Transition Region And Coronal Explorer

Transition Region and Coronal Explorer (TRACE, or Explorer 73, SMEX-4) was a NASA heliophysics and solar observatory designed to investigate the connections between fine-scale magnetic fields and the associated plasma structures on the Sun by providing high-resolution images and observation of the solar photosphere, the transition region, and the solar corona. A main focus of the TRACE instrument was the fine structure of coronal loops low in the solar atmosphere. TRACE was the third spacecraft in the Small Explorer program, launched on 2 April 1998, and obtained its last science image on 21 June 2010, at 23:56 UTC. It reentered the atmosphere 600 km south of Perth, Australia on 18 July 2025, at 11:37 UTC.

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