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• Introduction
• Objectives
• Satellite characteristics
• Enquiries

Introduction

Geoscience Australia is no longer a distributor of imagery from the Advanced Land Observing Satellite (ALOS). A five-year Memorandum of Understanding (MOU) with the Japan Aerospace Exploration Agency (JAXA) granted Geoscience Australia the data distribution rights for Australia, New Zealand, Papua New Guinea and the South Pacific Islands. This MOU expired in December 2010, consequently no new ALOS data is available from Geoscience Australia.

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. 

Objectives

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

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

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

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 kilometres).

Swath width - triplet mode (forward, nadir and backwards) (most commonly used mode)	35 kilometres (at nadir) with 35 x 35 kilometre footprint per scene.
Swath width - wide swath mode	70 kilometres (at nadir) with 70 x 35 kilometre footprint per scene.
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

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 also may allow simultaneous observation with PALSAR.

Swath width	70 kilometres (at nadir) with a 70 x 70 kilometre footprint per scene.
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

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 Geoscience Australia.
• ScanSAR or wide beam mode will allow acquisitions of about 250-350 kilometre width by sacrificing spatial resolution. This is considered to be useful for sea ice extent and rainforest monitoring. This mode is suited for direct downlink by international ground stations such as Geoscience Australia.
• 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 please see JAXA/PALSAR.
ALOS product technical specifications are available from ALOS Product Descriptions and Formats.