Derek M. Tournear is an American physicist and defense official that served as the director of the Space Development Agency.

[3] His doctoral supervisor was Elliott Bloom, and he completed his dissertation "Non-Quiescent X-ray Emission from Neutron Stars" in August 2003.

[6] Tournear was teamed with Ball Aerospace as the principal investigator for a DARPA Pulsar-based navigation program led by Darryll Pines.

Tournear supported the development and operation of Harris corporation entering into the small sat and prime contract business with the launch of a completely internally funded demonstration satellite named "HSAT".

[12] From May 2019 to August 2020, Tournear served as the Principal Director for space in the office of the Under Secretary of Defense for Research and Engineering in The Pentagon.

[18][19][20] Tournear earned a reputation at Space Development Agency as a leader who pushed the limits, making a lot of waves, and angering bureaucrats with a relentless pursuit of speed and warfighter focus.

No details of the cause for the removal and suspension was given, but Tournear had been no stranger to controversy as he sought to be a disruptive agent in the arena of defense satellite procurement.