The Advanced Land Observing Satellite (ALOS) series, operated by the Japan Aerospace Exploration Agency (JAXA), provides a wealth of open and free satellite data. While not a traditional consumer product, this data is a valuable resource for researchers, students, and enthusiasts interested in Earth observation, mapping, and disaster monitoring. This article outlines the available ALOS data types, access methods, and key considerations for users in the UK and globally, based exclusively on the provided source material.
Introduction to ALOS Open and Free Data
The ALOS series, including ALOS-1 and ALOS-2, was developed to support mapping, land-coverage observation, disaster monitoring, and resource surveying. JAXA has established programmes to make data from these satellites available at no cost under specific conditions. The data is primarily intended for scientific and research purposes rather than direct consumer use. Key datasets include optical imagery from instruments like PRISM and AVNIR-2, and radar data from the PALSAR-2 instrument.
Available Data Types and Instruments
ALOS-1 Optical Data
ALOS-1 carried several instruments, and their data is available through specific services. The instruments and their operational periods are documented, providing context for the available datasets. - PRISM (Portable Remote Imaging Spectrometer): Operated from 2006 to 2011, this instrument collected high-resolution panchromatic and multispectral data. - AVNIR-2 (Advanced Visible and Near Infrared Radiometer Type 2): Also operational from 2006 to 2011, AVNIR-2 provided multispectral data in four bands. - PALSAR (Phased Array L-band Synthetic Aperture Radar): This radar instrument was operational from 2006 to 2011 and collected data without spectral resolution.
ALOS-2 PALSAR-2 Radar Data
ALOS-2, launched in 2014, features the PALSAR-2 radar instrument. JAXA provides open and free access to specific PALSAR-2 products, particularly ScanSAR L1.1 and L2.2 data. These products have been released for various observation periods, including data from August 2014 to the present. For example, following the earthquakes in southeastern Turkey in February 2023, JAXA conducted emergency disaster observations and released corresponding PALSAR-2 ScanSAR L1.1 data for free via its G-Portal. The file size for a single L1.1 data product can be substantial, approximately 30 GB.
How to Access Free ALOS Data
Accessing ALOS-1 Optical Data
The ALOS Optical Online Dissemination Service provides access to ALOS-1 PRISM L1B, AVNIR-2 L1C, and ALOS African Coverage optical data collections. Users can browse and search available products through a web interface, which allows navigation by tree view, filename, or on a geographical map. To download any product, users must register on the ESA Earth Online Portal and sign in to the service. Registration is required for data download, but browsing is freely available.
Accessing ALOS-2 PALSAR-2 Data
PALSAR-2 ScanSAR L1.1 and L2.2 products are available through JAXA’s G-Portal. Users can download these data free of charge. JAXA has provided updates on product availability, such as the release of data for the period from August 2014 to February 2023 in April 2023. In cases of G-Portal outage, alternative provision methods for Open and Free data have been announced. For instance, in October 2024 and February 2025, alternative provisions were made available due to service interruptions. Additionally, software update documents for PALSAR-2 ScanSAR L2.2 products have been published.
Accessing ALOS World 3D Elevation Data
ALOS World 3D (30m) is a global elevation dataset derived from ALOS data. It can be accessed through the Global Elevation Data Download Tool provided by OpenTopography. This web-based application allows users to download elevation data for any region worldwide by selecting an area on an interactive map, choosing a dataset (such as ALOS World 3D), and selecting an output format (GeoTiff, ASCII Grid, or IMG). Before downloading, users must obtain a free OpenTopography API key by signing up for an account on the OpenTopography website. The ALOS World 3D dataset has a global coverage from 82°N to 82°S with a resolution of 30 metres.
Eligibility and Usage Considerations
The provided source material does not specify geographic restrictions for accessing ALOS open data; it is generally available to users worldwide, including those in the UK. However, users should be aware of the following: - Registration Requirements: Access to ALOS-1 optical data requires registration on the ESA Earth Online Portal. Access to ALOS-2 radar data via G-Portal and elevation data via OpenTopography requires account creation on their respective platforms. - Data Volume: ALOS radar data files are large (e.g., ~30 GB per file), which may require sufficient storage and bandwidth for download. - Intended Use: The data is provided for research and educational purposes. The source material does not mention any restrictions on commercial use, but users should consult the specific terms of service for each platform.
Practical Steps for UK Users
- For ALOS-1 Optical Data: Visit the ALOS Optical Online Dissemination Service. Register for an account on the ESA Earth Online Portal if you do not have one. Log in to browse and download data.
- For ALOS-2 Radar Data: Go to JAXA’s G-Portal to download PALSAR-2 ScanSAR L1.1 and L2.2 products. Create an account if required.
- For ALOS World 3D Elevation Data: Visit the OpenTopography website, sign up for an account to receive a free API key, and then use the Global Elevation Data Download Tool to select your area of interest and download the data in your preferred format.
Conclusion
The ALOS satellite series offers valuable, free Earth observation data through several open-access programmes. UK-based researchers, students, and enthusiasts can obtain optical imagery from ALOS-1 via the ESA Earth Online Portal, radar data from ALOS-2 via JAXA’s G-Portal, and global elevation data from ALOS World 3D via OpenTopography. While the data is freely available, users must register on the respective platforms and should be prepared for potentially large file sizes. The availability of emergency data, such as that for the 2023 Turkey earthquakes, highlights the programme’s role in disaster response. For the most current information on data availability and access procedures, users should refer directly to the official platform websites.