[1] It would have studied the Sun during its solar maximum, the last before the beginning of the Orion program.
The Solar Sentinels were proposed to be part of the NASA program Living With a Star.
This would be a challenge to scientists and engineers working on these probes, as this is one-fourth the distance between the Earth and the Sun.
The Near Earth Sentinel (NES) would study the solar corona in UV and visible light.
It would have been part of a group of four missions, including the Solar Dynamics Observatory and the Geospace missions (Radiation Belt Storm Probes and Ionosphere-Thermosphere Storm Probes), from the Living With a Star program.