Pressure Gauges

Description

Three cold-cathode magnetron type density gauges (Redhead ionization gauges), each with its own high voltage supply and output electrometer, were flown to measure the density of the neutral atmosphere as a function of altitude, time, latitude, and solar and geomagnetic activity. One gauge was designated as NRC-528 and the other two as GCA-R5 to reflect different origins. Mounted on the satellite equator was one gauge of each designation, with the third gauge mounted 55 deg above the equator. The metal-ceramic GCA-R5 gauges had an internal magnetic field of about 0.1 T and contained radioactive material deposited on the anode to permit operation at low atmospheric densities (less than 10.E-17 g/cc) with the anode potential fixed at 3500 V. The GCA-R5 equatorially mounted gauge had a linear range switchable electrometer output, and high-resolution current measurements were obtained. The remaining two gauge outputs were through logarithmic electrometers. All electrometers were calibrated once each turn-on. The time resolution of the measurements was 2 s, which was equal to the satellite spin period and corresponded to a spatial resolution of 6 km along the orbit path. Further details regarding the experiment operation can be found in G. P. Newton et al., "Direct in situ measurements of wave propagation in the neutral thermosphere," J. Geophys. Res., v. 74, n. 1, p. 183, 1969. Data from this investigation no longer exist. The geophysical results were published.