From the TRICE-2 Investigations to the TRACERS Mission.

On the morning of December 8, 2018, two sounding rockets were launched into the northern hemisphere cusp region to investigate the spatial and temporal nature of cusp structures. The two rockets, designated Twin Rockets to Investigate Cusp Electrodynamics 2 (TRICE-2), consisted of a high- and a low-flyer rocket launched two minutes apart. The TRICE-2 mission was a pathfinder for the upcoming Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) mission and carried almost identical payloads to those proposed for the twin spacecraft of the TRACERS mission. Results from the TRICE-2 mission are summarized, including observed cusp features (low energy ions in the cusp, overlapping cusp ion dispersions and cusp ion signatures) and the connection of the cusp structures to ionospheric convection cells, provided by SuperDARN radar observations, to show the advantages of coordinated space and ground-based observations. A description is provided for how these results - and those of other experiments which made measurements of particles and waves in the cusp and in the dayside magnetosphere - have guided the science objectives of the TRACERS mission.