Duration: 12 months
Potentially hazardous asteroids (PHA) present challenging subjects for physical characterisation. While normally we can wait until a small solar system body of interest arrives at favourable viewing geometry with PHAs we are likely not to be afforded such luxury. Due to spacecraft mission timelines and for planetary defence purposes we might need to observe our targets in unfavourable conditions, such as across crowded star fields. The direct motivation for this idea is the upcoming observing campaign for asteroid Didymos and its moon Dimorphos ahead of the arrival of the ESA Hera mission in 2026. In order to constrain the changing mutual orbit of the the bodies we will need to perform observations in mid-2024 while the asteroids cross the galactic plane. We have been awarded time with the ESO NTT telescope to do this. We plan to deal with photometry of PHA in such a crowded field by removing contribution from background stars, which will often be brighter than the asteroid, through new difference image analysis (DIA) tools. The state-of-the art DIA tools have been developed to deal with images from large surveys, using image templates from extensive campaigns. Such template images are later removed from science images to seek for changes in the star field indicating transient events. Creation of DIA template images can take months, for example the upcoming LSST survey is not expected to complete template development until the end of year 1 of operations. We will develop an urgently needed more quick-response tool, tailored to the medium-sized telescopes we will be using for PHA characterisation.
