Multiyear Ground-based Survey Photometry of Active Comet 103P/Hartley 2 and Centaur (2060) Chiron: A Tale of Two Comets in the Pre-LSST Era

Comets and Centaurs trace the evolution of trans-Neptunian objects (TNOs) into the inner solar system. Their activity reflects the interplay between volatile sublimation, dust dynamics, and, in some cases, ring scattering. Yet the long-term behavior of individual objects remains less constrained. To probe this evolutionary transition, we use wide-field survey photometry from the Asteroid Terrestrial-impact Last Alert System (ATLAS), Zwicky Transient Facility, and targeted Las Cumbres Observatory observations of the Jupiter-family comet (JFC) 103P/Hartley 2 during its 2023/24 apparition, and the Centaur (2060) Chiron across 2020–2025, including its 2021 outburst. For 103P, heliocentric activity slopes are asymmetric about perihelion, with a steep inbound index ( n r , pre = − 3.48 ± 0.08 ) and flatter outbound value ( n r ,post = −1.16 ± 0.04), consistent with enhanced relative dust contribution postperihelion. With reduced brightness versus prior apparitions, this behavior matches reported secular fading trends. Dust mass-loss rates are ∼4–16 kg s −1 for assumed grain properties. Colors exhibit a blueward trend near perihelion, consistent with enhanced gas contamination of the g band, with possible phase-dependent scattering. Periodogram analysis recovers a ∼18.7 hr activity-linked period near perihelion. For Chiron, subtracting a quiescent baseline reveals exponential decay from the 2021 outburst on a ∼1.4 yr timescale. Seasonal phase curves flatten from β o = 0.150 ± 0.034 mag deg −1 in 2021 to ≲0.09 mag deg −1 by 2023–2025, converging with quiescent behavior. Broadband colors remain unchanged at ATLAS ( c − o ) = 0.22 ± 0.09 mag. The extended duration of this activity suggests a new epoch of persistent, low-level activity and/or evolving ring scattering. These two objects bracket the TNO-to-JFC evolutionary sequence, with 103P near the volatile-depleted end, and Chiron still volatile-rich and capable of episodic activity.