Pre-encounter update on (486958) 2014MU69 and occultation results from 2017 and 2018

Following success of three stellar occultations in 2017 involving the New Horizons extended mission target: (486958) 2014 MU69, we identified one more opportunity for a stellar occultation prior to encounter on 2019 Jan 1. This latest event was predicted for 2018 August 4, visible from northern South America and north-central Africa. The star was relatively bright at G=13.4, from Gaia DR2. The final prediction reached a 1σ crosstrack uncertainty of 13 km (0.4 mas). We will present results from the 2018 stellar occultation campaign involving 24 portable systems deployed by the New Horizons project. Additional contributions will be discussed, so far from Mexican and Colombian astronomers. These observations, when combined with HST astrometry are important for the navigation of New Horizons to its upcoming encounter. Furthermore, the albedo and shape are directly constrained thus providing essential input for optimizing the encounter sequence. One of the more critical things we would like to know is if the body is a single object or a close binary as is very common in the Cold Classical Kuiper Belt. The observations from 2017 will be reviewed for the constraints provided and a new occultation dataset is highly likely to either show two objects or essential rule out that option. This work and especially the latest occultation effort would not have been possible without the financial support of the New Horizons mission, NASA, CNES, imaging data from the Hubble Space Telescope, astrometric support from the Gaia mission, and logistical support from Senegal as well as assistance from the US Embassies in Dakar and Bogota.