I thought this story was pretty amazing:
You will recall that after visiting Pluto in 2015, New Horizons was re-directed for an encounter with a Kuiper Belt Object - 2014 MU69.
Not much is known of this object, and getting spectral data, estimates of its size, etc is pretty challenging, because transits across stars are extremely rare. NASA came up with a way of creating an artificial transit - flying their 747 which is equipped with a 2.5 metre telescope on a path to create a transit, not visible from any other telescope:
http://www.theregister.co.uk/2017/07...orizons_visit/