Brown et al (2024) recently presented a search of the publicly available Pan-STARSS1 (PS1) data for “Planet Nine” using known asteroids as a means of characterizing the depth and completeness of the search. Although this method is effective, it does have limitations. One can only calibrate the search where the sky-plane density of asteroids is high enough to permit a reliable estimate of the detection efficiency. Although hundreds of asteroids can appear in an individual PS1 exposure near the ecliptic, there are relatively few asteroids with very high inclinations. Thus, a calibrated search of regions at high ecliptic latitudes requires a different method.
Injecting a sample of synthetic PSF-matched, moving sources directly into the discovery images and re-reducing the data before carrying out the search, the gold standard approach, is not computationally feasible given the volume of PS1 data. However, if we had a means of determining the likelihood that a candidate synthetic source, of a given brightness, sky-plane location, and focal plane location, would be detected and recorded by the Pan-STARRS Image Processing Pipeline (IPP), this would be essentially equivalent to injecting synthetic sources into the images. Fortunately, nearly all of the ingredients needed for this are provided, on a per-image basis, by the IPP. We present our results on developing and using this approach to complete a characterized search for TNOs in Pan-STARRS1 data. This method could also be used to place meaningfully limits on the number of distant dwarf planets and extreme TNOs remaining to be discovered in the Pan-STARRS data, as well as the number of interstellar comets.
A catalog-based approach to characterizing searches will be increasingly important for surveys such as Rubin, Euclid, and Roman, for which injecting synthetic moving sources directly into the images will be even more challenging.