AIRSPEX 2005 was performed using four instruments during the flight over Longyeardalen: 2 imaging spectrographs with different spectral resolutions, a webcamera and a digital camera. All instruments were connected to a GPS for coincident sampling. Figure 3 shows a spectrograph which is similar to the BigSpex in our flight campaign. It contains three lenses (L1, L2 and L3), entrance slit (S1) and a prism with a tramsitting grating (i.e.grism, GP) in order to diffract the incoming light as a function of wavelength onto a Charge Coupled Device (CCD) detector at the exit.

Figure 3. Spectral imager used in AIRSPEX 2005.

Spectrograph specifications


Range: 374 - 700 nm
FWHM: 2 nm
sensitivity: 0.00015 lux
Entrance slit dimension: 4.5 x 0.025 mm
Focal lengths:
L1 (front lens): 12 mm
L2 (collector lens): 42 mm
L3 (camera lens): 25 mm

Grism: 30 deg Littrow prism and a transmitting holographic grating with 600 grooves/mm

The CCD:
Size: 6.837 x 4.9468 mm
# pixels: 795 x 596
Pixelsize: 8.6 um x 8.3 um

range: 425-820 nm
FWHM: < 5 nm
Entrance slit dimension: 4.8 x 0.025 mm
Focal lengths:
L1 (front lens): 50 mm
L2 (collector lens): 50 mm
L3 (camera lens): 50 mm

Prism - Grating - Prism (PGP)

The CCD (extended sensitivity in NIR region)
Size:6.4 x 4.8 mm

The result is viewed as a spectral image. This spectrogram is a function of wavelength (see range of spectrograph) and position along the slit. The spectrograph is moved along the target and samples continously throughout the predetermined flight tracks. It is necessary to calculate the swath width to know the spatial resolution of the path we are flying over, see Figure 1b in the introduction. This is defined as a function of the altitude (z), the width of the entrance slit (w) and the focal length of the front lense (f1),

The SW of our flights was 300, 700 and 1100 meters for 900, 2000 and 3000 meter tracks respectively.

We recorded the spectral images from DRONESPEX to a digital video recorder. The BIGSPEX was recorded to a digital tape recorder.

Camera specifications

An off-the-shelf webcam, removed from its original housing and inserted into a metal, ruggedized enclosure was used.

The Single-lens Reflex (SLR) camera chosen was the 6.17 megapixel FujiS2 Pro, with a Sigma 50mm lens attached and focused at infinity.

(Finished -MMK 10.05.2005)