Advanced Visible and Near-Infrared Radiometer (AVNIR)
Observation ConceptAdvanced Visible and Near-Infrared Radiometer (AVNIR) is an optical sensor for measuring surface reflectance in 3 visible bands and 1 near-infrared band. The three visible bands are indicated by blue, green and red while the near-infrared band is suitable to observe vegetation. AVNIR has 4 multispectral bands of 16m resolution and 1 panchromatic band of 8m resolution.
AVNIR scans about 80km swath width along the cross track, using the large lineararray CCDs with 5,000 pixels (multispectral band) and 10,000 pixels (panchromatic band).
AVNIR Observation Concept
The observation area is limited because of narrow swath width. In order to compensate this disadvantage, the pointing capability acquires the wide range of target within +/- 40 degrees around the nadir. Similar to OCTS, AVNIR has optical and electrical calibration functions so that sensitivity can be monitored.
Planned MissionsAVNIR is a high resolution optical sensor for the wide range of the Earth surface monitoring. The AVNIR data is used to understand vegetation and soil conditions in order to contribute to solving such phenomena as desertification and deforestation of tropical forests. In the land and urban utilization, the observation data of artificial structures and plant distribution profile contributes to creating better living environment. Other observation data such as surface reflectance and radiance plays a key role in evaluation of energy balance of the earth.
Given the fact that all the environmental issues have been addressed at the local and regional levels, the AVNIR data with high resolution is valuable for the global environment observation community.
Configuration and Specification of SensorAVNIR is composed of two units, the Scanning Radiometer Unit (SRU) which mainly consists of optical components and the Electronic Unit (ELU) which mainly processes the image data.
The observation light is reflected by a pointing mirror with 0.5 degrees drive angles. Optics in SRU adopts a Catadioptric Schimidt optical system as amirror while spectrum is splitted into 4 multispectral bands and 1 panchromatic band by combined effects of optical prism and interference filter.
After the optical signals are converted to electrical signals, Charged Coupled Devices (CCDs) scan those signals and output to the ELU. As CCDs have a capability of changing the integration time of the optical signals, sensitivity can be well maintained even in the dark area.
The electrical signals are amplified in the Process Amplifier, and then converted to the digital signals. The digital signals are processed in Image Processing Assembly and transmitted to bus module. The multispectral observation data is compressed by about 10% in order to reduce the transmission data rate.
Earth Observation Research Center
Last Update: 5 Febrary 1998