Man-made very low frequency (VLF) waves and naturally generated plasma waves are frequently observed in the Earth's inner radiation belt (L ∼ 1.2-2) and slot region (L ∼ 2-3). Man-made VLF waves (tens of kHz) come from ground-based transmitters (Clilverd et al., 2008;Helliwell & Katsufrakis, 1974;Zhao et al., 2019) or spaceborne transmitters such as the Demonstration and Science Experiments (DSX) satellite (Scherbarth et al., 2009). Natural plasma waves cover a wide band from extremely low frequency (ELF) to VLF, including lightning-generated whistlers (LGWs) and plasmaspheric hiss and so on. LGWs (f ∼ 100-10 kHz) are injected from the troposphere after lightning strikes (Inan et al., 2007;Záhlava et al., 2019). Plasmaspheric hiss (f ∼ 20-4000 Hz) may be excited by the anisotropic instability of hot electrons (Chen et al., 2012) or originates from the inward penetration of whistler-mode chorus waves (Bortnik et al., 2009). The hiss intensity depends on solar wind dynamic pressure, plasma flow velocity, orientation of interplanetary magnetic field (IMF) (L.

In this paper, a tracking method for optoelectronic imaging platform of tethered balloon based on difference global positioning system/inertial navigation system is presented in detail. The location and attitude information of optoelectronic imaging platform, the azimuth and elevation angles of camera’s line of sight are used by this method to locate the ground target at the centre point of the camera’s field of view through corresponding coordinate transformation. And then, the method makes use of the update position and attitude information to solve the theoretical point of camera’s line of sight inversely. Finally, an angle control commend will be sent to the inertially-stabilized turntable on the optoelectronic imaging platform, which will adjust its azimuth and elevation angle to make the camera’s line of sight to the ground target. A lot of experiments are conducted, and the results show that the initial ground target is always in the centre of camera’s field of view no matter how the balloon’s position and attitude change, and the new location data of ground target has little difference with the initial location data, while the difference between them is close to 0.

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