Calibrations of ground based airglow imaging interferometer for the upper atmospheric wind field measurement

Abstract

Ground based airglow imaging interferometer (GBAⅡ) prototype made by our group is used to successfully detect the atmospheric wind velocity and temperature at the altituded of 90-100 km. In order to improve GBAⅡ's velocity accuracy, its calibrations are studied in this paper where covered are the calibration of imaging interference fringe center position, CCD dark noise and flat field, the decay coefficient of GBAⅡ's optical system, the phase step length, GBAⅡ's optical path difference with the angle of incidence, GBAⅡ instrument response and the zero wind speed phase calibration, etc. The theoretical and experimental researches of calibration show the following conclusions. The fringe center coordinates by shooting 30 imaging interference fringes are confirmed on the pixel of CCD (123.3, 121.1) by using the least squares method; by 632.8 nm laser for the CCD flat field calibration, the parameters of CCD's flat field coefficients, dark intensity, dead pixels and the imaging interference fringes before and after flat field are all obtained, respectively; the comparison between GBAⅡ's one edge fringe bright whose incidence angle of 10.24 and the center fringe bright whose incidence angle of 0 shows that the edge fringe phase is stepped by 0.356 fringes relative to the center fringe. After taking the sample of 200 imaging interference fringes, from the sine fit curve of the phase step interval at an incident angle of 10.24, the fitted root mean square (RMS) deviation is obtained to be 90.34% and the step interval of 4.06 nm for one interference fringes is corresponding to the stepped phase of 0.0094up; According to the forward formula, GBAⅡ's system decay coefficient calibration is performed after taking imaging interference fringes by IDL programming, the RMS deviation of fitted curve is 99.98%; GBAⅡ's response is 4.9710-3 counts (Rayleigh)-1 from the 632.8 nm laser experiment; GBAⅡ's zero wind speed calibration phases are obtained to be -9.2442 and -68.6353 for the 532.0 nm and 632.8 nm lasers for the outdoor experiment, respectively. This paper provides a series of calibration methods for GBAⅡ and these methods are all verifies experimentally. These calibration methods can support the upper atmospheric wind field passive measurement.