The parallel adjustment (also called alignment or boresight) of the transmitting laser and the receiving telescope is essential for an atmospheric lidar system, which could be carried out manually or automatically. Manual alignment is time-resuming and lack of quantitative assessment. A high accurate and efficient self-aligning mechanism is urgently needed for automating the lidar system. Firstly, a brief overview of the fundamental principle of the atmospheric lidar and the importance of self-alignment is given. Next, the self-aligning methodology is reviewed, especially, the scanning method of transmitting laser and the criteria to judge the self-aligning result are introduced. In the end, the merits and drawbacks for different self-aligning methods are summarized.

The atmospheric aerosol optical thickness and the precipitable water vapor provide the essential evaluation basis for the astronomical site selection, and important reference for astronomical observation. DTF type sun-photometer is used to observe the diurnal, seasonal variation of the aerosol optical thickness, ngstrm index and the precipitable water vapor in clear and cloudless weather from September 2013 to January 2015 in Delingha, Qinghai Province, China. The results show that the region of the aerosol optical thickness and the precipitable water vapor type can be divided into six kinds and has some seasonal characteristics. During different seasons, the aerosol optical thickness is the minimum in autumn, nearly in other seasons, and the precipitable water vapor is the largest in summer, obviously more than other seasons. The ngstrm index is the minimum in spring, the largest in winter and nearly in summer and autumn. Overall the small aerosol optical thickness, the low amounts of precipitable water vapor, and the clean air make Delingha an appropriate site for astronomical observation.

The spatio-temporal characteristics and pollution sources of NO2 in Nanjing metropolitan area are analyzed by using cosine curve function and HYSPLIT model of back trajectory analysis, on the basis of NO2 column densities data of the Ozone Monitoring Instrument (OMI) from January 2006 to December 2014 and land use type data. The results indicate that tropospheric NO2 column densities in study area increased distinctly year by year from 2006 to 2014 and showed obvious seasonal variation, i.e. highest in winter while lowest in summer. There are mainly two aspects of tropospheric NO2 contaminant sources in study area. The one is the effect of atmospheric transport affecting the seasonal variation of NO2, and the other is that different land use types have great impact on column density of NO2.

In the HITRAN database, the temperature of the line is modified to the temperature, and then the synthetic calibration spectra are obtained. The synthetic calibration spectra and the spectra obtained by the experiments were performed by nonlinear least squares fitting, and thus the standard of CH4 concentrations was obtained at different temperatures. This inversion algorithm has a high accuracy at room temperature, but with the increase of temperature, the error of the concentration gradually increased. The high-temperature gas temperature correction is carried out by FTIR for the correction of high temperature spectral parameters, better synthetic calibration spectra can be obtained by using partition given temperature correction coefficient method, and combining HITRAN database.

Based on near-infrared continuous-wave diode lasers, a rapidly swept cavity ringdown spectrometer was developed. By rapidly sweeping the cavity length based on a PZT transducer, the longitude mode between the laser source and cavity was matched and dis-matched. Thus, the optical signal inside cavity finished its ring down and the measurement of the ring-down rate. The experiments show that not only the significant advantage in sensitivity achieve 10-9 cm-1 , but also the great stable and reliable performances of the spectrometer. The quantitative capability of the instrument was also demonstrated by measuring the absorption spectroscopy of CH4 around 1653.72 nm. The instrument was used to monitor the concentration changes of ambient CH4 by measuring the absorbing peak value with a fixed wavelength source.

Considering the limited calibration accuracy of FY-3A/VIRR sensor, and limited opportunities for calibration, the cross-calibration method of infrared channel of VIRR with high-precision MODIS of the onboard polar-orbit satellite TERRA is introduced. The cross-calibration is implemented by using the satellite data in January, March and September of 2013. The results show that the brightness temperature of VIRR calculated by using cross-calibration coefficients is nearly equal to the observed value of MODIS, and the vast majority of brightness temperature bias is less than 1 K. The validation results showed that cross-calibration coefficients has universality.

RossThick-LiSparseR model and RossThick-LiTransitN model are typical kernel-driven models. The models can simulate surface bidirectional reflectance accurately. Data of surface targets on soybeans, orchard, lawn, hardwood and corn were measured at visible waveband and near infrared waveband. The inversion of the kernel-driven bidirectional reflectance distribution function(BRDF) model was implemented by regularization method. The ability of two models is accessed by comparing the retrieving results. It is found that RossThick-LiSparseR model has advantage in retrieving albedo at visible and near infrared waveband. The two models have the same ability to retrieve Black-sky albedo.

It is important for researching climate change and monitoring environment to obtain aerosol optical depth accurately. With the aerosol optical depth products derived from satellites increasing, comparison between different aerosol optical depth products can offer an important basis for users to choose the appropriate products. MODIS aerosol products’ applicability for four kinds of underlying surfaces with AERONET ground-based observations data was analyzed. The comparison shows that: in China region, for the suburb, forest, lake, the optimal one is MODIS sixth version retrieval algorithm. The fifth version algorithm is suitable for the urban underlying surface. The conclusions can provide references for selecting MODIS aerosol products in China region.

Based on the cross-sensitivity of fiber Bragg grating(FBG) temperature sensor, a new encapsulation method of high sensitivity of FBG temperature sensor is proposed. By setting a spring in the metal tube, the temperature was measured with pressure isolated. The purpose is to enhance the temperature sensitivity coefficient of FBG and to eliminate cross-impact of stress. Through experiments, the temperature characteristics and stress impact of packaged FBG are introduced. The results show that the wavelength offset is only caused by the change of temperature which is not influenced by the peripheral pressure. Meanwhile, the packaged FBG has good linearity and repeatability, which can be used to monitor temperature accurately.

Accurate control of the temperature of photoacoustic systems is helpful to improve the detection sensitivity and stability. The temperature controller is composed of microcontroller STC12C5A60S2 and temperature sensor Pt1000. The four-wire method of Pt1000 effectively eliminates the error due to the lead resistance. The temperature signal processing circuit adopts instrument amplifier AD620. 14 bit high rate ADC (analog to digital converter) TLC3574 is used to transfer temperature voltage acquired by microcontroller and its reference voltage is provided by LM4040. The driver circuit of Peltier is H-bridge MOSFETS controlled by PWM wave from STC12C5A60S2. The duty ratio of PWM wave determines the current direction and conduction time to realize heating or cooling. The control range of temperature is from 0 ℃ to 40 ℃ and the sensitivity is 0.06 ℃.