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CORRECTION OF SENSOR ALIGNMENT OF ADEOS-IUGLI
T. Hashimoto ^ *, K. Yamamoto", T. Igarashi *
* Japan Aerospace and Exploration Agency (JAXA)/Earth Observation Research and application Center (EORC),
1-8-10, Harumi, Chuo-ku, Tokyo 104-6023, Japan
(hashi, kath, igarashi)@eorc.jaxa.jp
KEY WORDS: Photogrammety, Geometric, Accuracy, Optical, Sensor, Correction
ABSTRACT:
The Advanced Earth Observing Satellite (ADEOS)-II was successfully launched in December 2002 by Japan Aerospace and
Exploration Agency (JAXA: former NASDA). The Global Imager (GLI) onboard the ADEOS-II is an optical mechanical scanner
with 36 channels and the spatial resolution of 1 km and 250m at nadir. It observes about 1,600km in width with the FOV of +/-45
degrees. The same areas are observed every 4 days. JAXA has conducted the initial checkout of GLI image properties just after the
launch of the satellite. In the checkout activities, the absolute geometric accuracy was examined. The accuracy was evaluated
utilizing ground control point(GCP)s which were automatically extracted by the template matching between GLI image chips and
coastline database. The examination for many images showed the geometric accuracy was about a few kilo-meters on the ground.
Most of the errors were static, in other words, every image has the almost same geometric errors in both amplitude and direction.
Such error patterns were seemed to be induced by the miss-alignments of the GLI sensor. The authors corrected the alignments of
the GLI sensor based on the collinearity condition in the photogrammety. After the correction, the geometric accuracy was improved
to about one pixel even in 250m channel images.
1. INTRODUCTION
1.1 GLI sensor
The GLI is an optical sensor which observes solar light
reflected from the Earth's surface including land, ocean and
cloud, or infrared radiation, globally and frequently measures
the physical data such as surface temperature, vegetation
distribution, and ice distribution. These data might be used for
acquiring the global circulation of carbon, monitoring cloud,
snow, ice and sea surface temperature, and grasping the primary
marine production. The GLI succeeds the mission of the Ocean
Color and Temperature Scanner (OCTS) onboard the ADEOS
that was launched in August, 1996, with more precision and
more observation targets. The GLI has 23 channels in visible
and near-infrared region (VNIR), 6 channels in short
wavelength infrared region (SWIR), and 7 channels in middle
and thermal infrared region (MTIR) for its multi spectral
observation. The ground resolution is 1km at the nadir, a part of
the channels in VNIR and SWIR has a resolution of 250m at the
nadir which are used for observing vegetation and clouds. The
observation region by mechanical scanning is 12 or 48 pixels
(12km) in the along-track direction and 1600km in the cross-
track direction. The cross track scanning is performed
mechanically by rotating the scan mirror. It has also the tilting
function for preventing sun glint. The tilting angle is about +20
degree or -20 degree from the progressing direction.
e Sun-synchronous sub-recurrent orbit
altitude 802.92 km inclination 98.62 deg
eriod 101 minutes recurrent period | 4 days
Table 1. Orbit of ADEOS-II
Corresponding author.
The GLI data are received at the Earth Observation Center
(EOC) of JAXA, and processed to standard products. They are
transferred to the EORC for generating higher level products.
1.2 Scan Geometry of GLI
The GLI scans the geo-surface from the East to the West. The
light from the Earth is reflected on the scan mirror, and
reflected on 45 deg. mirror, main mirror and sub mirror, then
reached the detectors as shown in Figure | (JAXA/EORC,
2003). The detectors are arrayed on five different focal planes
(refer to Figure 2). Both sides (A and B) of the scan mirror are
used for scanning. The difference of normal vectors of both
sides results in the different distortion on the image.
Finally, the view vector (b.,b.,b,) in the satellite
coordinates is expressed by the function of following
parameters.
(b. 5 b,)= f(@, 0. m, n, A! B, a, 5) (1)
where — « —scan angle
0 — tilt angle
(m, n) 7 detector address
A/B — difference of mirror A/B side
a — alignment for scanning axes
s = SaUGLI alignment
