Go to JPL Horizons. Table Settings: only need "20. Observer range & range-rate" AND "39. Range & range-rate 3-sigmas". RNG_3sigma = uncertainty range in km. (Soln.date: 6 April 2017 generates RNG_3sigma = 620915473 for 3 October 2019.)
"Sentry: Earth Impact Monitoring". NASA/JPL Center for NEO Studies. Retrieved 24 September 2024. (Use Unconstrained Settings to reveal impact probability below 1e-6)