![background image](http://html1.mh-extra.com/html/campbell/skyvue-8m/skyvue-8m_product-manual_489150011.webp)
2.1 Introduction
The SkyVUE 8M is a light detection and ranging (LIDAR) ceilometer that emits short pulses of
near infrared light into the atmosphere from a semiconductor laser. The pulses of infrared light
are scattered back by aerosols including cloud droplets. The time between transmission of the
pulse and the return signal gives the range, and therefore height, of the scattering aerosols. The
variation in the strength of the back-scattered light signal with height gives a profile of scatter
coefficients and allows identification of cloud bases. If significant scattering is detected without a
defined cloud base, then a vertical visibility can be calculated.
The control system of the SkyVUE 8M is divided into three modules, DSP, TOP and PSU as
follows:
DSP (Digital Signal Processor) is the main data processing and communications unit of the
SkyVUE 8M. It hosts two separate time keeping circuits that are cross checked. An alarm is
triggered if the circuits disagree.
TOP (top of the unit) provides safety shutdown features such as over and under laser output
level. It also contains the calibration circuitry and dirty windows system.
PSU (Power Supply Unit) controls the power supply including battery charging and deep
discharge protection.
The SkyVUE 8M has a rugged environmental enclosure that protects the instrument from the
harshest conditions and will measure the atmosphere with high stability and repeatability.
2.1.1 Cloud height detection
A scatter profile is measured as described in
Measurement of the attenuated backscatter profile
Cloud height detection is carried out as described in
(p. 96). Up to four
cloud heights can be detected.
If clouds are not detected, the SkyVUE 8M will give one of these reports:
l
No significant backscatter.
l
Full obscuration determined but no cloud base detected. This is reported if the criteria for
detecting cloud base is not met but the integrated scattering coefficient reaches the limit
of vertical visibility below a set height limit. The default value is 2000 m (6560 ft) but can be
changed by the user. The height at which this occurs is given as vertical visibility.
SkyVUE™8M Tactical LIDAR Ceilometer
6