SECRETARY'S REPORT 161 



ultraviolet-sensitive television camera tubes, Schwarzschild telescope 

 systems, calibration lamps, a digital television photometric system, and 

 automatic identification and cataloging of stars. 



The ultraviolet-sensitive television camera tubes required much 

 research and development. The Project has been working for 4 years 

 with Westinghouse Research Laboratories to procure these devices. 

 Problems solved during the past year include Westmghouse's develop- 

 ment of a new target material that has increased the tube's sensitivity 

 and its suitability as a stellar photometer. Laboratory measurements 

 of the spectral response of this tube were made by Dr. Om P. Rustgi. 



The telescope system to be used with Celescope requires the produc- 

 tion of strongly aspheric optical surfaces mounted so as to survive the 

 mechanical environment of satellite launching, and to be insensitive 

 to large variations in temperature. 



For calibration of Celescope equipment in orbit, it was necessary to 

 obtain two types of ultraviolet point sources. One, utilizing a low- 

 pressure mercury-vapor arc, radiates intensely at 2,537 A. The other, 

 utilizing a low-pressure xenon arc, radiates intensely at 1,470 A. The 

 latter lamp required considerable developmental work in order to meet 

 requirements for small size and power consumption, long life, and 

 high efficiency. Dr. Rustgi and Clifford Miles have made laboratory 

 tests of these sources. 



The requirement to use a television system as a stellar photometer 

 posed problems of accuracy, reliability, linearity, and dynamic range 

 not encountered in the usual type of television data transmission. The 

 system, as developed by Electro-Mechanical Research, Inc., has proved 

 able to meet the performance requirements. 



Finally, George Szabo, Mrs. Gail Wald, and Stephen Strom have 

 prepared an ultraviolet identification catalog and are preparing tech- 

 niques for automatic compilation and publication of the Celescope 

 observational material. 



The accurate measurement of the number and direction of high- 

 energy gamma rays from the universe is a difficult instrumentation 

 problem. The importance of the measurement, however, justifies 

 great effort toward its accomplishment. Dr. Fazio has completed a 

 theoretical study of the production of gamma rays by cosmic radiation 

 in our galaxy. Using the results of these calculations, he is planning 

 further gamma-ray astronomy instruments for future orbiting observ- 

 atories. A new type of detector for high-energy gamma rays, a mul- 

 tiplate spark chamber, is now being developed at the Observatory. 



A program of spectroscopic observations of bright stars, which Dr. 

 Whitney initiated at the Agassiz Station of Harvard College Observ- 

 atory, will provide data for the theoretical work on the spectra of nor- 

 mal stars. Drs. Wright and Hodge have located Population II 



