><td>4.263</td><td>−33.3</td><td>5.221</td><td>14.816</td><td>13.003</td><td>1.9</td><td>171.3</td></tr><tr><td>Pgt</td><td>4069408331058914560</td><td>17 56 11.95484 −23 04<br>17.09827</td><td>12.6</td><td>35.870</td><td>−0.43</td><td>−2.43</td><td></td><td>−33.6</td><td></td><td>14.578</td><td>0</td><td>−23.1</td><td>127.2</td></tr><tr><td>J430274</td><td>2043-06-13 17:43:42.54</td><td>17 55 15.78203 −23 04<br>23.11536</td><td>11.1</td><td>0.806</td><td>179.54</td><td>−16.20</td><td>4.259</td><td>2.4</td><td>3.985</td><td>11.534</td><td>9.923</td><td>101.6</td><td>173.1</td></tr><tr><td>Pgt</td><td>4070137715246205568</td><td>17 55 15.78250 −23 04<br>23.92118</td><td>7.1</td><td>2.489</td><td>−0.33</td><td>−2.43</td><td></td><td>2.1</td><td>11.331</td><td>11.305</td><td>0</td><td>−23.1</td><td>104.8</td></tr><tr><td>J430339</td><td>2043-06-27 22:54:16.9</td><td>17 47 25.33650 −23 04<br>45.90459</td><td>2.9</td><td>5.388</td><td>0.16</td><td>−16.11</td><td>4.256</td><td>−14.9</td><td>4.005</td><td>8.936</td><td>7.611</td><td>15.1</td><td>171.5</td></tr><tr><td>Pgt</td><td>4068789787093980672</td><td>17 47 25.33758 −23 04<br>40.51642</td><td>1.7</td><td>16.633</td><td>0.52</td><td>−2.42</td><td></td><td>−15.7</td><td>5.263</td><td>8.701</td><td>0</td><td>−23.1</td><td>71.1</td></tr><tr><td>J430433</td><td>2043-07-13 03:18:39.12</td><td>17 39 41.37292 −23 03<br>52.48115</td><td>3.1</td><td>3.900</td><td>180.58</td><td>−13.77</td><td>4.318</td><td>12.1</td><td>5.488</td><td>10.722</td><td>9.429</td><td>285.0</td><td>155.3</td></tr><tr><td>Pgt</td><td>4116554874369464960</td><td>17 39 41.37006 −23 03<br>56.38046</td><td>1.8</td><td>12.212</td><td>1.35</td><td>−2.40</td><td></td><td>10.3</td><td>2.499</td><td>10.317</td><td>0</td><td>−23.1</td><td>75.7</td></tr><tr><td>J430537</td><td>2043-09-23 13:48:15.37</td><td>17 37 39.31108 −23 14<br>07.51003</td><td>15.9</td><td>10.435</td><td>3.46</td><td>15.65</td><td>5.223</td><td>−35.1</td><td>4.111</td><td>11.549</td><td>10.549</td><td>55.7</td><td>85.0</td></tr><tr><td>Pgt</td><td>4116713135287242624</td><td>17 37 39.35681 −23 13<br>57.09370</td><td>8.8</td><td>39.534</td><td>1.57</td><td>−2.22</td><td></td><td>−39.1</td><td></td><td>11.283</td><td>0</td><td>−23.3</td><td>155.2</td></tr><tr><td>J450004</td><td>2045-09-03 10:19:11.65</td><td>22 33 41.12388 −10 31<br>16.26580</td><td>2.6</td><td>8.605</td><td>157.89</td><td>−15.83</td><td>3.997</td><td>21.0</td><td>5.663</td><td>8.127</td><td>7.389</td><td>201.2</td><td>175.2</td></tr><tr><td>Pgt</td><td>2602776092914341248</td><td>22 33 41.34351 −10 31<br>24.23785</td><td>2.4</td><td>24.947</td><td>−23.93</td><td>1.29</td><td></td><td>25.0</td><td>1.143</td><td>7.874</td><td>0</td><td>−10.3</td><td>82.5</td></tr><tr><td>J480014</td><td>2048-08-19 13:35:07.18</td><td>05 38 13.82080 +22 49<br>12.67217</td><td>5.8</td><td>1.138</td><td>177.71</td><td>26.78</td><td>5.469</td><td>3.2</td><td>3.030</td><td>9.043</td><td>7.717</td><td>272.9</td><td>61.6</td></tr><tr><td>Pgt</td><td>3404219910928409856</td><td>05 38 13.82409 +22 49<br>11.53468</td><td>3.2</td><td>4.516</td><td>−1.51</td><td>2.64</td><td></td><td>5.0</td><td>14.563</td><td>9.360</td><td>0</td><td>22.8</td><td>174.7</td></tr></tbody></table>
<figure><img src="image_9.png" /><figcaption>**Figure 5.** Maps of the sky showing the apparent paths of Jupiter, Saturn, Uranus, and Neptune as viewed from Earth. The brightness of the background is proportional to the logarithmic areal density of stars in the 2MASS catalog (Skrutskie et al. 2006) with apparent magnitude $K \le 15$. The Milky Way appears as a bright wavy band. Upper left: Jupiter's position is marked at yearly intervals with white symbols for 2020–2029, red symbols for 2030–2039, and cyan symbols for 2040–2050. Upper right: Saturn's position between 2020 and 2050 is marked with + symbols at 5 yr intervals as labeled. Lower left: the position of Uranus between 1975 and 2050 is marked with + symbols at 5 yr intervals. The filled black dots mark the position of Uranus at times of previous stellar occultation observations between 1977 and 2007, described in detail in French et al. (2023b). Uranus next crosses the Milky Way in 2026–2027, resulting in a higher frequency of occultations during that period. Lower right: the position of Neptune between 1975 and 2050 is marked with + symbols at 5 yr intervals. The filled black dots mark the position of Neptune at times of previous stellar occultation observations, both published (Roques et al. 1994) and under active investigation. Neptune's slow motion across the sky will be far removed from the Milky Way for more than three decades, accounting for the small number of high-S/N Neptune occultations in our prediction list.</figcaption></figure>

2048, the times of Milky Way crossings, as noted above, and coincidentally are the times when Saturn's rings are most open as viewed from Earth, enhancing the prospects for high radial resolution observations of the rings during these occultations.

To illustrate the range of event geometries and the varying aspect of Saturn and its rings, Figure 7 shows a gallery of views of Earth at mid-occultation, and Figure 8 shows the corresponding sky-plane views of Saturn for the 24 brightest predicted events in the *K* band with composite event type *RgtPgt* between 2023 and 2047. (The end date is chosen to avoid overrepresentation of the large number of predicted events in the period 2047–2050, evident in Table 9, owing to Saturn's traversal of the Galactic center region of the Milky Way at that time.) Table 10 provides detailed information about these events.

There are only a few occultations with $K \le 8$ by Saturn between 2023 and 2029, after which there are numerous high-S/N opportunities to observe the atmosphere and the rings

unblocked by the planet. The brightest of these is the 2032 April 7 event ($K=4.78$, $G = 5.72$, $V=5.80$), with a nearly diametric ring occultation observable from Hawaii. High-S/N atmosphere observations should be possible for this occultation. However, even this bright star is only about 5% the brightness of the 1989 July 3 occultation star 28 Sgr in the *K* band, and the icy rings have a high albedo in this wavelength region. The rings are darker in the *L* band near $\lambda \sim 3 \mu$m, where future high-altitude or spacecraft observations may be possible for this and later occultations.

### 5.3. Uranus

The Uranian rings were first detected during the widely observed 1977 March 10 occultation of the bright star SAO 158687 (Bhattacharyya & Bappu 1977; Brahic 1977; Elliot et al. 1977; Hubbard et al. 1977; Millis et al. 1977; Morrisby et al. 1977; Tomita 1977; Chen et al. 1978), and a
<figure><img src="image_10.png" /><figcaption>**Figure 6.** Sub-Earth (solid line) and subsolar (dashed line) latitudes vs. time for Saturn, Uranus, and Neptune. These are equivalent to the ring opening angles *B* and *B'* defined in the text. For Uranus and Neptune, previous stellar occultation observations are shown as filled black dots. For each planet, selected predicted occultations are shown as red dots for stars brighter than the cutoff value shown in each panel. The times of the Voyager 2 encounters with Uranus and Neptune are marked by arrows.</figcaption></figure>

rich set of subsequent Earth-based occultations revealed that these narrow and sharp-edged rings were eccentric and inclined, precessing under the gravitational influence of the oblate central planet (see Nicholson et al. 2018 and French et al. 2023b for recent reviews). Atmospheric occultations during some of these events provided information about the stratospheric temperature profiles (see Young et al. 2001 for results from the 1998 November 6 occultation, and references therein to prior events) and the oblateness of the planet (Baron et al. 1989).

Our search resulted in the identification of 1173 predicted occultations by Uranus and/or its rings for the period 2023–2050 for a limiting magnitude $K \le 15$. Table 11 lists

the number of predicted events per year as a function of *K* magnitude. The format is the same as for Table 9. The distribution of events in time is very nonuniform, resulting from the planet's intermittent traversal of the dense star fields of the Milky Way, separated by long periods in relatively star-free regions of the sky. This is evident in Figure 5 (lower left), which shows the apparent path of Uranus in the sky plane as viewed from Earth between 1975 and 2050. Uranus crossed the Milky Way roughly in the direction of the Galactic center between 1985 and 1990, providing abundant opportunities for high-S/N ring and planet occultations. The subsequent reduction in the density of stars along the planet's path, combined with the nearly edge-on aspect of the rings
<figure><img src="image_11.png" /><figcaption>**Figure 7.** Gallery of Earth views from Saturn at mid-occultation for the 24 brightest predicted events in the K band with composite event type RgtPgt between 2023 and 2047.</figcaption></figure>

<table><caption>**Table 9**
Saturn Planet/Ring Occultations 2023–2050</caption><thead><tr><th>Year</th><th>K &lt; 5<br>P/R</th><th>K 5–6<br>P/R</th><th>K 6–7<br>P/R</th><th>K 7–8<br>P/R</th><th>K 8–9<br>P/R</th><th>K 9–10<br>P/R</th></tr></thead><tbody><tr><td>2023</td><td>...</td><td>...</td><td>...</td><td>1/0</td><td>...</td><td>...</td></tr><tr><td>2024</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>...</td><td>...</td></tr><tr><td>2025</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td></tr><tr><td>2026</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>3/3</td></tr><tr><td>2029</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>2/2</td><td>2/3</td></tr><tr><td>2030</td><td>...</td><td>1/1</td><td>1/1</td><td>1/1</td><td>2/2</td><td>3/4</td></tr><tr><td>2031</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>2/2</td><td>3/4</td></tr><tr><td>2032</td><td>1/1</td><td>...</td><td>...</td><td>4/4</td><td>4/4</td><td>8/8</td></tr><tr><td>2033</td><td>...</td><td>...</td><td>1/1</td><td>2/2</td><td>1/1</td><td>6/7</td></tr><tr><td>2034</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/2</td><td>6/7</td></tr><tr><td>2035</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>0/1</td></tr><tr><td>2036</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>4/4</td></tr><tr><td>2037</td><td>...</td><td>...</td><td>1/1</td><td>2/2</td><td>...</td><td>0/1</td></tr><tr><td>2038</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0</td><td>0/1</td></tr><tr><td>2041</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>...</td></tr><tr><td>2043</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>1/1</td></tr><tr><td>2044</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>6/6</td></tr><tr><td>2045</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>4/4</td></tr><tr><td>2046</td><td>...</td><td>...</td><td>4/4</td><td>3/4</td><td>16/16</td><td>21/23</td></tr><tr><td>2047</td><td>1/1</td><td>4/4</td><td>5/6</td><td>13/13</td><td>29/33</td><td>40/41</td></tr><tr><td>2048</td><td>...</td><td>...</td><td>0/1</td><td>2/2</td><td>9/9</td><td>23/26</td></tr><tr><td>2049</td><td>...</td><td>...</td><td>1/1</td><td>2/2</td><td>5/5</td><td>5/6</td></tr><tr><td>Totals</td><td>2/2</td><td>5/5</td><td>13/15</td><td>33/33</td><td>79/82</td><td>136/151</td></tr></tbody></table>

and the decommissioning of high-speed InSb aperture photometers at major observatories, resulted in a virtual absence of Uranus occultation observations in the past two decades. The most recent published observations were the 2002 November 29 occultation (K = 11.4) observed from Palomar Observatory and the 2006 September 20 occultation (V = 10.746, K = 8.408) observed from the IRTF (French et al. 2023b). The next traversal of the Milky Way will not occur until 2033 in the less dense stellar regions opposite to the Galactic center. Until then, the frequency of high-S/N stellar occultations by Uranus and its rings will be at a typical cadence of one every few years.

The Earth view of the Uranus ring system varies substantially over time, as shown in Figure 6 for the period 1975–2050. The solid line shows the sub-Earth latitude, with an annual periodic term reflecting the relative inclinations of the orbits of Earth and Uranus, and the dashed line shows the subsolar latitude.<fnref n="15" /> The most recent Uranus RPXs occurred in

<footnote n="15">¹⁵ Here, we follow the NASA/JPL Horizons convention of using the International Astronomical Union (IAU) definition of the pole direction of Uranus. In our tabulated results, we specify the ring elevation angle B, following the convention used at NASA's Planetary Data System Ring-Moon Systems node. This angle is positive on the side of the ring plane defined by positive angular momentum, and negative on the opposite side. The direction of positive angular momentum points toward the IAU-defined north side of the ring plane for Jupiter, Saturn and Neptune, but the IAU-defined south side of the ring plane for Uranus, with the result that B is the negative of the IAU-defined sub-Earth latitude shown in Figure 6.</footnote>
<figure><img src="image_12.png" /><figcaption>**Figure 8.** Gallery of sky-plane geocentric views of Saturn and its rings at mid-occultation for the 24 brightest predicted events in the *K* band between 2023 and 2047 with composite event type *RgtPgt*.</figcaption></figure>

~2008 and the next will not occur until ~2050. Black dots mark the times of previously observed occultations, and red dots mark predicted Uranus occultations for stars with $K \le 11$. These are most frequent near 2033, the time of the next Milky Way crossing, as noted above, and coincidentally (just as for Saturn) are the times when the rings are most open as viewed from Earth, enhancing the prospects for high radial resolution observations of the rings.

The accuracy of our predictions is dependent in part on the accuracy of the Uranus ephemeris. Using Uranus ring occultation observations from 1977 to 2006, French et al. (2023a, 2023b) detected a small but significant quasi-linear drift between the *ural16.bsp* ephemeris and true sky-plane positions of Uranus since 1986, the epoch of the Voyager 2 flyby that provided a very accurate instantaneous value for the planet's position. Making use of these ring observations, the JPL has released a new Uranus ephemeris (*ural61.bsp*) that removes this drift. We have used this revised ephemeris for all of our Uranus predictions.

To illustrate the range of event geometries and the varying aspect of Uranus and its rings, Figure 9 shows galleries of views of Earth at mid-occultation, and Figure 10 shows the corresponding sky-plane views of Uranus for the 24 brightest predicted events in the *K* band with ring event type *Rgt* for 2023–2050. (Note that several of these events have no planet occultations.) Table 12 provides detailed information about this subset of our full prediction list.

The full set of prediction details is available in the SOM. Saunders et al. (2022) identified 56 near-IR Uranus occultations between 2025 January 1 and 2035 December 31 visible from low-Earth orbit, with a solar exclusion angle of 30°. Our computed geometry matches the subset of these events that satisfy our SGT limit of ≥45°, more appropriate for ground-based observations.

