Acousto-optic (AO) technology enables the characterization of Mars atmosphere

Artist’s impression of ExoMars over MarsThe European Space Agency’s (ESA) ExoMars programme aims to analyse the Martian environment and provide answers on the possibility of life on Mars.

A key part of the 2016 mission includes a Mars orbiter called Trace Gas Orbiter (TGO), which carries the NOMAD instrument. NOMAD combines three spectrometers to perform high-sensitivity orbital ExoMars with instrumentsidentification of atmospheric components, employing G&H acousto-optic tunable filter (AOTF) devices.

The successful testing of NOMAD on board the ExoMars 2016 Trace Gas Orbiter (TGO) was announced by ESA on 29 November 2016. NOMAD is a 3-channel spectrometer, 2 of which operate in the IR spectral region.

G&H space qualified AOTFTwo of our AOTFs have been integrated into NOMAD. Both AOTFs are fundamentally similar in concept with each acting as an order-sorter in a diffraction-grating based spectrometer. Effectively, the AOTFs select the order (and thus the wavelength-window) at which the grating diffracts. The first AOTF has a 5 mm aperture and operates in the infrared (IR) wavelength range. It is used on the “SO” (solar occultation) IR channel.

The second AOTF is essentially a larger version of the “SO” AOTF and draws upon our unique ability to routinely grow high quality large boules of single crystal tellurium dioxide (TeO2) at our facility in Cleveland, Ohio. At 15 mm, the aperture is three times the size of the SO AOTF, thus enabling a nine-fold increase in the throughput. This is a critical factor for the design and performance of the instrument. It is part of the “LNO” (limb, nadir and occultation) IR channel.

The NOMAD instrument is operating effectively and has already given an indication of its potential through first measurements recently reported.

AO technology inherently offers key advantages of delivering electrically- controlled solid-state components that are rugged with no moving parts and compatible with operation in a vacuum and extended temperatures. G&H AOTFs are specially developed to survive in the stringent environment of space with the required attention to design and manufacture  that ensures the development of highly reliable space hardware. We are able to use the experience gained from designing and fabricating devices for such demanding environments to further advances in AO device design for terrestrial applications.

G&H design and manufacture high-reliability space-qualified hardware based on acousto-optics, fiber optics and precision optics. We push the performance envelope of photonics technology in order to enable next-generation communication, navigation and remote sensing systems and applications, including Earth observation and deep space planetary exploration.