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

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 ≤ 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 ≤ 5 in 2032 and 2047. Ten Uranus ring occultations are predicted with K ≤ 10 for the period 2023–2050. Neptune traverses star-poor regions of the sky until 2068, resulting in only 13 predicted occultations for K ≤ 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 ≤ 15 between 2023 and 2050. Details of all predicted events are included in the Supplementary Online Material.

Earth-based stellar occultations have proven to be a powerful and versatile tool of solar system discovery and exploration. 1 Planetary occultations have revealed the stratospheric thermal structure of Jupiter (Baum and Code 1953;Hubbard et al. 1972;Vapillon et al. 1973;Veverka et al. 1974;Raynaud et al. 2004;Hubbard et al. 1995;Raynaud et al. 2003;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;Smith et al. 1989;Sicardy et al. 1991;De Pater et al. 2018;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,b). 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 the Pluto's tenuous atmosphere , determined the properties of its atmospheric waves (Person et al. 2008), and revealed properties of its atmospheric haze from multi-wavelength 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. 2022;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 by Triton (Marques Oliveira et al. 2022) and Pluto (Young et al. 2022a) 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 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 TESS 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 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 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-SNR 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 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 important of continued occultation surveillance of our chosen targets. The Appendix describes the contents of the SOM, including documentation of the machine-readable tables.

IDENTIFICATION OF OCCULTATION CANDIDATES
Previous occultation predictions for the outer planets often required dedicated astrometry and photometry of candidate stars (Klemola and Marsden 1977;Klemola et al. 1981;Mink and Klemola 1985;Nicholson et al. 1988; Klemola and Mink 1991;Mink et al. 1992). Bosh and 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 at http://www2.lowell.edu/users/amanda/occs2000/. More recently, Mink (1995) made use of the PPM catalog (Roeser and Bastian 1988;Röser and Bastian 1991;Roeser and Bastian 1993) to produce a statistical overview of stellar occultations between 1950-2050 and summary online tables of predicted events for 2000-2050 with closest-approach distances less than 30 ′′ for Jupiter 2 , Saturn 3 , Uranus 4 , and Neptune 5 . Saunders et al. (2022) identified several promising Uranus and Neptune occultations between 2025-2035, including SNR estimates for ground-based and space-based observations. For the present survey, we expand on these prediction lists by making use of the Gaia 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 DR2 catalog, significantly reducing the prediction uncertainty the smaller targets Titan and Triton towards the end of our prediction period. We make use as well of the Two Micron All-Sky Survey (2MASS) (Skrutskie et al. 2006) for apparent stellar magnitudes in the K band (λ ∼ 2.2 µm).
Most high-SNR 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 λ = 2.2 µm or the weaker methane band near λ = 0.89 µm to reduce the observed brightness of the planet relative to the occultation star. With the expectation that future high-SNR 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≤10 or brighter for Jupiter and Saturn, and K≤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∼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 planets. We include K, G, and RP magnitudes so that observers can estimate the expected SNR 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 moderate-sized telescopes at visual wavelengths. We tabulate the frequency of occultations by these targets as a function of both K and G magnitudes.

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≤15 for the Jupiter and Saturn candidate searches, and G≤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 arcsec of the 2MASS catalog position at epoch. We included a magnitude-dependent correction for the proper motion derived from the Gaia EDR3 catalog (Cantat-Gaudin and Brandt 2021), but equally applicable to the DR3 proper motions as well (personal communication T. Contat-Gaudin). We also took account of propagated position error estimates, using the prescription of Butkevich and 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 km. This level of agreement is quite sufficient for our present purposes. Other occultation prediction software is available from the International Occultation Timing Association (IOTA) 6 , and the geometry of occultation circumstances can also be computed using the NASA/JPL Horizons software. 7 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 km level in the sky plane for our target objects.

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 8 prediction efforts, which focus instead on relatively short-term 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.

OCCULTATION GEOMETRY
We restricted our set of occultations to those with 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;De Pater et al. 2018;French et al. 2023b). 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. For Saturn, Uranus and Neptune, the planetary event type is appended with 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.

