The Advanced Land Observing Satellite (ALOS) was launched on January 24, 2006. Since then, it 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 JAXA’s flagship for high-resolution Earth observation. In order to contribute to cartography, regional environment monitoring, disaster management support, and resource survey, ALOS has three mission instruments: PRISM, AVNIR-2, and PALSAR. It is the only Earth observation satellite that is capable of attaining two conflicting goals: global data collection and high resolution (2.5m). To attain these goals, a variety of platform and mission technologies were developed. In particular, high-resolution optical sensor technology, phased-array synthetic aperture radar technology, precision attitude and position determination and control technology, and high-speed data handling technology were developed. This paper gives an overview of the ALOS mission and spacecraft with a particular emphasis on the critical platform and mission technologies. This also reviews the last 15 months’ operations and on-orbit status of the ALOS spacecraft, with the flight data analysis of the bus subsystems and the mission subsystems.

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The Advanced Land Observing Satellite (ALOS) has been developed to contribute to the fields of mapping, precise regional land coverage observation, disaster monitoring, and resource surveying. Because the mounted sensors need high geometrical accuracy, precise orbit determination for ALOS is essential. So ALOS mounts the GPS receiver. This paper deals with the precise orbit determination experiments for ALOS using Global and High Accuracy Trajectory determination System (GUTS) and the evaluation of the orbit determination accuracy by Satellite Laser Ranging (SLR) data.

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The Advanced Land Observing Satellite (ALOS) was launched on January 24, 2006 and has been operated successfully since then. This satellite has the attitude dynamics characterized by three large flexible structures, four large moving components, and stringent attitude/pointing stability requirements. Presented in this paper are flight data analyses of ALOS’s attitude, rate, and linear acceleration, as well as a brief overview of the design approaches to attitude control and stabilization. The analyses not only yield attitude control and stabilization performances but also exhibit unique dynamic behaviors due to flexible structural modes, thermally induced paddle motion, paddle drive, inter-satellite communication antenna drive, and AVNIR-2 mirror drive. Efforts to improve attitude stability by updating feedback and feedforward control laws are also described.

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This paper describes the updated calibration results of optical instruments onboard the Advanced Land Observing Satellite (ALOS, nicknamed “Daichi”), which was successfully launched on January 24th, 2006 and continuously works very well. ALOS has an L-band Synthetic Aperture Radar called PALSAR and two optical instruments i.e., the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) and the Advanced Visible and Near Infrared Radiometer type-2 (AVNIR-2). PRISM consists of three panchromatic radiometers, and is used to derive a digital surface model (DSM) with high spatial resolution that is an objective of the ALOS mission. The geometric calibration is important in generating a precise DSM by stereo pair image of PRISM. AVNIR-2 has four radiometric bands from blue to near infrared and uses for regional environment and disaster monitoring etc. The radiometric calibration is also important for AVNIR-2 as well as PRISM. This paper describes updated accuracies of the standard products of PRISM and AVNIR-2 including methodologies of radiometric-and geometric-calibrations.

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This paper summarizes the geometric and radiometric calibration results of the PALSAR achieved during the ALOS initial calibration phase, which covers five months between May 16 2006 and October 23, 2006, and the half-year of the operational phase. All the PALSAR modes, FBS (fine beam single), FBD (Fine beam dual), SCANSAR, DSN (band limited SAR), and POL (Full polarimetry) were calibrated and validated using in-total 500 calibration points collected world widely and distributed target data from the Amazon. Through the characterization of the PALSAR, antenna pattern determination, and polarimetric calibration, we performed the adjustments of the PALSAR radiometric and geometric model installed on the SAR processor (SIGMA-SAR). Using the reference points, we finally confirmed that the geometric accuracy of the FBS, FBD, DSN, and POL modes is 9.3m, that of SCANSAR is 70m, and radiometric accuracy is 0.64 dB. Polarimetric calibration was successful that amplitude balance of VV/HH is 0.025dB and the phase balance is 0.32 degrees.

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