Atmospheric density above 158 kilometers inferred from magnetron and drag data from the satellite OV1-15 (1968-059A)

A cold-cathode magnetron pressure gage and a C-band radar beacon were part of the complement of experiments aboard the polar-orbiting atmospheric research satellite OV1-15 (1968-059A). Over the period July 13–15, 1968, when the perigee of the satellite was near the equator at about local noon, the atmospheric density height-profiles were repeatedly measured down to 158 km. The profiles agreed in the northern and southern hemispheres below 200 km, but above 200 km the northern profile was greater than the southern, in approximate agreement with the Jacchia model that includes a symmetric density bulge at the subsolar latitude at 1400-hr local time. During a moderate magnetic disturbance the atmospheric density at latitudes below about 40° increased with an amplitude and lag that are adequately described by the Jacchia model. The duration of the density enhancement was observed to be several hours longer than the duration of the geomagnetic disturbance. At latitudes above 40° (which were available to us only in the southern hemisphere) the density enhancement decreased markedly with increasing latitude. The drag-determined density near perigee was the same, within the estimated errors, as that determined from the gage measurement, in contrast to the factor-of-2 discrepancy found in a similar comparison of data from the satellite Explorer 17.