The Extreme ultraviolet Coronal Mass Ejection and Coronal Connectivity Observatory (ECCCO) is a NASA Small Explorer Mission currently conducting a concept study.

The mission consists of a single spacecraft with two instruments, a wide-field extreme ultra-violet imager and a unique imaging EUV spectrograph. ECCCO’s observations would contribute to understanding the middle corona, the dynamics of eruptive events leaving the Sun, and the conditions that produce the outward streaming solar wind. "ECCCO will answer fundamental questions about the origins of the mass and energy flow that link the Sun to the outer corona and overall heliosphere, the 'bubble' of space encompassing the solar system 'inflated' by the solar wind."

• Katharine Reeves from the Smithsonian Astrophysical Observatory is ECCCO's Principal Investigator.
• Daniel Seaton from the Southwest Research Institute is ECCCO's Deputy Principal Investigator.