Jorge Juan
Spanish naval officer and scientist (1713-1773) who, with Antonio de Ulloa, served on the Franco-Spanish geodesic mission to Quito (1735-1744) that measured a degree of the meridian at the equator and helped settle the shape of the Earth. Their published account was translated across Europe; their confidential report on colonial abuses is part of the record too.
Why this wins its question: The equator mission is told in English as La Condamine's story; the Spanish officers who co-ran it and published its fullest account are supporting cast. This object binds their role to the modern history of the expedition and to their own digitized 1748 account.
Claims
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Jorge Juan and Antonio de Ulloa were the Spanish scientific officers attached to the Franco-Spanish geodesic mission to the Quito region (1735-1744), which measured an arc of meridian at the equator to determine whether the Earth is flattened at the poles.
The mission's measurements, together with the Lapland expedition, confirmed the Newtonian oblate figure of the Earth, and Juan and Ulloa's published account of the voyage (1748) circulated in European translation.
Juan and Ulloa separately delivered a confidential report to the crown documenting administrative abuses against the Indians in Peru — evidence that the imperial system produced its own internal critics with official standing.
Juan later applied the mission's scientific capital to Spanish naval reform, in shipbuilding and in the teaching of exact sciences to naval officers.