72 ANlSrUAL REPORT SMITHSONIAN INSTITUTION, 196 2 



The work of the laboratory also includes a broad program of basic 

 research on the vacuum ultraviolet I'adiation of atoms and molecules 

 of astrophysical importance with 1- and 3-meter vacumn spectro- 

 gi'aphs and a shock tube and flash tube as sources. 



Trying to account for the effect of solar-radiation pressure on the 

 drag of the Explorer IX satellite, Dr. Luigi G. Jacchia, assisted by 

 Jack Slowey, fomid that the computed variations of orbital eccen- 

 tricity for that satellite are 3 percent too small when the old value 

 of the solar constant, 1.9-1 ly. min"\ is used; the discrepancy disappears 

 when use is made of the new value, 2.00 ly. min"^, proposed in 1960 by 

 F. S. Johnson to accomit for the excess ultraviolet radiation. This 

 experience suggests that artificial satellites, of appropriate construc- 

 tion and in appropriate orbits, could be used for a better determination 

 of the solar constant, although there remain serious difficulties con- 

 nected with the earth's albedo and with the reflectivity and the spin of 

 the satellite. 



Dr. Max Krook proceeds with his theoretical investigations into 

 the further development and application of methods for determining 

 the structure of nongray atmospheres. He is also applying, in a num- 

 ber of cases, methods developed in continuum theories in gas dynamics 

 to problems of the flow of rarefied gases ; examining various problems 

 in the dynamics of ionized gases (e.g., the structure of shock fronts 

 in the presence of magnetic fields) ; and studying the exact solution 

 of one-dimensional problems in the kinetic tlieoi-y of gases. 



Dr. Charles A. "Wliitney has completed several projects related to his 

 long-range studies of stellar atmospheres and stellar pulsation. He 

 has devised a simple but powerful new computational method for the 

 smoothing of spectrophotometric data, a central problem of obser- 

 vational astrophysics hitherto dependent on subjective procedures. 

 His comparison of theoretical with observed duration of line-splitting 

 in the spectrum of a pulsating variable (W Virginis) reveals excellent 

 accord with previous observations. His investigation of the reaction 

 of a stellar atmosphere to abrupt variations in heat flux from below 

 lias resulted in a formula that will aid in distinguishing between fluctu- 

 ations from variable heating and those from sound waves propagating 

 through the atmosphere. From his study of the structure of shock 

 fronts in hydrogen he has found, with the aid of Amgelo J. Skalaf uris, 

 that radiation produced by recombination behind the shock heats 

 and ionizes the gas ahead of the shock, thus significantly altering the 

 flow and temperature patterns. 



With the assistance of Mr. Skalafuris and W. Kalkofen, Dr. Whit- 

 ney has studied ionization relaxation with a one-level atom, an essential 

 aspect of the general shock problem, and has drawn some significant 

 conclusions on temperatures which, with other results, will bear im- 

 portantly on the whole program in this area. 