## 5.4. Neptune

The first modern occultation observation of Neptune occurred on 1968 April 7, when the planet occulted the star BD −17 4388 (Kovalevsky & Link 1969). The results were used to estimate the oblateness of Neptune, and this success ushered in a series of subsequent observation campaigns that provided a time and spatial history of the stratospheric temperature of the planet, as reviewed in detail by Roques et al. (1994). After the occultation discovery of the Uranian rings, concerted efforts were made to detect rings around Neptune, ultimately resulting in the unexpected discovery and subsequent characterization of incomplete ring arcs (Hubbard et al. 1986; Sicardy et al. 1986, 1991). French et al. (1998) combined central flash observations from three atmospheric occultations to derive information about Neptune’s stratospheric winds, and Uckert et al. (2014) investigated temperature variations in the upper stratosphere from a 2008 July 23 single-chord stellar occultation of the star USNO-B1.0 0759-0739128 ($I = 12.60$).
<table><caption>Table 10
Geocentric Saturn Occultation Predictions 2023–2047</caption><thead><tr><th>Event ID<br>Event Type</th><th>C/A Epoch<br>Source ID</th><th>ICRS Star Coord at Epoch<br>Geocentric Object Position</th><th>σ(α<sub>*</sub>) (km)<br>σ(δ<sub>*</sub>) (km)</th><th>C/A (")<br>C/A (10<sup>3</sup> km)</th><th>PA (deg)<br>P (deg)</th><th>ν<sub>sky</sub> (km s<sup>-1</sup>)<br>B (deg)</th><th>Dist (au)<br>r̄ (km s<sup>-1</sup>)</th><th>Lat I (deg)<br>Lat E (deg)</th><th>K<br>D<sub>*</sub> (km)</th><th>G<br>G<sub>*</sub></th><th>RP<br>DUP</th><th>E λ (deg)<br>φ (deg)</th><th>S-G-T<br>M-G-T</th></tr></thead><tbody><tr><td>S23001<sup>**</sup></td><td>2023-04-15 06:21:28.59</td><td>22 24 49.19365 −11 23<br>18.66374</td><td>4.3</td><td>0.607</td><td>160.37</td><td>28.51</td><td>10.410</td><td>−25.1</td><td>7.832</td><td>8.640</td><td>8.330</td><td>38.0</td><td>50.9</td></tr><tr><td>PgtX</td><td>2602435862784961664</td><td>22 24 49.20752 −11 23<br>19.23506</td><td>3.3</td><td>4.582</td><td>5.89</td><td>8.54</td><td></td><td>34.7</td><td>0.786</td><td>9.025</td><td>0</td><td>−11.3</td><td>14.5</td></tr><tr><td>S24001<sup>***</sup></td><td>2024-08-06 17:12:21.22</td><td>23 18 59.47989 −06 43<br>01.47226</td><td>7.0</td><td>8.196</td><td>153.78</td><td>−15.13</td><td>8.814</td><td>87.4</td><td>7.716</td><td>9.161</td><td>8.444</td><td>136.2</td><td>146.4</td></tr><tr><td>PgtRgt</td><td>2631163146681256448</td><td>23 18 59.72295 −06 43<br>08.82476</td><td>7.2</td><td>52.390</td><td>5.01</td><td>2.62</td><td></td><td>34.2</td><td>0.913</td><td>8.857</td><td>0</td><td>−6.6</td><td>171.7</td></tr><tr><td>S29002<sup>*</sup></td><td>2029-07-19 00:57:19.09</td><td>03 22 51.43791 +16 17<br>15.28928</td><td>2.3</td><td>3.011</td><td>167.39</td><td>22.88</td><td>9.562</td><td>10.0</td><td>7.241</td><td>10.369</td><td>9.477</td><td>99.7</td><td>63.7</td></tr><tr><td>PgtRgt</td><td>54522689973491584</td><td>03 22 51.48358 +16 17<br>12.35144</td><td>1.9</td><td>20.879</td><td>−1.23</td><td>−22.65</td><td>23.656</td><td>34.2</td><td>1.510</td><td>10.515</td><td>0</td><td>16.4</td><td>158.5</td></tr><tr><td>S30003</td><td>2030-03-07 22:38:48.34</td><td>03 11 19.24980 +15 42<br>35.64960</td><td>1.9</td><td>4.128</td><td>341.70</td><td>23.38</td><td>9.523</td><td>−47.3</td><td>6.224</td><td>8.804</td><td>8.027</td><td>262.9</td><td>62.7</td></tr><tr><td>PgtRgt</td><td>31196722588576128</td><td>03 11 19.16004 +15 42<br>39.56916</td><td>1.6</td><td>28.512</td><td>−0.88</td><td>−22.12</td><td>26.008</td><td>−12.2</td><td>2.163</td><td>8.974</td><td>0</td><td>15.8</td><td>21.6</td></tr><tr><td>S30004</td><td>2030-08-03 07:16:30.77</td><td>04 19 53.06611 +19 31<br>03.90032</td><td>2.4</td><td>0.761</td><td>171.77</td><td>22.68</td><td>9.482</td><td>−0.3</td><td>5.508</td><td>9.224</td><td>8.203</td><td>4.4</td><td>64.1</td></tr><tr><td>PgtRgt</td><td>48224275053110272</td><td>04 19 53.07384 +19 31<br>03.14766</td><td>1.9</td><td>5.230</td><td>−2.95</td><td>−25.38</td><td>23.045</td><td>11.3</td><td>3.908</td><td>9.361</td><td>0</td><td>19.6</td><td>110.3</td></tr><tr><td>S30005</td><td>2030-08-17 21:05:04.31</td><td>04 24 07.02059 +19 39<br>15.03689</td><td>2.4</td><td>8.458</td><td>173.02</td><td>16.34</td><td>9.255</td><td>62.3</td><td>7.562</td><td>9.005</td><td>8.493</td><td>143.9</td><td>77.1</td></tr><tr><td>PgtRgt</td><td>48279147555452544</td><td>04 24 07.09344 +19 39<br>06.64162</td><td>1.8</td><td>56.775</td><td>−3.07</td><td>−25.46</td><td>4.862</td><td>66.0</td><td>0.902</td><td>8.786</td><td>0</td><td>19.7</td><td>48.6</td></tr><tr><td>S31003</td><td>2031-08-01 13:08:54.06</td><td>05 12 56.43379 +21 30<br>44.94500</td><td>2.5</td><td>6.481</td><td>355.77</td><td>28.96</td><td>9.663</td><td>−48.4</td><td>7.961</td><td>12.171</td><td>11.050</td><td>291.5</td><td>49.6</td></tr><tr><td>PgtRgt</td><td>3414247177797508736</td><td>05 12 56.39959 +21 30<br>51.40868</td><td>1.5</td><td>45.422</td><td>−4.41</td><td>−26.57</td><td>19.422</td><td>−48.7</td><td>1.486</td><td>12.573</td><td>0</td><td>21.5</td><td>152.1</td></tr><tr><td>S32003</td><td>2032-03-14 04:10:44.16</td><td>05 00 57.02045 +21 27<br>54.29471</td><td>2.7</td><td>3.296</td><td>349.89</td><td>13.54</td><td>9.096</td><td>−28.7</td><td>7.132</td><td>10.149</td><td>9.274</td><td>200.7</td><td>82.6</td></tr><tr><td>PgtRgt</td><td>3412182058740339712</td><td>05 00 56.97903 +21 27<br>57.53943</td><td>2.0</td><td>21.744</td><td>−4.11</td><td>−26.73</td><td>13.019</td><td>−16.4</td><td>1.513</td><td>9.726</td><td>0</td><td>21.5</td><td>49.0</td></tr><tr><td>S32005</td><td>2032-04-07 06:17:50.19</td><td>05 07 55.43570 +21 42<br>17.13583</td><td>5.6</td><td>0.451</td><td>172.74</td><td>24.40</td><td>9.473</td><td>−0.0</td><td>4.775</td><td>5.723</td><td>5.437</td><td>146.9</td><td>60.4</td></tr><tr><td>PgtRgt</td><td>3415147613398691200</td><td>05 07 55.43982 +21 42<br>16.68826</td><td>4.0</td><td>3.099</td><td>−4.29</td><td>−26.85</td><td>24.527</td><td>6.5</td><td>3.014</td><td>5.939</td><td>0</td><td>21.7</td><td>98.9</td></tr><tr><td>S32009</td><td>2032-08-17 22:39:58.99</td><td>06 14 57.57298 +22 23<br>54.85276</td><td>2.4</td><td>6.537</td><td>1.46</td><td>28.12</td><td>9.609</td><td>−42.9</td><td>7.585</td><td>9.958</td><td>9.209</td><td>147.4</td><td>51.7</td></tr><tr><td>PgtRgt</td><td>3376976795931337600</td><td>06 14 57.58501 +22 24<br>01.38777</td><td>1.8</td><td>45.559</td><td>−5.76</td><td>−26.17</td><td>19.789</td><td>−54.4</td><td>1.125</td><td>10.328</td><td>0</td><td>22.4</td><td>171.6</td></tr><tr><td>S32013</td><td>2032-12-03 15:23:12.94</td><td>06 21 14.77166 +22 21<br>03.85494</td><td>2.5</td><td>5.649</td><td>182.81</td><td>−17.69</td><td>8.102</td><td>26.6</td><td>7.753</td><td>11.906</td><td>10.796</td><td>152.0</td><td>156.6</td></tr><tr><td>PgtRgt</td><td>3377160169558092928</td><td>06 21 14.75173 +22 20<br>58.21235</td><td>1.9</td><td>33.193</td><td>−5.87</td><td>−25.97</td><td>15.728</td><td>42.9</td><td>1.392</td><td>11.773</td><td>0</td><td>22.3</td><td>166.0</td></tr><tr><td>S33005</td><td>2033-01-30 11:01:27.46</td><td>06 02 28.97310 +22 33<br>04.32277</td><td>3.7</td><td>1.131</td><td>3.29</td><td>−13.24</td><td>8.237</td><td>−16.6</td><td>6.474</td><td>11.453</td><td>10.183</td><td>155.8</td><td>140.2</td></tr><tr><td>PgtRgt</td><td>3423718336601355904</td><td>06 02 28.97781 +22 33<br>05.45194</td><td>2.7</td><td>6.759</td><td>−5.54</td><td>−26.61</td><td>13.811</td><td>2.6</td><td>2.998</td><td>11.006</td><td>0</td><td>22.5</td><td>146.3</td></tr><tr><td>S33007</td><td>2033-04-20 13:13:12.07</td><td>06 08 27.81207 +22 46<br>13.59165</td><td>3.3</td><td>2.104</td><td>179.12</td><td>23.79</td><td>9.451</td><td>20.1</td><td>7.106</td><td>12.166</td><td>10.878</td><td>45.4</td><td>61.6</td></tr><tr><td>PgtRgt</td><td>3425270679517659520</td><td>06 08 27.81442 +22 46<br>11.48702</td><td>2.5</td><td>14.425</td><td>−5.66</td><td>−26.69</td><td>23.486</td><td>9.9</td><td>12.354</td><td>0</td><td>22.8</td><td>173.8</td><td>56.5</td></tr><tr><td>S33010</td><td>2033-04-26 08:41:41.37</td><td></td><td>2.0</td><td>4.779</td><td>179.55</td><td>26.10</td><td>9.534</td><td>39.5</td><td>7.255</td><td>11.023</td><td>10.006</td><td>108.1</td><td></td></tr></tbody></table>
<table><caption>Table 10
(Continued)</caption><thead><tr><th>Event ID<br>Event Type</th><th>C/A Epoch<br>Source ID</th><th>ICRS Star Coord at Epoch<br>Geocentric Object Position</th><th>σ(α<sub>*</sub>) (km)<br>σ(δ<sub>*</sub>) (km)</th><th>C/A (′′)<br>C/A (10<sup>3</sup> km)</th><th>PA (deg)<br>P (deg)</th><th>ν<sub>sky</sub> (km s<sup>-1</sup>)<br>B (deg)</th><th>Dist (au)<br>r̄ (km s<sup>-1</sup>)</th><th>Lat I (deg)<br>Lat E (deg)</th><th>K<br>D<sub>*</sub> (km)</th><th>G<br>G<sub>*</sub></th><th>RP<br>DUP</th><th>E λ (deg)<br>φ (deg)</th><th>S-G-T<br>M-G-T</th></tr></thead><tbody><tr><td>PgtRgt</td><td>3425075069527522816</td><td>06 10 39.39492 +22 46<br>37.24870</td><td>1.7</td><td>33.043</td><td>-5.70</td><td>-26.64</td><td>22.523</td><td>29.7</td><td></td><td>11.312</td><td>0</td><td>22.8</td><td>94.8</td></tr><tr><td>S37002</td><td>2037-02-15 02:44:09.31</td><td>06 10 39.39769 +22 46<br>32.46966</td><td>2.1</td><td>7.429</td><td>21.68</td><td>-20.15</td><td>8.248</td><td>-74.9</td><td>7.654</td><td>10.003</td><td>9.294</td><td>325.9</td><td>176.7</td></tr><tr><td>PgtRgt</td><td>3881962210025024896</td><td>10 07 29.39955 +13 16<br>06.38810</td><td>1.6</td><td>44.440</td><td>-6.13</td><td>-10.85</td><td>40.042</td><td>-23.3</td><td>0.905</td><td>10.011</td><td>0</td><td>13.1</td><td>176.1</td></tr><tr><td>S37003</td><td>2037-03-06 12:59:46.54</td><td>10 01 35.84616 +13 49<br>33.76525</td><td>2.4</td><td>7.240</td><td>200.56</td><td>-18.69</td><td>8.292</td><td>23.0</td><td>6.648</td><td>8.853</td><td>8.166</td><td>151.3</td><td>161.8</td></tr><tr><td>PgtRgt</td><td>615385869108696960</td><td>10 01 35.67165 +13 49<br>26.98510</td><td>1.6</td><td>43.542</td><td>-6.21</td><td>-11.56</td><td>34.100</td><td>73.0</td><td>1.432</td><td>8.779</td><td>0</td><td>13.6</td><td>80.2</td></tr><tr><td>S37004</td><td>2037-03-30 09:07:28.03</td><td>09 55 49.78581 +14 19<br>44.14548</td><td>2.9</td><td>1.492</td><td>18.96</td><td>-12.06</td><td>8.494</td><td>-38.6</td><td>7.435</td><td>11.026</td><td>9.996</td><td>184.5</td><td>136.6</td></tr><tr><td>PgtRgt</td><td>615301245368208128</td><td>09 55 49.81917 +14 19<br>45.55568</td><td>2.3</td><td>9.194</td><td>-6.28</td><td>-12.21</td><td>26.435</td><td>19.5</td><td>1.493</td><td>10.477</td><td>0</td><td>14.2</td><td>28.8</td></tr><tr><td>S46004</td><td>2046-02-05 02:28:59.57</td><td>17 17 34.79616 -21 37<br>16.33741</td><td>11.7</td><td>4.411</td><td>3.56</td><td>26.40</td><td>10.548</td><td>-36.4</td><td>7.791</td><td>12.996</td><td>11.607</td><td>87.4</td><td>55.7</td></tr><tr><td>PgtRgt</td><td>4115016039029356416</td><td>17 17 34.81584 -21 37<br>11.93441</td><td>7.5</td><td>33.744</td><td>4.53</td><td>26.59</td><td>22.066</td><td>-34.6</td><td>2.203</td><td>13.298</td><td>0</td><td>-21.7</td><td>46.3</td></tr><tr><td>S46020</td><td>2046-03-23 09:58:10.06</td><td>17 27 44.73429 -21 42<br>46.33527</td><td>16.8</td><td>1.619</td><td>357.69</td><td>4.53</td><td>9.811</td><td>-19.6</td><td>6.335</td><td>12.282</td><td>10.813</td><td>292.0</td><td>99.8</td></tr><tr><td>PgtRgt</td><td>4117826352042608384</td><td>17 27 44.72967 -21 42<br>44.71744</td><td>10.8</td><td>11.518</td><td>4.77</td><td>26.49</td><td>4.758</td><td>-4.4</td><td>5.115</td><td>10.670</td><td>0</td><td>-21.7</td><td>66.0</td></tr><tr><td>S46021*</td><td>2046-03-26 05:22:20.36</td><td>17 27 54.12477 -21 42<br>37.09412</td><td>44.8</td><td>0.106</td><td>175.32</td><td>3.15</td><td>9.765</td><td>-9.7</td><td>6.879</td><td>14.842</td><td>13.079</td><td>358.2</td><td>102.5</td></tr><tr><td>PgtRgt</td><td>4117826218935136512</td><td>17 27 54.12539 -21 42<br>37.19945</td><td>29.3</td><td>0.748</td><td>4.77</td><td>26.49</td><td>3.534</td><td>11.0</td><td></td><td>12.834</td><td>0</td><td>-21.7</td><td>25.7</td></tr><tr><td>S46029</td><td>2046-05-18 13:03:11.39</td><td>17 20 54.76091 -21 33<br>38.52132</td><td>14.4</td><td>1.515</td><td>183.86</td><td>-17.65</td><td>9.099</td><td>11.3</td><td>7.532</td><td>13.797</td><td>12.275</td><td>188.7</td><td>156.2</td></tr><tr><td>PgtRgt</td><td>4115052494691697792</td><td>17 20 54.75360 -21 33<br>40.03263</td><td>10.7</td><td>9.996</td><td>4.60</td><td>26.47</td><td>17.434</td><td>9.6</td><td>3.182</td><td>13.661</td><td>0</td><td>-21.6</td><td>45.6</td></tr><tr><td>S46033</td><td>2046-05-25 21:34:57.15</td><td>17 18 48.01096 -21 31<br>41.66501</td><td>11.2</td><td>0.402</td><td>183.78</td><td>-18.99</td><td>9.057</td><td>3.6</td><td>6.494</td><td>12.668</td><td>11.252</td><td>53.0</td><td>163.7</td></tr><tr><td>PgtRgt</td><td>4115099533179705856</td><td>17 18 48.00913 -21 31<br>42.06538</td><td>7.3</td><td>2.638</td><td>4.55</td><td>26.48</td><td>18.992</td><td>1.9</td><td>4.225</td><td>12.612</td><td>0</td><td>-21.6</td><td>53.8</td></tr><tr><td>S46035</td><td>2046-06-13 23:37:44.29</td><td>17 12 50.50336 -21 26<br>19.72822</td><td>8.6</td><td>0.525</td><td>183.61</td><td>-20.12</td><td>9.021</td><td>4.5</td><td>7.641</td><td>12.649</td><td>11.303</td><td>2.0</td><td>176.2</td></tr><tr><td>PgtRgt</td><td>4115816792713438208</td><td>17 12 50.50106 -21 26<br>20.25228</td><td>5.5</td><td>3.438</td><td>4.41</td><td>26.50</td><td>20.103</td><td>2.7</td><td>1.977</td><td>12.655</td><td>0</td><td>-21.5</td><td>55.9</td></tr><tr><td>S46043</td><td>2046-07-18 10:24:35.13</td><td>17 03 16.69742 -21 18<br>52.85802</td><td>9.6</td><td>3.369</td><td>2.30</td><td>-13.73</td><td>9.221</td><td>-21.7</td><td>6.020</td><td>11.030</td><td>9.759</td><td>163.9</td><td>141.4</td></tr><tr><td>PgtRgt</td><td>4127635408818049664</td><td>17 03 16.70716 -21 18<br>49.49172</td><td>6.3</td><td>22.531</td><td>4.17</td><td>26.54</td><td>12.823</td><td>-25.5</td><td>4.183</td><td>10.622</td><td>0</td><td>-21.4</td><td>43.2</td></tr></tbody></table>
<figure><img src="image_13.png" /><figcaption>**Figure 9.** Gallery of Earth views from Uranus at mid-occultation for the 24 brightest predicted events in the *K* band with ring event type *Rgt* for 2023–2050.</figcaption></figure>

<table><caption>**Table 11**
Uranus Planet/Ring Occultations 2023–2050</caption><thead><tr><th>Year</th><th><i>K</i> &lt; 7<br>P/R</th><th><i>K</i> 7–8<br>P/R</th><th><i>K</i> 8–9<br>P/R</th><th><i>K</i> 9–10<br>P/R</th><th><i>K</i> 10–11<br>P/R</th><th><i>K</i> 11–12<br>P/R</th><th><i>K</i> 12–13<br>P/R</th><th><i>K</i> 13–14<br>P/R</th><th><i>K</i> 14–15<br>P/R</th></tr></thead><tbody><tr><td>2023</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>0/2</td><td>3/6</td><td>3/9</td></tr><tr><td>2024</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/2</td><td>1/2</td><td>3/5</td><td>8/10</td></tr><tr><td>2025</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>1/4</td><td>8/14</td></tr><tr><td>2026</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>0/2</td><td>5/5</td><td>7/11</td><td>5/9</td></tr><tr><td>2027</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/3</td><td>2/4</td><td>4/6</td><td>10/21</td></tr><tr><td>2028</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>...</td><td>1/3</td><td>4/13</td><td>4/14</td></tr><tr><td>2029</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1</td><td>3/4</td><td>1/2</td><td>11/17</td><td>20/37</td></tr><tr><td>2030</td><td>...</td><td>...</td><td>...</td><td>0/1</td><td>2/2</td><td>2/4</td><td>7/12</td><td>13/18</td><td>16/29</td></tr><tr><td>2031</td><td>1/1</td><td>...</td><td>...</td><td>1/1</td><td>5/7</td><td>3/7</td><td>1/3</td><td>18/35</td><td>36/64</td></tr><tr><td>2032</td><td>...</td><td>...</td><td>1/2</td><td>...</td><td>0/1</td><td>2/7</td><td>7/15</td><td>15/24</td><td>36/54</td></tr><tr><td>2033</td><td>...</td><td>...</td><td>...</td><td>1/2</td><td>3/5</td><td>5/7</td><td>8/12</td><td>23/37</td><td>44/72</td></tr><tr><td>2034</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/4</td><td>4/8</td><td>4/11</td><td>18/29</td><td>34/67</td></tr><tr><td>2035</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/2</td><td>2/4</td><td>3/8</td><td>15/24</td><td>18/40</td></tr><tr><td>2036</td><td>...</td><td>...</td><td>1/1</td><td>...</td><td>1/3</td><td>3/5</td><td>5/6</td><td>13/19</td><td>20/34</td></tr><tr><td>2037</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/2</td><td>...</td><td>2/8</td><td>7/12</td><td>15/24</td></tr><tr><td>2038</td><td>...</td><td>1/1</td><td>...</td><td>...</td><td>1/2</td><td>1/1</td><td>2/3</td><td>5/13</td><td>14/25</td></tr><tr><td>2039</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/2</td><td>0/1</td><td>3/7</td><td>3/11</td><td>9/17</td></tr><tr><td>2040</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/3</td><td>0/2</td><td>0/1</td><td>2/4</td><td>15/19</td></tr><tr><td>2041</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/2</td><td>1/2</td><td>2/4</td><td>5/9</td></tr><tr><td>2042</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1</td><td>0/3</td><td>3/4</td><td>6/9</td></tr><tr><td>2043</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>1/1</td><td>5/5</td><td>3/4</td><td>2/3</td></tr><tr><td>2044</td><td>...</td><td>1/1</td><td>...</td><td>1/1</td><td>...</td><td>1/1</td><td>...</td><td>1/4</td><td>1/4</td></tr><tr><td>2045</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/3</td><td>1/2</td><td>1/1</td><td>2/3</td></tr><tr><td>2046</td><td>...</td><td>...</td><td>0/1</td><td>...</td><td>...</td><td>0/1</td><td>2/1</td><td>3/3</td><td>1/8</td></tr><tr><td>2047</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>3/2</td><td>4/4</td></tr><tr><td>2048</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1</td><td>1/1</td><td>1/3</td></tr><tr><td>2049</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1</td><td>2/0</td><td>...</td><td>1/3</td><td>3/3</td></tr></tbody><tfoot><tr><td>Totals</td><td>1/1</td><td>2/2</td><td>2/4</td><td>3/5</td><td>21/38</td><td>34/67</td><td>63/120</td><td>183/314</td><td>340/605</td></tr></tfoot></table>
<figure><img src="image_14.png" /><figcaption>**Figure 10.** Gallery of geocentric sky-plane views of Uranus and its rings at mid-occultation for the 24 brightest predicted events in the *K* band with ring event type *Rgt* for 2023–2050.</figcaption></figure>

Just as for Uranus, Neptune passed out of the dense star fields of the Milky Way in the mid-1980s, as shown in Figure 5 (lower right). Owing to Neptune’s long orbital period (165 yr), the next traversal of the Milky Way will not occur until about 2068. Consequently, very few high-S/N opportunities are available for Neptune occultations in the coming decades. Our search resulted in the identification of 88 predicted occultations by Neptune and/or its rings for the period 2023–2050 for a limiting magnitude *K* ≤ 15. Table 13 lists the number of predicted events per year as a function of *K* magnitude, excluding years with no predicted events. The format is the same as for Table 11.

