Advanced Land Observing Satellite ALOS

The Japanese Earth observing satellite program consists of two series: satellites mainly for atmospheric and marine observation, and the ones mainly for land observation. The Advanced Land Observing Satellite (ALOS) is a Satellite following the Japanese Earth Resources Satellite-1 (JERS-1) and Advanced Earth Observing Satellite (ADEOS) which will utilize advanced land observing technology, The ALOS will be used for cartography, regional observation, disaster monitoring, and resource surveying.
The ALOS has three remote-sensing instruments: the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) for digital elevation mapping, the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) for precise land coverage observation, and the Phased Array type L-band Synthetic Aperture Radar (PALSAR) for day-and-night and all-weather land observation. The ALOS will be launched by an H-IIA launch vehicle from the Tanegashima Space Center in 2002.

Main Characteristics

Launch:
Early 2002 / H-IIA Launch Vehicle
Tanegashima Space Center

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Life:
3 - 5 year

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Orbit:
Altitude=Approx. 700km, Sun-Synchronous Subrecurrent,
Inclination=Approx. 98deg., Period=Approx. 99min., Recurrent Perid=Approx. 45day,
Local time at Descending Node=10:30AM+-15min.

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Weight:
Approx. 3,850kg (at lift-off)

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Power:
Approx. 7000W (EOL)

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Experiment System

Objectives and History of Development

The ALOS is one of the largest Earth observing satellite in the world. Its objective are:

1. to provide maps for Japan and other countries including those in Asian-Pacific region (Cartography).
2. to perform regional observation for "sustainable development" (harmonization between Earth environment and development)(Regional Observation).
3. to conduct disaster monitoring around the world (Disaster Monitoring).
4. to survey natural resources (Resources Survey).
5. to develop technology necessary for future Earth observing satellites (Technology Development).

Beginning in 1993, NASDA has conducted a conceptual study of the ALOS satellite systems as well as fabrication and test of remote-sensing instruments. NASDA is currently conducting a phase-B study. The ALOS will be launched in 2002.

Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM)

The PRISM is a panchromatic radiometer with 2.5-meter spatial resolution. In obtain terrain data including elevation, the PRISM has three telescopes for forward, nadir and backward view. Precise land information can be obtained frequently by the PRISM.

Major Specifications of PRISM

Observation Band	0.52 - 0.77µm (Forward-Nadir-Backward)
Base/Height ratio	1.0
S/N	70
Spatial Resolution (IFOV)	2.5m (3.57µrad)
MTF	0.20
Swath Width	35km
Pointing Angle	+-1.5deg. (cross track)

Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2)

The AVNIR-2 is a visible and near infrared radiometer for observing land and coastal zones and provides better spatial land coverage maps and land-use classification maps for monitoring regional environment.
The instrument has a cross track pointing function for disaster monitoring.

Major Specifications of AVNIR-2

Observation Band	ch1: 0.42 - 0.50µm, ch2: 0.52 - 0.60µm, ch3: 0.61 - 0.69µm, ch4: 0.76 - 0.89µm
S/N	200
Spatial Resolution	10m
MTF	ch1 - 3: 0.25, ch4: 0.20
Swath Width	70km
Pointing Angle	+-40deg. (cross track)

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

The PALSAR is an active microwave sensor for cloud-free and day-and-night land observation and provides higher performance than the JERS-1's SAR. The sensor has a beam steerable in elevation and the ScanSAR mode, which allows us to obtain a wider swath than conventional SARs.
The development of the PALSAR is a joint project between NASDA and Japan Resources Observation System Organization (JAROS).

Major Specifications of PALSAR

Observation Mode	Fine Resolution Mode	ScanSAR Mode
Frequency	L-band
Polarization	HH or VV (option: HV or VH)
Spatial Resolution	10m (2 looks) 20m (4 looks)	100m
Swath Width	70km	250 - 360km (3 - 5scans)
Off-nadir Angle	18 - 48deg.
S/A	25dB
NE0	-25dB