As the Russian/Ukrainian Dnepr launch vehicle and corresponding launch services could no longer be provided by the Russian/Ukrainian International Space Company Kosmotras (ISCK), the joint NASA-GFZ Joint Steering Group has decided to exchange the GRACE-FO launcher. The corresponding contract was signed on  November 14, 2016 by the Board of GFZ and Iridium Satellite LLC. It stipulated a "Rideshare" between GRACE-FO and five Iridium-Next satellites on a Space-X Falcon-9 from Vandenberg Air Force Base in California. This also included a contract with Airbus Defence and Space who built the necessary Multi Satellite Dispenser and performed the Launch Service Management under contract of GFZ. The GRACE-FO satellites were finally launched on May 22, 2018, into a co-planar orbit with the following (GRACE-like) orbital parameters:  

• a = 500 ± 15 km
• i = 89.0 ± 0.1°
• e < 0.0025

Further information can be found here.