intensity of the incident radiation. This EMF 

 is transmitted to a recording potentiometer. 

 11-12 The Pyrheliometer Installation. — 



The installation consists of 1 topside pyr- 

 heliometer (which measures total incoming 

 radiation) and 2 inverted outboard pyrheliom- 

 eters (which measure reflected radiation from 

 the sea surface). The outboard instruments 

 are fastened to the ends of booms which sus- 

 pend them well clear of the sides of the ship. 

 The output of these instruments is recorded by 

 an electronic recording potentiometer which is 

 located below deck (fig. 11-1). 



11-13 Operating the Recorder. — The out- 

 board pyrheliometers should be uncovered 

 and the booms rigged out after the ship is in 

 open seas. The topside pyrheliometer should 

 be uncovered and then the recorder turned on. 

 The recorder is run continuously from 1 hour 

 before sunrise to 1 hour after sunset. The 

 recorder is turned off during the night to con- 

 serve chart paper. It is not necessary to rig 

 in the booms each night unless desired. 



11-14 Marking the Recorder Chart. — The 

 following information is entered on the re- 

 corder chart every 4 hours at 0800, 1200, 1600, 

 and 2000 local time with the corresponding 

 Greenwich mean time also noted: 



a. Date — giving day, month, and year. 



b. Time — as above. 



c. Ship's position and heading. 



d. Any pertinent remarks concerning opera- 

 tion of the equipment including the time of 

 cleaning the pxTheliometer bulbs. 



11-15 Maintenance. — The p>Theliometer 

 bulbs become encrusted with salt spray and 

 must be wiped clean at least once each day, and 



more often as necessary. The recorder should 

 be lubricated occasionall}' with a special oil, 

 which is provided. The battery should be 

 checked and replaced when the indicator 

 shows red. The chart paper roll should be 

 checked daily to prevent running out during 

 the day. When a roll is about two-thirds 

 used it tends to become loose on the takeup, or 

 bottom roller. When this happens, loosen 

 the takeup and carefully tighten the paper. 

 The printing mechanism shoidd be checked 

 frequently for proper inking on the chart. 



11-16 Precautions. — The pjTheliometer as- 

 sembly is durable enough to withstand fairly 

 heavy sea conditions; however, it is advisable 

 to rig in and secin-e the equipment if bad 

 storms and abnormally heavy seas are en- 

 countered. On naval vessels, the pyrheliom- 

 eter should be secured and the bulbs removed 

 and stored before any large caliber guns are 

 fired as the bulbs will be shattered by the 

 concussions. 



11-17 Storing and Shipping Pyrheliometer 

 Records. — Used chart paper rolls are labeled 

 indicating the ship's name and number, cruise 

 number and name, and dates of beginning and 

 ending of the roll. If the original roll boxes 

 are retained, the rolls may be stored and 

 shipped in them. If there are no such boxes 

 available, the rolls should be fanfolded, inserted 

 in heavy manila envelopes, and shipped in 

 covering envelopes or heavy wrapping paper. 

 These records should be forwarded at the end 

 of a cruise to — 



The Hydrographer 



U. S. Navy Hydrographic Office 



Washington 25, D. C. 



Attn: Code 5430 



112 



H. O. 607 



