Cosmology studies with GRB afterglows

GRB afterglows close to their peak intensity are among the brightest sources in the sky. We discuss how GRB optical-to-X-ray afterglows can be used as probes of the metal enrichment of the interstellar matter in the GRB host galaxies and of the heating history of the intergalactic matter in filaments and outskirts of clusters of galaxies along the line of sight. The key points of the proposed observation strategy are: 1) prompt GRB observations (from minutes to a few hours); 2) coordinated O-UV and X-ray observations; and 3) high resolution (1,500-6,000 in the 0.1-1 keV band and >10,000 in the OUV).