About ASAR

Northwest Passage
ASAR multitemporal image over Tokyo

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 data from the Envisat mission through different systems, depending on the data type of interest. ASAR data are freely available to registered users.

Download data from the Envisat mission through the ESA Online Dissemination System. The ASAR data is freely available to registered users.

  • The ASAR High Resolution data (Single Look Complex (SLC) and Precision (PRI)) can be downloaded from the On-The-Fly (OTF) service. The OTF was launched in September 2016 and available through
    ESA Online Dissemination.
  • The OTF service allows users to generate high resolution ASAR Single Look Complex (SLC) and Precision (PRI) Level 1 products directly from ESA's Level 0 data archive. The product types available are IMS, IMP, APS, APP and WSS. Level 0 scenes are also available.
  • The ASAR Medium Resolution data (MR) and Global Monitoring (GM1) can be downloaded from EO Data Gateway. It contains full mission L1 archive for ASAR MR data.
  • The ASAR Wave mode (WV) data can be downloaded from: Envisat ASAR WAVE FTP
  • The ASAR Auxiliary Data Files (ADF) can be downloaded from: ASAR Auxiliary Data

For further details on the ASAR OTF service, 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.

In addition, ASAR supported a Module Stepping Mode for monitoring of the antenna transmit/receive modules. All Envisat ASAR products, in accordance with ESA Earth Observation Data Policy, are freely available to users.


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.