The aspect of Neptune’s rings varies over time, as shown in Figure 6 (bottom) for the period 1975–2050. The solid line shows the sub-Earth latitude, with an annual periodic term reflecting the relative inclinations of the orbits of Earth and Neptune, and the dashed line shows the subsolar latitude. Black dots mark the times of previous successful Neptune occultations (Roques et al. 1994), and red dots mark all predicted events from 2023 to 2050 for *K* ≤ 12.5. We have not made detailed predictions for individual ring arcs because there is evidence that they are evolving on a decadal timescale, with the leading arcs, Liberté and Courage, having recently faded away (Souami et al. 2022).

To illustrate the range of event geometries and the varying orientation of Neptune and its rings, Figure 11 shows galleries of views of Earth at mid-occultation, and Figure 12 shows the corresponding sky-plane views of Neptune for the 24 brightest

predicted events in the *K* band with planet event type *Pgt* for 2023–2050. (Note that some of these events do not have ring occultations.) Table 14 provides detailed information for this set of events.

The full set of prediction details for *K* ≤ 15 is included in the SOM. Saunders et al. (2022) identified 14 near-IR Neptune occultations between 2025 January 1 and 2035 December 31 visible from low-Earth orbit, with a solar exclusion angle of 30°, of which six are visible from the ground. Our computed geometry matches the subset of these events that satisfy our SGT limit of ≥45°, more appropriate for ground-based observations.

The most promising near-term Neptune occultations are the 2023 October 18 and 2024 October 9 events, both of which intersect the planet and the unblocked orbits of the ring arcs. Uncertainties in the mean motions of the arcs make it challenging to predict the longitudes of the arcs, and thus the prospects for detecting them during any given occultation from a specific observing site are difficult to quantify. Improved ephemerides for the arcs may eventually be derived from JWST images, at which time it will be warranted to revisit our predictions to estimate the prospects for detecting arcs. In the meantime, the NASA/PDS Ring-Moon Systems node provides online tools that can be used to visualize the predicted locations of the arcs for a variety of assumed mean motions.<fnref n="16" /> Next in line are the 2032 September 5 (*K* = 8.5) and 2035 October 18

<footnote n="16">¹⁶ https://pds-rings.seti.org/tools/</footnote>
<table><caption>Table 12
Geocentric Uranus Occultation Predictions 2023–2050</caption><thead><tr><th>Event ID</th><th>C/A Epoch</th><th>ICRS Star Coord at Epoch</th><th>σ(α<sub>*</sub>) (km)</th><th>σ(δ<sub>*</sub>) (km)</th><th>C/A ("<sup>3</sup>)</th><th>PA (deg)</th><th>ν<sub>sky</sub> (km s<sup>-1</sup>)</th><th>Dist (au)</th><th>Lat I (deg)</th><th>Lat E (deg)</th><th>K</th><th>G</th><th>RP</th><th>E λ (deg)</th><th>S-G-T</th></tr><tr><th>Event Type</th><th>Source ID</th><th>Geocentric Object Position</th><th>f<sub>0</sub> (km)</th><th>g<sub>0</sub> (km)</th><th>C/A (10<sup>3</sup>)</th><th>P (deg)</th><th>B (deg)</th><th>ρ̇ (km s<sup>-1</sup>)</th><th>D<sub>*</sub> (km)</th><th>G<sub>*</sub></th><th>DUP</th><th>φ (deg)</th><th>M-G-T</th><th></th></tr></thead><tbody><tr><td>U30008</td><td>2030-01-25 08:17:12.56</td><td>04 52 12.89939 +22 33<br>45.77275</td><td>4.3</td><td>2.6</td><td>1.449</td><td>173.69</td><td>-12.59</td><td>18.575</td><td>4.0</td><td>10.236</td><td>13.269</td><td>12.376</td><td>184.5</td><td>129.4</td><td></td></tr><tr><td>PgtRgt</td><td>3413198248000757760</td><td>04 52 12.91090 +22 33<br>44.33261</td><td></td><td></td><td>19.520</td><td>-29.32</td><td>81.59</td><td>11.662</td><td>8.5</td><td>0.703</td><td>12.767</td><td>0</td><td>22.6</td><td>122.0</td><td></td></tr><tr><td>U30011</td><td>2030-03-19 05:21:06.97</td><td>04 52 13.08033 +22 34<br>11.50958</td><td>4.1</td><td>2.8</td><td>3.582</td><td>173.06</td><td>13.45</td><td>19.419</td><td></td><td>9.957</td><td>12.449</td><td>11.689</td><td>176.4</td><td>76.2</td><td></td></tr><tr><td>XRgt</td><td>3413198449863123072</td><td>04 52 13.11162 +22 34<br>07.95411</td><td></td><td></td><td>50.446</td><td>-29.30</td><td>81.58</td><td>0.037</td><td></td><td>0.768</td><td>12.018</td><td>0</td><td>22.6</td><td>96.7</td><td></td></tr><tr><td>U30034*</td><td>2030-10-13 22:01:31.53</td><td>05 26 40.70040 +23 17<br>50.97623</td><td>13.8</td><td>8.8</td><td>1.112</td><td>177.66</td><td>-7.56</td><td>18.680</td><td>8.8</td><td>10.149</td><td>12.326</td><td>11.605</td><td>89.2</td><td>117.8</td><td></td></tr><tr><td>PgtRgt</td><td>3416213864799115264</td><td>05 26 40.70373 +23 17<br>49.86481</td><td></td><td></td><td>15.068</td><td>27.62</td><td>80.90</td><td>7.273</td><td>1.0</td><td>0.630</td><td>11.270</td><td>0</td><td>23.3</td><td>34.3</td><td></td></tr><tr><td>U31023</td><td>2031-02-15 02:09:08.50</td><td>05 09 42.75173 +23 02<br>04.09133</td><td>10.6</td><td>7.2</td><td>1.057</td><td>355.51</td><td>-5.18</td><td>18.741</td><td>-4.0</td><td>4.194</td><td>9.526</td><td>8.105</td><td>260.7</td><td>112.7</td><td></td></tr><tr><td>PgtRgt</td><td>3415397339976857728</td><td>05 09 42.74577 +23 02<br>05.14505</td><td></td><td></td><td>14.367</td><td>0.83</td><td>82.14</td><td>5.016</td><td>-5.3</td><td></td><td>8.059</td><td>0</td><td>23.1</td><td>159.1</td><td></td></tr><tr><td>U31044</td><td>2031-08-06 10:46:57.05</td><td>05 40 11.78504 +23 28<br>48.06683</td><td>3.8</td><td>2.1</td><td>0.830</td><td>357.74</td><td>26.32</td><td>19.776</td><td>-11.1</td><td>10.176</td><td>12.730</td><td>11.951</td><td>329.0</td><td>47.9</td><td></td></tr><tr><td>PgtRgt</td><td>3404409812904057216</td><td>05 40 11.78269 +23 28<br>48.89603</td><td></td><td></td><td>11.907</td><td>42.68</td><td>78.95</td><td>25.834</td><td>3.4</td><td>0.700</td><td>13.028</td><td>0</td><td>23.5</td><td>85.7</td><td></td></tr><tr><td>U31055*</td><td>2031-09-09 03:25:40.91</td><td>05 45 02.14615 +23 31<br>19.54458</td><td>18.5</td><td>11.8</td><td>0.205</td><td>357.76</td><td>11.91</td><td>19.267</td><td>-10.2</td><td>10.015</td><td>11.532</td><td>10.964</td><td>47.3</td><td>79.3</td><td></td></tr><tr><td>PgtRgt</td><td>3427621572816169472</td><td>05 45 02.14560 +23 31<br>19.74884</td><td></td><td></td><td>2.860</td><td>46.90</td><td>78.14</td><td>12.061</td><td>8.4</td><td>0.616</td><td>10.969</td><td>0</td><td>23.5</td><td>6.2</td><td></td></tr><tr><td>U31089</td><td>2031-11-26 01:29:36.37</td><td>05 41 02.73872 +23 30<br>58.00451</td><td>4.6</td><td>2.6</td><td>0.869</td><td>178.44</td><td>-21.16</td><td>18.175</td><td>11.2</td><td>9.766</td><td>11.574</td><td>10.959</td><td>358.5</td><td>157.5</td><td></td></tr><tr><td>PgtRgt</td><td>3404413665492320896</td><td>05 41 02.74047 +23 30<br>57.13525</td><td></td><td></td><td>11.459</td><td>43.36</td><td>78.79</td><td>20.814</td><td>-3.7</td><td>0.677</td><td>11.635</td><td>0</td><td>23.5</td><td>56.7</td><td></td></tr><tr><td>U31101<sup>a</sup></td><td>2031-12-08 06:12:35.97</td><td>05 38 53.52466 +23 30<br>03.51695</td><td>53.5</td><td>29.3</td><td>0.778</td><td>358.16</td><td>-23.02</td><td>18.117</td><td>3.8</td><td>10.067</td><td>11.758</td><td>10.788</td><td>275.2</td><td>170.3</td><td></td></tr><tr><td>PgtRgt</td><td>3404402532936959488</td><td>05 38 53.52288 +23 30<br>04.29469</td><td></td><td></td><td>10.227</td><td>41.33</td><td>79.13</td><td>22.743</td><td>-10.5</td><td>0.531</td><td>11.911</td><td>0</td><td>23.5</td><td>93.0</td><td></td></tr><tr><td>U31102<sup>a</sup></td><td>2031-12-08 06:16:32.50</td><td>05 38 53.49479 +23 30<br>03.40218</td><td>299.9</td><td>182.3</td><td>0.880</td><td>358.16</td><td>-23.02</td><td>18.117</td><td>3.2</td><td>10.067</td><td>12.044</td><td>10.777</td><td>274.3</td><td>170.3</td><td></td></tr><tr><td>PgtRgt</td><td>3404402532934661120</td><td>05 38 53.49277 +23 30<br>04.28140</td><td></td><td></td><td>11.561</td><td>41.33</td><td>79.13</td><td>22.610</td><td>-10.7</td><td>0.531</td><td>12.196</td><td>0</td><td>23.5</td><td>93.0</td><td></td></tr><tr><td>U32016</td><td>2032-02-06 06:33:21.50</td><td>05 29 26.29907 +23 24<br>38.41802</td><td>3.6</td><td>2.7</td><td>0.105</td><td>357.09</td><td>-11.36</td><td>18.475</td><td>5.1</td><td>8.198</td><td>13.255</td><td>12.019</td><td>208.5</td><td>126.4</td><td></td></tr><tr><td>PgtRgt</td><td>3416228811285405568</td><td>05 29 26.29869 +23 24<br>38.52260</td><td></td><td></td><td>1.403</td><td>30.93</td><td>80.49</td><td>11.427</td><td>-6.0</td><td>2.858</td><td>12.641</td><td>0</td><td>23.4</td><td>164.5</td><td></td></tr><tr><td>U32021</td><td>2032-03-24 11:30:50.46</td><td>05 29 26.29906 +23 24<br>38.41771</td><td>3.8</td><td>2.9</td><td>3.250</td><td>356.93</td><td>12.00</td><td>19.233</td><td></td><td>8.198</td><td>13.255</td><td>12.019</td><td>87.6</td><td>79.1</td><td></td></tr><tr><td>XRgt</td><td>3416228811285405568</td><td>05 29 26.28641 +23 24<br>41.66337</td><td></td><td></td><td>45.339</td><td>30.92</td><td>80.49</td><td>5.540</td><td></td><td>2.976</td><td>12.700</td><td>0</td><td>23.4</td><td>72.4</td><td></td></tr><tr><td>U33063</td><td>2033-04-30 11:32:35.90</td><td>05 53 12.16049 +23 38<br>38.54607</td><td>4.4</td><td>2.9</td><td>0.938</td><td>359.32</td><td>26.12</td><td>19.649</td><td>-13.9</td><td>10.479</td><td>13.445</td><td>12.558</td><td>56.9</td><td>48.5</td><td></td></tr><tr><td>PgtRgt</td><td>3427825566583885184</td><td>05 53 12.15968 +23 38<br>39.48375</td><td></td><td></td><td>13.364</td><td>52.70</td><td>76.63</td><td>25.673</td><td>5.1</td><td>0.598</td><td>13.735</td><td>0</td><td>23.6</td><td>30.0</td><td></td></tr><tr><td>U33070</td><td>2033-08-22 23:49:15.47</td><td>06 20 03.48811 +23 35<br>31.11235</td><td>3.8</td><td>2.7</td><td>0.957</td><td>181.53</td><td>23.43</td><td>19.536</td><td>-10.4</td><td>9.480</td><td>11.220</td><td>10.622</td><td>126.6</td><td>55.1</td><td></td></tr><tr><td>PgtRgt</td><td>3377537095886180096</td><td></td><td></td><td></td><td>13.560</td><td>66.42</td><td>71.32</td><td>23.617</td><td>19.3</td><td>0.817</td><td>11.392</td><td>0</td><td>23.6</td><td>33.7</td><td></td></tr></tbody></table>
<table><caption>Table 12
(Continued)</caption><thead><tr><th>Event ID</th><th>C/A Epoch</th><th>ICRS Star Coord at Epoch</th><th>σ(α<sub>*</sub>)</th><th>σ(δ<sub>*</sub>)</th><th>C/A (")</th><th>PA (deg)</th><th>v<sub>sky</sub> (km s<sup>-1</sup>)</th><th>Dist (au)</th><th>Lat I (deg)</th><th>Lat E (deg)</th><th>K</th><th>G</th><th>RP</th><th>E λ (deg)</th><th>S-G-T</th></tr><tr><th>Event Type</th><th>Source ID</th><th>Geocentric Object Position</th><th>f<sub>0</sub> (km)</th><th>g<sub>0</sub> (km)</th><th>C/A (10<sup>3</sup>)</th><th>P (deg)</th><th>B (deg)</th><th>r̄ (km s<sup>-1</sup>)</th><th></th><th></th><th>D<sub>*</sub> (km)</th><th>G<sub>*</sub></th><th>DUP</th><th>φ (deg)</th><th>M-G-T</th></tr></thead><tbody><tr><td></td><td></td><td>06 20 03.48628 +23 35 30.15520</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>U33117</td><td>2033-12-11 23:07:39.05</td><td>06 18 09.99702 +23 38 35.93996</td><td>3.3</td><td>2.3</td><td>1.944</td><td>2.12</td><td>-22.45</td><td>18.001</td><td>-6.8</td><td>10.056</td><td>11.920</td><td>11.276</td><td>27.2</td><td>165.6</td><td></td></tr><tr><td>PgtRgt</td><td>3425562217600045184</td><td>06 18 10.00228 +23 38 37.88176</td><td></td><td></td><td>25.374</td><td>65.56</td><td>71.70</td><td>20.260</td><td>-9.5</td><td>0.604</td><td>12.046</td><td>0</td><td>23.6</td><td>56.9</td><td></td></tr><tr><td>U36026</td><td>2036-04-04 19:59:28.45</td><td>06 46 18.75718 +23 23 37.50621</td><td>6.1</td><td>4.9</td><td>1.193</td><td>5.33</td><td>8.78</td><td>18.863</td><td>-23.7</td><td>8.915</td><td>11.020</td><td>10.371</td><td>328.5</td><td>85.5</td><td></td></tr><tr><td>PgtRgt</td><td>3379627306147808000</td><td>06 46 18.76526 +23 23 38.69378</td><td></td><td></td><td>16.326</td><td>74.62</td><td>65.71</td><td>9.058</td><td>12.2</td><td>1.166</td><td>10.126</td><td>0</td><td>23.4</td><td>15.7</td><td></td></tr><tr><td>U36032*</td><td>2036-04-17 18:00:46.68</td><td>06 47 28.93351 +23 22 14.87368</td><td>6.8</td><td>5.0</td><td>3.590</td><td>185.10</td><td>15.08</td><td>19.076</td><td></td><td>10.331</td><td>12.445</td><td>11.776</td><td>345.8</td><td>73.1</td><td></td></tr><tr><td>XRgt</td><td>3379612733322742784</td><td>06 47 28.91036 +23 22 11.29723</td><td></td><td></td><td>49.666</td><td>74.94</td><td>65.46</td><td>3.490</td><td></td><td>0.586</td><td>12.139</td><td>0</td><td>23.3</td><td>171.5</td><td></td></tr><tr><td>U37018</td><td>2037-04-30 13:15:41.94</td><td>07 08 05.69920 +22 56 48.96675</td><td>4.4</td><td>3.8</td><td>0.014</td><td>187.08</td><td>18.74</td><td>19.139</td><td>-28.7</td><td>10.050</td><td>12.132</td><td>11.466</td><td>49.8</td><td>65.6</td><td></td></tr><tr><td>PgtRgt</td><td>3368245848972447232</td><td>07 08 05.69911 +22 56 48.95149</td><td></td><td></td><td>0.201</td><td>79.84</td><td>60.92</td><td>21.238</td><td>28.8</td><td>0.647</td><td>12.061</td><td>0</td><td>22.9</td><td>124.4</td><td></td></tr><tr><td>U37025</td><td>2037-05-15 11:17:47.17</td><td>07 10 30.94921 +22 52 40.55814</td><td>5.1</td><td>4.7</td><td>1.328</td><td>187.14</td><td>24.91</td><td>19.352</td><td>-13.2</td><td>10.224</td><td>11.134</td><td>10.790</td><td>65.2</td><td>51.7</td><td></td></tr><tr><td>PgtRgt</td><td>3368274504994506112</td><td>07 10 30.93730 +22 52 39.23937</td><td></td><td></td><td>18.643</td><td>80.36</td><td>60.39</td><td>26.392</td><td>26.1</td><td>0.493</td><td>11.373</td><td>0</td><td>22.8</td><td>49.3</td><td></td></tr><tr><td>U38002</td><td>2038-01-02 19:37:46.68</td><td>07 35 30.42467 +22 07 41.38425</td><td>6.2</td><td>5.3</td><td>0.570</td><td>189.56</td><td>-22.84</td><td>17.736</td><td>36.5</td><td>7.855</td><td>10.298</td><td>9.565</td><td>77.4</td><td>169.9</td><td></td></tr><tr><td>PgtRgt</td><td>865677841359417216</td><td>07 35 30.41789 +22 07 40.82172</td><td></td><td></td><td>7.330</td><td>85.08</td><td>54.75</td><td>27.384</td><td>-30.7</td><td>1.806</td><td>10.442</td><td>0</td><td>22.0</td><td>135.2</td><td></td></tr><tr><td>U38017</td><td>2038-02-06 23:11:54.78</td><td>07 29 13.70384 +22 21 36.72236</td><td>5.1</td><td>4.2</td><td>1.137</td><td>188.56</td><td>-20.02</td><td>17.817</td><td>32.5</td><td>10.480</td><td>11.628</td><td>11.215</td><td>347.7</td><td>152.8</td><td></td></tr><tr><td>PgtRgt</td><td>866402758821944960</td><td>07 29 13.69167 +22 21 35.59708</td><td></td><td></td><td>14.692</td><td>83.95</td><td>56.18</td><td>22.847</td><td>-21.9</td><td>0.438</td><td>11.629</td><td>0</td><td>22.3</td><td>122.0</td><td></td></tr><tr><td>U39021</td><td>2039-02-21 03:57:48.52</td><td>07 47 22.61794 +21 42 15.37628</td><td>4.5</td><td>3.6</td><td>2.761</td><td>190.01</td><td>-17.29</td><td>17.840</td><td></td><td>10.003</td><td>12.151</td><td>11.482</td><td>267.0</td><td>143.0</td><td></td></tr><tr><td>XRgt</td><td>674533650447999360</td><td>07 47 22.58353 +21 42 12.65574</td><td></td><td></td><td>35.729</td><td>87.01</td><td>52.04</td><td>15.511</td><td></td><td>0.681</td><td>11.993</td><td>0</td><td>21.6</td><td>167.3</td><td></td></tr><tr><td>U40024</td><td>2040-09-27 05:12:06.65</td><td>08 36 22.58698 +19 11 28.83981</td><td>6.1</td><td>4.1</td><td>0.242</td><td>193.73</td><td>22.56</td><td>19.070</td><td>-47.8</td><td>10.257</td><td>12.118</td><td>11.496</td><td>45.0</td><td>57.6</td><td></td></tr><tr><td>PgtRgt</td><td>659766114072052608</td><td>08 36 22.58294 +19 11 28.60272</td><td></td><td></td><td>3.353</td><td>93.84</td><td>40.54</td><td>34.346</td><td>50.7</td><td>0.586</td><td>12.249</td><td>0</td><td>19.0</td><td>43.2</td><td></td></tr><tr><td>U43014</td><td>2043-12-02 10:11:23.97</td><td>09 36 36.40808 +14 59 50.91957</td><td>6.8</td><td>7.1</td><td>0.998</td><td>207.71</td><td>-2.54</td><td>18.079</td><td>62.4</td><td>10.500</td><td>12.670</td><td>11.985</td><td>280.7</td><td>108.0</td><td></td></tr><tr><td>PgtRgt</td><td>617976559021588608</td><td>09 36 36.37606 +14 59 50.03401</td><td></td><td></td><td>13.083</td><td>99.88</td><td>25.75</td><td>5.511</td><td>-37.7</td><td>0.530</td><td>10.428</td><td>0</td><td>14.8</td><td>116.8</td><td></td></tr><tr><td>U44001*</td><td>2044-01-06 16:51:33.19</td><td>09 33 54.11947 +15 14 29.11231</td><td>9.3</td><td>7.0</td><td>1.565</td><td>19.50</td><td>-17.60</td><td>17.593</td><td>26.5</td><td>9.838</td><td>11.732</td><td>11.121</td><td>145.2</td><td>144.5</td><td></td></tr><tr><td>PgtRgt</td><td>618790957835883648</td><td>09 33 54.15557 +15 14 30.58589</td><td></td><td></td><td>19.971</td><td>99.64</td><td>26.43</td><td>35.903</td><td>-43.3</td><td>11.593</td><td>0</td><td></td><td>15.0</td><td>143.5</td><td></td></tr></tbody></table>
<figure><img src="image_15.png" /><figcaption>Figure 11. Gallery of Earth views from Neptune at mid-occultation for the 24 brightest predicted events in the K band with planet event type *Pgt* for 2023–2050.</figcaption></figure>

