02 Oct 2002
Coherent develops the first terahertz laser to go into space and monitor the health of the ozone layer.
Coherent and NASA's Jet Propulsion Laboratory (JPL) have developed the first terahertz laser that will go into space. The 2.5 THz source is also the first gas laser to meet the stringent performance requirements for a mission lasting over five years.
The device, codenamed the Laser Local Oscillator (LLO), will be mounted on NASA's Earth Observing System (EOS) AURA satellite and launched in 2004. EOS AURA will be the first satellite to measure the chemistry of the lower atmosphere with multiple instruments. Operating at 118.8 µm, the LLO will monitor the concentration of the hydroxyl radical (OH) molecule, which removes ozone from the atmosphere.
The LLO is methanol laser pumped by a carbon dioxide laser. It emits 31 mW at 2.5 THz. With space and weight at a premium on the satellite, the whole system measures just 75 x 30 x 10 cm and weighs only 21 kg.
One of the biggest challenges facing the development team was heating management, according to Coherent's manager of engineering and specialty products Eric Mueller. "You can't depend on air-cooling when you're in a vacuum," he says. "We had to design the whole system so that every component - down to the last resistor - had a conductive heat path."
JPL scientists are currently testing the LLO and claim to have seen no degradation in performance over the past eight to nine months. "The laser needs to operate on the ground for two years prior to the launch and then five years in orbit, without ever being serviced," says Mueller.
NASA says that the measurements taken by AURA will be valuable for diagnosing the potential for severe loss of Arctic ozone. The results will also determine whether the stratosphere is responding to the effects of the 1987 Montreal Protocol to eliminate the production of ozone-depleting chemicals.
Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.