The recently selected ESA mission Comet Interceptor should, in the early 2030s, encounter a long period comet (LPC) or interstellar object entering the inner Solar System for the first time. However, in case no suitable LPC is discovered in time, a list of backup targets has been assembled (Schwamb et al., RNAAS 4, 21, 2020), which contains known short period comets. Although these targets have well-known orbits which makes them suitable backup targets from a mission-planning point of view, their compositions and nucleus properties are still poorly characterized.
We are conducting new imaging and spectroscopic observations of these backup targets to provide the mission science team with necessary information on the potential mission targets and to assist mission design in planning for specific encounter scenarios. The observations will also advance ground-based studies of comets by providing high-quality spectra of the brightest targets when they are near perihelion, and constraints on distant activity and/or nucleus properties when they are far from perihelion. We have been awarded dedicated time for imaging and spectroscopy since semester 2020B on the 2.5-m Isaac Newton Telescope in La Palma and since 2021A on the 4.1-m SOAR telescope in Chile, allowing us to monitor the targets regardless of hemisphere. For the brighter objects, we are also obtaining medium resolution IFU spectroscopy with MUSE on the 8.2-m VLT and imaging on the 1-m Las Cumbres Observatory telescope network. Successful observations so far have included spectroscopy and imaging of 7P/Pons-Winnecke, and imaging of 8P/Tuttle and P/2016 BA14. As expected, 26P/Grigg-Skjellerup, 73P/Schwassmann-Wachmann 3, 189P/NEAT, 289P/Blanpain, and 300P/Catalina were not detected in deep imaging. Observations will continue in semester 2021B, and we will report on our ongoing analyses.