202 
ANNUAL REPORT SMITHSONIAN INSTITUTION, 1948 
DATA CALCULATED FROM SLOPE OF PRESSURE 
CURVE . 
DATA CALCULATED FROM RAM PRESSURE. 
BALLOON DATA. 
ALTITUDE - KM. ABOVE SEA LEVEL 
TEMPERATURE DEGREES 
KELVIN 
Ficure 8.—Variation of temperature with altitude. 
Radio pulse ionosphere height-find- 
ing methods in wide use today (39) 
can at most measure directly the index 
of refraction at certain points, whereas 
rocket-borne experiments may be 
designed to measure directly both the 
index of refraction and the ion density 
N at all points reached by the rocket. 
The V-2 reaches altitudes correspond- 
ing to the top of the E layer. Since in 
the E layer there is at present am- 
biguity as to the ratio of free electrons 
to ions, rocket-borne experiments are 
the most direct way to determine 
whether the parameter on the right- 
hand side of the expression should be 
in terms of electrons, ions, or both. 
A determination of data such as these 
will permit more accurate knowledge 
of many of the factors affecting long- 
distance radio propagation, such as 
delay times, velocities of propagation, 
