MERLIN LAE

MERLIN Laser Electronics

EM Model of the two LAE boxes LAEU (left) and LAEP (right).
EM Model of the two LAE boxes LAEU (left) and LAEP (right).

Scientific Purpose

The MERLIN mission, developed by DLR German Space Administration, and CNES, the French Space Agency, is dedicated to the methane (CH4) monitoring. Methane, as an important component of the global carbon cycle, is significant to the warming of the Earth’s climate.

The mission is based on a small satellite for space-based measurement of spatial and temporal distribution of the atmosperic methane columns on a global scale. Launch is planned for 2027.

Instrument Description

The Laser Electronics (LAE) is the only electrical interface (I/F) towards the MERLIN transmitter’s solid state laser (LAS). The LAS is a seeded single frequency Nd:YAG master oscillator power amplifier S/S laser with subsequent Optical Parametric Oscillator (OPO) for wavelength conversion towards 1645nm output wavelenght. The LAE provides:

  • control for oscillator cavity length by piezo sine wave excitation using a cavity dither approach,
  • high power current pulses towards laser diodes,
  • fast rising, high voltage pulses to the Pockels cell for active q-switching of the oscillator,
  • OPO cavity length control via a further piezo,
  • closed loop thermal control of the optical bench employing two loop heat pipes, and
  • high accuracy thermal control of the two OPO crystals via resistive heaters.

All tasks are fulfilled by dedicated hardware driver modules whose analogue parameters and required timing are controlled by a complex FPGA, making the LAE an almost self-standing unit that can be parameterized, monitored and triggered by the Instrument Control Unit via a Space Wire I/F.

Model Philosophy and Present Status

Following a breadboarding phase for all hardware drivers, an elegant Engineering Model (EM) was built. Its as far as possible representativeness to the planned Proto-Flight-Model (PFM) successfully allowed qualifying ESD- and shock-tests. In addition to standalone functional verification, concept validation was performed by LAE integration and operation with a LAS breadboard (BB) and Frequency Reference Unit (FRU) EM during a transmitter BB campaign. At present, the LAE CDR process is performed prior to PFM manufacture.

The LAE consists of two boxes: The LAEP box is mounted directly at the laser housing and accommodates the Pockels cell driver, the other one (LAEU) is mounted onto the common panel and provides all other functionalities.

EM Model of the LAEU showing the 4 compartments during assembly.
EM Model of the LAEU showing the 4 compartments during assembly.

Specifications

Mass (LAEU and LAEP) ≈ 6.1 kg
LD current pulses to OSC 55 A ... 80 A
LD current pulses to AMP 70 A ... 130 A
Q-switch voltage pulses to PC up to 4.1 kV
Max. repetition freq. 20 Hz
DC supply 27 ... 37 V
Input power ≈ 60.5 W
Output power to LAS ≈ 27.8 W
Operational temperature range -20°C ... +45°C

The German part of the MERLIN project is funded by the German Federal Ministry for Economic Affairs and Energy under DLR contract 50 EP 1601.

Contact

To request more info, please write E-Mail to Dr. Josef Dalcolmo, E-Mail: dalcolmo@vh-s.de.