determination from one day to the next. In the TRANSIT program an 
orbit is determined for each day based solely on the data obtained 
on that day so that each determination is totally independent of 
all preceding data. Hence, the day-to-day consistency of orbit 
parameters is a very good indication of the precision of the system. 
The determination of orbit parameters through most of the radiating 
life of TRANSIT 1-B is given in Figs. 2 through 9. It will be seen 
that the first four or five points show a much larger scatter than 
the subsequent points (particularly in Figs. 7 and 9). This results 
from the fact that for this initial period the satellite was still 
spinning and the spin caused a modulation on reception that was 
interpreted by the ground equipment as a change in the Doppler 
frequency. After this initial period the satellite was despun— 
and the data became much cleaner. It can be seen, particularly 
from Figs. 2 and 3 that, after the spinning period, the scatter of 
the day-to-day determinations of orbit parameters is generally well 
within one half of a kilometer or one quarter of a mile. 
The nature of the long term variation of the orbit 
parameters, particularly Figs. 2, 3, 4, and 5, is quite interesting. 
It is seen that both apogee and perigee exhibit a linear decrease 
with a sine wave oscillation superimposed. This oscillation has an 
amplitude of about 6 km and its period is the period of the preces- 
sion of perigee. Thus the sine wave terms in the formulae given 
for apogee and perigee are zero when perigee occurs at the equator 
and reaches its extreme values when perigee reaches the extremes 
of latitude. The linear decrease of apogee and perigee is due, of 
course, to drag. The effect of drag on apogee is five times as 
great as the effect on perigee. This is reasonable since most of 
the drag occurs as the satellites goes through perigee. This re- 
sults in a velocity decrease at perigee so that the satellite does 
not swing out quite as far at apogee the next time around. 
2/ Using the yo-yo technique. See "The TRANSIT Program", June 1960 
~ Astronautics 
102 
