Fig. 1. Laser induced breakdown spectroscopy experimental system

Fig. 2. Physical image of insulator simulation sample

Fig. 3. Results of sample 1 (0.0713 mg/cm²) and sample 5 (1.1675 mg/cm²). (a)(d) Original microscope images; (b)(e) grayscale processed images; (c)(f) binarization results (white part is the dust-covered area)

Fig. 4. Change in the dust area ratio of the insulator sample with NSDD

Fig. 5. Partial spectral diagram of NSDD simulated sample for insulator (NSDD of 0.0730 mg/cm², detection delay of 300 ns)

Fig. 6. Comparison of spectrogram between insulator simulation sample and natural pollution samples (starting time for samples 1 and 2 was October 1990 and November 2004, respectively)

Fig. 7. Relative intensity of characteristic spectral lines of different gray density samples changes with detection delay. (a) Simulation sample 1 (0.0713 mg/cm²); (b) simulation sample 5 (1.1675 mg/cm²); (c) simulation sample 7 (3.3270 mg/cm²); (d) simulation sample 10 (6.2299 mg/cm²)

Fig. 8. Insulator simulation sample NSDD calibration results