Yuji Osawa

PRISM: a panchromatic three-line sensor for mapping onboard ALOS

This paper reports the results of the preliminary design and testing of the Panchromatic Remote Sensing Instrument for Stereo Mapping (PRISM) Bread-Board Model (BBM). PRISM is one of the major mission instruments to be installed on the Advanced Land Observing satellite (ALOS) which is expected to launch in early 2003 on a Japanese H-IIA vehicle. The PRISM system is designed to provide accurate data for making and updating maps on the 1/25,000 scale. That requires the PRISM system to be a high performance sensor with spatial resolution of 2.5 m and a wide swath of 70 km. To realize both capabilities, the optical system utilizes three-mirror, off axis anastigmatic designs with more than 28,000 detector elements which is realized by using multiple CCD senors. PRISM has three independent telescopes for stereoscopic imagery. These telescopes are arranged in order to obtain forward, nadir, and backward looking data. A set of three images is used for Digital Elevation Model (DEM) extraction. The current BBM phase of the project is underway to confirm the feasibility of the design. At the same time, the preliminary design is being used to understand the functions and characteristics of entire PRISM system.

Advanced Visible and Near-Infrared Radiometer type 2 (AVNIR-2)

Advanced visible and near infrared radiometer type 2(AVNIR- 2) is a high resolution land observation sensor, which will be loaded on ALOS. AVNIR-2 is composed of a multispectral and panchromatic subsystem. THese former subsystem is recently named as AVNIR-2; same with the old instrument name. The latter subsystem is named PRISM. The multispectral subsystem has ground resolution of 10m and four spectral bands which have same spectral range with that of AVNIR loaded on ADEOS. PRISM has three line detectors and characteristics of B/H equals 1.0 and ground resolution of 2.5m. By means of these characteristics, topographic maps with contour of 5m elevation interval are planned to be produced from those panchromatic data. Because observing data rate of PRISM is very high, on-board lossy data compression will be applied in order to reduce down link data rate. In this report, influences of the on-board lossy compression for terrain elevation measurements are evaluated. As the results, it is clear that: (1) measurement error of terrain elevation does not increase by on-board lossy data compression, (2) measurement error of terrain elevation decreases by on-board lossy data compression under the condition of turbid atmosphere and (3) measurement error of terrain elevation decreases in spite of atmospheric conditions when block coding is used as a lossy compression method.

Advanced Land Observing Satellite (ALOS): mission objectives and payloads

This paper introduces outline of Japanese high-resolution earth observation satellite called ALOS, which NASDA plan to launch in 2002. Main mission objectives comprise DEM generation for GIS, environmental and hazard monitoring. NASDA have completed the investigation of users requirements and preliminary design of hardware for the ALOS. As a result, the ALOS will equip both optical and microwave sensors to fulfill the requirements. DEM will be generated by the optical sensor with stereoscopic observation capability by three-line-sensor with 2.5 m resolution. Multi-spectral information will be acquired by AVNIR-II, a multi-spectral optical sensors with 5m resolution and 4 bands. The microwave sensor, a L-band synthetic aperture radar (SAR), which is a follow-on of the JERS-1/SAR, has capabilities of look-angle change and the ScanSAR mode.