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 2028-12-29 (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 anti-solar point as an open circle. In this instance, the geocentric C/A occurred at 2028-12-29 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 sky ) of the target relative to the star at the C/A time, and D, the target distance from Earth in AU. 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 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 Fig. 2 for the 2028-12-29 Uranus occultation. For each labeled site, the altitude of Uranus is shown as a solid line and the altitude of theSunis 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 (Fig. 1,bottom panel). 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.

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:  Figure 2. Altitude of Uranus (solid lines) and the Sun (dashed lines) relative to the the horizon during the 2028-12-29 Uranus occultation, for the labeled observing sites (Table 2). See text for details • σ(α * ) and σ(δ * ) are estimated star position errors (expressed in km in the sky plane) propagated from the Gaia DR3 catalog epoch to the time of each occultation, from the method of Butkevich and Lindegren (2014) as implemented in the 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 RUWE (renormalized unit weight error) 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.
• 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 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.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.
• G * is the velocity-corrected apparent G magnitude of the occultation star, according to the prescription where v sky is the sky plane velocity in km s −1 (Gomes-Júnior et al. 2022). This function increases the predicted SNR of slow occultations and downgrades the SNR of rapid occultations.
• 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.
• XXX N TARGETOCCS and XXX N RINGOCCS 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.
We identified a total of 1844 Jupiter occultations between 2023-2050 for stars brighter than K≤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 years, 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≤4 between 2023-2050, but there are many events with K≤9.
To illustrate the range of event geometries and the varying aspect of Jupiter over this time interval, we include here the brightest (K mag) 24 Jupiter occultations between 2023-2050 with planetary event types Pt or Pgt . Figure 3 shows a gallery of views of Earth at mid-occultation and Fig. 4 shows the corresponding sky-plane views of Jupiter.  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. As noted previously, an indication of the relative accuracy of the Gaia DR3 star positions is given by the RUWE (renormalized unit-weight error) catalog entry. Values of RUWE ≤1.4 indicate a reliable astrometric solution. 9 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 a is appended to the Event ID when a nearby event has the same 2MASS ID, resulting in a corresponding K magnitude ambiguity.
The path of Jupiter across the sky is shown in 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.

Saturn
The 1989-07-03 occultation of the bright star 28 Sgr (K=1.48) was predicted by Taylor (1983) 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 1991-10-02/03 (Elliot et al. 1993), providing useful information about the pole direction and radius scale of Saturn's ring system. On 1998-11-14, 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≤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.  (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-SNR Neptune occultations in our prediction list.
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 Fig. 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. Table 9. Saturn Planet/Ring Occultations 2023-2050 Year K < 5 K 5-6 K 6-7 K 7-8 K 8-9 K 9-10 P/R P/R P/R P/R P/R P/R The ring opening angle of Saturn's rings varies over time, as shown in Fig. 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 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 of the rings during these occultations.
To illustrate the range of event geometries and the varying aspect of Saturn and its rings, Fig. 7 shows a gallery of views of Earth at mid-occultation and Fig. 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 2023-2047. (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.   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 2023-2047 with composite event type RgtPgt.  There are only a few occultations with K≤ 8 by Saturn between 2023 and 2029, after which there are numerous high-SNR opportunities to observe the atmosphere and the rings unblocked by the planet. The brightest of these is the 2032-04-07 event (K=4.78, G=5.72, V=5.80), with a nearly diametric ring occultation observable from Hawaii. High-SNR atmosphere observations should be possible for this occultation. However, even this bright star is only about 5% the brightness of the 1989-07-03 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 λ ∼ 3µm, where future high altitude or spacecraft observations may be possible for this and later occultations.

