in fact it was his work in calculating the orbits of two comets from observations which had been made in 1532 and 1661 that led to his election to the académie des sciences . méchain's memoir on these comets was presented to the academy for the grand prix of 1782 and in it he showed, unexpectedly, that they were not two appearances of the same comet but indeed different comets.

This is all lower case. Can you fix that?
In fact it was his work in calculating the orbits of two comets from observations which had been made in 1532 and 1661 that led to his election to the Académie des Sciences . Méchain's memoir on these comets was presented to the Academy for the Grand Prix of 1782 and in it he showed, unexpectedly, that they were not two appearances of the same comet but indeed different comets.