MERLIN Frequency Reference Unit

The satellite MERLIN (Methane Remote Sensing LIDAR Mission) is a German-French cooperation.

MERLIN mission goal

MERLIN is a mission to observe the concentration of the greenhouse gas methane.

In this cooperation CNES signs responsible for the Satellite Bus, which is a Myriade Evolution, and DLR signs responsible for the Instrument. The instrument on MERLIN is a pulsed high power LIDAR (Light Detecting and Ranging) operating precisely at the methane absorption lines at 1645 nm wavelength.

The MERLIN Frequency Reference Unit FRU

To enable the required emission wavelength at 1645 nm a frequency reference unit (FRU) is part of the instrument on the satellite. The FRU contains a methane cell, several diode lasers (1064 nm and 1645 nm emission wavelength), a wavemeter and the associated control electronics for stabilizing the diode laser emissions and the high power laser pulse frequency to the methane cell and the wavemeter.

Key and driving requirements of the MERLIN FRU

  • An absolute laser frequency accuracy of  10 MHz
  • 5 mW of optical output power at 1645 nm

SpaceTech's role in the MERLIN FRU project

Since January 2015 SpaceTech is responsible for the development of FRU in subcontract to the instrument prime Airbus DS (Ottobrunn). 

In Phase B extension the work focussed on the development of the preliminary design of the FRU subsystem as well as on breadboarding of dedicated subassemblies to verify the achievable performance of the selected design. Phase B ended with the successful PDR.

In the current Phase C/D, the FRU development continues with the EM, the QM and the actual flight model.

Interesting links on MERLIN


CNES Site on MERLIN (French)

Article: The absolute frequency reference unit for the spaceborne methane-sensing lidar mission MERLIN (CEAS Space Journal)


Das diesem Bericht zugrundeliegende FE-Vorhaben wird im Auftrag des Bundesministeriums für Wirtschaft und Energie (BMWi) unter dem Förderkennzeichen 50EP1301 durchgeführt. Die Arbeiten sind Teil einer Kooperation zwischen DLR Raumfahrt-Management und CNES beim deutsch-französischen MERLIN-Satellitenprojekt. STI führt die Arbeiten im Unterauftrag der Firma Airbus DS GmbH, Ottobrunn durch. Die Verantwortung für den Inhalt dieser Veröffentlichung liegt beim Autor