As part of an ongoing investigation of airglow emissions of the upper atmosphere, an intensified CCD imaging spectrograph has been developed for a sounding rocket project called GEMINI (general excitation mechanisms in nightglow). The instrument, known as LISA (limb-imaging spectrograph for airglow), will be used to measure the limb profiles of some important nighttime airglow emission features. The observed limb profiles will be analyzed to provide atmospheric temperatures and density profiles of excited atomic and molecular species of interest to specific modelling problems in the mesopause and lower thermosphere. The GEMINI rocket is to be launched from White Sands Missile Range, New Mexico, in late 1993 or early 1994. The payload will be three-axis stabilized and absolute pointing will be derived from a star video camera. We describe the design capabilities of the LISA instrument, which include a spectral range of 310 to 390 nm, a wavelength resolution of ~0.3 nm, a height resolution of 1 km, and a theoretical count rate of 0.04 count R-1 s-1, where R represents rayleighs. The imager design is discussed and we present the results of some laboratory tests performed by means of an artificial source of the oxygen nightglow emission.