recievers to fleet units, two more land based mobile receivers, plus a large central processing 

 site next year. The images presented in this report are exclusively from the mobile remote- 

 site receivers. 



The sensors consist of two scanning radiometers. One is a two channel scanning radio- 

 meter for high resolution visual data (HR) and for high resolution infrared data (HRIR). It 

 employs one scanning mirror and a beam splitter which separates the incoming radiation by 

 allowing transmission of visual radiation (HR .4-1 . 1/x m) and reflection of the infrared 

 (HRIR 8-13^ m) radiation. The second sensor is for very high resolution visual data (VHR) 

 and very high resolution infrared data (WHR), visual and infrared sensors with the same wave- 

 length bands as the high resolution sensor (HR). The spatial resolution of these sensors is a 

 function of geomety. When specifying resolution, reference is made to the maximum spatial 

 resolution at satellite subpoint, 2 nautical miles for the HR sensor and 1/3 n.mi. for the 

 VHR-WHR sensor. Spatial resolution is however a function of distance from satellite subpoint 

 and the resolutions degrade laterally to the extremities of each sweep or scan line to 14 n.mi. 

 for HR-HRIR and 2 n.mi. for VHR-WHR. The sensors produce an analog signal proportional 

 to the amount of incoming radiation. The analog signal is processed in two modes, it is 

 digitized and transmitted in real time to remote sites, and it is tape recorded in analog form 

 for later transmission to readout stations in the U.S. 



The visual range sensors have sensor responses approaching zero at 0.4/xm and again at 

 1.1^ m, with the peak of sensitivity at 0.8/i.m. The half-power points are at approximately 

 0.57 and 0.97/x m. Since the strictly visual range is from 0.4 to 0.7/j. m, a large part of what 

 the visual sensors detect is a reflection of near infrared energy. The sensor measures the 

 total radiation received in the full spectral range, and effectively integrates the sensor- 

 response equation. The analog output (video) signal is proportional to the area under the 

 sensor-response curve. The brightness level of this video data is thus proportional to the 

 total radiation in the range received while the amount of radiation at any given wavelength 

 may vary. The spectral response beyond the Q.JjJ. m point is useful in enhancing the contrast 

 between vegetation and water, but some phenomena might become visible in the imagery 

 that would be invisible to the unaided eye. 



The infrared sensors use the 8-13/u.m atmospheric "window", which is relatively trans- 

 parent to emitted radiation in this spectral range. This is an "imperfect window" however, 

 with data contaminated by normal atmospheric constituents: namely ozone, carbon dioxide, 

 water vapor, and aerosols. Of these contaminants, ozone and water vapor are most important. 

 This contamination causes a variable amount of the radiation emitted from the sea surface 

 to be absorbed and scattered. Natural variations in the amount of ozone and its distribution 

 in the troposhere add only very small uncertainty to the infrared data. Water vapor has the 

 most serious effect on the accuracy of sea surface temperatures from the infrared sensors. 

 Nowhere in the 8-13^ m range is the atmosphere completely transparent to infrared radia- 

 tion, but water vapor absorption is least from 9.5-10.5/i m increasing away from this 

 narrow band. 



The data from the HRIR sensors have been found to be a useful indicator of variations 

 in sea surface temperatures, and thus an important source of coastal oceanographic data. 

 The HRIR data, properly displayed provides a chart of sea surface temperature variations. 



