# # Program information file # PROGRAM_ID 2023A067 PROGRAM_TITLE SpeX observations of C/2022 E3 [ZTF] and C/2021 T4 [Lemmon]: Exploring the overall coma composition of comets PROGRAM_INV1 Ron Vervack PROGRAM_INV2 Neil Dello Russo PROGRAM_INV3 Boncho Bonev PROGRAM_INV4 Mike DiSanti PROGRAM_INV5 Erika Gibb PROGRAM_SCICAT comets PROGRAM_ABSTRACT_BEG Semester 2023A represents an excellent opportunity to observe two comets: C/2022 E3 [ZTF] and C/2021 T4 [Lemmon], hereafter E3 and T4, respectively. Our proposed study emphasizes four science objectives for which the IRTF/SpeX combination is ideal: [1] sample overall gas emission by observing strong but overlapping emissions between 2.8 and 4.2 um, [2] sample the dust continuum from 0.7 to 4.2 um to investigate the dust environment, [3] implement building a database of moderate-resolution comet spectra, and [4] help establish a greater context for all ground-based comet observations. Owing to its large spectral grasp, SpeX enables a survey of the overall 'organics' region between 3.2-3.6 um simultaneously with other gas emissions [e.g., H2O]. At the same time, measurements of the underlying continuum provide information on cometary dust grains and ice signatures, both of which are important in understanding formation conditions in the solar nebula. Because the resolution and wavelength grasp of JWST/NIRSpec and of most near-IR spacecraft instruments are comparable to [or less than] those of SpeX, a long-term database of SpeX comet observations will aid in the analyses and interpretation of such data, thereby addressing the IRTF's role in supporting NASA missions. Specific reasons for targeting these two comets are that E3 is both bright and a JWST target [private comm.], whereas T4 is fainter and represents an opportunity to explore the lower limit of the feasibility of SpeX comet observations, which could potentially expand the range of comets for which meaningful near-IR probes of coma chemistry are possible. To achieve our objectives, we will use the LXD-short and SXD settings of SpeX. Guidedog is sufficient for guiding, so MORIS is not needed. The 0.3 arcsec slit will be used for E3 and the 0.8 arcsec slit for T4. Our observing request includes two dates for each comet and totals 18.5 hours. PROGRAM_ABSTRACT_END