He began his career in 1981 as a researcher at the Astronomy Laboratory, French National Scientific Research Center, where he worked on the European scientific satellites project Hipparcos and ISO.
In 1985 he joined the Department of Industry and was assigned to the Space Office where he was particularly in charge of relations with the space industry.The Minister for the Postal Service, Telecommunications and Space appointed Le Gall as advisor for space affairs in 1985.
In this position, he participated in the definition of CNES and ESA programs.
In 1993, he joined Novespace, a subsidiary of CNES, of which he was Managing Director.
Le Gall was appointed as CNES Deputy Managing Director in 1996.
In this function, he was the French Representative to the ESA.
In 1998, he was appointed as Chairman and CEO of Starsem.In 2001, he joined Arianespace as COO.