Terahertz technology takes to the skies

Citation

(2003), "Terahertz technology takes to the skies", Sensor Review, Vol. 23 No. 2. https://doi.org/10.1108/sr.2003.08723bab.001

Terahertz technology takes to the skies

Terahertz technology takes to the skies

Keywords: Ozone, Satellites, Lasers, NASA

In our previous issue (SR 23:1 "The fast moving world of terahertz technology") we reported on some of the emerging applications of terahertz (THz) radiation and this technology is now poised to help to protect the planet from atmospheric ozone depletion.

Researchers from NASA's Jet Propulsion Laboratory (JPL) and US laser specialists Coherent Inc. have developed a unique THz frequency laser that will be mounted in NASA's Earth Observing System (EOS) Aura satellite, due to be launched in January 2004. EOS Aura is a NASA mission, run from its Goddard Space Flight Centre in Greenbelt, Maryland, to study the Earth's ozone, air quality and climate. It is designed exclusively to conduct research into the composition, chemistry and dynamics of the Earth's upper and lower atmosphere employing multiple instruments on a single satellite. It is the third in a series of major Earth observing satellites to study the environment and climate change and is part of NASA's Earth Science Enterprise.

The THz laser, dubbed the laser local oscillator (LLO), aims to quantify the atmospheric concentration of hydroxyl radicals which are involved in the ozone depletion process. Further, the AURA instrument package will help to assess whether the 1987 Montreal Protocol (which banned and phased-out certain ozone-depleting compounds such as CFCs) is having a significant effect.

The LLO is a methanol laser, pumped by a CO₂ laser and emits a power of 31mW at a frequency of 2.5 THz (i.e. 118.8 microns). The laser has been designed to be as light and compact as possible and weighs just 21 kg, with dimensions of 75 x 30 x 10 cm but as it will operate in a vacuum, air cooling is clearly impossible, so thermal management is a further critical design issue. To resolve this it has been necessary to configure the entire system so that each individual component has a conductive heat path. Power will be supplied by a solar panel on the Aura. This will generate a DC voltage which will be converted to the radio frequency (RF) energy needed to excite the carbon dioxide laser. All of the electronics, including the RF power supply, have a power consumption of only 120W. Another design factor is reliability, as the LLO's performance must remain constant during the entire 5 year Aura mission. It is presently being tested at JPL and will need to operate for 2 years on the ground before it is deemed to be suitable for launch. So far, no performance degradation has been seen during more than 9 months of testing.