Swarm constellation options Separation of Swarm-B and Swarm-A/C orbital planes B  A/C Keep separation in the range DLTAN 4h-8h (60-120 deg) as long as possible B  A/C Continue with the natural drift Separation of Swarm-A and Swarm-C orbital planes A  C Increase DRAAN 1.4 deg  2.8 deg or 10.0 deg “Inertial” pearl of strings (= same orbit) as close of possible “Earth fixed” pearl of strings (= same ground track). 20 seconds apart As close as possible Orbit altitude of B Keep Swarm-B at ~500 km for as long as possible Reach the 2030 solar minimum with Swarm-B Orbit altitude of A/C Reach the 2020 solar minimum with Swarm-A/C with an altitude around 350 km and then extend the mission as much as possible Reach the 2030 solar minimum with Swarm-A/C Maximal air drag density / acceleration

Option 4a Reach the 2020 solar minimum with Swarm-A/C with an altitude around 350 km and then stay as long as possible Solar Min Solar Max 450km 40kg 10kg 20km 10kg 10kg 8kg 40km 20kg 10kg 20kg 400km 60km 30kg 7kg 380km 5kg 42kg 50kg 25kg 33kg 350km 20kg All curves are for Swarm-A/C and 50th percentile case of solar activity