The Transition Region And Coronal Explorer (TRACE)

The objectives and the characteristics of TRACE, selected as a NASA small explorer mission for development and flight in late 1997, is presented. The TRACE science investigation explores the connections between fine-scale magnetic fields and the associated plasma structures on the sun. The instrument collects images of solar plasmas at temperatures from 10(exp 4) to 10(exp 7) K, with an arc second spatial resolution and good temporal resolution and continuum. TRACE and SOHO will gather simultaneous, digital measurements of all temperature regimes of the solar atmospheric, in both high-resolution imaging and spectroscopy, and magnetogram to photosphere. The 30 cm aperture TRACE telescope uses three normal-incidence coatings for the extreme ultraviolet and one for the ultraviolet on quadrants of the primary and secondary mirrors. Interference filters isolate five different ultraviolet bands. The images are aligned and internally stabilized against spacecraft jitter. TRACE will be launched into a sun-synchronous orbit, allowing continuous observing for eight months of the baseline one-year mission. It will be operated in coordination with the SOHO experiment operations facility.