This paper describes the updated results of calibration and validation to assess the accuracies for optical instruments onboard the Advanced Land Observing Satellite (ALOS, nicknamed “Daichi”), which was successfully launched on January 24th, 2006 and it is continuously operating very well. ALOS has an L-band Synthetic Aperture Radar called PALSAR and two optical instruments i.e. the Panchromatic Remotesensing Instrument for Stereo Mapping (PRISM) and the Advanced Visible and Near Infrared Radiometer type-2 (AVNIR-2). PRISM consists of three radiometers and is used to derive a digital surface model (DSM) with high spatial resolution that is an objective of the ALOS mission. Therefore, geometric calibration is important in generating a precise DSM with stereo pair images 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 and image quality evaluation are also important for AVNIR-2 as well as PRISM.
This paper describes updated results of geometric calibration including geolocation determination accuracy evaluations of PRISM and AVNIR-2, image quality evaluation of PRISM, and validation of generated PRISM DSM. These works will be done during the ALOS mission life as an operational calibration to keep absolute accuracies of the standard products.
The SPICA mission aims to achieve high spatial resolution and unprecedented sensitivity in the mid to farinfrared
wavelength astronomy. We derived a set of pointing requirements from SPICA's mission requirements.
Disturbance management over the SPICA system and an implementation of isolators are necessary, because
cryogenic coolers' disturbances could generate vibration. Alignment and random pointing errors for focal-plane
instruments are reduced with a focal-plane guidance camera. Furthermore, an additional focal-plane camera and
a tip-tilt mirror actuator are installed for coronagraph mode. This paper presents an overview of the SPICA
pointing requirements and a feasibility study to achieve the requirements.
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. It is the Earth
observation satellite that is capable of attaining 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 31 months' operations and on-orbit status of the ALOS spacecraft with the flight data analysis. The
assessment and calibration of the mission-related platform performances such as orbit determination and control
accuracies, attitude determination and control accuracies, attitude stability, and pixel geolocation determination accuracy
are also reported along with our efforts to improve these performances.
The Advanced Land Observing Satellite (ALOS) is required to achieve stringent attitude determination accuracy (3.0×10-4deg on-board and 1.4×10-4deg ground-based), position determination accuracy (1m ground-based), and attitude stability (3.9 × 10-4deg/5sec) in order to provide precise geometric accuracy for high-resolution images without ground control points. It is designed to yield the geolocation determination accuracy of 6m from attitude and position estimates and that of 3m with an additional high-bandwidth measurement. Presented in this paper are ALOS's platform and ground systems technologies developed for achieving the attitude determination accuracy and the position determination accuracy. They include a precision star tracker, optimal attitude estimation algorithms (real-time and off-line), an alignment change reduction, a jitter sensor, a precision GPS receiver, and a ground-based position estimation algorithm. The star tracker provides the best star position accuracy (random error: 9.0arcsec, and bias error: 0.74arcsec). The on-board attitude determination algorithm estimates attitude quaternion by applying an extended Kalman filter. The off-line attitude estimation introduced an extended-Kalman-filter-based smoother. To minimize the alignment change, the sensors are placed on the optical bench subject to precise temperature control. The jitter sensor provides precise angular information (0.010arcsec) from 2Hz to 500Hz and extends the attitude determination bandwidth. The dual-frequency GPS receiver capable of measuring pseudoranges and carrier phases allows the ground-based position determination with sub-meter accuracy.