ENCYCLOPEDIA OF Espionage, Intelligence, and Security Volume ...

DosimetrySEE ALSOFBI (United States Federal Bureau of Investigation)Homeland Security, United States DepartmentWeapons of Mass DestructionDoppler Radar.SEE Stealth Technology.Doo Transmitter❚ LARRY GILMANDosimetryA Doo radio transmitter, officially known as a T-1151 radiotransmitter, is a radio transmission device camouflagedas a pile of animal droppings or, in its most common form,a large single fecal dropping from an animal indigenous tothe area of intended use. Regardless, the external form ofthe device was designed to discourage close examinationand thus, detection or disruption.Initially developed by United States military intelligenceabout 1970, the Doo transmitter was a homingdevice camouflaged as dog or monkey feces for use inVietnam. At just over four inches long and three-quartersof an inch in height, this inconspicuous spy tool was smallenough to be carried easily. It could send or receiveradio messages, usually by Morse code. The effectivelycamouflaged beacon was positioned throughout the junglesof Vietnam, where it transmitted a radio signal thathelped aircraft pinpoint key enemy ground sites for strikesor reconnaissance. The device often had a peat mosscrusted shell.Because the Doo transmitter was often left undisturbed,operational life was often a function of the batterylife of its nickel-cadmium battery array. This advantagewas often essential when the transmitter was utilized as ahoming device. Because the device gave the appearanceof fecal matter, it was often left undisturbed and thus aretained high efficiency as a homing beacon even whenplanted days or weeks before a mission.Another operational advantage of the Doo transmitterwas its capacity to remain concealed long after itsoperational usefulness ended. Accordingly, in addition todetection avoidance while operational, the long-term detectionavoidance qualities of the transmitter did not allowthe enemy the intelligence advantages of knowing that aparticular site was at one time used as a transmission orrendezvous point.The Doo transmitter design reflects an open concealmentdesign concept used by intelligence agencies. Suchopen concealment devices remain easily visible, only theoperational nature of the device is concealed.SEE ALSOShoe TransmitterShort-Wave TransmittersVietnam WarEncyclopedia of Espionage, Intelligence, and SecurityDosimetry measures the amount of radiation energy absorbedover a given period of time by an object (e.g.,human body) or by part of that object (e.g., an organ ortumor). Here, radiation refers not only to ionizing radiationof the sort emitted by radioactive materials—fast particlesand gamma rays—but to light, radio waves, or ultrasound.Dosimetry is essential wherever radiation is utilized totreat cancer; the treatment must deliver a sufficient doseto target tissues without delivering too large a dose toother parts of the body. Dosimetry is also needed, whereverradioactive materials are handled in significant quantities,to track the cumulative exposure of individuals andto moniotor for accidental releases of radioactive material.A device that measures cumulative radiation exposureis a dosimeter. A Geiger counter is a radiation detector,but not a dosimeter, because it gives only a momentto-momentreading of radiation intensity; a strip of photographicfilm, however, whose degree of exposure indicateshow much radiation it has absorbed (up to its saturationlimit), can act as a dosimeter. Filmstrip dosimetersare, in fact, still used to measure exposure to ionizingradiation. By grading the sensitivity of a specially formulatedfilm strip from one end to the other, it can be made toindicate net, cumulative radiation exposure as a bar ofdarkening that grows from the most sensitive end of thefilm to the least sensitive end. Such ”badge dosimeters“are common in the nuclear weapons and nuclear-powerindustries. However, they have the disadvantage that theymust be developed to be read, and so do not give thebearer immediate knowledge of their exposure level.Another type of dosimeter is the pen ionizationdosimeter. These devices contain a long, narrow chamberfilled with a few cubic centimeters of nonconducting gas.A metallic contact touches the interior of the chamber ateach end. When the dosimeter is to be used, an initialelectric charge is placed on the gas tube; that is, animbalance of electrons is created between the two ends.Since the gas in the tube is normally nonconducting,electrons cannot travel through it to even out the chargeimbalance. However, ionizing radiation passing throughthe gas forcibly frees electrons from atoms in the gas (i.e.,partly ionizes the gas), and these negatively charged electronsare free to flow toward the end of the tube having apositive charge. The more ionizing radiation the pendosimeter is exposed to, therefore, the more of its initial359