NSSDCA ID: 1971-036A-02
Mission Name: San Marco 3The objectives of the San Marco 3 satellite mission included (1) to measure the equatorial thermospheric density, temperature, and neutral composition as a function of atmospheric heating, and (2) to study the correlations between three sets of neutral density measurements, each obtained using a different technique, namely, direct particle count, instantaneous satellite drag, and integrated satellite drag. The composition of the neutral equatorial atmosphere was measured in situ over five complete cycles of local solar time. The mass analyzer was a double-focusing magnetic sector instrument and was a modification of the sensors flown on Explorer 17 (63-009A-01) and Explorer 32 (66-044A-02). Entering through a knife-edged orifice, the atmosphere particles struck the walls of a gold-plated stainless steel thermalization chamber. They were ionized by electron bombardment in the dual-filament enclosed ion source which was also gold-plated. Simultaneous measurements were obtained of the following species: helium (4), atomic oxygen (16), molecular nitrogen (28), molecular oxygen (32), and argon (40). The analyzer could be tuned by ground command, and therefore occasional measurements were made of the concentrations of the following species: atomic nitrogen (14), water vapor (18), and carbon dioxide (44). Linear range-switching electrometers were used. Since the spectrometer was mounted with its entrance orifice normal to the satellite spin axis, which was maintained nearly perpendicular to the orbit plane, the ion source concentrations were spin-modulated with a spin period ranging from 10 to 6 s. From these modulated signals, the ambient concentrations were obtained. Preliminary results showed good agreement between the total mass density values obtained from the three techniques. Some of the data obtained are presented in G. P. Newton et al., "Local time variation of equatorial thermospheric composition determined by the San Marco 3 NACE," J. Geophys. Res., v. 80, n. 16, p. 2289, 1975. Data from this investigation no longer exist.
Mass: 14 kg
Power (avg): 12 W
Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office
Name | Role | Original Affiliation | |
---|---|---|---|
Dr. George P. Newton | Principal Investigator | NASA Headquarters |