연안지식 > 위성영상소개 > 주요위성영상소개

ALOS

ALOS 는 2006년 1월 일본의 JAXA(Japan Aerospace Exploration Agency)에서 발사한 지구관측 위성이다.
ALOS 는 PRISM, AVNIR-2, PALSAR 세 가지의 센서로부터 영상을 획득할 수 있다는 것이 장점이다.

ALOS major specifications

Launch Date	January 24, 2006
Launching Vehicle	H - ＩＩA
Launch Site	Tanegashima Space Center, Japan
Spacecraft Mass	Approx. 4 tons
Generated Power (Solar paddle)	Approx. 7kw (at End Of Life)
Designed EOL	3-5 years
Orbit	Sun Synchronous, Sub recurrent
	Repeat Cycle: 46 days
	Sub-Cycle : 2 days
	Altitude : 691.65km (Above the equator)
	Inclination : 98.16 deg.
Attitude Determination Accuracy	2.0 x 10-4 deg. (off-line, with GCP)
Position Determination Accuracy	1m (off-line)
Data Rate	240Mbps (Via Data Relay Test Satellite)
Data Rate	120Mbps (Direct Transmission)
On-board Data Recorder	Solid-state Data Recorder (90Gbytes)

※PRISM (Panchromatic Remote-sensing Instrument for Stereo Mapping) PRISM은 2.5m 의 공간해상도를 갖는 Panchromatic 밴드의 영상으로서 스테레오 영상 획득에 적합하다.

PRISM Major Characteristics

Number of Bands	1 (Panchromatic)
Wavelength	0.52 to 0.77 micrometers
Number of Optics	3 (Nadir; Forward; Backward)
Base-to-Height ratio	1.0 (between Forward and Backward view)
Spatial Resolution	2.5m (at Nadir)
Swath Width	70km (Nadir only) / 35km (Triplet mode)
S/N	>70
MTF	>0.2
Number of Detectors	28000 / band (Swath Width 70km)
Number of Detectors	14000 / band (Swath Width 35km)
Pointing Angle	-1.5 to +1.5 degrees(Triplet Mode, Cross-track direction)
Bit Length	8 bits

※Note: PRISM cannot observe the areas beyond 82 degree north latitude and 82 degree south latitude.

AVNIR-2 (Advance Visible and Near Infrared Radiometer type 2

AVNIR-2은 ALOS 의 또 다른 광학 센서로서 Visible 과 Near Infrared 파장대에서 영상을 획득할 수 있다.

AVNIR-2 Major Characteristics

Number of Bands	4
Wavelength	Band 1 : 0.42 to 0.50 micrometers
	Band 2 : 0.52 to 0.60 micrometers
	Band 3 : 0.61 to 0.69 micrometers
	Band 4 : 0.76 to 0.89 micrometers
Spatial Resolution	10m (at Nadir)
Swath Width	70km (at Nadir)
S/N	>200
MTF	Band 1 through 3 : >0.25
MTF	Band 4 : >0.20
Number of Detectors	7000/band
Pointing Angle	- 44 to + 44 degree (Triplet Mode, Cross-track direction)
Bit Length	8 bits

※Note: AVNIR-2 cannot observe the areas beyond 88.4 degree north latitude and 88.5 degree south latitude.

PALSAR (The Phased Array type L-band Synthetic Aperture Radar)

APALSAR 는 L 밴드의 주파수를 갖는 SAR 영상이다.

APALSAR Major Characteristics

Mode

Fine Scan

SAR

Polarimetric(Experimental mode)*1

Center Frequency

1270MHz(L-band)

Chirp Bandwidth

28MHz, 14MHz

14MHz, 28MHz,

14MHz

Ploarization

HH or W, HH+HV or W+VH

HH or W

HH+HV+VH+W

Incident angle

8 to 60 deg. 8 to 60 deg

18 to 43 deg

8 to 30 deg

Range Resolution

7 to 44m, 14 to 88m

100m(multi look)

24 to 89m

Observation Swath

40 to 70km, 40 to 70km

250 to 350km

20 to 65km

Bit Length

5 bits, 5 bits

5 bits

3 or 5 bits

Data rate

240Mbps, 240Mbps

120Mbps, 240Mbps

240Mbps

NE sigma zero *2

< -23dB (Swath Width 70km)

< -25dB

< -29dB

< -25dB (Swath Width 60km)

S/A *2,*3

> 16dB (Swath Width 70km)

> 21dB

> 19dB

> 21dB (Swath Width 60km)

Radiometric accuracy scene

1dB / orbit: 1.5 dB

size of Antenna

azimuth :8.9m x elevation :3.1m

※Note: PALSAR cannot observe the areas beyond 87.8 deg. north latitude and 75.9 deg. south latitude when the off-nadir angle is 41.5 deg.
1 Due to power consumption, the operation time will be limited.
2 Valid for off-nadir angle 34.3 deg. (Fine mode), 34.1 deg. (ScanSAR mode), 21.5 deg. (Polarimetric mode)
3 S/A level may deteriorate due to engineering changes in PALSAR.

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ALOS