Prospects of a New $L_5$ Trojan Flyby Target for the Lucy Mission

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Main Authors: Manzano, Luis E. Salazar, Gerdes, David W., Napier, Kevin J., Lin, Hsing Wen, Adams, Fred C., Frincke, Tessa, Marchi, Simone, Noll, Keith S., Spencer, John
Format: Preprint
Published: 2025
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author Manzano, Luis E. Salazar
Gerdes, David W.
Napier, Kevin J.
Lin, Hsing Wen
Adams, Fred C.
Frincke, Tessa
Marchi, Simone
Noll, Keith S.
Spencer, John
author_facet Manzano, Luis E. Salazar
Gerdes, David W.
Napier, Kevin J.
Lin, Hsing Wen
Adams, Fred C.
Frincke, Tessa
Marchi, Simone
Noll, Keith S.
Spencer, John
contents NASA's Lucy spacecraft is en route to conduct the first close encounter with Jupiter's Trojans. While most scheduled flybys lie in the $L_4$ cloud, the only $L_5$ target is the Patroclus-Menoetius binary. Since each flyby offers unique insights into target and population properties unattainable from Earth, we examine the feasibility of including an additional, yet unknown, $L_5$ target while minimizing the impact on Lucy's primary mission. We use the background $L_5$ Trojans brighter than the completeness limit to model their absolute magnitude, spatial, and orbital distributions. A semi-analytical approach estimates the number of Trojans accessible to Lucy for a given $Δv$ budget in both pre- and post-Patroclus scenarios. Our results indicate that, while it is unlikely that any suitable Trojan lies on Lucy's nominal path, a moderate $Δv$ investment ($35-50\,\mathrm{m/s}$) could enable a sub-kilometer ($500-700\,\mathrm{m}$) flyby prior to the Patroclus encounter. Post-Patroclus, the likelihood of a similar flyby is $\sim60\%$ for $Δv\sim$ 50 m/s. Simulations with synthetic Trojans reveal that potential targets cluster near the node opposite to the encounter window, producing an optimal search period in late 2026 for both scenarios. Surveying the densest $10\%$ of this region would require under 5 nights with Subaru/HSC or under 2 nights with Rubin, using shift-and-stack techniques. A successful sub-kilometric flyby would expand Lucy's Trojan target size range and provide new constraints on collisional evolution and the long-standing asymmetry in the $L_4/L_5$ clouds. This nodal-clustering strategy could guide target searches in future Lucy extensions or other planetary flyby missions.
format Preprint
id arxiv_https___arxiv_org_abs_2508_03687
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Prospects of a New $L_5$ Trojan Flyby Target for the Lucy Mission
Manzano, Luis E. Salazar
Gerdes, David W.
Napier, Kevin J.
Lin, Hsing Wen
Adams, Fred C.
Frincke, Tessa
Marchi, Simone
Noll, Keith S.
Spencer, John
Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
NASA's Lucy spacecraft is en route to conduct the first close encounter with Jupiter's Trojans. While most scheduled flybys lie in the $L_4$ cloud, the only $L_5$ target is the Patroclus-Menoetius binary. Since each flyby offers unique insights into target and population properties unattainable from Earth, we examine the feasibility of including an additional, yet unknown, $L_5$ target while minimizing the impact on Lucy's primary mission. We use the background $L_5$ Trojans brighter than the completeness limit to model their absolute magnitude, spatial, and orbital distributions. A semi-analytical approach estimates the number of Trojans accessible to Lucy for a given $Δv$ budget in both pre- and post-Patroclus scenarios. Our results indicate that, while it is unlikely that any suitable Trojan lies on Lucy's nominal path, a moderate $Δv$ investment ($35-50\,\mathrm{m/s}$) could enable a sub-kilometer ($500-700\,\mathrm{m}$) flyby prior to the Patroclus encounter. Post-Patroclus, the likelihood of a similar flyby is $\sim60\%$ for $Δv\sim$ 50 m/s. Simulations with synthetic Trojans reveal that potential targets cluster near the node opposite to the encounter window, producing an optimal search period in late 2026 for both scenarios. Surveying the densest $10\%$ of this region would require under 5 nights with Subaru/HSC or under 2 nights with Rubin, using shift-and-stack techniques. A successful sub-kilometric flyby would expand Lucy's Trojan target size range and provide new constraints on collisional evolution and the long-standing asymmetry in the $L_4/L_5$ clouds. This nodal-clustering strategy could guide target searches in future Lucy extensions or other planetary flyby missions.
title Prospects of a New $L_5$ Trojan Flyby Target for the Lucy Mission
topic Earth and Planetary Astrophysics
Instrumentation and Methods for Astrophysics
url https://arxiv.org/abs/2508.03687