Embedded Files
Spectrometer
The instrument has an Offner-based imageing spectrometer (HORIBA Hyperspectral PoliSpectra® H116) with the following specifications:
Spectral resolution: 1.2-3.0nm @ T=-10°C
0.6-1.2nm @ T>=20°C
Spectral dispersion: 303-766.6nm / 2048 pixels → 34.8 nm/mm ≙ 0.23 nm/pixel
Smiley / keystone: ±0.4 nm ≙ ~10 pixels (focus dependent)
14 µm slit width
Spectral camera
The camera attached to the spectrometer (Sylent 4.2MP-U-6.5-BI CMOS camera) has the following specifications:
Full detector 2048x2048 pixels
above spatial pixel 910, all pixels are "blind" pixels (not illuminated)
the instrument reads 936 spatial pixels (910 illuminated, and 26 blind pixels for dark current correction)
the instrument reads 320 spectral pixels in the range 420-490nm to limit the data acquisition to the range relevant for the retrieval for NO2
12-bit A/D converter
Nonlinearity: 10% (value obtained from laboratory calibration)
Read Noise median: STD=1.0-18.9 e- (value obtained from laboratory calibration)
Full well: 53 ke-
gain: 2.0 counts/e- (value obtained from laboratory calibration)
Rolling shutter, 50MHz pixel readout rate, 43 fps frame rate
Lenses
The lenses attached to the camera can be exchanged manually. Two lenses are available:
Navitar optical lens UV0635BDM
65° "wide" field of view ≙ 5km in the valley of Innsbruck → 5.5m/pixel
focal length: 6mm
f#: 3.5-16
Navitar optical lens UV1054B
6° "narrow" field of view ≙ 450m in the valley of Innsbruck → 0.5m/pixel
focal length: 105mm
f#: 4.0-22
Webcam
The instrument is equipped with a webcam for visual weather inspection.
Figure B1: Instrument mounted on the tracker.
Figure B2: Spectrometer system inside the instrument head enclosure.
Power supply
Two solar panels are installed for power generation, together with an inverter battery that serves as backup battery storage to keep the instrument alive during bad weather periods.
Temperature control
Two passive coolant heat shield are attached to the head for cooling the system. Inside the enclosure, four heater elements and five temperature sensors are attached to the spectrometer to control the instrument above 15°C operation temperature. A thermal plate is attached to camera in order to deviate the heat generated during operation.
Tracker
The instrument is mounted on a tracker with two degrees of freedom - 360° in azimuthal and elevation directions. The LuftBlick TR1 tracker, which was developed for Pandora with support of ESA in 2018 [Müller et al., 2018] and has since then been successfully used in the Pandonia Global Network, has been adapted for this version. Since the KARLOS head weighs more than the Pandora headsensor, we use the next larger size of stepper motors in the adapted version (see section 2.1 of Müller et al. [2018]). The tracker is powered by 220V AC from the power supply grid.
Collimator
The instrument has a collimator attached on top of the telescope (a separate one for the narrow and wide field of view lenses; not shown in figures B1 and B2). This is needed to avoid the direct solar beam scattering off the first lens.
Page updated
Report abuse