each of these conditions is reached at different times in the life 
of the satellite. Thus, there is considerable variation of the 
total amount of input thermal radiation and of the total power input 
from solar cells. Since the maximum electrical power and maximum 
thermal input occurs Simultaneously, a serious battery temperature 
and overcharge condition is likely to occur in 100% sunlight orbits. 
This problem was responsible for the failures that eventually 
occurred in both TRANSIT 1-B and TRANSIT 2-A. Recently a very 
simple solution to this problem has been found by the proper choice 
of satellite configuration and limited attitude stabilization. 
Imagine a satellite in the shape of a drum with a 
magnet aligned with the symmetry axis of the drum. [If proper damp- 
ing is provided and competing torques are kept low, such a satellite 
will be constrained by the magnetic torques to have its symmetry 
axis in the same plane as the earth's magnetic axis. Since the 
magnetic axis of the earth is approximately the rotation axis, the 
symmetry axis of the satellite will lie approximately in the orbital 
plane. It is then seen that during the 100% sunlight axis, when the 
orbital plane is at right angles to the earth-sun line, then the 
satellite's symmetry axis will also be approximately orthogonal to 
earth-sun line; in other words, the sun will illuminate the edge of 
the drum at all times and not the top and bottom. 
In the other extreme case, when the sun lies in the 
plane of the orbit, it is clear that tke sun will illuminate the 
top and bottom of the drum-shaped satellite a reasonable percent 
of the time. It is clear that by making the top and bottom of the 
satellite large in area compared to the edge, it is possible to 
arrange that the effective received solar radiation at the satel- 
lite is just as great in the 60% sunlight case as it is in the 100% 
Sunlight case. 
By the use of the design principle outlined above, a 
configuration has been developed for the operational TRANSIT satel- 
lite in which the total temperature extremes will vary by no more 
100 
