Narrow-band photometry of comet 9P/Tempel 1 from Deep Impact

In this work, we processed narrow-band images of comet 9P/Tempel 1 using data taken with the Medium Resolution Imager (MRI) on board the Deep Impact spacecraft through comet specific filters, i.e. CN(387 nm), OH(309 nm), C2(514 nm)[1], and two continuum filters (Ultraviolet at 345 nm and Green at 526 nm). These filters were designed to detect the emission from gas species and the reflected sunlight from the dust in the coma. All images were pre-processed using the standard Deep Impact pipeline which includes bias and dark subtraction, flat fielding [2]. Our imaging analysis includes images taken before and after the impact in order to reveal the coma morphology. We used the continuum filters to subtract the dust contamination from the gas images. From this data set, we derived the 2D color maps of the dust, constructed by comparing different continuum color filter images, and continuum removed column density maps of C2, CN, and OH. In addition, we used an inversion model to derive the potential surface activities from column density images of different species in the coma [3], assuming that solar illumination modulates the potential activity to produce gas emissions.

[1] Farnham, T. L., Schleicher, D. G., & A’Hearn, M. F. 2000, Icarus, 147, 180

[2] Klaasen, K. P., A’Hearn, M. F., Besse, S., et al. 2013, Icarus, 225, 643

[3] Combi, M., Shou, Y., et al. 2020, Icarus, 335, 113421

Acknowledgements: All authors acknowledge support from NASA-80NSSC19K0245 (Discovery Data Analysis Program).