control box was mounted in each airplane. The intervalometer was placed in the nose compartment, and the control box was located to the right of the , pilot, Pre actuating signals to the camera were fed through aicroawitches actuated by two separate cams driven by a common motor, This arrange- ment provided two speeds, "fast" (approximately 3 signals per second) and "slow" (approximately 3 signals per minute), Either could be select- ed manually by the pilot by means of a switch on the control box, Two Camera speeds were required in order to economise on film, yet obtain rapid photographs in the radiation cloud. In addition, there was a third position marked "auto" which automatically changed the speed from "slow" to "fast" when the ambient radiation exceeded a given level, us- ually set between 1 and 10 r/hr. in the next paragraph. This part of the circuit is described A dynamotor driven by the airplane's 28-volt power supply provided de, which was converted to -700 volts de by means of ea mitivolts +150 vibrator, amplifier, and filter, This ~700 volts was connected to ground through an Anton 5980/BS~-2 Geiger-Muller tube and a 1.2-megohm resistor. A 0,000l-microfarad condenser connected the junction of these two elemnts to the grid of a CK58l4 tube and, in conjunction with the resistor, determined the quench of the Geiger-Muller tube, As the radiation field increased, the Geiger-Muller tube broke down more often, sending negative pulses through the condenser to a CK58&14 tubs. These pulses were ampli- fied and inverted in a subsequent stage and wre fed through the coil of a relay. When the repetition rate becam sufficiently great (at a rate somewhat lower than the maximm allowed by the quench circuit), the direct-current component of the pulses became sufficient to close the relay, which in turn closed a second relay which switched the interval con- trol from "slow® to "fast." When the radiation rate diminished suffici- ently, the interval control reverted to "slow" automatically. 2.2.6 Photopanel, The camera and photopanel located in the nose of the aircraft were used to photograph the meters from the Sigmatron and Bioscel, whose sensing elements were located in the cockpit, Also installed in the photopanel wre a clock, altimeter, acceleromter, and airspeed indicator, When correlated with the radiac instrument readings, these gave «a record of tims in cloud, altitude of penetration, and condi~ tions of flight within the cloud. Ths photopanel also contained a small marker light. This was controlled by a toggle switch on the photopanel control box, Using this light the pilot could mark the film at specific times, such as cloud entry and exit. The camera used was a Vought lé-mm recording camera loaded with 100 ... feet of Eastman Special Emlsion (SO 1112) fila, This film 4s not fogged by gamma doses of less than 500 r, Suitable lighting was included to provide the intense light required for this special film, The lights and the camera utilized the aircraft's 28-volt power supply, 2.3 UESCRIPTION OF REQUIRED DATA In order to satisfy the purposes of this project, accurate informa~ tion was required on the following parameters: 18 (1) tims of penetration BEST AVAILABLE COPY