Uranus
The Uranian rings were first detected during the widely observed 1977-03-10 occultation of the bright star SAO 158687 (Bhattacharyya and Bappu 1977;Brahic 1977;Chen et al. 1978;Elliot et al. 1977;Hubbard et al. 1977;Millis et al. 1977;Morrisby et al. 1977;Tomita 1977), and a 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. (2023a) 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 1998-11-06 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≤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 non-uniform, 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 Fig. 5 (lower left), which shows the apparent path of Uranus in the sky planet as viewed from Earth between 1975 and 2050. Uranus crossed the Milky Way roughly in the direction of the galactic center between 1985-1990, providing abundant opportunities for high-SNR 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 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 2002-11-29 occultation (K=11.4) observed from Palomar Observatory and the 2006-09-20 occultation (V=10.746, K=8.408) observed from the IRTF (French et al. 2023a). 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-SNR 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 Fig. 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 sub-solar latitude. 10 The most recent Uranus ring plane crossings (RPXs) occurred in ∼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≤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 of the rings.  Year K<7 K 7-8 K 8-9 K 9-10 K 10-11 K 11-12 K 12-13 K 13-14 K 14-15 P/R P/R P/R P/R P/R P/R P/R P/R P/R  To illustrate the range of event geometries and the varying aspect of Uranus and its rings, Fig. 9 shows galleries of views of Earth at mid-occultation and Fig. 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 the several of these events have no planet occultations.) Table 12 provides detailed information this subset of our full prediction list.
The full set of prediction details is available in the SOM. Saunders et al. (2022) identified near-IR 56 Uranus occultations between 2025-01-01 and 2035-12-31 visible from low-Earth orbit, with a solar exclusion angle of 30 • . Our computed geometry matches the subset of these events that satisfy our Sun-Geocenter-Target limit of ≥ 45 • , more appropriate for ground-based observations.  Figure 10. Gallery of geocentric sky plane views of Uranus and its rings at mid-occultation for for the 24 brightest predicted events in the K band with ring event type Rgt for 2023-2050.   Year K < 9 K 9-10 K 10-11 K 11-12 K 12-13 K 13-14 K 14-15 P/R P/R P/R P/R P/R P/R P/R 2023 -

Neptune
The first modern occultation observation of Neptune occurred on 1968-04-07, when the planet occulted the star BD −17 4388 (Kovalevsky and 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. 1986Sicardy et al. , 1991. French et al. (1998)  Just as for Uranus, Neptune passed out of the dense star fields of the Milky Way in the mid-1980's, as shown in Fig. 5 (lower right). Owing to Neptune's long orbital period (165 years), the next traversal of the Milky Way will not occur until about 2068. Consequently, very few high-SNR 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 Fig. 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 sub-solar latitude. Black dots mark the times of previous successful Neptune occultations (Roques et al. 1994), and red dots mark all predicted events from 2023-2050, 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, Fig. 11 shows galleries of views of Earth at mid-occultation and Fig. 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 2025-01-01 and 2035-12-31 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 Sun-Geocenter-Target limit of ≥ 45 • , more appropriate for ground-based observations.   The most promising near-term Neptune occultations are the 2023-10-18 and 2024-10-09 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. 11 Next in line are the 2032-09-05 (K=8.5) and 2035-10-18 (K=9.5) events, both with excellent planet occultations and unblocked sampling of the ring regions.

Titan
The first extensive occultation observations of Titan's atmosphere were obtained during the 1989-07-03 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 to 45. Subsequently, Sicardy et al. (2006) reported on two Titan stellar occultations that occurred on 2003-11-14. 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).

