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The study of cometary composition is important for understanding our solarsystem's early evolutionary processes. Carbon dioxide (CO2) is a commonhypervolatile in comets that can drive activity but is more difficult to studythan other hypervolatiles due to severe telluric absorption. CO2 can only bedirectly observed from space-borne assets. Therefore, a proxy is needed tomeasure CO2 abundances in comets using ground-based observations. The fluxratio of the [O I] 5577 A line to the sum of the [O I] 6300 A and [O I] 6364 Alines (hereafter referred to as the [O I] line ratio) has, with some success,been used in the past as such a proxy. We present an [O I] line ratio analysisof comet 45P/Honda-Mrkos-Pajdu\v{s}\'akov\'a (HMP), using data obtained withthe Tull Coud\'e Spectrograph on the 2.7-meter Harlan J. Smith telescope atMcDonald Observatory, taken from UT February 21-23, 2017 when the comet was atheliocentric distances of 1.12-1.15 AU. HMP is a hyperactive Jupiter familycomet (JFC). Icy grains driven out by CO2 sublimation have been proposed as adriver of hyperactivity, but the CO2 abundance of HMP has not been measured.From our [O I] line ratio measurements, we find a CO2/H2O ratio for HMP of 22.9+/- 1.4%. We compare the CO2/H2O ratios to the active fractions of the ninecomets (including HMP) in the literature that have data for both values. Wefind no correlation. These findings imply that CO2 sublimation driving out icygrains is not the only factor influencing active fractions for cometary nuclei.

Inferring the CO2 Abundance in Comet 45P/Honda-Mrkos-Pajdu\v{s}\'akov\'a  from [O I] Observations: Implications for the Source of Icy Grains in  Cometary Comae