Diurnal density variations measured by the San Marco 3 satellite in the equatorial atmosphere

Abstract

A first analysis is presented of the San Marco 3 density data which were obtained on a continuous instantaneous basis by the ‘balance’ experiment during the period May 3 through November 2, 1971, in the latitude belt of ±3.2°. This analysis has been carried out in two ways: selecting constant altitude points (200–350 km) over a perigee revolution (24‐hour local time variation) and reducing to the same altitude the data of the passes of single days. The main results for the diurnal variations are as follows. The Jacchia type R coefficient is strongly altitude dependent and increases between 200 and 280 km; R variation with UT is also apparent and may be related to the semiannual perturbation; and a significant content of 8‐hour and 6‐hour harmonics is present on the bulge profiles.

Equatorial composition in the 137- to 225-km region from the San Marco 3 Mass Spectrometer

“…The total oxygen concentrations (O + 202) were determined by assuming that atomic oxygen, which entered the antechamber, only recombined to form molecular oxygen and was not permanently lost. Comparisons of the mass densities calculated from the mass spectrometer composition with the mass densities from the in situ drag force measurements [Broglio et al, 1973] at altitudes where atomic oxygen is the dominant gas have confirmed this assumption to be essentially correct. The total mass density computed from molecular nitrogen, total oxygen content, argon, and helium is independent of how oxygen is distributed in its atomic and molecular form.…”

“…These first thermospheric composition measurements from a satellite at altitudes as low as 137 km provide a direct com-Copyright ¸ 1974 by the American Geophysical Union. The Italian satellite SM 3, launched on April 27, 1971, into a 3ø-inclination orbit, carried an in situ (active) dragmeasuring experiment [Broglio et al, 1973], the neutral atmospheric composition experiment (Nace), and the neutral atmospheric temperature experiment (Nate). The Nace employed a closed source, magnetic mass spectrometer with a gold-plated ion source and antechamber to measure the primary atmospheric gases N2, Ar, He, total oxygen content (02 and O), and possible contaminant gases CO, CO2, and H20.…”

Local time and altitude variation of equatorial thermosphere midnight density maximum (MDM): San Marco drag balance measurements

“…The signal-to-noise ratio is optimized taking advantage of the spin modulated signal for an estimated noise level less than 10% at 500 km, decreasing with altitude, to less than 1% at 260 km. The force to density conversion used a drag coefficient of 2.17 (Broglio et al, 1976, Arduini et al, 1993. The measurement is continuous over orbit sections lasting from 5 to 8 minutes for SM3 to much longer periods extending to 50 minutes for SM5.…”

Broglio Drag Balance for neutral thermosphere density measurement on UNICubeSAT

“…An instrument capable of directly measuring the drag force is the Broglio Drag Balance Instrument (DBI), which was flown in the five San Marco satellites, weighing about 100 kg, designed, built, launched and operated by the Scuola di Ingegneria Aerospaziale in cooperation with NASA between 1963and 1988(Jacchia and Verniani, 1965Broglio, 1967Broglio, , 1969Broglio et al, 1976;Arduini et al, 1993Arduini et al, , 1996a The original instrument can be adapted to be flown on board nanosatellites and, due to recent electronics miniaturization, the hardware can be scaled down to fit inside a standard Cubesat nanosatellite bus, which is a 10 cm side cube, weighing 1 kg described in Heidt et al (2000).…”