Errors in lidar measurements of the air density in the middle atmosphere are analyzed. A lidar was placed onboard the ISS. A solid-state Nd:YAG-laser, operating at the 3rd and 4th harmonics with wavelengths of 355 and 266 nm, was used as a lidar transmitter. Calculations were performed for the lidar with reasonable parameters: pulse energy of 0.4 (355 nm) and 0.2 J (266 nm), pulse repetition frequency of 20 Hz, accumulation time of 60 s, radius of the receiving mirrors of 0.3 and 0.5 m, field of view of the receiving telescope of 1 and 0.1 mrad, filter bandwidth of 0.5, 1, and 10 nm, and spatial resolution of 1 km. The results showed that radiation at a wavelength of 355 nm can cover altitude range, on average, from 75 km at night and from 55 km in the daytime to 10 km depending on the parameters of the lidar with 10% measurement errors (calculations were not carried out below 10 km). When operating with radiation at 266 nm for 10% measurement error, the sensing range can be expanded to the upper mesosphere at 90 km and penetrate deeper into the atmosphere to 38 km. Thus, the use of two harmonics allows the altitude range of air density measurements from the ISS to be expanded from 90 km down to the troposphere.
air density, middle atmosphere, lidar
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