The multispectral camera is an important payload for Mars exploration, which provides visible and near-infrared images of the Martian surface, from crucial observations of landscape morphology, geology, and atmospheric science may be derived.

Spectral calibration is an essential step in the calibration process of the multispectral camera for Mars exploration and the precision of spectral calibration has a direct impact on the accuracy of data inversion. To fit the spectral response, Gaussian function is the most common method for determining the central wavelength and spectral bandwidth.

However, some spectral responses are not close to Gaussian distribution. For example, the spectral response of the Chinese Mars multispectral camera in the near-infrared band rapidly diminishes after reaching its maximum, which cause a large deviation from the camera output. Are there any methods to improve the precision of Mars multispectral data inversion?

A research team from Xi'an Institute of Optics and Precision Mechanics (XIOPM) of the Chinese Academy of Sciences (CAS) proposed a novel method to improve the precision of Mars multispectral data inversion. The results were published in Results in Physics.

Analog spectral response with different methods. (Image by XIOPM)

The new approach is taken the spectral response of a multispectral camera as a weight function, and a generalized weighted method is proposed to redefine the central wavelength and spectral bandwidth of the multispectral camera.

To compare the accuracy of the generalized weighted method and the Gaussian method in defining the central wavelength and spectral bandwidth, and their effects on spectral reconstruction, eight spectral responses were simulated. Besides, the central wavelength and spectral bandwidth defined by the two methods were further tested by experiments.

The simulation and experimental results showed that the relative output deviation of the proposed method was lower than that of the Gaussian method, and the relative radiation error was also reduced.

The generalized weighted method provides another way for the definition of central wavelength and spectral bandwidth, and improves the precision of Mars multispectral data inversion.