Specim Owl Thermal instrument

The Specim OWL is a multiband thermal instrument covering ​LWIR (specifically 7.6 to 12.3 μm) with 103 bands. In combination with SWIR measurements, this range enables better classification of minerals, particularly silicates.

As with the Sensors/Hawk, the detector technology is ​Mercury Cadmium Telluride, this time tuned for LWIR rather than SWIR. This means there may be a number of bad pixels that need to be masked out. The OWL has also been found to have "blinking" pixels (also called "naughty", as they're not reliably bad), which switch between two different levels during the capture - at the time of writing, these are masked out, though it is hoped that data can be recovered from them in future.

In order to calibrate the sensor, a pair of black bodies can be mechanically moved in front of the sensor lens one by one and a capture made. Under normal operational conditions, this is done automatically at the end of every line, after the autodark (closed shutter dark frames) capture. The black bodies should generally be set to bracket the temperature range of interest. The sensor response has been rated as essentially linear.

The instrument and, more importantly, measurements are vulnerable to water absorption, so a desiccant cartridge is used to maintain conditions internally. The system (detector and optics) is temperature stabilised

The official Specim page can be found at ​http://www.specim.fi/index.php/products/airborne/aisaowl

Data quality and calibration/validation reports may be found in the Reports section.

Instrument parameters

All numbers provided by Specim 15 May 2014:

Measurement	Value
Measured FOV (total)	24.20 degrees
Measured FOV (from centre)	-11.79 degrees, 12.41 degrees
Paraxial FOV	-11.80 degrees, 12.39 degrees
Sensor IFOV	0.063 degrees or 1.103 mrad
Lens focal length	42.886
- Focal length evaluation wavelength	10014.19nm
Optical axes position (central pixel)	187.7
Max distortion	0.0755mm or 0.0210 degrees or 0.171%

Instrument type is "OWL3", serial number is ??????. The evaluation was made with an objective of type OLEL43, serial number 011402.

Internal hardware configuration

Details about the internal hardware (e.g. camera type, link protocol, optics, etc) are currently unknown, but will added here if they become generally available.

Raw file format

As with the other sensors, an ENVI BIL format is used. The data are stored in raw binary (16 bit) and the metadata in the accompanying .hdr file. Filenames are of the form NAME_YYYY-mm-DD_HH-MM-SS.{raw|hdr}, where NAME is assigned by the operator.

Black body captures are stored exactly as normal camera data are. Filenames are as above, but prepended with T1_ or T2_ depending on which black body was viewed.

Navigation / timing system

See Sensors/SpecimNavSync.