ALOS satellite data

The Advanced Land Observing Satellite (ALOS, also known as Daichi) is a Japanese satellite launched on 24 January 2006. For most of 2006, the satellite underwent extensive calibration validation before products were released.

The satellite provides high quality, low cost Earth observation data for topographical mapping, disaster and environmental monitoring and climate change studies. ALOS also provides an alternative source of data and a level of back-up to the Landsat series of satellites.

A five-year Memorandum of Understanding (MOU) with the Japan Aerospace Exploration Agency (JAXA) grants Geoscience Australia the data distribution rights for Australia, New Zealand, Papua New Guinea and the South Pacific Islands.

Overview of ALOS web pages and how to order

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Objectives

ALOS is one of the largest Earth observing satellites in the world. Its objectives are to:

1. provide maps for Japan and other countries including those in Asia-Pacific region;
2. perform regional observation for sustainable development (harmonisation between Earth environment and development);
3. conduct disaster monitoring around the world;
4. survey natural resources; and
5. develop technology necessary for future Earth observing satellites.

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Satellite characteristics

Launch date	24 January 2006
Expected life	3-5 years
Altitude	Approx. 692 kilometres
Orbit	Sun-Synchronous Sub-recurrent
Inclination	98.16°
Period	98.7 minutes
Recurrent period	46 days
Local time at descending node	10:30AM ±15 minutes
Weight	3850 kilograms

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The ALOS satellite carries three main sensors

1. PRISM: Panchromatic Remote-sensing Instrument for Stereo Mapping

The PRISM sensor is mainly designed for mapping. It consists of three sets of telescopes for forward, nadir and backward viewing with each telescope providing 2.5 metre spatial resolution. These specifications facilitate generation of precise Digital Elevation Models (DEM), and achieve the accuracy for 1:25,000 scale maps. The PRISM also has a capability to acquire in wide swath mode (70 kilometre) although it is expected most acquisitions will be in triplet mode (35 kilometre swath).

Swath width – triplet mode (forward, nadir and backwards) (most commonly used mode)	35 kilometre (at nadir)
Swath width – wide swath mode (mainly for disaster response)	70 kilometre (at nadir)
Spatial resolution	2.5 metres (at nadir)
Wavelength	0.52 - 0.77 µm (visible green)
Scanning method	Push broom with 6 CCDs for Nadir telescope and 8 CCDs for each Forward and Backward telescopes.
Stereo imaging base-height ratio	1.0
Pointing angle	±1.5° capability +1.2° for odd numbered cycles -1.2° for even numbered cycles
Quantisation	8 bits

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2. AVNIR-2: Advanced Visible and Near Infrared Radiometer type 2

The AVNIR-2 sensor is useful for observing land and coastal zones and provides better spatial land coverage maps and land-use classification maps for monitoring regional environments. The instrument has a cross track pointing function for disaster monitoring. This may also allow simultaneous observation with PALSAR.

Swath width	70kilometre (at nadir)
Spatial resolution	10 metres (at nadir)
Wavelength	band 1: 0.42 - 0.50 µm (visible blue) band 2: 0.52 - 0.60 µm (visible green) band 3: 0.61 - 0.69 µm (visible red) band 4: 0.76 - 0.89 µm (near infrared)
Scanning method	Push broom with 1 CCD for each band.
Pointing angle	±44 degrees
Quantisation	8 bits

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3. PALSAR: Phased Array type L-band Synthetic Aperture Radar

The PALSAR is an active microwave sensor for cloud-free and day-and-night land observation. It has a number of modes:

• Fine beam or high resolution mode is the main mode and chiefly used for detailed regional observations and repeat-pass interferometry. Data in this mode can be acquired as single polarisation (FBS) or as dual polarisation (FBD).
• Direct downlink mode is suited for direct downlink by international ground stations such as ACRES.
• ScanSAR or wide beam mode will allow acquisitions of about 250-350km width by sacrificing spatial resolution. This is considered to be useful for sea ice extent and rain forest monitoring. This mode is suited for direct downlink by international ground stations such as ACRES.
• Polarimetric mode will operate on an experimental basis. Polarisation is changed in every pulse of the transmission signal and dual polarisation signals are simultaneously received.

Observation mode (Descriptor)		Fine beam single (FBS High resolution)	Fine beam dual (FBD High resolution)	Direct downlink (DSN)	ScanSAR wide beam (WB1, WB2)	Polarimetric (PLR)
Frequency		L band (1.27GHz)
Polarisation *Default mode		HH* or VV	HH+HV* or VV+VH	HH* or VV	HH* or VV	HH+HV +VH +VV*
Direct downlink		No	No	Yes	Yes	No
Incidence angle		9.9 - 50.8°	9.9 - 50.8°	9.9 - 50.8°	24.6 - 27.1°	9.7 - 50.8°
Spatial resolution	Range	10 metres	20 metres	20 metres	100 metres	30 metres
	Azimuth	6.25 metres (2 looks) 12.5 metres (4 looks)	6.25 metres (2 looks) 12.5 metres (4 looks)	12.5 metres (4 looks)	100 metres	12.5 metres (4 looks)
Swath width		70 kilometres	70 kilometres	70 kilometres	250 kilometres(3 scans) 300 kilometres (4 scans) 350 kilometres (5 scans)	30 kilometres

For more information on PALSAR, please see Japan Aerospace Exploration Agency (JAXA).
For ALOS product technical specifications, please see ACRES technical documents.

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Enquiries and orders for ALOS data

Please refer to the Overview of ALOS web pages - How to Order.
If you have further enquiries, please contact ACRES.