<table><caption>Table 13
Neptune Planet/Ring Occultations 2023–2050</caption><thead><tr><th>Year</th><th>K &lt; 9<br>P/R</th><th>K 9–10<br>P/R</th><th>K 10–11<br>P/R</th><th>K 11–12<br>P/R</th><th>K 12–13<br>P/R</th><th>K 13–14<br>P/R</th><th>K 14–15<br>P/R</th></tr></thead><tbody><tr><td>2023</td><td>...</td><td>1/1</td><td>...</td><td>1/1</td><td>...</td><td>...</td><td>...</td></tr><tr><td>2024</td><td>...</td><td>1/1</td><td>...</td><td>...</td><td>1/1</td><td>2/2</td><td>1/2</td></tr><tr><td>2025</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>0/1</td><td>...</td></tr><tr><td>2026</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td></tr><tr><td>2027</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>2/2</td><td>1/1</td></tr><tr><td>2028</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>...</td><td>1/1</td><td>...</td></tr><tr><td>2029</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/2</td><td>2/2</td></tr><tr><td>2030</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1</td></tr><tr><td>2031</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/2</td></tr><tr><td>2032</td><td>1/1</td><td>...</td><td>...</td><td>1/1</td><td>...</td><td>...</td><td>1/1</td></tr><tr><td>2033</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>...</td><td>...</td><td>2/2</td></tr><tr><td>2035</td><td>...</td><td>1/1</td><td>...</td><td>...</td><td>1/1</td><td>3/3</td><td>3/3</td></tr><tr><td>2036</td><td>...</td><td>...</td><td>...</td><td>2/2</td><td>1/1</td><td>...</td><td>2/2</td></tr><tr><td>2037</td><td>...</td><td>...</td><td>...</td><td>0/1</td><td>...</td><td>2/2</td><td>...</td></tr><tr><td>2038</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>...</td><td>1/1</td></tr><tr><td>2040</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1</td><td>1/0</td><td>...</td></tr><tr><td>2041</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>3/3</td><td>3/2</td></tr><tr><td>2042</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/1</td><td>...</td><td>3/3</td></tr><tr><td>2043</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0</td></tr><tr><td>2044</td><td>...</td><td>...</td><td>0/1</td><td>...</td><td>...</td><td>...</td><td>1/1</td></tr><tr><td>2045</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>1/1</td></tr><tr><td>2046</td><td>...</td><td>...</td><td>1/0</td><td>...</td><td>...</td><td>2/2</td><td>3/3</td></tr><tr><td>2047</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>4/3</td><td>1/1</td></tr><tr><td>2048</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1</td></tr><tr><td>2049</td><td>...</td><td>...</td><td>...</td><td>1/1</td><td>...</td><td>2/2</td><td>4/2</td></tr><tr><td>Totals</td><td>1/1</td><td>3/3</td><td>1/1</td><td>7/8</td><td>10/10</td><td>25/24</td><td>34/32</td></tr></tbody></table>
<figure><img src="image_16.png" /><figcaption>**Figure 12.** Gallery of geocentric sky-plane views of Neptune and its rings at mid-occultation for the 24 brightest predicted events in the *K* band with planet event type *Pgt* for 2023–2050.</figcaption></figure>

(*K* = 9.5) events, both with excellent planet occultations and unblocked sampling of the ring regions.

## 5.5. Titan

The first extensive occultation observations of Titan's atmosphere were obtained during the 1989 July 3 occultation of 28 Sgr that successfully probed Saturn's rings and atmosphere as well, as described above. Sicardy et al. (1999) analyzed a dozen atmospheric lightcurves and derived profiles of density and temperature between altitude levels *z* = 290–500 km (pressures *P* from 110 to 1.4 μbar). The horizontal stratification of the atmosphere was determined from comparison of multiple adjacent chords, with typical horizontal-to-vertical aspect ratios of 15–45. Subsequently, Sicardy et al. (2006) reported on two Titan stellar occultations that occurred on 2003 November 14. The lightcurves revealed a sharp inversion layer near 515 ± 6 km altitude (*P* ≈ 1.5 μbar). Central flashes observed during the first occultation provided constraints on the zonal wind regime at *z* = 250 km. Simultaneous observations of the flashes at various wavelengths enabled the measurement of the wavelength dependence of atmospheric hazes. These results demonstrate the value of continued Earth-based occultation surveillance of Titan's atmosphere even after the highly successful Cassini and

Huygens remote and in situ observations (Coustenis et al. 2010).

