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====== Ceilometer CT25K ======

//Mentor: [[http://www.geomet.uni-koeln.de/das-institut/mitarbeiter/schween/|J.H. Schween]]//

===== Principle =====
A ceilometer measures the cloud base height, called //ceiling// in aviation. It is based on the light detecting and ranging (LIDAR) principle, i.e. it sends laser pulses and measures the backscattered light. From travel time the distance of the back scattering object can be determined. From strength and attenuation of the backscattered signal the backscatter coefficient is determined. The instrument identifies cloud bases by caluclating visibility from the backscatter coefficient and identifying the height from which on you cant see the ground any more. If the lower clouds are transparent it can detect up to three distinct cloud layers. In clud free cases we can use the backscatter profile for an estimate of boundary layer height.

===== Instrument =====
{{:instruments:ceilo:img_2776_1.jpg?200|}}\\
Current setup at [[http://www.fz-juelich.de/|Research Center Jülich]] on the roof of IEK-8.

===== Data =====
  * If you are interested in receiving data please contact the instrument mentor: // [[http://www.geomet.uni-koeln.de/das-institut/mitarbeiter/schween/|J.H. Schween]]//

  * [[http://atmos.meteo.uni-koeln.de/~hatpro/dataBrowser/dataBrowser2.html?site=JOYCE&date=-1&UpperLeft=Ceilo_ct25k_Backscatter&UpperRight=Ceilo_ct25k_Instrument-status|Quicklook archive]]



[[http://atmos.meteo.uni-koeln.de/~hatpro/jue/ceilo/current/index.html|Current data:]]


<html>
<a href="http://atmos.meteo.uni-koeln.de/~hatpro/jue/ceilo/current/index.html" target="_blank">
<img src="http://atmos.meteo.uni-koeln.de/~hatpro/jue/ceilo/current/bscat.png" width=420>
</a> click to enlarge
</html>       

===== History ====
^  Period  ^  Place  ^  Project  ^
| 11/10/2010 - today | [[http://www.fz-juelich.de/|Research Center Jülich]], Germany |  |
| 09/2007 - 05/10/2010 | [[http://www.fz-juelich.de/icg/icg-4/index.php?index=500|Selhausen]], Germany | [[http://www.tr32.de|TR32]] |
| winter months 2008/2009 | [[http://www.schneefernerhaus.de/|UFS]], Zugspitze, Germany | [[http://atmos.meteo.uni-koeln.de/tosca/| TOSCA]] |
| 2006 - 2007 | Nangatchori, Benin | [[http://amma-international.org/|AMMA]] |

===== Specifications =====

See manual section 1.2.6 {{:instruments:ceilo:ct25k-1_manual.pdf#22|page 8}} 
       and section 5.2.2 {{:instruments:ceilo:ct25k-1_manual.pdf#69|page 56}}.

^  Parameter  ^  Specification  ^ 
| Wavelength | 905 nm |
| Pulse Power | 16 W typical |
| Pulse energy | 1.6μJ ±20%((factory adjustment)) |
| Average Power | 8.9 mW |
| Pulse Width | 100 ns |
| Pulse Repetition Rate (PRR): | 5.57 kHz |
| Number of pulses (PQTY): | 65,536((65,536=2^16=64*1024=4^(7+1) the 7 contained in the last is what you find in the status message)) |
| Averaging time: | 11.7sec (=PQTY/PRR) |
| Time resolution | 15sec ((=> 3.3sec for processing and data transmission)) |
| Range resolution | 50ft = 30m (see [[internal:instruments:ceilometer:ceilo_readme#resolution_height_and_range|here]]) |
| Range | 200...25,000 ft. (60...7500 m) |
| Laser Divergence | ± 0.53×0.75 mrad (edge×diagonal((the laser is a diode with square shape. The beam thus a pyramid with different opening angles for neighbouring and opposite edges))) | 
| Field-of-View Divergence | ± 0.66 mrad | 
| Telescope diameter | 145mm |
| Tilting angle | 2.5° as of Aug 21 2015 (7° before...)  |
| Size | 760 x 280 x 245 mm |
| Power Consumption | 365 W |
| Weight    | 40 kg |
| Manufacturer |[[http://www.vaisala.com/en/meteorology/Pages/default.aspx|Vaisala]] |