The measurement of UHECR spectrum with the HiRes experiment in stereo mode

In this paper, the energy spectrum of UHECR with energy above 1018.2eV has been measured with HiRes detector in stereo mode. The cosmic ray events reconstruction has been presented briefly. A new direction reconstruction method has been introduced. The resolution of arrival direction is about 0.44 degree and the energy resolution is about 10%. The detector aperture is studied in detail, and an aerosol free aperture is given. At last, the result on the UHECR spectrum is presented and its uncertainty is discussed.