Triton
Our final occultation target is Triton, whose tenuous atmosphere was first studied quantitatively using the Voyager 2 Radio Science Subsystem (RSS) 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) and Elliot et al. (2000) reported on the 1997-11-18 stellar occultation by Triton and found evidence for distortion and increasing pressure in its atmosphere since the 1989 Voyager 2 flyby. On 2017-10-05, Triton occulted the 13th magnitude star UCAC4 410-143659 as seen from the Eastern US, North Atlantic, and Europe, including the Stratospheric Observatory for Infrared Astronomy (SOFIA) 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.
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. (2022a) for a recent example), high-SNR Triton occultation opportunities are quite scarce, owing to Neptune's path across fallow star fields (Fig. 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 obit 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 * ≤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 Fig. 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. Year G * 10-11 G * 11-12 G * 12-13 G * 13-14 G * 14-15 G * 15-16 G * 16-17 G * 17-18 G * 18-19 P/g/t P/g/t P/g/t P/g/t P/g/t P/g/t P/g/t P/g/t P/g/t 1/0/0 0/0/1 0/0/0 1/0/0 2/3/3 1/2/2 2/1/1 2/0/2 0/2/1  Figure 14. Gallery of Earth views from Triton at mid-occultation for predicted occultations with K ≤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. 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 2029-06-08 occultation of a bright star (K=9.85, G=11.03). Three days later, the 2029-11-11 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-SNR Triton occultation opportunities, the possibility of observing any of the upcoming events from CHEOPS and other space platforms should be explored.
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 ≤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 Fig. 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 σ: Our fitted value of σ = 69 mas is consistent with quoted 2MASS accuracy of 70-80 mas over the magnitude range of 9 ≤ K ≤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 Fig. 15. We find that 38% of the stars have computed r < σ, very close to the expected 1-σ 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-σ and 2-σ 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 mas 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 (Renormalized Unit Weight Error), 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 the approximately 8% of stars with RUWE>1.4, as shown by the red curve in the upper panel of Fig. 15. The fitted value of σ = 79 mas is modestly greater than σ = 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 -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 magnitudes fainter than the K magnitude for the Jupiter and Saturn searches, and no more than 4 magnitudes 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 arcsec. 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.

JWST and Earth-orbiting spacecraft occultation opportunities
The recent successes of CHEOPS in observing the 2020-06-11 Quaoar occultation (Morgado et al. 2022) and of JWST in observing the 2022-10-18 stellar occultation by Chariklo's rings (Santos-Sanz et al. 2022) 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.

Practical considerations
Our goal in presenting occultation predictions extending to 2050 is to provide planetary scientists with an accurate sense of prospects for high-SNR 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 2020-10-13 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 GDR2 and GEDR3. Over the span of roughly 20 years, 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.

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.
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 SOM described in the Appendix. 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) 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 filename 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. 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

