diagnose plasma turbulence occurring in space and laboratory plasmas. ASIS can record infrared, visible, and ultra-violet (UV) emissions to determine the profiles of plasmas and the structures of plasma turbulence. IRIS can further identify the plasma waves and their characteristic features, such as wavelengths and density fluctuations in the turbulence. ASIS and IRIS experiments in Puerto Rico and Alaska are aimed at controlled studies of naturally occurring and RF heated plasma turbulence with applications to improved satellite and radio communications as well as plasma fusion research.

ASIS consists of a primary lens that images the sky telecentrically through filters in a six-position filter wheel containing narrow-band interference filters. Three primary lenses are designed for different experimental conditions, each with its own telecentric lens elements. They are (1) 24mm/F4.0 fish-eye - 180 deg. field of view (FoV), (2) 45mm/F2.8 - 76 deg. FoV, and (3) 210mm/F4.0 - 19 deg. FoV. The center wavelength of some types of interference filters is temperature dependent. A stand-alone proportional temperature controller is provided with the ASIS to keep the temperature of the filters at approximately room temperature. The temperature can be controlled remotely via a standard serial interface.

The primary image is then re-imaged either onto the front of an image intensifier or directly onto the CCD chip. The image intensifier has gain control capability. If the intensifier is used, the output image is then re-imaged onto the CCD of the CCD camera head. The camera head is thermo-electrically cooled to provide a decreased dark-noise accumulation and allow longer integration times. In addition, there is a liquid-cooling assist option, where water or glycol is circulated with the liquid circulation unit provided. Liquid cooling is also provided for the image intensifier cooler. The liquid lines to the camera and intensifier cooler may be connected in series, in parallel, or independently.

The CCD camera head is connected to the camera electronics unit, which supplies power, timing signals and the data interface both to the camera head and back to the host computer. The camera electronics unit has the capability for dual-speed conversion. When using the image intensifier, the fast conversion should be used, and when using the bare CCD, the slow conversion should be used. The camera head has an internal shutter directly in front of the CCD window that is used for the exposure time.

A shutter at the front of the ASIS is used as a capping shutter (sunlight directly hitting the interference filters can damage them). A light detector at the front of ASIS is used as an automatic override to avoid overexposure and possible damage to the image intensifier. A standard serial interface is used to control the filter wheel, intensifier and shutter operations.

Under the supervision of Professor Min-Chang Lee, students learn how to perform different kinds of calibrations, including dark noise, relative spectra, and vignetting as well as gaining experience in operating instrument-specific software and graphing data on Matlab. ASIS, together with MIT PSFC's Ionospheric Radar Integrated System (IRIS), can provide powerful plasma diagnostics of plasma turbulence occurring in space and laboratory plasmas.

77 Massachusetts Avenue, NW16, Cambridge, MA 02139, info@psfc.mit.edu