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# Program information file
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PROGRAM_ID           2023A061
PROGRAM_TITLE        iSHELL Studies of Bright Comet C/2022 E3: Multi-Molecule Coma Thermal Physics and Coordination with JWST
PROGRAM_INV1         Nathan Roth
PROGRAM_INV2         Neil Dello Russo
PROGRAM_INV3         Ron Vervack
PROGRAM_INV4         Michael DiSanti
PROGRAM_INV5         Boncho Bonev
PROGRAM_SCICAT       comets
PROGRAM_ABSTRACT_BEG
We propose using iSHELL to measure the composition and coma spatial distributions of volatiles in a dynamically new, bright Oort cloud comet C/2022 E3 [ZTF; hereafter E3] near closest approach in early February and in coordination with JWST in mid-February. Small geocentric distance [D=0.29 au] coupled with high intrinsic brightness and predicted strong outgassing will enable studies of inner coma thermal physics and the first coordinated comet studies between IRTF and JWST during its inaugural cycle, laying the foundation for future mission support. 

We will use three iSHELL settings [Lp1, M2, and a custom L-band setting] to fully and efficiently characterize the composition and coma thermal physics in E3, sampling multiple strong transitions of H2O, CO, OCS, H2CO, CH3OH, C2H6, CH4, HCN, NH3, and C2H2 during two epochs. 

Leveraging highly favorable observing geometry and comet brightness during Epoch 1, we will conduct a spatial-spectral study of CO, CH3OH, C2H6, CH4, HCN, and H2O near closest approach by mapping their column densities and rotational temperatures along the 15'' long iSHELL slit using two mutually orthogonal slit orientations, thereby testing mechanisms of molecular production and coma heating. These studies will improve our understanding of the thermal structure of comet comae using a comprehensive, multi-molecule approach.

In Epoch 2 we will conduct the first coordinated IRTF/JWST comet studies, cataloging molecular production in E3 on multiple dates bookending the JWST observations. iSHELL's long slit capability and high spectral resolution will enable highly complementary studies to JWST, recovering molecular emission beyond the 3''x3'' JWST field-of-view, providing a measure of absolute flux calibration, and removing spectral confusion between multiple cometary volatiles throughout the 2.9-5.0 um range. 

This work can only be achieved utilizing the large spectral grasp, unique daytime observing capability, and superior active IR-guiding of iSHELL.
PROGRAM_ABSTRACT_END