# # Program information file # PROGRAM_ID 2024B088 PROGRAM_TITLE C/2017 K2 in the Rearview Mirror: Do LPCs look the same inbound and outbound? PROGRAM_INV1 Theodore Kareta PROGRAM_INV2 Megan Firgard PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT comets PROGRAM_ABSTRACT_BEG C/2017 K2 [PANSTARRS, hereafter 'K2'] is a Long Period Comet [LPC] which reached perihelion in December 2022. K2 is best known for being detectably active at 24 AU from the Sun -- and probably as far 35 AU -- making it probably the most distant activity detected in a comet. LPCs are rarely discovered so far out and are rarely so bright, so K2 presents a rare opportunity to study how cometary activity works so far from the Sun. In this proposal, we seek to repeat observations made at the IRTF in 2021 at a heliocentric distance of 6.49 AU inbound at a similar distance outbound. Combined with an application of state-of-the-art models, this will provide constraints on how the size of ice grains, the overall iciness of K2's coma, and the distribution of dust grain sizes in the coma of K2 - and how it has evolved from 2021 to 2024. This will provide constraints on how distant activity in comets works and thus contextualize many other observations made of the comet as it approached perihelion. PROGRAM_ABSTRACT_END