Our search identified 1769 Titan occultations from 2023 to 2050 for a limiting magnitude *K* ≤ 15. Just as for Saturn, the frequency of predicted occultation opportunities for Titan varies dramatically over the coming decades. Table 15 shows the number of events by year and *K* magnitude. Since scientifically useful results can be obtained from Titan occultations using medium-sized telescopes at visual wavelengths, we include the statistics for events with magnitude *G*\* ≤ 19 in Table 16. Each entry is of the form *P*/g/t, where *P* indicates the number of predicted occultations for which Titan's shadow crosses the Earth but which are not predicted to be observable from any of our selected sites, *g* indicates the number of predicted occultations in which the geocentric chord intersects Titan but not from our altitude-limited observing sites, and *t* indicates the number of events observable from one of the 13 topocentric sites under our usual altitude constraints. Qualitatively, *P* events can in many instances be challenging to observe, *g* events may be observable from large telescopes that are not in our selected set, and *t* events are predicted to be observable from at least one of our observing sites while satisfying the usual Sun and target altitude constraints. The typical cadence of bright (*K* ≤ 9, *G*\* ≤ 12) events is about one every other year until 2046–2048, when Saturn and Titan cross the densest regions
<table><caption>Table 14
Geocentric Neptune Occultation Predictions 2023–2050</caption><thead><tr><th>Event ID<br>Event Type</th><th>C/A Epoch<br>Source ID</th><th>ICRS Star Coord at Epoch<br>Geocentric Object Position</th><th>σ(α<sub>*</sub>) (km)<br>σ(δ<sub>*</sub>) (km)</th><th>C/A (")<br>C/A (10<sup>3</sup> km)</th><th>PA (deg)<br>P (deg)</th><th>ν<sub>sky</sub> (km s<sup>-1</sup>)<br>B (deg)</th><th>Dist (au)<br>r̄ (km s<sup>-1</sup>)</th><th>Lat I (deg)<br>Lat E (deg)</th><th>K<br>D<sub>*</sub> (km)</th><th>G<br>G<sub>*</sub></th><th>RP<br>DUP</th><th>E λ (deg)<br>φ (deg)</th><th>S-G-T<br>M-G-T</th></tr></thead><tbody><tr><td>N23002</td><td>2023-10-18 02:57:07.97</td><td>23 44 21.02634 -03 04<br>57.66860</td><td>5.1</td><td>0.514</td><td>157.20</td><td>-20.44</td><td>29.030</td><td>7.4</td><td>11.366</td><td>14.660</td><td>13.616</td><td>285.8</td><td>151.0</td></tr><tr><td>PgtRgt</td><td>2639715216842421504</td><td>23 44 21.03963 -03 04<br>58.14225</td><td>3.4</td><td>10.818</td><td>-41.03</td><td>-21.45</td><td>24.177</td><td>41.4</td><td></td><td>14.684</td><td>0</td><td>-3.0</td><td>111.4</td></tr><tr><td>N24001*</td><td>2024-01-19 05:07:27.08</td><td>23 43 56.90963 -03 04<br>31.98483</td><td>121.0</td><td>0.288</td><td>335.52</td><td>21.94</td><td>30.430</td><td>1.6</td><td>13.274</td><td>15.018</td><td>14.343</td><td>161.3</td><td>56.8</td></tr><tr><td>PgtRgt</td><td>2639725730922360960</td><td>23 43 56.90166 -03 04<br>31.72277</td><td>80.8</td><td>6.355</td><td>-41.00</td><td>-21.52</td><td>26.254</td><td>-29.8</td><td>0.199</td><td>15.118</td><td>0</td><td>-2.9</td><td>46.5</td></tr><tr><td>N24004*</td><td>2024-10-09 00:36:23.19</td><td>23 53 34.80647 -02 08<br>27.13561</td><td>6.1</td><td>0.502</td><td>156.84</td><td>-22.69</td><td>28.946</td><td>6.1</td><td>9.068</td><td>11.430</td><td>10.707</td><td>331.5</td><td>161.8</td></tr><tr><td>PgtRgt</td><td>2449274030476179456</td><td>23 53 34.81963 -02 08<br>27.59619</td><td>5.6</td><td>10.529</td><td>-42.04</td><td>-20.63</td><td>27.771</td><td>41.6</td><td></td><td>11.567</td><td>0</td><td>-2.0</td><td>92.7</td></tr><tr><td>N25002***</td><td>2025-10-07 16:53:36.65</td><td>00 02 12.02238 -01 15<br>34.15602</td><td>22.4</td><td>0.214</td><td>156.75</td><td>-23.27</td><td>28.918</td><td>-9.0</td><td>12.624</td><td>14.794</td><td>14.096</td><td>90.9</td><td>165.6</td></tr><tr><td>PgtRgt</td><td>2449616081671057024</td><td>00 02 12.02800 -01 15<br>34.35244</td><td>10.3</td><td>4.484</td><td>-42.90</td><td>-19.82</td><td>31.329</td><td>29.0</td><td>0.296</td><td>14.958</td><td>0</td><td>-1.1</td><td>22.3</td></tr><tr><td>N28001</td><td>2028-01-19 08:22:25.33</td><td>00 16 12.87501 +00 13<br>14.47638</td><td>31.8</td><td>0.344</td><td>154.78</td><td>17.92</td><td>30.263</td><td>35.5</td><td>13.225</td><td>16.799</td><td>15.617</td><td>120.5</td><td>65.4</td></tr><tr><td>PgtRgt</td><td>2545537441718802304</td><td>00 16 12.88479 +00 13<br>14.16520</td><td>18.6</td><td>7.550</td><td>-44.16</td><td>-18.49</td><td>23.923</td><td>-1.2</td><td>0.333</td><td>16.680</td><td>0</td><td>0.4</td><td>148.0</td></tr><tr><td>N28002</td><td>2028-06-08 10:31:42.71</td><td>00 32 23.72894 +01 56<br>34.34487</td><td>5.2</td><td>0.278</td><td>159.59</td><td>15.92</td><td>30.204</td><td>38.2</td><td>11.254</td><td>13.196</td><td>12.575</td><td>313.2</td><td>69.6</td></tr><tr><td>PgtRgt</td><td>2544493455427430656</td><td>00 32 23.73541 +01 56<br>34.08442</td><td>4.1</td><td>6.088</td><td>-45.39</td><td>-16.87</td><td>26.715</td><td>-10.6</td><td>0.596</td><td>12.949</td><td>0</td><td>2.1</td><td>96.1</td></tr><tr><td>N29001</td><td>2029-05-19 06:52:55.15</td><td>00 38 43.65120 +02 35<br>48.97429</td><td>8.5</td><td>0.577</td><td>158.36</td><td>25.32</td><td>30.523</td><td>53.0</td><td>13.292</td><td>14.632</td><td>14.147</td><td>29.6</td><td>48.3</td></tr><tr><td>PgtRgt</td><td>2550603540326304000</td><td>00 38 43.66541 +02 35<br>48.43754</td><td>6.5</td><td>12.783</td><td>-45.79</td><td>-16.20</td><td>39.473</td><td>6.9</td><td>0.199</td><td>14.888</td><td>0</td><td>2.8</td><td>114.4</td></tr><tr><td>N32002</td><td>2032-09-05 15:51:18.68</td><td>01 04 39.16217 +05 06<br>35.93430</td><td>10.9</td><td>0.936</td><td>155.97</td><td>-19.36</td><td>29.002</td><td>29.6</td><td>8.475</td><td>10.109</td><td>9.558</td><td>153.4</td><td>146.3</td></tr><tr><td>PgtRgt</td><td>2552125131275826816</td><td>01 04 39.18769 +05 06<br>35.08023</td><td>6.4</td><td>19.681</td><td>-47.00</td><td>-13.26</td><td>26.551</td><td>71.2</td><td>1.898</td><td>10.074</td><td>0</td><td>5.3</td><td>154.5</td></tr><tr><td>N32003</td><td>2032-11-23 03:02:42.04</td><td>00 57 23.03121 +04 21<br>33.53876</td><td>9.2</td><td>1.148</td><td>159.39</td><td>-15.23</td><td>29.152</td><td>51.4</td><td>11.890</td><td>13.316</td><td>12.803</td><td>266.4</td><td>134.0</td></tr><tr><td>PgtRgt</td><td>2551779163070218880</td><td>00 57 23.05822 +04 21<br>32.46412</td><td>6.1</td><td>24.274</td><td>-46.72</td><td>-14.07</td><td>30.325</td><td>-8.4</td><td>11.555</td><td>12.815</td><td>12.370</td><td>88.3</td><td>60.9</td></tr><tr><td>N33002</td><td>2033-06-11 02:02:49.21</td><td>01 13 12.62605 +06 02<br>16.99800</td><td>7.2</td><td>0.656</td><td>340.02</td><td>19.95</td><td>30.325</td><td>51.4</td><td>11.890</td><td>13.316</td><td>12.803</td><td>266.4</td><td>134.0</td></tr><tr><td>PgtRgt</td><td>2576622765738672384</td><td>01 13 12.61104 +06 02<br>17.61501</td><td>5.7</td><td>14.418</td><td>-47.28</td><td>-12.33</td><td>41.034</td><td>-61.3</td><td>0.451</td><td>12.812</td><td>0</td><td>6.2</td><td>141.6</td></tr><tr><td>N35003</td><td>2035-08-26 10:06:00.86</td><td>01 31 02.70022 +07 41<br>16.79568</td><td>27.5</td><td>0.672</td><td>155.31</td><td>-13.21</td><td>29.194</td><td>12.4</td><td>13.205</td><td>16.625</td><td>15.510</td><td>257.2</td><td>128.6</td></tr><tr><td>PgtRgt</td><td>2566530554665743232</td><td>01 31 02.71911 +07 41<br>16.18487</td><td>18.0</td><td>14.234</td><td>-47.58</td><td>-10.20</td><td>26.455</td><td>57.5</td><td>16.175</td><td>0</td><td>7.9</td><td>39.2</td><td>177.2</td></tr><tr><td>N35005</td><td>2035-10-10 12:57:32.31</td><td>01 27 12.82180 +07 17<br>09.94514</td><td>11.3</td><td>0.854</td><td>337.99</td><td>-24.20</td><td>28.842</td><td>-69.6</td><td>12.862</td><td>14.332</td><td>13.809</td><td>168.9</td><td>173.5</td></tr><tr><td>PgtRgt</td><td>2566173934941174400</td><td>01 27 12.80029 +07 17<br>10.73695</td><td>5.7</td><td>17.865</td><td>-47.53</td><td>-10.63</td><td>47.847</td><td>-20.9</td><td>0.232</td><td>14.539</td><td>0</td><td>7.5</td><td>84.1</td></tr><tr><td>N35006*</td><td>2035-10-18 20:32:31.84</td><td>01 26 20.70963 +07 11<br>58.53716</td><td>11.2</td><td>1.003</td><td>338.27</td><td>-24.35</td><td>28.839</td><td>-78.0</td><td>9.534</td><td>12.901</td><td>11.820</td><td>46.7</td><td>177.2</td></tr><tr><td>PgtRgt</td><td>2566151184502925312</td><td>01 26 20.68469 +07 11<br>59.46989</td><td>6.4</td><td>20.979</td><td>-47.52</td><td>-10.73</td><td>30.495</td><td>17.4</td><td>11.032</td><td>13.163</td><td>12.496</td><td>316.8</td><td>48.4</td></tr><tr><td>N36001</td><td>2036-06-04 11:38:04.68</td><td></td><td>8.1</td><td>0.210</td><td>340.27</td><td>25.17</td><td>30.495</td><td>17.4</td><td>11.032</td><td>13.163</td><td>12.496</td><td>316.8</td><td>48.4</td></tr></tbody></table>
<table><caption>Table 14
(Continued)</caption><thead><tr><th>Event ID<br>Event Type</th><th>C/A Epoch<br>Source ID</th><th>ICRS Star Coord at Epoch<br>Geocentric Object Position</th><th>σ(α<sub>*</sub>) (km)<br>σ(δ<sub>*</sub>) (km)</th><th>C/A (′′)<br>C/A (10<sup>3</sup> km)</th><th>PA (deg)<br>P (deg)</th><th>ν<sub>sky</sub> (km s<sup>-1</sup>)<br>B (deg)</th><th>Dist (au)<br>r̄ (km s<sup>-1</sup>)</th><th>Lat I (deg)<br>Lat E (deg)</th><th>K<br>D<sub>*</sub> (km)</th><th>G<br>G<sub>*</sub></th><th>RP<br>DUP</th><th>E λ (deg)<br>φ (deg)</th><th>S-G-T<br>M-G-T</th></tr></thead><tbody><tr><td>PgtRg</td><td>2571920768686360320</td><td>01 37 13.19027 +08 20<br>50.47105<br>50.66903</td><td>4.9</td><td>4.652</td><td>-47.63</td><td>-9.52</td><td>73.564</td><td>-39.1</td><td>0.675</td><td>13.412</td><td>0</td><td>8.5</td><td>175.3</td></tr><tr><td>N36003</td><td>2036-06-16 12:09:48.36</td><td>01 38 21.67204 +08 26<br>48.47893</td><td>9.0</td><td>0.376</td><td>340.96</td><td>20.49</td><td>30.332</td><td>9.2</td><td>11.274</td><td>13.051</td><td>12.453</td><td>297.3</td><td>59.6</td></tr><tr><td>PgtRg</td><td>2571943656567597312</td><td>01 38 21.66377 +08 26<br>48.83464</td><td>5.3</td><td>8.278</td><td>-47.63</td><td>-9.37</td><td>60.471</td><td>-48.3</td><td></td><td>13.077</td><td>0</td><td>8.6</td><td>36.5</td></tr><tr><td>N36004</td><td>2036-10-26 12:36:37.97</td><td>01 34 07.81260 +07 56<br>19.45741</td><td>10.9</td><td>0.980</td><td>338.84</td><td>-24.08</td><td>28.846</td><td>-78.0</td><td>12.326</td><td>13.738</td><td>13.247</td><td>159.4</td><td>171.4</td></tr><tr><td>PgtRgt</td><td>2565887099845330048</td><td>01 34 07.78880 +07 56<br>20.37112</td><td>5.6</td><td>20.498</td><td>-47.60</td><td>-9.81</td><td></td><td>-29.8</td><td>0.297</td><td>13.939</td><td>0</td><td>8.1</td><td>87.3</td></tr><tr><td>N38001</td><td>2038-01-27 09:27:09.21</td><td>01 38 37.16971 +08 25<br>12.23641</td><td>16.9</td><td>0.997</td><td>334.47</td><td>11.11</td><td>29.995</td><td>-39.4</td><td>12.995</td><td>14.737</td><td>14.162</td><td>116.6</td><td>78.9</td></tr><tr><td>PgtRgt</td><td>2571895656013097984</td><td>01 38 37.14076 +08 25<br>13.13604</td><td>8.6</td><td>21.688</td><td>-47.62</td><td>-9.32</td><td></td><td>-78.9</td><td>0.239</td><td>14.099</td><td>0</td><td>8.6</td><td>174.6</td></tr><tr><td>N41001</td><td>2041-07-03 10:31:46.47</td><td>02 21 31.58020 +12 15<br>31.13356</td><td>21.5</td><td>0.562</td><td>163.61</td><td>18.26</td><td>30.236</td><td>60.9</td><td>12.709</td><td>14.512</td><td>13.907</td><td>316.1</td><td>64.2</td></tr><tr><td>PgtRgt</td><td>73052518917687552</td><td>02 21 31.59101 +12 15<br>30.59482</td><td>13.4</td><td>12.315</td><td>-46.87</td><td>-4.17</td><td>119.164</td><td>-0.7</td><td>0.280</td><td>14.413</td><td>0</td><td>12.4</td><td>119.6</td></tr><tr><td>N41007</td><td>2041-11-15 21:53:48.53</td><td>02 15 47.20450 +11 40<br>57.73039</td><td>19.5</td><td>1.029</td><td>161.43</td><td>-23.11</td><td>28.864</td><td>32.7</td><td>13.074</td><td>15.326</td><td>14.592</td><td>10.7</td><td>162.2</td></tr><tr><td>PgtRgt</td><td>72596049793554048</td><td>02 15 47.22681 +11 40<br>56.75483</td><td>17.3</td><td>21.544</td><td>-47.06</td><td>-4.80</td><td></td><td>85.2</td><td>0.244</td><td>15.483</td><td>0</td><td>11.9</td><td>110.4</td></tr><tr><td>N42004</td><td>2042-10-27 10:16:30.91</td><td>02 26 47.28244 +12 35<br>47.96408</td><td>18.5</td><td>0.081</td><td>161.22</td><td>-24.41</td><td>28.817</td><td>-24.6</td><td>12.459</td><td>14.581</td><td>13.889</td><td>207.2</td><td>174.7</td></tr><tr><td>PgtX</td><td>74364167570243072</td><td>02 26 47.28423 +12 35<br>47.88708</td><td>15.2</td><td>1.700</td><td>-46.66</td><td>-3.47</td><td></td><td>32.6</td><td>0.326</td><td>14.797</td><td>0</td><td>12.8</td><td>24.8</td></tr><tr><td>N46001</td><td>2046-01-31 07:17:34.03</td><td>02 47 01.60013 +14 15<br>06.48169</td><td>15.6</td><td>0.733</td><td>148.87</td><td>3.91</td><td>29.749</td><td>55.2</td><td>10.532</td><td>12.497</td><td>11.862</td><td>162.3</td><td>92.7</td></tr><tr><td>PgtX</td><td>32828466563598336</td><td>02 47 01.62622 +14 15<br>05.85536</td><td>13.1</td><td>15.815</td><td>-45.67</td><td>-1.08</td><td></td><td>26.0</td><td>0.818</td><td>10.725</td><td>0</td><td>14.4</td><td>155.8</td></tr><tr><td>N46003</td><td>2046-07-17 01:12:00.03</td><td>03 05 35.37395 +15 37<br>10.20050</td><td>38.8</td><td>0.930</td><td>346.66</td><td>17.48</td><td>30.218</td><td>-25.0</td><td>13.336</td><td>16.283</td><td>15.437</td><td>94.0</td><td>65.7</td></tr><tr><td>PgtRgt</td><td>30960533746904704</td><td>03 05 35.35908 +15 37<br>11.10584</td><td>33.6</td><td>20.392</td><td>-44.47</td><td>1.13</td><td></td><td>-86.5</td><td>0.283</td><td>16.137</td><td>0</td><td>15.8</td><td>125.9</td></tr><tr><td>N47006</td><td>2047-11-03 08:15:46.33</td><td>03 11 23.56472 +15 56<br>12.47354</td><td>16.6</td><td>0.537</td><td>164.23</td><td>-24.16</td><td>28.838</td><td>-1.3</td><td>12.402</td><td>14.373</td><td>13.732</td><td>242.0</td><td>170.2</td></tr><tr><td>PgtRgt</td><td>31391714103977088</td><td>03 11 23.57484 +15 56<br>11.95685</td><td>13.4</td><td>11.230</td><td>-44.04</td><td>1.87</td><td>325.106</td><td>56.1</td><td>0.335</td><td>14.579</td><td>0</td><td>16.1</td><td>6.3</td></tr><tr><td>N49005</td><td>2049-10-31 14:26:09.08</td><td>03 30 10.79228 +17 08<br>58.17776</td><td>12.7</td><td>0.357</td><td>165.48</td><td>-23.41</td><td>28.864</td><td>-10.7</td><td>11.036</td><td>13.363</td><td>12.646</td><td>156.4</td><td>163.4</td></tr><tr><td>PgtRt</td><td>54870341808035968</td><td>03 30 10.79852 +17 08<br>57.83247</td><td>9.2</td><td>7.467</td><td>-42.49</td><td>4.07</td><td></td><td>46.3</td><td>0.671</td><td>13.534</td><td>0</td><td>17.3</td><td>133.9</td></tr></tbody></table>
<table><caption>**Table 15**
Titan Occultations 2023–2050 (by K Magnitude)</caption><thead><tr><th>Year</th><th>K ≤ 5<br>P/g/t</th><th>K 5–6<br>P/g/t</th><th>K 6–7<br>P/g/t</th><th>K 7–8<br>P/g/t</th><th>K 8–9<br>P/g/t</th><th>K 9–10<br>P/g/t</th><th>K 10–11<br>P/g/t</th><th>K 11–12<br>P/g/t</th><th>K 12–13<br>P/g/t</th><th>K 13–14<br>P/g/t</th><th>K 14–15<br>P/g/t</th></tr></thead><tbody><tr><td>2023</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>...</td><td>1/0/0</td><td>5/0/2</td></tr><tr><td>2024</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td><td>0/1/2</td><td>1/2/1</td><td>4/2/2</td></tr><tr><td>2025</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/2</td><td>1/0/0</td><td>0/0/1</td><td>2/2/2</td></tr><tr><td>2026</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>...</td><td>...</td><td>1/0/1</td><td>1/0/1</td><td>1/2/1</td></tr><tr><td>2027</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/0/0</td><td>3/2/3</td><td>...</td><td>0/1/4</td></tr><tr><td>2028</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/2</td><td>3/0/0</td><td>1/2/1</td></tr><tr><td>2029</td><td>...</td><td>...</td><td>0/0/1</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/2</td><td>1/1/0</td><td>1/1/1</td><td>2/1/2</td></tr><tr><td>2030</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/3/4</td><td>2/0/1</td><td>0/3/5</td><td>5/2/4</td></tr><tr><td>2031</td><td>1/0/0</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td><td>...</td><td>1/1/0</td><td>1/2/2</td><td>1/2/3</td><td>7/1/3</td><td>15/10/11</td></tr><tr><td>2032</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td><td>0/0/1</td><td>3/0/1</td><td>2/2/5</td><td>10/6/10</td><td>16/12/22</td></tr><tr><td>2033</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>0/3/6</td><td>3/2/3</td><td>9/9/11</td><td>14/13/20</td></tr><tr><td>2034</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td><td>1/0/0</td><td>1/0/1</td><td>2/0/0</td><td>2/0/1</td><td>3/5/8</td></tr><tr><td>2035</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>3/2/4</td><td>2/0/1</td><td>2/2/3</td><td>5/2/4</td></tr><tr><td>2036</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/0</td><td>...</td><td>...</td><td>...</td><td>0/1/0</td><td>1/1/3</td><td>1/2/4</td></tr><tr><td>2037</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/0/0</td><td>1/0/0</td><td>0/3/3</td><td>2/3/3</td></tr><tr><td>2038</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/0/1</td></tr><tr><td>2039</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td><td>0/1/1</td><td>1/0/1</td></tr><tr><td>2040</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/0/1</td><td>1/1/1</td><td>2/1/1</td><td>2/0/1</td></tr><tr><td>2041</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/1</td><td>2/0/0</td><td>0/3/4</td></tr><tr><td>2042</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>1/3/3</td><td>1/4/6</td></tr><tr><td>2043</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>0/0/2</td><td>1/0/1</td><td>1/0/3</td><td>2/2/2</td></tr><tr><td>2044</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>...</td><td>1/1/2</td><td>1/0/2</td><td>1/1/2</td><td>4/0/5</td></tr><tr><td>2045</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>1/0/0</td><td>1/0/0</td><td>1/1/5</td><td>6/2/6</td><td>10/5/11</td></tr><tr><td>2046</td><td>...</td><td>...</td><td>...</td><td>1/0/1</td><td>2/0/0</td><td>0/1/2</td><td>4/4/8</td><td>4/2/8</td><td>14/13/23</td><td>33/18/41</td><td>49/46/80</td></tr><tr><td>2047</td><td>...</td><td>...</td><td>...</td><td>1/2/3</td><td>3/3/6</td><td>8/4/7</td><td>22/18/32</td><td>55/44/81</td><td>93/71/124</td><td>89/61/112</td><td>11/11/18</td></tr><tr><td>2048</td><td>...</td><td>...</td><td>...</td><td>2/0/0</td><td>0/0/1</td><td>...</td><td>3/1/3</td><td>9/1/2</td><td>6/14/21</td><td>21/15/36</td><td>51/46/68</td></tr><tr><td>2049</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>1/1/2</td><td>2/1/2</td><td>2/4/6</td><td>7/2/5</td><td>16/11/11</td></tr><tr><td>Totals</td><td>1/0/0</td><td>0/0/0</td><td>0/0/1</td><td>4/2/4</td><td>5/5/8</td><td>10/7/13</td><td>35/25/49</td><td>88/60/119</td><td>138/114/206</td><td>201/132/253</td><td>225/187/298</td></tr></tbody></table>

of the Milky Way. For the years 2047 and beyond (when Saturn crosses the Milky Way), the number of Titan events is quite large. The decrease in the number of predicted events in 2047 for $K = 13–15$ compared to $K = 12–13$ (and similarly for $G_* \ge 18$ compared to $G_* = 17–18$) reflects the challenge of matching Gaia stars with their counterparts in the 2MASS catalog in dense star regions.

Figure 13 shows the 24 brightest (K band) predicted Titan occultations between 2023 and 2047, restricted to events with at least one topocentric or geocentric sky-plane chord that intersects Titan's shadow (event types *Pg*, *Pgt*, or *Pt*). The solid black lines show the shadow midline, marked by dots at 60 s time intervals. The direction of the shadow motion is marked by the red arrow. The outline of the target shadow is shown as a red circle, and the projected shadow boundaries of the northern/southern limbs are shown as blue lines when they intersect the Earth and as red lines elsewhere. The antisolar point is marked by an open circle. Table 17 includes the geometric information for these 24 events. In the prediction tables for Titan and Triton, we include $C/A_p$, the sky-plane separation between the target satellite and the central planet at the epoch of closest approach, to enable observers to estimate the potential contribution of scattered light to the photometric aperture for the target satellite. Details of these and all other predicted Titan occultations are included in machine-readable form on the SOM, as documented in the Appendix.

### 5.6. Triton

Our final occultation target is Triton, whose tenuous atmosphere was first studied quantitatively using the Voyager 2 Radio Science Subsystem occultation observations made during the spacecraft's final giant planet flyby in 1989 (Tyler et al. 1989). It has been successfully observed during several subsequent extensive Earth-based occultation campaigns as well. As noted by Bertrand et al. (2022), both Triton and Pluto exhibit volatile cycles of $N_2$, $CH_4$, and CO, and the consequent changes in surface pressure with time are accessible remotely using stellar occultations. Olkin et al. (1997) derived the thermal structure of Triton's atmosphere from the 1993 and 1995 occultations, and Elliot et al. (1998, 2000) reported on the 1997 November 18 stellar occultation by Triton and found evidence for distortion and increasing pressure in its atmosphere since the 1989 Voyager 2 flyby. On 2017 October 5, Triton occulted the 13th-magnitude star UCAC4 410-143659 as seen from the eastern United States, North Atlantic, and Europe, including the Stratospheric Observatory for Infrared Astronomy aircraft (Person et al. 2018). A remarkable set of observations of this event from 90 European stations, including 42 detections of the central flash, enabled the detailed investigation of Triton's atmosphere and a comprehensive reexamination of the full history of occultation observations (Marques Oliveira et al. 2022), drawing into question the reliability of the evidence for surface-pressure changes in the 1990s.
<figure><img src="image_17.png" /><figcaption>Figure 13. Gallery of the 24 brightest (K band) predicted Titan occultations between 2023 and 2047, restricted to events with at least one topocentric or geocentric sky-plane chord that intersects Titan's shadow (event types *Pg*, *Pgt*, or *Pt*). Each occultation is labeled by the C/A epoch, the *K* and *G* stellar magnitudes, and the event type.</figcaption></figure>

