The Gaofen-7 (GF-7) satellite system adds a footprint camera that shares the same optical path as its laser altimeter to ensure consistent spatial referencing between the laser footprint point and the obtained optical images. However, this introduces additional errors between the two different loads while ensuring the geometric relations of the laser altimeter and footprint camera. First, the accuracy and error analyses of laser altimeter and footprint camera are carried out based on the working mode of the GF-7 satellite laser altimeter and footprint camera in this study. A rigorous sensor model of laser geometric positioning is proposed based on the coupled footprint camera, which is achieved for the geometric correlation of laser spots on the ground and the focal plane of footprint camera. The satellite laser altimeter simulation platform was used to analyses the various error sources on the geometric positioning of the laser altimeter, and GF-7 satellite data were used to verify the proposed geometric positioning model of the laser altimeter and footprint camera. The results show that the positioning error of GF-7 footprint camera is less than 5 m (RMSE) relative to the dual-line array image, which can provide ground control points for stereo mapping.

Due to the difference in surface reflectivity, the laser measurement waveform data recorded in full waveform have a saturation phenomenon. When the signal is saturated, the echo waveform produces peak clipping and pulse spreading, which seriously restrict the accuracy of laser measurement results and the usability of data. Therefore, we conducted a ranging investigation on the “peak clipping” phenomenon of the saturated waveform and found a nonlinear time delay in the range, which is between the two extreme cases of saturated “dead time” and Gaussian fitting peak time as pulse signal reception time. Subsequently, based on the consistent relationship between the geometric characteristics of the high- and low-gain channels of the space-borne laser altimeter, we constructed a laser waveform saturation compensation model, namely, the laser pulse flight time delay compensation and the laser waveform peak intensity compensation, and carried out the data saturation compensation and validation with the dual-channel measurement data from the GaoFen-7 (GF-7) satellite. The experimental results showed that the saturation compensation model (SCM) proposed in this paper could restore the features of the saturated waveform signal and effectively improve the accuracy of the laser ranging. The accuracy of the laser waveform fitting result after saturation compensation improved from 0.7 ns (0.11 m) to 0.14 ns (0.02 m), which greatly improved the usability of the saturated laser measurement waveform data.

Using N2O4 donor symmetric ligand H2L and dca co-ligand, two new isostructural dinuclear CuII–LnIII complexes [Cu(Cl)(L)Ln(NO3)(CH3OH)(H2O)(dca)] [Ln=Ho (1CuHo), Gd (2CuGd)] [H2L = 6,6′-((1E,1′E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))bis(2-methoxyphenol); dca=dicyanamide] were designed, synthesized and studied. In the two isostructural compounds, the geometric environment around the nine-coordinated Ln(III) ions is muffin, whereas the geometry of the penta-coordinated Cu(II) ions is square pyramid. The magnetic properties of both complexes were also studied. Direct current magnetic susceptibility measurements indicate ferromagnetic interactions between the Cu(II) ion and Gd(III) ion in complex 2CuGd. Alternating current (ac) magnetic measurements indicate that complex 1CuHo displays slow magnetic relaxation behaviour.