The Improved Limb Atmospheric Spectrometer-II (ILAS-II) is a satellite-borne solar occultation sensor developed by the Environment Agency of Japan for measuring ozone, other gas species, and aerosols/PSCs that are related to the ozone chemistry in the stratosphere. The ILAS-II instrument will be installed on board the ADEOS-II satellite that will be put into a sun-synchronous polar orbit by the National Space Development Agency of Japan (NASDA) in November 2001. The ILAS-II measurement is a continuation of that of ILAS on board ADEOS, which obtained data from November 1996 to June 1997. The main components of ILAS-II are four spectrometers and a sun-edge sensor. The spectrometers include an infrared spectrometer to cover about 6 to 12 micrometer in wavelength, a mid-infrared spectrometer 3 to 5.7 micrometer, a narrow band spectrometer around 12.8 micrometer, and a visible spectrometer 753 to 784 nm. The first two spectrometers are used for measuring gas and aerosol/PSC profiles, while the third is for ClONO2 measurements. The visible spectrometer is used for pressure/temperature measurements as well as aerosol/PSC extinction coefficients. The ILAS_II instrument has already completed its development and environment tests, and now is undergoing satellite system environment tests at NASDA. This paper outlines the characteristics and performance results from laboratory tests along with the present status of development of its data processing algorithm and operational software.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.