<table><caption>Table 16
Titan Occultations 2023–2050 (by $G_*$ Magnitude)</caption><thead><tr><th>Year</th><th>$G_*< 9$<br>P/g/t</th><th>$G_* 9-10$<br>P/g/t</th><th>$G_* 10-11$<br>P/g/t</th><th>$G_* 11-12$<br>P/g/t</th><th>$G_* 12-13$<br>P/g/t</th><th>$G_* 13-14$<br>P/g/t</th><th>$G_* 14-15$<br>P/g/t</th><th>$G_* 15-16$<br>P/g/t</th><th>$G_* 16-17$<br>P/g/t</th><th>$G_* 17-18$<br>P/g/t</th><th>$G_* 18-19$<br>P/g/t</th></tr></thead><tbody><tr><td>2022</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td></tr><tr><td>2023</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>0/0/1</td><td>...</td><td>...</td><td>3/0/0</td><td>2/0/1</td><td>1/0/0</td></tr><tr><td>2024</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td><td>1/0/1</td><td>1/3/2</td><td>2/2/2</td><td>1/0/0</td><td>...</td><td>...</td></tr><tr><td>2025</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>...</td><td>1/0/1</td><td>0/0/1</td><td>0/1/1</td><td>1/0/0</td><td>1/1/1</td><td>...</td></tr><tr><td>2026</td><td>...</td><td>...</td><td>0/0/1</td><td>...</td><td>...</td><td>0/0/1</td><td>2/0/0</td><td>1/1/1</td><td>0/1/1</td><td>...</td><td>...</td></tr><tr><td>2027</td><td>...</td><td>...</td><td>...</td><td>...</td><td>3/2/3</td><td>1/0/0</td><td>1/0/0</td><td>0/0/2</td><td>0/1/2</td><td>...</td><td>...</td></tr><tr><td>2028</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>...</td><td>...</td><td>...</td><td>2/0/1</td><td>2/0/0</td><td>...</td><td>0/2/1</td></tr><tr><td>2029</td><td>0/0/1</td><td>...</td><td>...</td><td>0/0/1</td><td>1/0/1</td><td>...</td><td>0/1/0</td><td>0/1/1</td><td>...</td><td>3/0/0</td><td>0/1/2</td></tr><tr><td>2030</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td><td>1/2/3</td><td>1/0/1</td><td>2/4/8</td><td>2/1/1</td><td>1/0/0</td><td>1/0/0</td></tr><tr><td>2031</td><td>...</td><td>1/0/0</td><td>0/1/1</td><td>1/0/0</td><td>...</td><td>0/0/1</td><td>2/4/2</td><td>3/1/4</td><td>11/4/8</td><td>7/7/4</td><td>1/0/0</td></tr><tr><td>2032</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1/1</td><td>1/0/1</td><td>3/2/5</td><td>5/6/9</td><td>7/4/11</td><td>11/4/7</td><td>3/4/6</td></tr><tr><td>2033</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/2</td><td>1/0/0</td><td>6/5/4</td><td>7/5/9</td><td>6/6/12</td><td>6/8/10</td><td>1/3/3</td></tr><tr><td>2034</td><td>...</td><td>...</td><td>0/1/1</td><td>...</td><td>2/0/1</td><td>2/0/0</td><td>1/1/1</td><td>1/1/2</td><td>0/2/3</td><td>2/1/2</td><td>1/0/1</td></tr><tr><td>2035</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/2/3</td><td>3/0/2</td><td>1/0/0</td><td>1/3/4</td><td>1/1/1</td><td>1/0/1</td><td>3/0/1</td></tr><tr><td>2036</td><td>...</td><td>...</td><td>0/1/0</td><td>...</td><td>...</td><td>0/0/1</td><td>0/1/1</td><td>1/1/1</td><td>1/1/2</td><td>0/1/2</td><td>...</td></tr><tr><td>2037</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>2/0/0</td><td>1/1/1</td><td>...</td><td>1/2/2</td><td>1/2/2</td><td>0/1/1</td></tr><tr><td>2038</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td><td>2/0/1</td></tr><tr><td>2039</td><td>...</td><td>1/0/0</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>1/0/0</td><td>2/1/2</td><td>3/1/1</td><td>...</td><td>...</td></tr><tr><td>2040</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>0/0/1</td><td>1/0/0</td><td>1/0/0</td><td>0/1/2</td><td>1/1/1</td><td>0/1/1</td></tr><tr><td>2041</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/1</td><td>1/2/3</td><td>1/3/3</td><td>0/2/2</td><td>0/0/1</td></tr><tr><td>2042</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>1/0/2</td><td>2/1/2</td><td>...</td><td>0/1/1</td></tr><tr><td>2043</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/2</td><td>0/0/2</td><td>1/0/0</td><td>1/0/2</td><td>4/0/3</td><td>1/0/2</td><td>...</td></tr><tr><td>2044</td><td>...</td><td>...</td><td>...</td><td>0/0/2</td><td>1/1/1</td><td>0/0/1</td><td>1/0/1</td><td>0/1/2</td><td>4/2/7</td><td>4/3/5</td><td>5/2/4</td></tr><tr><td>2045</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>5/0/1</td><td>2/1/5</td><td>4/2/7</td><td>4/3/5</td><td>5/2/4</td></tr><tr><td>2046</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>3/4/7</td><td>3/2/9</td><td>10/10/21</td><td>31/22/45</td><td>40/31/49</td><td>20/15/32</td></tr><tr><td>2047</td><td>...</td><td>...</td><td>...</td><td>1/0/1</td><td>0/2/3</td><td>8/7/12</td><td>20/9/20</td><td>34/38/67</td><td>65/46/84</td><td>96/64/120</td><td>58/48/76</td></tr><tr><td>2048</td><td>1/0/0</td><td>...</td><td>...</td><td>...</td><td>1/0/1</td><td>8/2/5</td><td>10/8/14</td><td>20/22/40</td><td>31/18/35</td><td>16/16/20</td><td>5/11/16</td></tr><tr><td>2049</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1/1</td><td>3/2/4</td><td>2/3/6</td><td>11/2/5</td><td>6/8/6</td><td>5/2/4</td><td>1/1/0</td></tr><tr><td>Totals</td><td>1/0/1</td><td>1/0/0</td><td>1/3/3</td><td>2/0/4</td><td>11/7/18</td><td>34/18/42</td><td>62/40/75</td><td>107/98/182</td><td>185/130/241</td><td>200/145/236</td><td>103/91/149</td></tr></tbody></table>
<table><caption>Table 17
Geocentric Titan Occultation Predictions 2023–2047</caption><thead><tr><th>Event ID<br>Event Type</th><th>C/A Epoch<br>Source ID</th><th>ICRS Star Coord at Epoch<br>Geocentric Object Position</th><th>σ(α<sub>*</sub>) (km)<br>σ(δ<sub>*</sub>) (km)</th><th>C/A (mas)<br>C/A (km)</th><th>C/A<sub>p</sub> (′′)<br>C/A<sub>p</sub> (10<sup>3</sup> km)</th><th>PA (deg)<br>v<sub>sky</sub> (km s<sup>-1</sup>)</th><th>K<br>Dist (au)</th><th>G<br>G<sub>*</sub></th><th>RP<br>DUP</th><th>E λ (deg)<br>φ (deg)</th><th>S-G-T<br>M-G-T</th></tr></thead><tbody><tr><td>Ti270002</td><td>2027-01-17 05:16:35.32</td><td>00 35 52.75277 +01 17 02.67516</td><td>1.6</td><td>43.4</td><td>155.2</td><td>158.41</td><td>12.206</td><td>13.665</td><td>13.161</td><td>173.8</td><td>72.3</td></tr><tr><td>Pgt</td><td>2544199022533680640</td><td>00 35 52.75383 +01 17 02.63485</td><td>1.2</td><td>303.6</td><td>1086.6</td><td>20.76</td><td>9.657</td><td>13.706</td><td>0</td><td>1.4</td><td>35.6</td></tr><tr><td>Ti270012</td><td>2027-12-12 15:03:43.31</td><td>01 20 42.16092 +05 39 45.85592</td><td>1.9</td><td>138.5</td><td>70.6</td><td>177.41</td><td>12.083</td><td>13.685</td><td>13.132</td><td>73.5</td><td>120.8</td></tr><tr><td>Pgt</td><td>2564400353966267904</td><td>01 20 42.16133 +05 39 45.71753</td><td>1.5</td><td>879.7</td><td>448.6</td><td>-10.74</td><td>8.756</td><td>13.010</td><td>0</td><td>5.8</td><td>45.8</td></tr><tr><td>Ti300013</td><td>2030-11-14 16:06:35.26</td><td>04 18 27.83854 +19 15 28.26051</td><td>1.5</td><td>320.5</td><td>202.9</td><td>176.69</td><td>11.001</td><td>13.051</td><td>12.348</td><td>129.6</td><td>165.6</td></tr><tr><td>Pgt</td><td>47846386650613888</td><td>04 18 27.83984 +19 15 27.94049</td><td>1.1</td><td>1884.3</td><td>1193.0</td><td>-20.91</td><td>8.105</td><td>13.100</td><td>0</td><td>19.3</td><td>34.8</td></tr><tr><td>Ti300014</td><td>2030-11-20 19:54:31.10</td><td>04 15 57.28372 +19 10 10.91518</td><td>2.6</td><td>433.0</td><td>191.6</td><td>165.26</td><td>11.419</td><td>14.184</td><td>13.326</td><td>65.9</td><td>172.3</td></tr><tr><td>Pgt</td><td>48580826058239104</td><td>04 15 57.29149 +19 10 10.49641</td><td>2.0</td><td>2539.4</td><td>1123.8</td><td>-22.17</td><td>8.086</td><td>14.296</td><td>0</td><td>19.2</td><td>112.1</td></tr><tr><td>Ti300019</td><td>2030-12-04 00:42:14.43</td><td>04 11 38.12678 +19 00 40.41809</td><td>2.8</td><td>291.6</td><td>89.6</td><td>351.42</td><td>11.384</td><td>14.536</td><td>13.567</td><td>339.9</td><td>172.7</td></tr><tr><td>Pgt</td><td>48515645634144384</td><td>04 11 38.12371 +19 00 40.70638</td><td>1.8</td><td>1708.7</td><td>525.7</td><td>-25.34</td><td>8.081</td><td>14.793</td><td>0</td><td>19.1</td><td>58.7</td></tr><tr><td>Ti310004</td><td>2031-02-10 23:31:01.56</td><td>03 59 27.72426 +18 40 43.98225</td><td>2.7</td><td>176.4</td><td>149.8</td><td>356.77</td><td>8.126</td><td>11.096</td><td>10.216</td><td>286.7</td><td>100.0</td></tr><tr><td>Pgt</td><td>49815371458307328</td><td>03 59 27.72358 +18 40 44.15856</td><td>1.5</td><td>1130.7</td><td>959.7</td><td>7.91</td><td>8.838</td><td>10.089</td><td>0</td><td>18.8</td><td>120.2</td></tr><tr><td>Ti310013</td><td>2031-04-06 15:20:29.51</td><td>04 13 49.58603 +19 33 34.61858</td><td>2.8</td><td>73.0</td><td>176.9</td><td>343.20</td><td>11.412</td><td>13.726</td><td>12.948</td><td>359.1</td><td>48.9</td></tr><tr><td>Pgt</td><td>48650640750399488</td><td>04 13 49.58453 +19 33 34.68845</td><td>1.9</td><td>512.2</td><td>1241.9</td><td>28.86</td><td>9.677</td><td>14.124</td><td>0</td><td>19.6</td><td>117.1</td></tr><tr><td>Ti310045</td><td>2031-12-11 08:15:38.17</td><td>05 12 58.64159 +21 23 52.08454</td><td>2.7</td><td>423.7</td><td>181.5</td><td>349.35</td><td>12.104</td><td>14.525</td><td>13.745</td><td>235.0</td><td>178.4</td></tr><tr><td>Pgt</td><td>3414242371731554304</td><td>05 12 58.63598 +21 23 52.50090</td><td>1.7</td><td>2472.5</td><td>1058.5</td><td>-17.35</td><td>8.047</td><td>14.371</td><td>0</td><td>21.4</td><td>139.2</td></tr><tr><td>Ti320058</td><td>2032-12-07 16:19:18.61</td><td>06 19 56.75434 +22 23 19.77808</td><td>4.2</td><td>111.7</td><td>89.5</td><td>0.68</td><td>9.734</td><td>11.816</td><td>10.757</td><td>133.7</td><td>161.0</td></tr><tr><td>Pgt</td><td>3376835332590836352</td><td>06 19 56.75447 +22 23 19.88933</td><td>4.0</td><td>653.5</td><td>524.1</td><td>-24.07</td><td>8.070</td><td>12.017</td><td>0</td><td>22.4</td><td>136.7</td></tr><tr><td>Ti330004</td><td>2033-01-06 05:15:52.96</td><td>06 09 48.31132 +22 29 37.30113</td><td>2.7</td><td>413.9</td><td>175.2</td><td>5.74</td><td>11.427</td><td>14.792</td><td>13.821</td><td>267.9</td><td>166.5</td></tr><tr><td>Pgt</td><td>3425060019962276096</td><td>06 09 48.31431 +22 29 37.71300</td><td>1.9</td><td>2417.2</td><td>1023.5</td><td>-23.10</td><td>8.051</td><td>14.948</td><td>0</td><td>22.5</td><td>101.9</td></tr><tr><td>Ti330015</td><td>2033-01-21 07:53:52.71</td><td>06 05 03.96488 +22 32 17.62869</td><td>4.2</td><td>207.3</td><td>199.0</td><td>8.51</td><td>11.551</td><td>15.369</td><td>14.310</td><td>212.3</td><td>150.0</td></tr><tr><td>Pgt</td><td>3423753280456077184</td><td>06 05 03.96710 +22 32 17.83372</td><td>2.7</td><td>1225.0</td><td>1176.4</td><td>-18.68</td><td>8.147</td><td>15.295</td><td>0</td><td>22.5</td><td>93.6</td></tr><tr><td>Ti330019</td><td>2033-02-07 10:44:13.31</td><td>06 01 01.01860 +22 35 53.71673</td><td>3.0</td><td>221.0</td><td>151.5</td><td>187.41</td><td>11.156</td><td>14.529</td><td>13.546</td><td>151.8</td><td>131.7</td></tr><tr><td>Pgt</td><td>3424479542243561600</td><td>06 01 01.01655 +22 35 53.49761</td><td>2.2</td><td>1334.0</td><td>915.3</td><td>-14.62</td><td>8.324</td><td>14.189</td><td>0</td><td>22.6</td><td>30.8</td></tr><tr><td>Ti330048</td><td>2033-04-29 06:16:21.57</td><td>06 11 52.91394 +22 47 57.53864</td><td>5.0</td><td>105.5</td><td>95.1</td><td>179.09</td><td>12.198</td><td>15.609</td><td>14.637</td><td>141.9</td><td>53.9</td></tr><tr><td>Pgt</td><td>3425048921766933632</td><td>06 11 52.91407 +22 47 57.43319</td><td>3.8</td><td>731.7</td><td>660.2</td><td>21.88</td><td>9.566</td><td>15.707</td><td>0</td><td>22.8</td><td>51.9</td></tr><tr><td>Ti340019</td><td>2034-12-14 17:28:56.38</td><td>08 26 03.16052 +19 31 13.48742</td><td>1.9</td><td>392.2</td><td>159.4</td><td>185.92</td><td>9.131</td><td>10.768</td><td>10.205</td><td>141.3</td><td>138.2</td></tr><tr><td>Pgt</td><td>663719098892922368</td><td>08 26 03.15767 +19 31 13.09648</td><td>1.5</td><td>2363.4</td><td>960.9</td><td>-15.57</td><td>8.308</td><td>10.496</td><td>0</td><td>19.4</td><td>176.1</td></tr><tr><td>Ti350016</td><td>2035-05-31 02:15:39.82</td><td>08 14 02.35795 +20 23 58.66834</td><td>2.0</td><td>354.8</td><td>146.4</td><td>7.53</td><td>11.114</td><td>12.014</td><td>11.681</td><td>201.7</td><td>52.1</td></tr><tr><td>Pgt</td><td>675667727972573056</td><td>08 14 02.36128 +20 23 59.01890</td><td>1.7</td><td>2492.9</td><td>1028.2</td><td>30.62</td><td>9.689</td><td>12.477</td><td>0</td><td>20.3</td><td>132.9</td></tr><tr><td>Ti350023</td><td>2035-11-02 10:27:10.27</td><td>09 22 41.63863 +16 09 03.71639</td><td>2.2</td><td>129.2</td><td>149.6</td><td>194.46</td><td>11.811</td><td>13.122</td><td>12.667</td><td>302.8</td><td>81.3</td></tr><tr><td>Pgt</td><td>630955851406340480</td><td>09 22 41.63640 +16 09 03.59132</td><td>1.8</td><td>864.4</td><td>1000.8</td><td>17.44</td><td>9.227</td><td>12.974</td><td>1</td><td>16.0</td><td>107.7</td></tr><tr><td>Ti440009</td><td>2044-04-02 10:13:00.69</td><td>15 49 49.00538 -17 44 24.69766</td><td>3.0</td><td>304.9</td><td>144.7</td><td>5.35</td><td>11.582</td><td>13.235</td><td>12.681</td><td>253.4</td><td>133.5</td></tr><tr><td>Pgt</td><td>6260639759982275712</td><td>15 49 49.00737 -17 44 24.39410</td><td>1.9</td><td>2038.4</td><td>967.8</td><td>-14.31</td><td>9.219</td><td>12.872</td><td>0</td><td>-17.9</td><td>169.7</td></tr><tr><td>Ti460039</td><td>2046-02-15 12:15:59.16</td><td>17 21 10.67768 -21 39 40.67730</td><td>8.6</td><td>250.5</td><td>148.3</td><td>8.64</td><td>10.446</td><td>15.038</td><td>13.828</td><td>291.3</td><td>65.4</td></tr><tr><td>Pgt</td><td>4115039163112958208</td><td>17 21 10.68038 -21 39 40.42961</td><td>5.8</td><td>1889.6</td><td>1118.3</td><td>24.14</td><td>10.399</td><td>15.242</td><td>0</td><td>-21.7</td><td>169.8</td></tr><tr><td>Ti460055</td><td>2046-02-25 04:03:25.25</td><td>17 23 26.53304 -21 41 01.04837</td><td>12.7</td><td>19.5</td><td>163.8</td><td>355.66</td><td>11.568</td><td>16.133</td><td>14.938</td><td>45.5</td><td>74.6</td></tr><tr><td>Pgt</td><td>4114873927148098944</td><td>17 23 26.53293 -21 41 01.02894</td><td>8.9</td><td>144.9</td><td>1217.0</td><td>19.26</td><td>10.247</td><td>16.093</td><td>0</td><td>-21.7</td><td>47.7</td></tr><tr><td>Ti460107</td><td>2046-04-18 11:12:30.37</td><td>17 27 08.16215 -21 39 01.01547</td><td>9.5</td><td>106.9</td><td>99.5</td><td>345.24</td><td>10.888</td><td>15.477</td><td>14.282</td><td>247.6</td><td>125.6</td></tr><tr><td>Pgt</td><td>4120809601964982528</td><td>17 27 08.16020 -21 39 00.91207</td><td>6.7</td><td>730.5</td><td>678.6</td><td>-2.83</td><td>9.419</td><td>13.354</td><td>0</td><td>-21.7</td><td>86.6</td></tr><tr><td>Ti460115</td><td>2046-04-27 15:28:23.29</td><td>17 25 30.94523 -21 38 59.78180</td><td>6.3</td><td>52.2</td><td>160.3</td><td>12.37</td><td>9.818</td><td>14.629</td><td>13.379</td><td>174.2</td><td>134.9</td></tr><tr><td>Pgt</td><td>4120818260633400832</td><td>17 25 30.94603 -21 38 59.73085</td><td>4.2</td><td>351.5</td><td>1080.5</td><td>-14.67</td><td>9.292</td><td>14.293</td><td>0</td><td>-21.7</td><td>41.2</td></tr><tr><td>Ti460217</td><td>2046-07-06 15:53:39.31</td><td>17 06 10.12253 -21 19 29.86495</td><td>4.2</td><td>167.8</td><td>93.7</td><td>178.63</td><td>10.640</td><td>13.591</td><td>12.734</td><td>94.0</td><td>153.3</td></tr><tr><td>Pgt</td><td>4127597372598625280</td><td>17 06 10.12282 -21 19 30.03273</td><td>2.8</td><td>1110.5</td><td>619.5</td><td>-11.80</td><td>9.124</td><td>13.019</td><td>0</td><td>-21.4</td><td>119.1</td></tr><tr><td>Ti460228</td><td>2046-07-15 16:12:42.40</td><td>17 03 42.86466 -21 19 56.13922</td><td>4.3</td><td>252.8</td><td>146.7</td><td>188.32</td><td>11.736</td><td>13.573</td><td>12.958</td><td>79.7</td><td>144.2</td></tr><tr><td>Pgt</td><td>4127655023922897664</td><td>17 03 42.86204 -21 19 56.38937</td><td>2.8</td><td>1684.8</td><td>978.0</td><td>-18.46</td><td>9.189</td><td>13.486</td><td>0</td><td>-21.4</td><td>9.0</td></tr><tr><td>Ti460264</td><td>2046-10-11 02:59:51.99</td><td>17 08 24.28928 -21 40 40.27244</td><td>5.2</td><td>276.2</td><td>106.1</td><td>9.65</td><td>10.382</td><td>13.560</td><td>12.649</td><td>192.9</td><td>60.7</td></tr><tr><td>Pgt</td><td>4115610148914409344</td><td>17 08 24.29261 -21 40 40.00017</td><td>3.3</td><td>2102.7</td><td>807.7</td><td>28.84</td><td>10.497</td><td>13.957</td><td>0</td><td>-21.7</td><td>77.2</td></tr></tbody></table>
<table><caption>**Table 18**
Triton Occultations 2023–2050 (by *K* Magnitude)</caption><thead><tr><th>Year</th><th><i>K</i> 9–10<br>P/g/t</th><th><i>K</i> 10–11<br>P/g/t</th><th><i>K</i> 11–12<br>P/g/t</th><th><i>K</i> 12–13<br>P/g/t</th><th><i>K</i> 13–14<br>P/g/t</th><th><i>K</i> 14–15<br>P/g/t</th></tr></thead><tbody><tr><td>2025</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1/0</td></tr><tr><td>2027</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td></tr><tr><td>2029</td><td>1/0/0</td><td>0/0/1</td><td>...</td><td>1/0/0</td><td>...</td><td>...</td></tr><tr><td>2031</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td><td>0/1/1</td><td>...</td></tr><tr><td>2035</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>0/0/1</td><td>...</td></tr><tr><td>2036</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td><td>...</td><td>0/0/1</td></tr><tr><td>2038</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td><td>...</td></tr><tr><td>2040</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td></tr><tr><td>2043</td><td>...</td><td>...</td><td>...</td><td>0/1/0</td><td>1/0/0</td><td>1/0/1</td></tr><tr><td>2045</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td><td>...</td><td>...</td></tr><tr><td>2046</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td></tr><tr><td>2048</td><td>...</td><td>...</td><td>0/1/1</td><td>...</td><td>...</td><td>0/1/0</td></tr><tr><td>Totals</td><td>1/0/0</td><td>0/0/1</td><td>2/1/1</td><td>1/2/2</td><td>2/2/3</td><td>3/3/3</td></tr></tbody></table>

