The instrument is configured for monostatic monitoring; which consist in generating an infrared signal from the interferometer, send this signal to the retro-reflector to be reflected back to the FTIR and collected by a MCT detector. The air path between the instrument and reflector is absorbing part of the infrared signal and provides the atmospheric transmission signature.

OP-MR monostatic monitoring configuration

The silicon carbide (SiC) globar emitted light is modulated by the FTIR before being sent to the retroreflector and collected by the MCT detector after travelling back and forth between the FTIR sensor and retroreflector, thus the only AC signal detected is the IR source modulated energy and all the environment non-modulated energy is DC signal filtered out by the amplifier. Excluding the environment radiance from the air transmittance is important to avoid the addition of environment emitted energy over the air transmission measurement, which would reflect in gas concentration measurement error.

The OP-MR photo-voltaic MCT detector combined with the design of its amplifier provide a highly linear response function in respect to the variation of energy intensity; the linearity of response is very important to precisely model the chemical signature and measure gas concentration.

  • Consists in sending an active signal back and forth to a retroreflector, measuring the transmitted signal through the observation path length
  • The air path between the FTIR and retroreflector is absorbing part of the infrared signal and provides the atmospheric transmission signature
  • The OP-MR monostatic monitoring configuration offers the advantage of excluding the passive radiation emitted by the environment from the measurements

Characteristics

From Spec Sheet:

  • Spectral Range: 740 to 6660 cm−1 (1.5 – 13.5 µm)
  • Spectral Resolution: 1, 2, 4, 8, 16, and 32 cm−1 at all wavelengths
  • Spectral Stability: Better than 0.01 cm−1
  • Scan Speed: 5 cm/s, fixed
  • Sensitivity: SNR 1000 to 1 peak-to-peak
  • Instrument Field of View: 5 mrad (10” Cassegrain telescope)
  • Detectors: 77 K cooled photovoltaic MCT detector (Liquid Nitrogen or Optional: Stirling cooler)