About ASAR

ASAR multi-temporal image over Tokyo
ASAR multi-temporal image over Tokyo, Japan

The Advanced Synthetic Aperture Radar (ASAR) instrument was an active radar sensor on-board the Envisat satellite, which was operational from March 2002 until the unexpected loss of contact in April 2012. ASAR built upon the Active Microwave Instrument (AMI) carried aboard the ERS satellites.

ASAR was built by Matra Marconi Space (MMS) UK, now Airbus Defence and Space.

Applications for this sensor are many and include the study of the ocean, such as waves, sea ice extent and motion, and land surface studies, such as deforestation and ground movement.




Users can download ASAR data from the Envisat mission through different systems, depending on the data type of interest.
  • All ASAR L0, High- and Medium resolution Level 1 imagery data products are made available through the ESA (A)SAR Online Dissemination Service
  • ASAR L1 and L2 Wave products are accessible from the ESA Dissharm FTP server after specific product registration
  • The ASAR Auxiliary Data Files (ADF) can be downloaded directly from: ASAR Auxiliary Data

More info can be found in the section for ASAR Products information and from the Data Description for each product type in the section below.

All Envisat ASAR products, in accordance with ESA Earth Observation Data Policy, are freely available to ESA EO Sign In registered users.

For further details on the (A)SAR Online Dissemination Service (OTF), or other ASAR data products, including information on user access and forthcoming data releases, contact the ESA TellUs Service


ASAR was a high-resolution imaging radar, operated in 5 distinct measurement modes:

  • Image Mode (IM)
  • Alternating Polarisation Mode (AP)
  • Wide Swath Mode (WS)
  • Global Monitoring Mode (GM)
  • Wave Mode (WV)

To each measuring mode correspond several product file type, depending on different processing

Within each mode, several different image swaths were used. IM, AP and WS modes were designated as High Rate (HR) modes and had a downlink rate of 100 Mbps. GM and WV were Low Rate (LR) modes and had a data generation of 0.9 Mbps. More info can be found in the ASAR Product information web page.



The following tools are available for visualising, processing or analysing ASAR data.

Sentinel-1 Toolbox

Sentinel-1 Toolbox (S1TBX) consists of a collection of processing tools, data product readers and writers and a display and analysis application to support the large archive of data from ESA SAR missions including Sentinel-1, ERS-1 and 2 and Envisat.

Read more

Sentinel Application Platform

Sentinel Application Platform (SNAP) is a common architecture for all Sentinel Toolboxes. It is ideal for Earth Observation processing and analysis due to technological innovations.

Read more

ASAR Cal/Val

The goal of ASAR calibration and validation activities was to verify the accuracy and quality of data the instrument acquired.

ASAR Quality Control Reports

Quality Control is monitoring routinely the status of the spacecraft (payload and platform) and to check if the derived products meet the quality requirements along mission life-time. Product anomalies, daily, monthly and bulk processing reports are available for ASAR quality monitoring.