<table><caption>**Table 19**
Triton Occultations 2023–2050 (by *G*<sub>*</sub> Magnitude)</caption><thead><tr><th>Year</th><th><i>G</i><sub>*</sub> 10–11<br>P/g/t</th><th><i>G</i><sub>*</sub> 11–12<br>P/g/t</th><th><i>G</i><sub>*</sub> 12–13<br>P/g/t</th><th><i>G</i><sub>*</sub> 13–14<br>P/g/t</th><th><i>G</i><sub>*</sub> 14–15<br>P/g/t</th><th><i>G</i><sub>*</sub> 15–16<br>P/g/t</th><th><i>G</i><sub>*</sub> 16–17<br>P/g/t</th><th><i>G</i><sub>*</sub> 17–18<br>P/g/t</th><th><i>G</i><sub>*</sub> 18–19<br>P/g/t</th></tr></thead><tbody><tr><td>2025</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>0/1/0</td></tr><tr><td>2027</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td><td>...</td><td>...</td><td>...</td></tr><tr><td>2029</td><td>1/0/0</td><td>0/0/1</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td><td>...</td><td>...</td><td>...</td></tr><tr><td>2031</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/1/1</td><td>...</td><td>...</td><td>...</td></tr><tr><td>2035</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>...</td><td>0/0/1</td><td>...</td><td>...</td></tr><tr><td>2036</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/0/1</td><td>...</td></tr><tr><td>2038</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td><td>...</td><td>...</td><td>...</td></tr><tr><td>2040</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td></tr><tr><td>2043</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/0</td><td>...</td><td>2/0/0</td><td>0/0/1</td><td>...</td></tr><tr><td>2045</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td><td>...</td><td>...</td><td>...</td><td>...</td></tr><tr><td>2046</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>...</td><td>1/0/0</td><td>...</td></tr><tr><td>2048</td><td>...</td><td>...</td><td>...</td><td>...</td><td>0/1/1</td><td>...</td><td>0/1/0</td><td>...</td><td>...</td></tr><tr><td>Totals</td><td>1/0/0</td><td>0/0/1</td><td>0/0/0</td><td>1/0/0</td><td>2/3/3</td><td>1/2/2</td><td>2/1/1</td><td>2/0/2</td><td>0/2/1</td></tr></tbody></table>

In view of their similarities and examples of outer solar system objects with tenuous atmospheres, both Triton and Pluto are appealing targets for future near-term occultation observations. (We excluded Pluto from our list of candidate targets because its long-term ephemeris is much less accurate than Titan's and Triton's.) Although Pluto continues to be successfully observed on a frequent basis (see Young et al. 2022 for a recent example), high-S/N Triton occultation opportunities are quite scarce, owing to Neptune's path across fallow star fields (Figure 5). Marques Oliveira et al. (2022) identified several challenges to accurate Triton occultation predictions, including uncertainties in planetary/satellite ephemeris errors and star positions, although a recent orbit and dynamical model for Triton (Wang et al. 2023) yielded orbit differences from JPL ephemerides NEP081 and NEP097 below 300 km (about 15 mas). This is well below the diameter of both the Earth and Triton and quite adequate to enable secure identification of potential Triton occultation opportunities over the coming decades that are worthy of eventual closer examination. Table 18 shows the frequency of predicted events by year and *K* magnitude for *K* ≤ 15 from 2023–2050 in

the same format as for Titan, and Table 19 shows the corresponding results for $G_* \le 19$, excluding years that have no predicted events. Only 22 Triton occultations are predicted over this long period, highlighting the importance of taking advantage of the best opportunities as they arise. The complete gallery of predicted Triton events is shown in Figure 14. Detailed predictions for the complete set are given in Table 20, and in machine-readable form on the SOM, as documented in the Appendix.

Several of the predicted Triton occultations have challenging observing geometry, with the nighttime occultation path passing over remote areas of the Earth, such as the 2029 June 8 occultation of a bright star (K = 9.85, G = 11.03). Three days later, the 2029 November 11 occultation (K = 10.26, G = 11.88) is observable from Tenerife (TEN) at an elevation angle of 39° when the Sun is 10° below the horizon. Given the rarity of high-S/N Triton occultation opportunities, the possibility of observing any of the upcoming events from the CHaracterising ExOPlanets Satellite (CHEOPS) and other space platforms should be explored.
<figure><img src="image_18.png" /><figcaption>**Figure 14.** Gallery of Earth views from Triton at mid-occultation for predicted occultations with $K \le 15$ between 2023 and 2050. Each occultation is labeled by the closest geocentric approach epoch, the *K* and *G* stellar magnitudes, and the event type.</figcaption></figure>

# 6. Discussion and Conclusions

## 6.1. Comparison of Gaia and 2MASS Star Positions

An underlying assumption of our prediction catalog is that we have accurately matched the 2MASS and Gaia counterparts for each event. Since it is likely that the proper-motion-corrected Gaia positions are much more accurate than the typical positional uncertainty of 100 mas (rms) for $K \le 14$ 2MASS stars (Skrutskie et al. 2006), our working hypothesis is that the offsets _r_ between these positions are due primarily to scatter in the 2MASS catalog. To test this notion, we show in Figure 15 a histogram of the differences between the 2MASS and Gaia positions for all stars in our initial lists of occultation candidates for all targets. The upper panel shows a fit to the histogram assuming a Rayleigh distribution appropriate for the one-sided variable _r_ with a Gaussian random distribution of standard deviation $\sigma$:

$$f(_r) = \frac{-_r}{\sigma^2} e^{-r^2/2\sigma^2}. \qquad (2)$$

Our fitted value of $\sigma = 69$ mas is consistent with the quoted 2MASS accuracy of 70-80 mas over the magnitude range of $9 \le K \le 14$ (Cutri et al. 2003), although the actual distribution of position differences has a somewhat larger contribution over the range 150–500 mas than implied by the model Rayleigh distribution. To explore this in more detail, we plotted the

cumulative distribution of the offsets _r_ in the lower panel of Figure 15. We find that 38% of the stars have computed _r_ < $\sigma$, very close to the expected $1\sigma$ cumulative probability of $1 - e^{-1/2} = 0.393$ for a Rayleigh distribution. For a two-sided Gaussian distribution, it is customary to think of $1\sigma$ and $2\sigma$ results as having cumulative probabilities of 68% and 95%, and we have estimated the position offsets corresponding to these probabilities to be _r_ = 131 and 391 mas, respectively, as labeled in the figure.

These results suggest that there is a somewhat more pronounced tail to the distribution of 2MASS position errors than expected for a Gaussian process. An alternative possibility that there are uncertainties in the Gaia positions or proper motions at the level of a few hundred milliarcseconds seems to be less likely because of the many internal tests of the accuracy of the Gaia catalog astrometry (Gaia Collaboration et al. 2021; Gaia Collaboration 2022). However, Dunham et al. (2021) point out that Gaia stars with high RUWE, a measure of the quality of the astrometric solution, have been shown to have significant astrometric offsets that can be important for occultations of small targets such as asteroids. Also of concern is the “Duplicated Source Flag,” indicating that the star’s astrometric information might be degraded by unresolved close duplicity. To assess whether stars with high RUWE have significantly larger Gaia-2MASS offsets, we performed a separate Rayleigh distribution fit to
<table><caption>Table 20
Geocentric Triton Occultation Predictions 2023–2050 for $K \le 15$</caption><thead><tr><th>Event ID<br>Event Type</th><th>C/A Epoch<br>Source ID</th><th>ICRS Star Coord at Epoch<br>Geocentric Object Position</th><th>σ(α<sub>*</sub>) (km)<br>σ(δ<sub>*</sub>) (km)</th><th>C/A (mas)<br>C/A (km)</th><th>C/A<sub>p</sub> (′′)<br>C/A<sub>p</sub> (10<sup>-3</sup> km)</th><th>PA (deg)<br>v<sub>sky</sub> (km s<sup>-1</sup>)</th><th>K<br>Dist (au)</th><th>G<br>G<sub>*</sub></th><th>RP<br>DUP</th><th>E λ (deg)<br>φ (deg)</th><th>S-G-T<br>M-G-T</th></tr></thead><tbody><tr><td>Tr25001</td><td>2025-09-17 06:07:07.37</td><td>00 04 15.18297 -01 01 59.70659</td><td>50.4</td><td>31.6</td><td>9.0</td><td>163.16</td><td>14.288</td><td>18.519</td><td>17.207</td><td>273.2</td><td>173.6</td></tr><tr><td>Pg</td><td>2449604188905639040</td><td>00 04 15.18358 -01 01 59.73679</td><td>32.8</td><td>661.0</td><td>188.0</td><td>-20.71</td><td>28.887</td><td>18.557</td><td>0</td><td>-0.9</td><td>119.5</td></tr><tr><td>Tr25002</td><td>2025-11-12 16:45:45.85</td><td>23 59 18.61005 -01 33 51.53200</td><td>19.0</td><td>120.8</td><td>13.6</td><td>335.68</td><td>14.615</td><td>17.226</td><td>16.431</td><td>56.7</td><td>129.0</td></tr><tr><td>P</td><td>2449519290288023168</td><td>23 59 18.60673 -01 33 51.42195</td><td>13.6</td><td>2562.3</td><td>288.8</td><td>-16.49</td><td>29.255</td><td>17.017</td><td>0</td><td>-1.4</td><td>146.6</td></tr><tr><td>Tr27001</td><td>2027-01-05 23:14:15.27</td><td>00 07 19.05139 -00 42 13.10351</td><td>11.0</td><td>286.7</td><td>8.3</td><td>143.12</td><td>13.210</td><td>15.225</td><td>14.581</td><td>268.3</td><td>76.4</td></tr><tr><td>P</td><td>2545699104287361664</td><td>00 07 19.06286 -00 42 13.33285</td><td>6.6</td><td>6257.3</td><td>181.7</td><td>16.01</td><td>30.090</td><td>14.983</td><td>0</td><td>-0.6</td><td>96.6</td></tr><tr><td>Tr29001</td><td>2029-01-16 16:21:20.60</td><td>00 24 10.27298 +01 02 14.46954</td><td>7.1</td><td>200.4</td><td>15.5</td><td>335.99</td><td>12.537</td><td>14.375</td><td>13.765</td><td>4.7</td><td>69.5</td></tr><tr><td>P</td><td>2547000135781016320</td><td>00 24 10.26755 +01 02 14.65264</td><td>6.0</td><td>4388.9</td><td>339.9</td><td>18.26</td><td>30.190</td><td>14.276</td><td>0</td><td>1.2</td><td>47.0</td></tr><tr><td>Tr29002</td><td>2029-06-08 11:30:48.14</td><td>00 40 29.16671 +02 45 54.80459</td><td>9.1</td><td>269.8</td><td>6.6</td><td>352.41</td><td>9.849</td><td>11.026</td><td>10.601</td><td>300.7</td><td>67.2</td></tr><tr><td>P</td><td>2550622133240584704</td><td>00 40 29.16433 +02 45 55.07274</td><td>6.2</td><td>5916.6</td><td>145.4</td><td>14.47</td><td>30.240</td><td>10.675</td><td>0</td><td>2.9</td><td>26.4</td></tr><tr><td>Tr29003*</td><td>2029-06-11 05:23:26.00</td><td>00 40 39.44754 +02 46 59.57364</td><td>51.2</td><td>234.4</td><td>7.0</td><td>329.29</td><td>10.259</td><td>11.883</td><td>11.368</td><td>29.8</td><td>69.8</td></tr><tr><td>Pt</td><td>2550622232023925632</td><td>00 40 39.43955 +02 46 59.77603</td><td>44.5</td><td>5133.7</td><td>154.4</td><td>18.77</td><td>30.193</td><td>11.814</td><td>0</td><td>2.9</td><td>59.1</td></tr><tr><td>Tr31001</td><td>2031-02-07 20:42:33.71</td><td>00 42 01.57927 +02 52 55.87517</td><td>13.0</td><td>154.7</td><td>15.4</td><td>336.22</td><td>11.685</td><td>14.946</td><td>13.845</td><td>282.5</td><td>52.4</td></tr><tr><td>P</td><td>2550443668759500416</td><td>00 42 01.57511 +02 52 56.01671</td><td>12.0</td><td>3415.0</td><td>339.6</td><td>25.85</td><td>30.443</td><td>15.225</td><td>0</td><td>3.1</td><td>131.1</td></tr><tr><td>Tr31002</td><td>2031-10-08 15:33:58.35</td><td>00 53 02.38231 +03 55 24.67432</td><td>14.9</td><td>53.7</td><td>6.6</td><td>150.84</td><td>13.682</td><td>15.137</td><td>14.624</td><td>123.1</td><td>178.1</td></tr><tr><td>Pgt</td><td>2551697971008471808</td><td>00 53 02.38406 +03 55 24.62743</td><td>12.9</td><td>1123.6</td><td>138.6</td><td>-27.61</td><td>28.852</td><td>15.487</td><td>0</td><td>4.1</td><td>93.0</td></tr><tr><td>Tr35001</td><td>2035-10-05 12:01:09.75</td><td>01 27 43.93686 +07 20 07.74648</td><td>25.8</td><td>98.8</td><td>10.9</td><td>333.31</td><td>13.049</td><td>15.808</td><td>14.941</td><td>188.1</td><td>168.5</td></tr><tr><td>Pt</td><td>2566175343690470144</td><td>01 27 43.93388 +07 20 07.83479</td><td>10.9</td><td>2068.4</td><td>228.5</td><td>-26.74</td><td>28.856</td><td>16.124</td><td>0</td><td>7.5</td><td>144.4</td></tr><tr><td>Tr35002</td><td>2035-10-10 14:17:23.75</td><td>01 27 12.82180 +07 17 09.94514</td><td>11.3</td><td>112.7</td><td>5.6</td><td>330.87</td><td>12.862</td><td>14.332</td><td>13.809</td><td>148.9</td><td>173.5</td></tr><tr><td>Pt</td><td>2566173934941174400</td><td>01 27 12.81811 +07 17 10.04359</td><td>5.7</td><td>2357.8</td><td>116.5</td><td>-27.10</td><td>28.844</td><td>14.662</td><td>0</td><td>7.5</td><td>83.4</td></tr><tr><td>Tr36001</td><td>2036-06-04 12:56:48.45</td><td>01 37 13.19027 +08 20 50.47105</td><td>8.1</td><td>251.0</td><td>5.3</td><td>153.15</td><td>11.032</td><td>13.163</td><td>12.496</td><td>297.0</td><td>48.4</td></tr><tr><td>P</td><td>2571920768686360320</td><td>01 37 13.19791 +08 20 50.24710</td><td>4.8</td><td>5551.2</td><td>118.3</td><td>27.85</td><td>30.492</td><td>13.522</td><td>0</td><td>8.5</td><td>175.8</td></tr><tr><td>Tr36002</td><td>2036-10-31 15:29:17.39</td><td>01 33 36.61897 +07 53 32.49827</td><td>73.2</td><td>200.6</td><td>14.8</td><td>153.57</td><td>14.428</td><td>17.691</td><td>16.693</td><td>111.0</td><td>166.2</td></tr><tr><td>Pt</td><td>2565881494913346176</td><td>01 33 36.62498 +07 53 32.31860</td><td>31.8</td><td>4200.2</td><td>310.0</td><td>-24.34</td><td>28.865</td><td>17.904</td><td>0</td><td>8.1</td><td>26.1</td></tr><tr><td>Tr38001</td><td>2038-12-21 22:36:10.10</td><td>01 46 59.08374 +09 09 42.25470</td><td>31.2</td><td>59.9</td><td>16.3</td><td>335.52</td><td>13.672</td><td>16.290</td><td>15.469</td><td>317.6</td><td>118.5</td></tr><tr><td>Pgt</td><td>2572227674164976128</td><td>01 46 59.08207 +09 09 42.30921</td><td>30.1</td><td>1274.5</td><td>346.5</td><td>-8.80</td><td>29.336</td><td>15.399</td><td>0</td><td>9.4</td><td>174.3</td></tr><tr><td>Tr40001</td><td>2040-10-05 12:43:39.56</td><td>02 11 17.56768 +11 18 16.80792</td><td>109.1</td><td>16.7</td><td>2.7</td><td>332.07</td><td>14.330</td><td>18.364</td><td>17.156</td><td>187.6</td><td>157.8</td></tr><tr><td>Pgt</td><td>73222698406292608</td><td>02 11 17.56715 +11 18 16.82265</td><td>118.9</td><td>349.3</td><td>55.9</td><td>-25.39</td><td>28.884</td><td>18.623</td><td>0</td><td>11.5</td><td>149.6</td></tr><tr><td>Tr43001</td><td>2043-06-25 09:43:57.52</td><td>02 37 43.74095 +13 34 30.89428</td><td>65.9</td><td>142.6</td><td>3.3</td><td>173.09</td><td>14.023</td><td>17.253</td><td>16.192</td><td>340.6</td><td>51.9</td></tr><tr><td>Pt</td><td>26895600603666432</td><td>02 37 43.74213 +13 34 30.75276</td><td>66.3</td><td>3145.9</td><td>72.2</td><td>21.37</td><td>30.426</td><td>17.324</td><td>0</td><td>13.8</td><td>95.7</td></tr><tr><td>Tr43002</td><td>2043-09-26 17:03:39.54</td><td>02 38 45.33322 +13 34 09.93323</td><td>37.9</td><td>267.6</td><td>13.8</td><td>334.38</td><td>13.201</td><td>16.245</td><td>15.317</td><td>138.9</td><td>141.3</td></tr><tr><td>P</td><td>26892856120403968</td><td>02 38 45.32528 +13 34 10.17456</td><td>35.0</td><td>5632.9</td><td>290.7</td><td>-19.61</td><td>29.019</td><td>16.224</td><td>0</td><td>13.8</td><td>63.8</td></tr><tr><td>Tr43003</td><td>2043-10-02 01:16:09.36</td><td>02 38 18.58223 +13 31 54.96788</td><td>16.9</td><td>13.3</td><td>16.9</td><td>339.82</td><td>12.025</td><td>14.776</td><td>13.924</td><td>10.4</td><td>146.7</td></tr><tr><td>Pg</td><td>26891550450337792</td><td>02 38 18.58192 +13 31 54.98040</td><td>14.6</td><td>280.3</td><td>354.5</td><td>-19.59</td><td>28.966</td><td>14.753</td><td>0</td><td>13.7</td><td>134.2</td></tr><tr><td>Tr43004</td><td>2043-12-05 15:50:18.42</td><td>02 31 40.83793 +13 00 20.93616</td><td>51.9</td><td>314.9</td><td>16.9</td><td>342.80</td><td>14.477</td><td>16.753</td><td>16.100</td><td>86.6</td><td>146.9</td></tr><tr><td>P</td><td>26451058604260992</td><td>02 31 40.83156 +13 00 21.23697</td><td>46.5</td><td>6618.0</td><td>354.7</td><td>-19.38</td><td>28.977</td><td>16.719</td><td>0</td><td>13.2</td><td>102.5</td></tr><tr><td>Tr45001</td><td>2045-10-24 10:18:54.48</td><td>02 54 06.15989 +14 43 04.64022</td><td>15.6</td><td>36.6</td><td>4.5</td><td>335.59</td><td>12.768</td><td>14.121</td><td>13.647</td><td>216.2</td><td>165.2</td></tr><tr><td>Pgt</td><td>32518438644356608</td><td>02 54 06.15885 +14 43 04.67357</td><td>11.2</td><td>766.4</td><td>94.1</td><td>-26.44</td><td>28.851</td><td>14.424</td><td>0</td><td>14.9</td><td>32.3</td></tr><tr><td>Tr46001</td><td>2046-03-02 05:33:32.53</td><td>02 48 29.27402 +14 23 42.02432</td><td>105.5</td><td>282.4</td><td>11.7</td><td>168.18</td><td>14.585</td><td>17.799</td><td>16.743</td><td>159.2</td><td>62.9</td></tr><tr><td>P</td><td>32087322711430784</td><td>02 48 29.27800 +14 23 41.74795</td><td>87.2</td><td>6195.4</td><td>257.7</td><td>17.08</td><td>30.252</td><td>17.628</td><td>0</td><td>14.6</td><td>123.1</td></tr><tr><td>Tr48001</td><td>2048-01-06 07:30:10.46</td><td>03 05 20.15502 +15 33 34.13969</td><td>23.0</td><td>5.1</td><td>16.7</td><td>348.41</td><td>11.666</td><td>14.919</td><td>13.891</td><td>188.9</td><td>123.3</td></tr><tr><td>Pgt</td><td>30958747040513152</td><td>03 05 20.15495 +15 33 34.14473</td><td>18.4</td><td>109.2</td><td>354.8</td><td>-11.25</td><td>29.265</td><td>14.294</td><td>0</td><td>15.7</td><td>115.3</td></tr><tr><td>Tr48002</td><td>2048-07-13 16:27:44.57</td><td>03 22 56.20484 +16 46 51.21500</td><td>55.8</td><td>7.8</td><td>2.3</td><td>358.27</td><td>14.285</td><td>16.472</td><td>15.799</td><td>232.2</td><td>58.6</td></tr><tr><td>Pg</td><td>54599793226129664</td><td>03 22 56.20482 +16 46 51.22279</td><td>43.0</td><td>171.5</td><td>50.4</td><td>18.41</td><td>30.336</td><td>16.382</td><td>0</td><td>17.0</td><td>86.9</td></tr></tbody></table>
<figure><img src="image_19.png" /><figcaption>**Figure 15.** Comparison of Gaia DR3 and 2MASS star positions.</figcaption></figure>

the approximately 8% of stars with RUWE > 1.4, as shown by the red curve in the upper panel of Figure 15. The fitted value of $\sigma = 79$ mas is modestly greater than $\sigma = 69$ mas for the full set of stars, and this high-RUWE population is not responsible for the excess of stars with _r_ between 150 and 500 mas relative to the model distribution. The lower panel shows the corresponding cumulative distribution for the high-RUWE stars (plotted in red), and the differences are slight relative to the full set of stars. We conclude that the larger astrometric error for the high-RUWE stars has only a slight effect on the differences in the Gaia and 2MASS catalog positions computed at the 2MASS epoch.

