Upper air pressure and density measurements from 90 to 220 kilometers with the Viking 7 rocket

Abstract

The density and pressure of the atmosphere from 90 to 220 km above White Sands, New Mexico, were determined from the Viking 7 rocket flight on 7 August 1951 at 11:00 a.m. MST. A Philips ionization gage was used to measure pressure and pressure changes on the side of the nose cone of the rolling rocket. Measured pressure in the 90 to 105 km region were corrected for velocity ram and residual gas, and were approximately one‐fourth of the Rocket Panel values. The derived pressure of 3×10−7 mm Hg at 220 km is twice the corresponding Rocket Panel value. Densities were measured from 120 to 185 km and at 220 km. The 220 km density value of 9×10−8 gm/m3 agrees with the Rocket Panel value. However, the density values at the lower altitudes are one‐fourth to one‐half those of the Rocket Panel. These lower density values in the 100 to 130 km region are in good agreement with values obtained from X‐ray absorption experiments. Scale heights, (RT/Mg), derived from the density data above 140 km, are approximately a factor of two higher than Rocket Panel values.

Empirical model of global thermospheric temperature and composition based on data from the Ogo 6 quadrupole mass spectrometer

“…The satellite was launched June 5, 1969 into an 820 inclination orbit with a 398 km perigee and 1100 km apogee and was operated until July, 1971. The reduction of the raw data to ambient densities makes use of the usual thermal transpiration equation in a moving coordinate system [Schultz et al, 1948;Horowitz and LaGow, 1957] and further includes corrections to the N2 densities as a result of CO contributions to the mass 28 peak, and corrections to atomic oxygen densities as a result of oxygen surface adsorption, recombination, and desorption [Hedin et al, 1972a]. For each gas species a density value is determined every 9 seconds.…”

Gas-Surface Interactions in Low-Earth Orbit

“…When the space age began, rocket and satellite measurements showed how gas-surface interactions occur on surfaces and within instruments in space: Atmospheric measurements by rocket-borne pressure gauges disagreed with theory, so the pressure gauges were spun to separate outgassing from the density measurement [18]. A similar difficulty was encountered when pressure gauges were flown on satellites [19].…”

On the Use of Ionization Gage Devices at Very High Altitude

“…If the body velocity is not zero, then the pressure relationship is less easily stated, but readily so upon assumption of a velocity distribution function. Many experimenters (7,13,14,15) have derived a relation which is seen to be the transpiration equation modified by a factor dependent upon the ratio of body to particle velocity. Thus Pi was defined only as the pressure in the chamber, implying total pressure.…”

“…Internally, however, it is assumed that the particle temperatures will be set by the wall temperature, adopting a unity accommodation coefficient. 7 A Maxwellian velocity distribution in the region being sampled follows the equilibrium assumption.…”

“…Since m can vary relatively from 1 (atomic hydrogen) to as much as perhaps 40 (argon), V g can have a range of about 6.5 to 1 for a given temperature. For purposes of evaluating the feasibility of the experimental approach, the minimum expected particle velocity can be taken as 1300 fps (argon at approximately 400 K), 7 See (15) for discussion of exceptions to this assumption. and the maximum as 15,000 fps (hydrogen atom at 1200 K) for any particle except the electron.…”