Given the task definition and input, reply with output. In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.

Passage: Bouguer, La Condamine, Godin and their colleagues measured arcs of the Earth's curvature on the Equator from the plains near Quito to the southern city of Cuenca. These measurements enabled the first accurate determination of the shape of the Earth, eventually leading to the establishment of the international metric system of measurement. When an International Commission for Weights and Measures was convened in Paris to settle the true length of the metre, it adopted on 22 June 1799 a standard metre based on the length of the half meridian connecting the North pole with the Equator. The French Academy of Sciences had commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Mechain, lasting from 1792 to 1799, which attempted to accurately measure the distance between a belfry in Dunkerque and Montjuic castle in Barcelona at the longitude of Paris Pantheon. This portion of the Paris meridian was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator. The metre was defined as the ten-millionth of the half meridian's length extrapolated from a Earth's flattening of 1/334 obtained from the results of the survey by Delambre and Mechain combined with those of the Peru meridian arc as established by La Condamine and his colleagues.
Link Information: Jean Baptiste Joseph, chevalier Delambre (19 September 1749 19 August 1822) Question: Which astronomer who went on an expedition for the French Academy of Sciences was the oldest?
Answer: Pierre Mechain