SOM
For example, the SOM/events/Neptune/ directory has the following structure and abbreviated contents: The SOM/tables/ directory contains tables of occultation predictions in both typeset form and in machine-readable form, with with a sub-directory for each target: Jupiter, Saturn, Uranus, Neptune, Titan, and Triton.
The table contents differ slightly for ringed/non-ringed 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 Neptune_predictions_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.
Neptune_predictions_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.    For each predicted occultation, the SOM includes visual and tabular overviews of the observing circumstances. We illustrate these using the 2028-12-19 Uranus occultation.
A single PDF file for each predicted occultation includes key observational data and plotted figures showing the event geometry. Figure B1 shows the summary page for this event. 13 Both the view of Earth and the sky plane plots are included in the same SOM subdirectory. The summary page includes information about the target object and occultation star, along with other geometrical information defined in more detail below. This text is included in a separate plain text file on the SOM. 14 At lower right, a finder chart image (created using the plot finder image from the Python astronplan.plots package) is shown, with the event star marked by crosshairs. At the bottom of the page, a convenient summary of the observability of the occultation from all 13 observing sites is included: • The observing site code, name, and topocentric Earth location are shown.
13 SOM/events/Uranus/2028/Uranus 2028-12-29T17 39 23.210 20230528a.pdf 14 SOM/events/Uranus/2028/Uranus 2028-12-29T17 39 23.210 20230528a.txt • The observability of each individual ring event and the planet limb occultations is summarized. In time order, each of the ten Uranus rings is marked during ingress with a + if the ring was observable, given the usual altitude constraints.
• The ingress and egress planet occultations are marked, followed in time order by the egress rings. 15 For example, from PIC (Pic du Midi), all ingress and egress ring events were observable, but the grazing occultation chord missed the atmosphere.
• The next column lists the complete interval over which any marked events were predicted to be observable.
• We include a summary observed event code (OEcode) for each site, in the following format: PXYRxy, where X is set to i if the target planet/satellite (denoted by P) ingress limb event is observable and Y is set to e if the egress limb event is observable. Similarly, x is set to i if any ingress ring events (denoted by R ) are observable from the given site (unblocked by the planet and meeting the standard altitude criteria), and y is set to e if any egress ring events are observable. If the given events are not observable, the appropriate letters are set to n. In this example, the OEcodes for the PIC and KAV observations are PnnRie and PnnRne, respectively; from KAV, only the outer five rings are observable during egress. An OEcode of PnnRnn indicates that neither the planet nor any ring occultations were observable for the site in question, such as PAL for this example.
For each site that has an OEcode indicating that a planet/target limb and/or ring occultation is observable, we include a separate page in the SOM PDF file that provides additional detailed information about the geometric circumstances of these events. Figure B2 shows this page for the predicted Pic du Midi observations of the 2028-12-29 Uranus event. Inset figures showing the Earth from Uranus and the altitude of the target and sun over time are included, available at full resolution in the SOM. The text shown includes details of the occultation event and included as a separate text file in the SOM. 16 At the bottom of the page, we include detailed predictions for each ring event and planet limb that intersects the sky plane chord for the occultation as observed from this site: • For each listed ring, we computed the ingress (I) and egress (E) predicted event times. (For Uranus, we use the full eccentric and inclined ring orbital elements for the rings, taken from French et al. (2023b); for the other planets, we assume circular and equatorial ring orbits).
• The UTC time of each predicted event is given, along with the altitudes of the target object and sun at the event time, the ring plane radius probed (taking into account the orientation of the possibly inclined, eccentric ring at the observed time and accounting for general relativistic bending by the oblate planet), and the ring plane radial velocity, labeled as r-dot, negative for ingress and positive for egress.
• If the planet occultation is observable, we include the predicted occultation time assuming the planetary shape/oblateness as specified in the kernel file pck00010.tpc. Our atmospheric event times do not take into account the refractive bending of the atmospheric half-light ray that typically amounts to one atmospheric scale height.
• Ring events that are blocked by the planet are marked with a b in cases where the rings are viewed nearly edge-on and the occultation sky plane chord intersects the rings only when in the shadow of the planet (not applicable in this instance).

C. MACHINE READABLE TABLES, LATEX SOURCE AND TYPESET FILES
The complete prediction list for each target is contained in both machine-readable and typeset form. The SOM/tables/ directory contains subdirectories for each target, within which is a single machine-readable file in the form support by the American Astronomical Society journals and described at https://journals.aas.org/mrt-overview/. Also included are the LaTeX source files used to typeset the tables for each target, and a PDF file containing the typeset tables. These make use of the document class aastex631.cls, provided in each target subdirectory.

D. EXAMPLE OCCULTATION SEARCHES
The body of this paper contains only a small subset of the full list of predicted events contained in the SOM. As part of the SOM documentation, we provide two example programs written in Python3 that perform searches of the entire database for occultations that match requested criteria. To run these example codes, users should first download the entire SOM repository to their local machines and then navigate to the SOM/doc/ directory. Both programs are provided as Python source files *.py and as Jupyter notebooks *.ipynb, with sample output files *.out produced by running the codes in their default configurations. The codes are intended to be illustrative only, and can be modified to conduct more sophisticated searches.

D.1. Example 1 -find selected occultations by geographical region
In the first example, the user specifies the following search criteria: • The list of targets to search • The corresponding upper limits on the K magnitude for each target • The range of dates for the search • The geographical regions to search (see Table 2 in the main body of the paper) Additional options are included that control the output of the search. In its default mode, the output file produce by the program includes: • A list of the available quantities in the Python table read from the Machine Readable (MR) file for each target • A summary of the requested search criteria • For each occultation found, a listing of the summary text file of observing circumstances for all sites • The SOM pathnames for the summary PDF and text files for each event • The summary PDF file is opened for user viewing for each identified occultation In its tersest mode, the default search results in the following output: ********** Contents of EventSearchExample1.out **************** Results of EventSearchExample1.