Planet matching and orbit determination in multi-planet systems for exoplanet direct imaging

Abstract

A key aspect of the search for earth-like exoplanets with direct imaging, is determining if the exoplanet is in the habitable zone. For mission design of potential future direct imaging missions, such as HabEx and LUVOIR, an efficient cadence of observations is needed. Previous work has shown that three epochs, spanning more than half a period, is the minimum to determine orbital parameters to 10%. One aspect that still needs improvement is the ability to fit multiple planets with limited prior information about which planet is which. Since data from direct observations is expected to consist of multiple objects at each epoch, looking at each epoch separately is not sufficient to decide whether 1) a detected object is part of an exosolar system and 2) which planet it corresponds to. Existing multi-planet trajectory matching libraries, such as “Orbits For The Impatient” (OFTI), currently require the user to specify which data points belong to which planet. This assumes that the user has already matched true-positive detections to planets. Additionally, this planet matching between detected objects needs to be taken into account when assessing the impact of observation scheduling on the accuracy of trajectory estimation. To address this need for fitting orbits to multiple objects with limited knowledge, we propose an approach that uses a Monte Carlo study of different observation schedules and planetary systems. For each case we automatically match observations to planets and check the accuracy of the match. By considering a large number of such cases, we provide constraints on the number of observations and their spacing necessary to “deconfuse” the detections. We present preliminary planet matching success rates for several observation schedules based on simulated planetary systems and assess the accuracy of trajectory fitting combined with OFTI.