To summarize, the offsets between the Gaia and 2MASS positions are broadly consistent with the estimated astrometric uncertainties of the 2MASS catalog positions, but there is a tail

to the distribution that either reflects a non-Gaussian distribution of 2MASS astrometric errors or is the result of occasional misidentification of the 2MASS star that corresponds to a given Gaia star. We have reduced the chances for misidentification by eliminating unrealistically reddened stars from our candidate pool. We do this by requiring that the Gaia *G* magnitude be no more than 5 mag fainter than the *K* magnitude for the Jupiter and Saturn searches, and no more than 4 mag fainter for the other searches. Nevertheless, it would be prudent for observers to make an independent assessment of the correspondence between the Gaia star positions quoted in our predictions and the coordinates of the 2MASS star we have claimed as a match, in cases where _r_ approaches our cutoff value of 1". We include _r_ and RUWE in the machine-readable tables, and set 2MASS DUPFLAG to 1 in instances where there are two or
more predicted events within a day of each other that have separate Gaia DR3 stars but have been matched to the same 2MASS star, so that observers can take appropriate cautions.

## 6.2. JWST and Earth-orbiting Spacecraft Occultation Opportunities

The recent successes of CHEOPS in observing the 2020 June 11 Quaoar occultation (Morgado et al. 2022) and of JWST in observing the 2022 October 18 stellar occultation by Chariklo's rings (Santos-Sanz et al. 2022b) are reminders of the possibility that current and future spacecraft may be in a position to observe occultations by the targets we have considered in this work. Given the substantial parallax associated with JWST's orbit compared to our geocentric positions, the prediction tables presented here cannot be used to identify events observable by JWST, but there may well be opportunities for CHEOPS or HST to observe some of our predicted events. We encourage those searches, which are beyond the scope of the present work.

## 6.3. Practical Considerations

Our goal in presenting occultation predictions extending to 2050 is to provide planetary scientists with an accurate sense of prospects for high-S/N Earth-based stellar occultations by Jupiter, Saturn, Uranus, Neptune, Titan, and Triton in the coming decades, with sufficient detail to support planning for observing campaigns. Given this long duration, however, it is inevitable that future improvements in astrometry, stellar proper-motion estimates, photometry, and planetary and satellite ephemerides will affect the details of some of our predicted events. For the giant planets and ring systems, the resulting geometrical changes are less likely to be consequential than for the smaller targets, Titan and Triton. As a cautionary example, Gaia proper-motion estimates change with each new catalog release. For the 2020 October 13 occultation of Plutino (28978) Ixion, Levine et al. (2021) found that the proper-motion solution for the star changed by roughly 0.46 mas yr⁻¹ between Gaia DR2 and Gaia EDR3. Over the span of roughly 20 yr, comparable changes in the estimated proper motion of our candidate stars could account for a change in star position at epoch of 10 mas, corresponding to potential north-south shifts in the predicted paths of Titan and Triton of ~65 and ~290 km, respectively. These are substantially less than the target diameters and do not call into question our identification of potentially observable occultations by these small objects. Nevertheless, for optimal positioning of portable telescopes to sample multiple occultation chords for Titan and Triton events, detailed updated predictions using the latest stellar catalog positions and planetary ephemerides should be made well in advance of any observing campaign.

## 6.4. Scientific Value of Long-term Occultation Observations

With the rapid increase in the discovery and characterization of extra-solar planets, the four giant planets in our own solar system provide valuable case studies of ice giant and Jupiter-scale worlds. In the era of JWST and future Earth-based and orbiting observing platforms, occultations can provide complementary information about planetary atmosphere and ring systems over the coming decades, such as documenting latitudinal and seasonal variations in planetary stratospheres and extending the long time baseline of high-resolution

observations of the ring systems of Saturn, Uranus, and possibly Neptune. Continued reconnaissance of Titan's atmosphere will be especially important in advance of the Dragonfly mission, scheduled to reach Saturn in 2034. Finally, provocative similarities between Triton's and Pluto's surface and atmospheric interactions and seasonal variability invite concerted efforts to take advantage of the rare opportunities to observe Triton's atmosphere through occultations in the coming decades.

## Acknowledgments

We are grateful to two anonymous referees for their detailed helpful suggestions. We thank the creators of SORA (Gomes-Júnior et al. 2022) for producing open-source software for the prediction and characterization of stellar occultations, which was developed with the support of ERC Lucky Star and LIneA/Brazil. We used SORA version 0.2.1 to determine the projected diameters and positional uncertainties of our candidate occultation stars.<fnref n="17" /> We also used SORA to confirm the completeness of our catalog search and to provide an independent check for the geometric quantities computed using our occultation prediction algorithms. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has also made use of the VizieR catalog access tool, CDS, Strasbourg, France (doi:10.26093/cds/vizier). The original description of the VizieR service was published in Ochsenbein et al. (2000). This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. We made extensive use of NASA's NAIF SPICE toolkit and ephemerides for this project (Acton 1996).

## Data Availability

Details of all of the occultation predictions are included in the Supplementary Online Material described in the Appendix.

# Appendix A

## Description of the Supplementary Online Material

Detailed occultation prediction tables and figures are available as SOM in NASA's Planetary Data System Ring-Moon Systems node at doi:10.17189/m9sk-g963. Users should download the entire repository to a local storage device, using the command `wget`, freely available from https://www.gnu.org/software/wget/. To download the entire SOM contents, enter the following commands from the command line of a terminal:

```
cd destdir (where destdir is the local directory within which the SOM directory will reside)
```

<footnote n="17">¹⁷ https://github.com/riogroup/SORA</footnote>
wget -c -r -nH --cut-dirs=2 https://pds-rings.seti.org/rms-annex/french23_occult_pred/SOM/

The top directory name is SOM/. The approximate data volume is 28 GB.

The abbreviated directory structure of the SOM/ directory is shown below. Each directory has its own aareadme.txt, with its file name including its home directory. The entire SOM can be navigated by opening the index.html file in a web browser. The SOM/docs/ directory contains two sample Python programs to illustrate simple occultation searches of the SOM. They can be easily modified for more complex searches.

### SOM/

aareadme.txt Brief description of SOM/ contents

index.html Open this file in a browser to navigate SOM directory

### doc/

aareadme.txt Description of SOM/doc/ contents

EventSearchExample\*.\* Example occultation search codes and output files

Occpred-manuscript.pdf Typeset version of prediction paper

Occpred-SOM.pdf Typeset version of SOM documentation

### tables/

aareadme.txt Description of SOM/tables/ contents

Jupiter/

Saturn/

......

### events/

aareadme.txt Description of SOM/events/ contents

Jupiter/

Saturn/

......

## A.1. SOM/

### Contents of the SOM/aareadme.txt file:

SOM/ is the top-level directory for Supplementary Online Material (SOM) for the paper "Earth-based Stellar Occultation Predictions for Jupiter, Saturn, Uranus, Neptune, Titan, and Triton: 2023–2050"

Authors: Richard G. French and Damya Souami

Publication: Planetary Science Journal (accepted July 2023)

SOM: Supplementary Online Material

The directory structure is shown below, with aareadme.

txt files in each subdirectory.

### SOM/

aareadme.txt Brief description of SOM/ contents

index.html Open this file in a browser to navigate SOM/ directory

### doc/

aareadme.txt Description of SOM/doc/ contents

EventSearchExample\*.\* Example occultation search codes and output files

To perform the example searches:

python3 EventSearchExample1.py

python3 EventSearchExample2.py

Occpred-manuscript.pdf Typeset version of occultation prediction paper

Occpred-SOM.pdf Typeset version of SOM documentation

### tables/

aareadme.txt Description of SOM/tables/ contents

Jupiter/

Saturn/

Uranus/

(Continued)

<table><tr><td>Neptune/</td><td></td></tr><tr><td>Titan/</td><td></td></tr><tr><td>Triton/</td><td></td></tr><tr><td>events/</td><td></td></tr><tr><td>aareadme.txt</td><td>Description of SOM/events/ contents</td></tr><tr><td>Jupiter/</td><td></td></tr><tr><td>Saturn/</td><td></td></tr><tr><td>Uranus/</td><td></td></tr><tr><td>Neptune/</td><td></td></tr><tr><td>Titan/</td><td></td></tr><tr><td>Triton/</td><td></td></tr><tr><td>Jupiter/</td><td></td></tr></table>

## A.2. SOM/doc/

### Contents of the SOM/doc/aareadme.txt file:

This directory contains:

### SOM/doc/

aareadme.txt Description of SOM/doc/ contents

EventSearchExample1.ipynb Example1 files

EventSearchExample1.py

EventSearchExample1.out

EventSearchExample2.ipynb Example2 files

EventSearchExample2.py

EventSearchExample2.out

Occpred-manuscript.pdf Typeset version of prediction paper

Occpred-SOM.pdf Typeset version of SOM documentation

## A.3. SOM/Events/

### Contents of the SOM/events/aareadme.txt file:

### The SOM/

events/ directory contains both summary and detailed occultation predictions with a subdirectory for each of six targets:

Jupiter Saturn Uranus Neptune Titan Triton

### For example, the SOM/events/

Neptune/ directory has the following structure and abbreviated contents:

### SOM/events/Neptune:

```
gallery of views of Earth from Neptune at mid-
occultation time
```

```
for 25 events per file
Neptune_globes_2023-05-03_to_2032-02-16.pdf
Neptune_globes_2032-09-05_to_2040-07-12.pdf
Neptune_globes_2041-07-03_to_2047-03-16.pdf
Neptune_globes_2047-07-01_to_2049-11-05.pdf
```

```
gallery of views of skyplane from Earth at mid-
occultation time
```

```
for 25 events per file
Neptune_skyplanes_2023-05-03_to_2032-02-16.pdf
Neptune_skyplanes_2032-09-05_to_2040-07-12.pdf
Neptune_skyplanes_2041-07-03_to_2047-03-16.pdf
Neptune_skyplanes_2047-07-01_to_2049-11-05.pdf
```
detailed information for each event is in sub-folders, by year:

Neptune/2023:

Overview summary PDF file for the event

with C/A time 2023-05-03T13_00_52.170

from prediction series YYYYMMDD 20230528

version a:

Neptune_2023-05-03T13_00_52.170_20230528a.pdf

Text file containing summary of this event:

Neptune_2023-05-03T13_00_52.170_20230528a.txt

full-size images of:

altitude of target as a function of time

globe (view of Earth from target)

skyplane (view of target and occultation chords)

Neptune_2023-05-03T13_00_52.170_20230528a.alt.jpg

Neptune_2023-05-03T13_00_52.170_20230528a.globe.jpg

Neptune_2023-05-03T13_00_52.170_20230528a.skyplane.jpg

Text file containing detailed predictions

for all observatories from which this event was

visible, subject to altitude constraints

Sun more then 5 degrees below horizon

target more then 5 degrees above horizon

The observatory code in this case is PAL

for Mt. Palomar 5m telescope.

See full list of observatory codes in the main

body of the paper:

Neptune_2023-05-03T13_00_52.170_PAL_20230528a.txt

## A.4. SOM/Tables/

Contents of the SOM/tables/aareadme.txt file:

The SOM/

tables/ directory contains tables of occultation predictions in both typeset

form and in machine-readable form, with a subdirectory for each target:

Jupiter, Saturn, Uranus, Neptune, Titan, and Triton.

The table contents differ slightly for ringed/

nonringed planets and for the satellite targets.

For example, the Neptune directory contains the following files:

./Neptune/

Neptune_tables.pdf Complete set of typeset tables, produced from the following LaTeX source files:

Neptune_tables.tex LaTeX file to produce Neptune_tables.pdf

Neptunestions_01_of_01.

tex Data tables referred to in Neptune_tables.tex

aastex631.cls LaTeX style sheet used for Neptune_tables.tex

Note that to get proper column alignment in the typeset output file, the input Neptune_tables.tex file must be typeset three times in succession.

Neptuneenteions_MR.txt Machine-readable version of complete set of predictions for Neptune.

The format of the machine-readable file is listed at the beginning of the file.

The header, file format, and first line of data (line-wrapped) for the file

Neptune/Neptunestions_MR.txt are as follows:

head -59 Neptune/Neptuneenteions_MR.txt | fold -124

Title: Earth-based Stellar Occultation Predictions for Jupiter, Saturn, Uranus, Neptune, Titan, and Triton: 2023-2050

Authors: Richard G. French & Damya Souami

Table: Occultation predictions for Neptune 2023-2050 for K<15

Byte-by-byte Description of file: Neptune-predictions_MR.txt

<table><thead><tr><th>Bytes</th><th>Format</th><th>Units</th><th>Label</th><th>Explanations</th></tr></thead><tbody><tr><td>1-8</td><td>A8</td><td>—</td><td></td><td>TARGET Occultation target</td></tr><tr><td>10-</td><td>A71</td><td>—</td><td></td><td>SUMMARY_PDF SOM pathname</td></tr><tr><td>80</td><td></td><td></td><td></td><td>to event summary PDF</td></tr><tr><td>82-</td><td>A11</td><td>—</td><td></td><td>EVENTID Event identification (target letter, YYnnn)</td></tr><tr><td>92</td><td></td><td></td><td></td><td>JD Julian date of closest approach (CA)</td></tr><tr><td>94-</td><td>F19.7</td><td>d</td><td></td><td>UTC_CA UTC of closest approach</td></tr><tr><td>112</td><td></td><td></td><td></td><td></td></tr><tr><td>114-</td><td>A27</td><td>—</td><td></td><td>EVENTTYPE Event type P: planet, g: geocentric t: topocentric</td></tr><tr><td>140</td><td></td><td></td><td></td><td>STARID Gaia star ID</td></tr><tr><td>142-</td><td>A10</td><td>—</td><td></td><td></td></tr><tr><td>151</td><td></td><td></td><td></td><td></td></tr><tr><td>153-</td><td>I22</td><td>—</td><td></td><td></td></tr><tr><td>174</td><td></td><td></td><td></td><td></td></tr><tr><td>176-</td><td>A36</td><td>—</td><td></td><td>STARPOS J2000 star position at epoch hh mm ss dd mm ss</td></tr><tr><td>211</td><td></td><td></td><td></td><td>STARERR_F E-W error in star position in skyplane (E positive)</td></tr><tr><td>213-</td><td>F7.1</td><td>km</td><td></td><td>STARERR_G N-S error in star position (N positive)</td></tr><tr><td>219</td><td></td><td></td><td></td><td></td></tr><tr><td>221-</td><td>F7.1</td><td>km</td><td></td><td>TARGPOS J2000 target position at epoch hh mm ss dd mm ss</td></tr><tr><td>227</td><td></td><td></td><td></td><td>CA closest approach distance of target and star in skyplane</td></tr><tr><td>229-</td><td>A36</td><td>—</td><td></td><td>PA position angle of CA</td></tr><tr><td>264</td><td></td><td></td><td></td><td></td></tr><tr><td>266-</td><td>F9.3</td><td>arcsec</td><td></td><td></td></tr><tr><td>274</td><td></td><td></td><td></td><td></td></tr><tr><td>276-</td><td>F10.2</td><td>deg</td><td></td><td></td></tr><tr><td>285</td><td></td><td></td><td></td><td></td></tr><tr><td>287-</td><td>F9.3</td><td>1000</td><td></td><td>RKM_CA sky plane separation at CA</td></tr><tr><td>295</td><td></td><td>km</td><td></td><td></td></tr><tr><td>297-</td><td>F9.2</td><td>km s<sup>-1</sup></td><td></td><td>VSKY sky plane velocity of target relative to star</td></tr><tr><td>305</td><td></td><td></td><td></td><td>DISTAU Observer-target distance</td></tr><tr><td>307-</td><td>F10.3</td><td>au</td><td></td><td></td></tr><tr><td>316</td><td></td><td></td><td></td><td></td></tr><tr><td>318-</td><td>F10.3</td><td>km s<sup>-1</sup></td><td></td><td>RDOT ring plane radial velocity</td></tr><tr><td>327</td><td></td><td></td><td></td><td></td></tr><tr><td>329-</td><td>F10.2</td><td>deg</td><td></td><td>P position angle of target pole</td></tr><tr><td>338</td><td></td><td></td><td></td><td></td></tr><tr><td>340-</td><td>F10.2</td><td>deg</td><td></td><td>BDEG ring opening angle</td></tr><tr><td>349</td><td></td><td></td><td></td><td></td></tr><tr><td>351-</td><td>F7.1</td><td>deg</td><td></td><td>LATI Ingress geodetic latitude</td></tr><tr><td>357</td><td></td><td></td><td></td><td></td></tr><tr><td>359-</td><td>F9.1</td><td>deg</td><td></td><td>LATE Egress geodetic latitude</td></tr><tr><td>367</td><td></td><td></td><td></td><td></td></tr><tr><td>369-</td><td>F9.3</td><td>mag</td><td></td><td>KMAG apparent K magnitude of occultation star</td></tr><tr><td>377</td><td></td><td></td><td></td><td>GMAG apparent G magnitude of occultation star</td></tr><tr><td>379-</td><td>F10.3</td><td>mag</td><td></td><td>GSTAR apparent G magnitude of occultation star, corrected for vsky</td></tr><tr><td>388</td><td></td><td></td><td></td><td>RPMAG apparent RP magnitude of occultation star</td></tr><tr><td>390-</td><td>F10.3</td><td>mag</td><td></td><td>DUP Source with multiple source identifiers (Gaia catalog entry)</td></tr><tr><td>399</td><td></td><td></td><td></td><td></td></tr><tr><td>401-</td><td>F10.3</td><td>mag</td><td></td><td></td></tr><tr><td>410</td><td></td><td></td><td></td><td></td></tr><tr><td>412-</td><td>I1</td><td>—</td><td></td><td></td></tr><tr><td>412</td><td></td><td></td><td></td><td></td></tr><tr><td></td><td>F9.3</td><td>km</td><td></td><td></td></tr></tbody></table>