Science Through Shadows: How Astronomical Alignments Reveal the Universe
On March 27, 2022, a star near Polymele—one of the Trojan asteroid targets on NASA’s Lucy mission—blinked out. Twenty-six teams of professional and amateur astronomers had spread across the observation corridor to catch it. Fourteen teams recorded the occultation exactly as expected. Two did not. Those two outliers, once cross-checked against the rest of the dataset, revealed that the asteroid had a satellite: a roughly 5 km, non-spherical body, orbiting approximately 200 km away. The satellite was too close to Polymele to be seen by Earth-based or Earth-orbiting telescopes without the precise shadow geometry that an occultation provides. No direct imaging method had caught it.
A year later, on Feb. 3, 2023, more than 100 portable telescopes spread across two continents observed another occultation of Polymele—this time with the goal of precisely characterizing the asteroid’s shape before Lucy’s scheduled 2027 flyby. The 2022 discovery had given the team a target. The 2023 campaign gave them geometry. Both campaigns used the same basic technique: a moving object casts a shadow across Earth’s surface as it passes in front of a star, and coordinated observers across the shadow corridor capture the shadow’s profile in timing residuals.
The reason this technique works where direct imaging fails is not complicated once you understand the geometry. No single telescope, however large or expensive, can be in two places at once. What you need is a distributed sensor network, coordinated in time, spread across geography. The more nodes you field, the more chances you catch an anomalous shadow trajectory. That is a measurement architecture problem, not a resolution problem.
That geometry is the actual engineering story behind NASA’s Science Through Shadows program, a public outreach initiative produced by the Fiske Planetarium at the University of Colorado Boulder. The program received a $2 million NASA Science Activation grant, awarded to Fiske and Douglas Duncan, an emeritus CU Boulder professor who directed the planetarium from 2002 to 2018 and serves as principal investigator. John Keller, Fiske’s current director, is the program’s operational lead. The stated mission is STEM outreach—videos distributed to more than 260 planetariums worldwide, portable planetarium units for underserved communities, eclipse prep campaigns. What the program also produces, quietly, is a field-tested argument that citizen science networks are legitimate precision measurement infrastructure.
John Keller put it plainly in the CU Boulder grant announcement: occultation precision surpasses even Hubble in certain geometries. That sounds counterintuitive until you think about what Hubble is actually doing—collecting photons from a fixed orbital vantage point. For shape characterization and topographic profiling of small solar system bodies, the occultation technique measures the shadow’s limb directly, giving you an edge profile without needing to resolve the object at all. It is not better imaging. It is a different measurement, and it does not require an $11 billion space telescope.
The Polymele discovery came from the Lucy mission occultation campaign. Marc Buie, occultation science lead at the Southwest Research Institute, a San Antonio-based nonprofit that manages the Lucy planetary science mission, organized the deployment. Lucy is en route to study Jupiter Trojan asteroids—primitive bodies thought to be relics of early solar system formation—with Polymele scheduled for a 2027 flyby. The 2022 satellite discovery was a side effect of the shape characterization effort: not something spotted in post-processing, but physically recorded by two telescopes that happened to be positioned in the corridor where the satellite’s own shadow happened to fall. A fact about the solar system, written in timing residuals.
On the heliospheric side of the program, the instrumentation scales up considerably—and the measurement problems are different.
NASA’s Parker Solar Probe, managed by the Johns Hopkins Applied Physics Laboratory, completed its closest solar approach on Dec. 24, 2024: 3.8 million miles from the solar surface at 430,000 mph. The spacecraft’s thermal protection system—a carbon foam heat shield approximately 4.5 inches thick—maintained a room-temperature interior while the shield exterior approached 1,800°F. The shield is rated to 2,600°F, which meant roughly 800 degrees of thermal margin at the mission’s most demanding pass. Project scientist Nour Rawafi and mission systems engineer John Wirzburger, both at APL, confirmed the spacecraft survived in optimal condition and has since completed additional perihelion passes in March and June 2025.
The science from the December 2024 closest approach arrived in a paper published in Astrophysical Journal Letters in December 2025. Angelos Vourlidas, WISPR instrument scientist at APL, reported that Parker had directly photographed solar material falling back toward the sun after a coronal mass ejection—what researchers call inflows. It was the first time scientists could directly measure the speed and size of those inflow blobs. The practical implication: magnetic field recycling from one CME can nudge a subsequent CME’s trajectory by a few degrees—enough to determine whether it hits Mars rather than misses. For spacecraft and personnel in transit, the difference is not academic.
PUNCH—Polarimeter to Unify the Corona and Heliosphere—launched March 11, 2025 on a SpaceX Falcon 9 and addresses a 60-year measurement gap between the solar corona, which Parker studies up close, and the established solar wind that interplanetary probes have sampled since the 1960s. The transition zone where coronal material becomes solar wind has historically been out of reach: too distant for coronagraphs, not yet structured enough for in-situ solar wind instruments. PUNCH’s four small satellites, also designed and operated by Southwest Research Institute, are deployed in Sun-synchronous low Earth orbit, spread along the day-night boundary for a continuous wide-angle view of the inner heliosphere. First light images of coronal mass ejections were presented at the American Astronomical Society meeting in Anchorage in June 2025.
Parker and PUNCH now provide the first simultaneous two-point observation of the full inner heliosphere. Parker measures conditions close to the source. PUNCH tracks propagation outward across the wide field. A CME that Parker probes near the sun can be followed through PUNCH’s imaging as it expands. That is sensor fusion applied to space weather—the kind of complementarity that requires no single instrument to do everything, just coordinated coverage across the geometry of the problem.
The eclipse campaigns sit closer to the distributed network model than to the single-instrument model. The April 2024 total solar eclipse produced measurement output that scales differently than aperture.
The Citizen Continental-America Telescopic Eclipse (CATE) 2024 effort deployed 35 teams along the totality path, collecting more than 47,000 corona images in polarized light. NASA operated two WB-57 high-altitude aircraft at 50,000 feet, extending the observation window for onboard instruments to six minutes and 20 seconds of totality—nearly double what any fixed ground station experienced. HamSCI, the Ham Radio Science Citizen Investigation network, enlisted 6,350 operators and collected 52 million data points on ionospheric response to the eclipse passage. The Nationwide Eclipse Ballooning Project, which put more than 800 students in the field, confirmed the presence of atmospheric gravity waves generated by the traveling shadow. These are not outreach activities that happen to produce incidental data. They are measurement campaigns that happen to involve a lot of people.
The NASA Science Activation framework behind all of this—which also supports portable planetarium distribution and STEM programming at museums in Oakland, California, and Detroit, Michigan, in partnership with NASA Astro Camp and the Houston Museum of Natural Science—makes an implicit claim worth stating plainly: the cost floor for precision astronomical measurement has dropped far enough that distributed portable networks are now competitive with single-aperture instruments for specific measurement geometries. That is not a claim against space telescopes. It is a claim about complementarity.
You fly the large space telescope to see what only resolution can reveal. You field the distributed network when the physics demands coverage across geography rather than concentration of aperture. The Polymele satellite was worth finding regardless of how it was found. The fact that portable ground-based telescopes found it—while direct imaging could not, because the satellite was too close to Polymele to resolve without an occultation—is just the answer to the question of which instrument is the right tool for that particular job. The answer changes depending on the geometry of what you are trying to measure. Hardware people usually figure that out eventually.