(Proposal ID) S15B-141 (PI) Doi, Mamoru (Proposal Title) Testing for time-varying dark energy with z>1 Type Ia Supernovae (Abstract) A key goal of observational cosmology is to constrain the nature of dark energy through the detailed, accurate and unbiased measurement of the expansion history of the Universe. The SNe Ia luminosity-distance relation is determined by the dark energy density evolution, rho_{DE}(z). The existing ground-based z<1 sample place strong constraints on rho_{DE}(z) out to z~1. To confirm dark energy at z>1 and test the new BOA results, it is necessary to use SNe Ia at 11.3 SN Ia which will be observed by HST ToO orbits to guarantee at least two colors to correct SN light curve for reddening.