Avir is developing technology for a remote sensor of chemicals using a new approach (patent pending) for differential absorption radiometry (DAR). The totally optical vapor analyzer (TOVA™) sensor can be packaged as a handheld device, unattended sensor, remote imager and more. It is optimized to provide near perfect correction for background absorption by at least one atmospheric species, e.g., water vapor. It replaces spectral scanning with detection at strong pre-selected spectral bands of chosen species and provides near perfect correction of absorption by pre-selected background species. The TOVA™ sensor is more efficient and thus more sensitive than alternative passive remote sensors. Integrating multiple DARs into a single system and using propietary algorithms can enhance specificity significantly. Remote sensing applications depend usually on interaction of radiation with the detected chemical. This interaction can be achieved by passing a laser beam through the atmosphere and detecting its attenuation or by collecting naturally occurring radiation and analyzing its spectrum. The latter does not require a light source and is called therefore “Passive Sensing”.

Passive sensing involves the detection of agents using naturally available radiation. All objects and gases emit infrared (IR) radiation — day and night and at all weather conditions — and, therefore, passive detectors attuned to sense this radiation can operate around-the-clock and do not require an artificial light source. A passive chemical vapor detector can identify agents through their unique pattern of IR absorptions (emissions).

Passive sensing has several advantages over active sensing. Eliminating the need for an artificial light source significantly reduces the cost, energy demands and complexity of the system thereby making it an ideal hand-held or unattended sensor. The primary drawback of passive sensing is the lack of longitudinal resolution (i.e., measurement of the distance to the target gas). Avir will configure its sensors as passive in order to reduce complexity. However, an active sensor configuration is also possible for uses that require the additional sensitivity or longitudinal resolution.