ASTRO utilizes slit-less spectroscopy with transmission grating, a long focal length lens, and a cooled CCD camera detector.

This instrument consists of a Richardson Grating Laboratory 11 x 11 cm plane transmission grating (35-54-20-660), an AF-S Nikkor f2.8/300 mm Nikon 300D IF-ED lens, and a two-stage thermoelectrically cooled back-illuminated 1024 x 1024 pixel Pixelvision CCD camera. An optional order separation filter.

Scientific objective: Spectral resolution of shock layer radiation. Resolve spectral lines of air plasma emissions at optical wavelengths for the measurement of excitation temperatures. Provide high spectral resolution and absolute calibration at high dynamic range. Limitation: only one measurement made in a brief time interval during the point of peak brightness.