Tandem-L is a challenging bi-static L-band SAR mission with the goal to provide substantial contributions to the better understanding of Earth system dynamics. Two identical 3-ton satellites proposed to launch in 2024 will be operated in close formation. Featuring latest digital beamforming techniques in combination with a large deployable reflector will enable SAR acquisitions with increased swath width and imaging resolution. Tandem-L will provide vital information for solving pressing scientific questions in the biosphere, geosphere, cryosphere, and hydrosphere. This paper elaborates on the challenging navigation and formation control requirements as derived from the mission objectives. The focus is on the orbit control strategy foreseen to meet the large and frequent formation adjustments implied by the observation concept. The optimized formation geometries and schedule are presented proofing the feasibility of this ambitious formation-flying mission.