The Polarized Radiation Interferometer for Spectral disTortions and INflation Exploration (PRISTINE) is a space mission which has been recently proposed to answer the ESA F-mission call, aimed at addressing two key questions of the ESA Cosmic Vision 2015 – 2025 programme:
1) What has powered inflation? and
2) How did the Universe evolve?
PRISTINE will address question 1 by mapping the Cosmic Microwave Background (CMB) anisotropies in temperature and polarisation, hence allowing to measure the large scale polarisation patterns caused by relic gravitational waves produced during inflation. Question 2 will be addressed by measuring the CMB spectrum with two orders of magnitude improvement over the limits obtained with the COBE/FIRAS instrument in 1992.