SECRETARY'S REPORT 151 



of the changing in orientation of the spin axis of several satellites.^ 

 The variation of the angular velocity of the satellites has been success- 

 fully correlated with the variation of the component of the magnetic 

 field normal to the spin axis. 



Dr. Richard H. Giese used optical observations (Baker-Nunn and 

 Moonwatch) to develop methods of attitude determination for cylin- 

 drical satellites with specular reflection.^ For diffuse reflecting cylin- 

 ders the formula for intensity as a function of arbitrary angles of 

 illumination and observation was derived and applied to numerical 

 computations for a tumbling cylinder. 



Phenomena in the earth's liigh atmosphere are being investigated 

 with several tools. As we have seen above, the atmospheric drag on 

 satellites has provided a sensitive measurement of density variations 

 above about 180 km. This altitude might be lowered if satellites of 

 very high density were launched. Dr. Charles Lundquist is examin- 

 ing the value of launching an ensemble of spherical satellites, some 

 with high densities, as a noninterference experiment on a development 

 flight of a large rocket vehicle. 



At altitudes between 80 and 100 km, the Doppler shifts in radar 

 returns from meteor trails may be used to measure the velocity and 

 direction of winds in the lower ionosphere. A project to make such 

 measurements and to study wind relationships ^ to other ionospheric 

 phenomena has been initiated by Dr. Mario Grossi in conjunction 

 with the Harvard-SAO Radio Meteor Project.^ 



Laboratory studies of atomic collision processes* are being com- 

 bined with a study of relevant problems in atmospheric physics in 

 the work of Dr. Nathaniel P. Carleton and his associates. Dr. Charles 

 H. Dugan, C. Papaliolios, and Miss Marion L. Shaw. The greatest 

 effort has been applied to investigation of excitation of metastable 

 states in O2, N2, and O by electron impact, and of the subsequent 

 reactions of these metastable states with other gases, including exci- 

 tation transfer and actual chemical reaction. Dr. Carleton, in collabo- 

 ration with L. R. Megill of the National Bureau of Standards 

 Boulder Laboratories, has used recent data on electron collisions to 

 study the problem of electron heating by electric fields in the iono- 

 sphere. The group is investigating, in particular, which features of 

 the airglow and aurora may be caused by electron-impact excitation 

 by the heated electrons. They conclude that the red lines of atomic 

 oxygen, 6300-6364 A, are almost certainly excited by this means in 

 low-latitude auroral forms, but that no other emission in the airglow 

 or aurora is so excited. 



The atmospheres and surfaces of other planets are being studied. 

 Dr. Carl Sagan has made theoretical studies of the expected limb- 



See footnotes on p. 164. 



