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--- tech:cloud_sensor [2009/01/27 18:51] – mates
+++ tech:cloud_sensor [Unknown date] (current) – external edit (Unknown date) 127.0.0.1
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-====== Mrakoměr ======
+====== Cloud sensing ======
 Because of an importance to protect the astronomical equipment against rain, masurement of the cloud cover is an important part of a decision scheme of an independent robotic observatory. It allows the system to detect the presence of a cloud cover, and up to some extent, supplement the information of observing conditions when the clouds are absent.
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 The basic principle of a cloudmeter is the fact, that the Earth surface tends to establish radiative equilibrium with anything above it - if overcast, there is a radiative equilibrium between the Earth
 surface and its cloud cover. On the other hand, when the clouds are not present, this condition disappears and the surface radiates into the universe. (Or tries to establish the equilibrium with the cosmic microwave background :-) )
+Of course, this principle works only in nighttime. During the day, Sun provides additional source of radiation and although the signal still can be used, it's interpretation is not straightforward.
+=====MRAKOMĚR=====
 {{ :tech:mrakomer2.jpg?200|The second prototype of Mrakomer (MM-2) in operation at the observatory of Ondřejov, CZ}}
-In the simplest way, this phenomenon was used in the first prototype of Mramomer - MM-1. It uses the Peltier
+Mrakoměr [[wp>IPA_for_Czech|[mrakomɲer] ]] is an [[wp>Open_hardware|Open Hardware]] project. After two prototypes, there are two (very similar) versions of the
+production devices. As of January 2009, there are 3 units known to be under operation. Furthermore, the second prototype - MM-2, is still operational as well.
+In the simplest way, this phenomenon was used in the first prototype of Mrakoměr - MM-1. It uses the Peltier
 cell inserted freely between the earth and the sky. The current generated by the cell is nonzero, and differs significantly when the clouds are present or absent.
-Further variants of the device used a less straightfordard, but equally effective way of detecting the clouds - measuring the effective temperature in the vertical direction. Second prototype - MM-2 is a moveable device, able to provide effective temperatures at various inclinacions. Further system - MM-3 and MM-4, which are considered to be a production line, are fixed for simplicity, providing only the temperature in the zenith.
+{{:tech:mrakomer3.jpg?200 |The first production sample of MM-3 after a tough night at BOOTES-IR, Sierra Nevada, Spain}}
+Further variants of the device use a less straightforward, but equally effective way of detecting the clouds - measuring the effective temperature of the sky with a solid-state thermopile infrared sensor. Second prototype - MM-2 is a movable device, able to provide effective temperatures at various inclinations. The production devices - MM-3 and MM-4, are fixed for simplicity, providing only the temperature in the zenith. MM-4 has, in comparison to MM-3 improved circuitry to provide fault-tolerancy against failure of the sensor, crash of the computer, and burning from lightning.
+Software support for Mrakoměr is natively in RTS-2 as a standalone device driver //rts2-sensord-mrakomer// and provides "BAD_WEATHER" signal in case that the readings suggest an overcast situation.
+More about mrakoměr can be found here: [[http://www.mlab.cz/]],
+description of MM-3 is here: [[http://www.mlab.cz/Designs/MRAKOMER3/DOC/description.pdf]]. Latest version is [[http://www.mlab.cz/Designs/MRAKOMER4/DOC/mrakomer41_en.pdf|MRAKOMĚR 4.1]] is sell by [[http://www.ust.cz/shop/product_info.php?cPath=29&products_id=43|UST]].
+===== LUNATICO AAGCV3 =====
+{{ :tech:lunatico_aagcw3.jpg?200|AAGCW3 image taken from the distributors website.}}
-Clouds reflect IR radiation. Lower the reflected radiation = less clouds. If you can measure it, you can estimate cloud cover from measurement.
+There is a commercial device, designed by [[http://www.aagware.eu/aag_cloudwatcher.htm| António Alberto  Peres Gomes]] and distributed by [[http://www.lunatico.es|Lunatico]], providing cloud sensing (and also light and rain sensing) in a similar way.
-More information can be obtained here: [[http://www.mlab.cz/Designs/MRAKOMER3/DOC/description.pdf]]
+See <code>man rts2-sensor-aag</code>  and [[https://azug.minpet.unibas.ch/wikiobsvermes/index.php/AAG_cloud_sensor| Cloud sensor]] for further documentation abou the device itself.