Mobile version

The location system LRR

The LRR is an array of mirrors that provides a target for laser tracking measurements from the ground. By analysing the round-trip time of the laser beam, we can locate where the satellite is on its orbit.


A laser retroreflector is attached to a mount on the nadir panel close to the RA antenna. It has two functions:

  • support-to-satellite ranging,
  • RA altitude calibration.

The LRR is a passive device which is used as a reflector by ground-based SLR (Satellite Laser Ranging) stations using high-power pulsed lasers. In the case of ERS-1, tracking using the LRR was mainly performed by the International Laser Ranging Service (ILRS).

The ILRS provides tracking for the satellite from its global network of laser ranging stations. Laser stations fire short laser bursts at ERS and time the interval before the pulse is reflected back. These ILRS stations are relatively few, but because their positions are very accurately known, they provide a set of independent reference measurements of ERS's position, which contribute to the satellite's precise orbit determination.


The operating principle of the LRR is therefore to measure on the ground the return trip time of laser pulses reflected from an array of corner cubes mounted on the Earth-facing side of the satellite. The corner cubes ensure that the laser beam is reflected back parallel to the incident beam. The detailed design of the cubes includes compensation for the aberration of the laser beam caused by the satellite's velocity: the satellite moves almost 40 metres between the emission and reception of the laser pulse from the SLR station, and this is compensated for by slight nonparallelism of the reflected beam.

The corner cubes are made of the highest-quality fused silica and work in the visible spectrum. Their performance is optimised at the two wavelengths (694 nm and 532 nm) commonly used in SLR stations. The corner cubes are symmetrically-mounted on a hemispherical surface with one nadir-pointing corner cube in the centre, surrounded by an angled ring of eight corner cubes.

This allows laser ranging in the field of view angles of 360° in azimuth and 60° in elevation around the perpendicular to the satellite's Earth-facing panel (positioned on the axis at point -Zs with respect to the satellite's centre of mass).

Further information on ERS (Esa website)


Rss feedsContactPartnersFAQLexiconMobile
You must enable cookies in your browser preferences to save the modifications
You are using an older version of Internet Explorer, please update to take full advantage of Aviso+ features

Customize the home page

View all widgets
Reduce display
Public profile
User profile

Select/Deselect widgets

Discover AVISO+

Customizable home, reading tools, products search guide, etc.. Discover step by step the features of the new site AVISO+.

Customizable homepage

The new home page is composed of blocks called "widgets".

Rearrange the blocks with a "Click & Drop".

Hide a widget with the cross at the top right. Reset or add a widget with the "wrench" icon. The "User" and "Public" profiles offer a predefined organization.

All the modifications are automatically saved as cookies on your machine so as to enable you to have your own specific AVISO+.

Reading tools

Ease your reading by choosing the page background colour (black/white) and/or by modifying the font size.

Browsing menu and breadcrum trail

To ease your browsing through AVISO+, you can use at any time the main banner items with the interactive submenus or use the browsing menu on the left side of the screen (it is open by default). For more readiness of the page contents, you can fold and unfold the browsing menu by clicking on the tab. At any time you can know where you are thanks to the browsing menu or the breadcrum at the top of the page.

Products search guide

The first submenu of the "Data" banner item leads you to a new search form enabling you to find quickier the product that suits your needs. The list of results is updated according to your selection criteria.

AVISO+ Multimedia

The first submenu of the "Multimedia" banner item leads you to AVISO+ collections of images and videos linked to altimetry and its applications. Have a nice visit!