Operating principles and detection characteristics of the Visible and Near-Infrared Imaging Spectrometer in the Chang'e-3

Abstract

The Visible and Near-Infrared Imaging Spectrometer (VNIS), using two acousto-optic tunable filters as dispersive components, consists of a VIS/NIR imaging spectrometer (0.45-0.95 µm), a shortwave IR spectrometer (0.9-2.4 µm) and a calibration unit with dust-proofing functionality. The VNIS was utilized to detect the spectrum of the lunar surface and achieve in-orbit calibration, which satisfied the requirements for scientific detection. Mounted at the front of the Yutu rover, lunar objects that are detected with the VNIS with a 45 • visual angle to obtain spectra and geometrical data in order to analyze the mineral composition of the lunar surface. After landing successfully on the Moon, the VNIS performed several explorations and calibrations, and obtained several spectral images and spectral reflectance curves of the lunar soil in the region of Mare Imbrium. This paper describes the working principle and detection characteristics of the VNIS and provides a reference for data processing and scientific applications.

Submicroscopic metallic iron in lunar soils estimated from the in situ spectra of the Chang'E‐3 mission

“…We chose the SA rather than other spectral matching methods because it is insensitive to effects of absolute reflectance related to the illumination geometry and instrument calibration. The comparison was performed over the wavelength range 0.68–2.20 μm, in order to avoid the effects of thermal emission from the lunar surface at longer wavelengths (>2.20 μm) and low SNR at shorter wavelengths (<0.68 μm) [ He et al , ]. The optimal fit for the mass fraction of SMFe was determined by minimizing the SA between the target spectrum and the modeled spectrum.…”

Mineral Abundances Inferred From In Situ Reflectance Measurements of Chang'E‐4 Landing Site in South Pole‐Aitken Basin

“…The FOV of the single‐pixel SWIR detector is 3.58°, and the measured area is a circle ~7 cm in diameter within the FOV of the CMOS camera. More details of the VNIS can be found in He et al () and Zhang et al ().…”

“…The FOV of the single-pixel SWIR detector is 3.58°, and the measured area is a circle~7 cm in diameter within the FOV of the CMOS camera. More details of the VNIS can be found in He et al (2014) and Zhang et al (2015). Figure 1c shows the CE-4 landing area and Yutu-2 Rover's path with six VNIS measurement sites during the first two lunar days, during which the rover moved a distance of~54 m away from the lander.…”

The Scientific Information Model of Chang&rsquo;e-4 Visible and Near-IR Imaging Spectrometer(VNIS) and In-Orbit Verification

“…The transducer converts the electric signal into ultrasonic vibrations in the crystal, which generate spatially periodic modulations. When an incident light is irradiated to the grating, the wavelength of the diffracted light is related to the frequency of the driving electric signal, and it can be changed by varying the frequency of the electric signal [4]. ~2 min According to this principle, by changing the driving frequency of AOTF crystal through rapid scanning of the time dimension, the wavelength of the diffracted monochromatic light passing through the AOTF changes sequentially, which is functionally equivalent to rapidly switching (in the order of 10μs) the transmission wavelength filter by electronic control.…”