SPECtre: A SPECtro-heliograph for the transition region

The SPECtro-heliograph for the Transition REgion (SPECTRE) experiment is one of the instruments of he Solar Heliospheric Activity Research and Prediction Program (SHARPP) suite initially foreseen aboard the NASA mission Solar Dynamics Observatory (SDO) of the International Living With a Star (ILWS) program. The scientific objective of the SPECTRE experiment was to characterize the rapid evolution of plasma in the transition region of the solar atmosphere, producing full-disk 1.2 arcsec-resolution images of the solar atmosphere at the very critical 63 nm OV spectral line, characterizing a solar plasma temperature of about 250,000 K. Unfortunately, NASA very recently and unexpectedly, during the instrument Phase A study, decided not to proceed with the realization of SHARPP. The authors of this paper think that all the work done so far in the definition of SPECTRE should not be lost. So, they have decided to summarize in this paper the main characteristics of this instrument and the results of the analysis so far performed: the hope is that in a next future this work can be used again for realizing an instrument having similar characteristics.