Initial Characterization of Active Transitioning Centaur, P/2019 LD2 (ATLAS), Using Hubble, Spitzer, ZTF, Keck, Apache Point Observatory, and GROWTH Visible and Infrared Imaging and Spectroscopy

We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD2 taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD2 has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by similar to 100 mu m-scale dust ejected at similar to 1 m s(-1) speeds with a similar to 1 ' jet pointing in the southwest direction. LD2 experienced a total dust mass loss of similar to 10(8) kg at a loss rate of similar to 6 kg s(-1) with Af rho/cross section varying between similar to 85 cm/125 km(2) and similar to 200 cm/310 km(2) from 2019 April 9 to 2019 November 8. If the increase in Af rho/cross section remained constant, it implies LD2's activity began similar to 2018 November when within 4.8 au of the Sun, implying the onset of H2O sublimation. We measure CO/CO2 gas production of less than or similar to 10(27) mol s(-1)/less than or similar to 10(26) mol s(-1) from our 4.5 mu m Spitzer observations; g-r = 0.59 0.03, r-i = 0.18 0.05, and i-z = 0.01 0.07 from GROWTH observations; and H2O gas production of less than or similar to 80 kg s(-1) scaling from our estimated C-2 production of Q(C2) less than or similar to 7.5 x 10(24) mol s(-1) from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD2 is similar to Jupiter-family comets having close encounters with Jupiter within similar to 0.5 Hill radius in the last similar to 3 y and within 0.8 Hill radius in similar to 9 y. Additionally, 78.8% of our orbital clones are ejected from the solar system within 1 x 10(6) yr, having a dynamical half-life of 3.4 x 10(5) yr.