Precision Pixel Geolocation Determination for the Advanced Land Observing Satellite (ALOS)

Paper number

IAC-08.C1.7.9

Author

Dr. Takanori Iwata, Japan Aerospace Exploration Agency (JAXA), Japan

Coauthor

Dr. Takeo Tadono, Japan Aerospace Exploration Agency (JAXA), Japan

Coauthor

Mr. Tetsuo Kawahara, NEC Corporation, Japan

Coauthor

Mr. Masakazu Abe, Japan

Year

2008

Abstract

	A conventional approach to geometric correction of high-resolution satellite images uses polynomial approximations of ground control points (GCP) extracted from acquired images. This approach, however, does not exploit a priori knowledge on satellite's attitude and orbit dynamics and thermal distortion characteristics and a full spectrum of information encoded in on-board measurements, and therefore results in difficulties in uniformly achieving geometric precision for globally observed data without GCPs and in correcting effects of attitude motion with higher frequency components. In addition, the extraction of GCPs prevents from processing mass volume images automatically. 
	On January 24, 2006, the Advanced Land Observing Satellite (ALOS) was launched by an H-IIA rocket into a sun-synchronous orbit. Throughout the last 25 months since the launch, ALOS has been operated successfully on orbit, delivering a variety of high-resolution images in numerous quantities and contributing to disaster management support many times. ALOS is a Japan Aerospace Exploration Agency (JAXA)'s flagship for high-resolution Earth observation. It is designed to contribute to: cartography, regional environment monitoring, disaster management support, and resource survey. In order to accomplish this mission, ALOS has three mission instruments including panchromatic stereoscopic radiometers, PRISM. 
	ALOS is the Earth observation satellite capable of attaining conflicting goals: global data collection with high resolution. This characteristics requires geolocation determination of globally observed images without GCPs. Therefore, ALOS is required to achieve stringent pointing determination accuracy, position determination accuracy, and attitude stability. For achieving these requirements, a variety of platform and ground systems technologies were developed. 
	Precision attitude estimates of arcsec accuracy were derived both on orbit and on the ground from measurements of a newly developed precision star tracker and gyros. The more precise ground-based attitude estimates exploits a novel repeated smoother algorithm based on extended Kalman filtering. An extended bandwidth option of attitude estimates at 675Hz was obtained using a jitter sensor and a new Wiener filtering architecture. Precision position estimates of submeter accuracy were derived by a square root information smoother from measurements of a newly developed dual-frequency GPS receiver. Orbit-periodic and long-term alignment changes between attitude sensors and between the star tracker and PRISM were estimated periodically and were calibrated for the ground-based attitude determination and pointing determination. A synthesis of all these estimates with proper coordinate transformations and calculations yielded ground-based pixel geolocation determination of 5m accuracy without GCPs. This paper presents these determination algorithms and their on-orbit calibration results.

Abstract document

IAC-08.C1.7.9.pdf

Manuscript document

IAC-08.C1.7.9.pdf (🔒 authorized access only).

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