Visible and Near-Infrared Imaging Spectrometer (VNIS) For Chang E-3

Abstract

To analyze the composition of lunar surface minerals, one of the scientific payloads of the Chang'E 3 Yutu rover, the Visible and Near-infrared Imaging Spectrometer (VNIS), was developed to detect lunar surface objects and to obtain their reflectance spectra and geometric images. The VNIS, which uses 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. It is capable of synchronously acquiring the full spectra of lunar surface objects and performing in-situ calibration. 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 Imbrium region. This paper introduces the VNIS, including its working principle, implementation, operation, and major specifications, as well as the initial scientific achievement of lunar surface exploration.

The Scientific Information Model of Chang’e-4 Visible and Near-IR Imaging Spectrometer (VNIS) and In-Flight Verification

“…The transducer converts the electric signal into ultrasonic vibrations in the crystal, which generate spatially periodic modulations. When incoming light is incident on the AOTF, 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 [12].…”

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

“…According to the basic principle of AOTF spectrophotometry, after passing through the AOTF, three lights are formed through the convergent lens, which are +1 level diffraction light, -1 level diffraction light and 0 level light [7]. When the system is designed, an InGaAs detector with a diameter of 1mm is placed at the convergence of the +1 level diffraction light, and a light filter is designed for the 0 level light, thereby suppressing the stray light.…”

AOTF spectrometers in space missions and their imaging capabilities

“…It is also a part of the analytical laboratory of the ExoMars 2020 rover mission [32]. AOTF spectrometers for surface characterization were developed in China; one of them successfully flown on Chang'e-3 lunar mission [33,34]. Similar pencil-beam AOTF spectrometers are being developed for Russian lunar landers, and to be installed at the ExoMars 2020 rover mast [35].…”