A new type of ion trap is used to measure the radiative lifetime of the NO+(a (3)Sigma(+)) metastable state. The ion trap is designed to store ion beams with an energy of a few keV and is well suited for the study of metastable states. The measured value for the radiative lifetime is tau(r)=760+/-30 ms, in good agreement with the last experimental values of Calamai and Yoshino [J. Chem. Phys. 101, 9480 (1994)], and with the theoretical value of Kuo et al; [J. Chem. Phys. 92, 4849 (1990)].