Optical calibration is facing challenges of functional enhancement and diversification of the future optical remote sensors. A few suggestions are proposed for the development and applications of new calibration techniques, in order to meet quantification requirements of next generation satellite missions with hyperspectral, higher resolution and 3D geodesy observation.

Currently, optical sensors usually need to build high-accuracy primary standard, and then transfer to user sensor based on a series of comparison chain, the precision of primary standard and standard transfer chain are the major sources of uncertainty. Combined with parametric downconversion method, theory and experiment results in recent years at home and abroad, the advantages of absolute sources and detectors of parametric downconversion are referred. Considering the need of practical application of calibration technique of parametric downconversion, the necessity, technique difficulty and solution of calibration technique of parametric downconversion are introduced when calibration technique of parametric downconversion transfers to broad band and analog detectors.

Automated vicarious calibration is a new direction for optical satellite radiometric calibration. By deploying automated instruments in test site, long-term surface reflectance and atmospheric pararmeters are measured which allow payloads to be calibrated with high frequencies and high precisions. Automated vicarious calibration methods and technologies are analysed in details. Aiming at calibration requirements, the scheme and key knowledges of new instruments are presented. The development prospects of automated vicarious calibration are also discussed.

To resolve the problem of mismatch between the target spectra viewed by remote sensors and spectra of calibration source, and effectively guarantee the calibration accuracy, the target spectra simulation technology is a very promising evolution trend for calibration sources. The development and applications of calibration source technology used to simulate target spectra in scene in the domain of optical calibration were presented. The design of a spectrally tunable light source based on digital micromirror device (DMD) was described as an example to illuminate the design method of sources based on spatial light modulator. Besides possessing the function of target spectra simulation, this novel calibration source can be combined with the standard detector. So it is useful to improve the calibration accuracy of sensors, and can be extremely promising for calibrating hyperspectral imagers.

In order to analyze the radiation property changing and the validity of calibration for HJ-1A/B CCD cameras, a validation method based on multi-spectral reflectance field targets is developed. Firstly, the in-flight validation method for radiation properties of HJ-1A/B CCD is introduced, and the equivalent radiance of HJ-1A/B CCD was calculated by using satellite-field synchronous measurements data in 2013. Then the radiometric calibration results of HJ-1A/B CCD are validated, and the trend of change of in-flight radiation properties of HJ-1A/B CCD is analyzed. The results show that the radiation properties of HJ-1A/B CCD change ceaselessly, and the attenuation of radiation properties of HJ-1A/B CCD is from 3.7% to 39.6% since launched, in-flight calibration for satellites is important to satisfy requirement of quantitative applications of remote sensing data.

In 1999, Dunhuang remote sensing satellite radiation calibration station began regular operation. With Dunhuang urban construction and economic development, the radiometric field surrounding has changed. A great field measurement campaign was conducted in Dunhuang site in summer, 2013. The CIMEL sunphotometer was used to measure the optical characterization of atmosphere in Dunhuang, and a lot of data were obtained about atmospheric optics in loud clearing condition of four days. Data from aerosol-bands of sunphotometer were used in a Langley method to determine spectral optical depths of aerosol. The aerosol optical depth at 550 nm in Dunhuang is about 0.3. The results showed that the aerosol concentration of atmosphere in Dunhuang was small and suitable for in-flight calibration for remote sensing satellite sensors.

ZY-1 02C panchromatic multispectral sensor(PMS) data has made an important role in national development. The calibration coefficient is the key to the breadth and depth of the application. The field calibration method is an effective way to the problem. A field calibration experiment of ZY-1 02C PMS was performed by the China Center for Resources Satellite Data and Application at the Dunhuang site during August 2012. The two-point calibration method was used to obtain PMS absolute calibration coefficients. The results were validated by the data of July 23, 2012 at the Xinjiang target site. It shows that absolute calibration coefficients are highly reliable and enough to meet the requirements of quantitative applications.

Onboard calibration accuracy of HJ-1B Satellite thermal infrared channel directly affects the quantitative application of remote sensing data. The response differences of each detector were ignored by the previous onboard calibration methods which focused on the whole channel. The look-up table, half-width and moments methods are used to calculate each detector’s calibration coefficients of HJ-1B thermal infrared channel based on the blackbody data transferred on Sep. 14th, 2009. The results show that the deviation is about 2 DN when the detectors scanning the adaptive blackbody, which bring errors from 0.28% to 0.45%. The 9th and 10th detectors have larger deviation than the others.

Space-borne differential optical absorption spectrometer is mounted on the Sun-synchronous orbit satellite, which quantitatively monitors the global air quality changes and the transmission of pollutant gases distribution. The onboard calibration is the basis to obtain accurate quantified imaging data, and the space-borne instrument adopts sunlight calibration mode and standard lamp calibration mode. In order to ensure the reliability and accuracy of onboard calibration, analysis and rational design of the calibration mechanism are needed.

Due to the need of post-launch calibration of hyperspectral imagers, three cross-calibration technical solutions are proposed. Matching technologies including field, time, geometry and spectrum in the process of cross-calibration are analysed. Algorithms and models in matching technologies are validated by the use of the data of HJ-1A/HSI, EO-1/Hyperion. By the application of three technical solutions with site-calibration method, the frequency of post-launch calibration can be improved and site-calibration coefficients can be validated quickly. The level of quantitative application of hyperspectral data can be promoted effectively.

Bidirectional reflection distribution function(BRDF) measurement uncertainty of the solar diffuser has direct impact on the on board absolute radiometric calibration accuracy. Conventional BRDF measurement apparatus is difficult to meet the requirements of on board absolute radiometric calibration in terms of measurement accuracy and function. In this context, a set of BRDF absolute measuring system was established. In the system, the high brightness, high uniformity integrating sphere radiation are used as light source, high-precision six-axis robot and indexing plate are used as BRDF gonioreflectometer, and wide spectrum of large dynamic range of the photoelectric detector is used as signal detection unit. Through geometry, electronics and other related physical quantities of high precision calibration and traceability, BRDF measurement uncertainty of solar diffuser less than 1% is achieved.