Correction of optical distance measurements for the fluctuating atmospheric index of refraction

Abstract

One of the main limitations, at present, to the accuracy of measurements of long baselines by optical methods is the uncertainty in the average index of refraction over the optical path due to nonuniformity and turbulence of the atmosphere [Thompson et al., 1960]. This uncertainty is due primarily to lack of knowledge of the air density, although a small correction for water vapor is also required. Our purpose in this note is to point out that simultaneous measurements of the optical distance over the same path for blue and red light can be used to provide the required correction for the atmospheric index of refraction. The application of this method to interferometric distance measurements has previously been discussed [Erickson, 1962a].

Effects of random path fluctuations on the accuracy of laser ranging systems

“…possible if two laser frequencies are employed instead of-one. The difference between the refraction at different wavelengths can be used to eliminate, to a great extent, the effects of atmospheric refraction on the range measurements [13][14][15].…”

Correction of group refraction index based on pulse trains interference

“…For convenience, we summarize the basic concepts of the wavelength-based two-color method; the details of this method can be obtained elsewhere (1)(2)(3)(4).…”

“…The twocolor method is well known for obtaining the absolute value of the length, without the need for precise information about the refractive index of air. The two-color technique has been widely used since the studies of Bender and Owens (1). As an alternative to the conventional two-color (namely, wavelength) absolute length-measurement technique, we propose the adjacent pulse repetition interval length (APRIL)-based two-color method.…”

Correction of refraction index based on adjacent pulse repetition interval lengths

“…Since the early stage of the two-color method [3], many contributions have been made to correction of the atmospheric index of refraction [4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”