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San Marco 2



San Marco 2 (San Marco-B) was the first satellite launched from a sea-based platform. The second satellite built by Italy, it was designed to study high altitude air density and its small-scale variations and to study equatorial electron density irregularities and ducted radio propagation above 200 km. The spacecraft was constructed and assembled by the Centro Ricerche Aerospaziali (CRA), University of Rome.

Similar to San Marco 1, San Marco 2 was a 66-cm-diameter spherical satellite with two experiments, one designed to make direct measurements of air density below 350 km, and the other an ionospheric beacon experiment developed to observe electron content between the Earth and the satellite. The spherical shape of the spacecraft was important to the air density experiment in that it provided a constant satellite cross section to the decelerating effects of the air. This simplified data interpretation and eliminated the need for satellite attitude control. The satellite structure comprised a cylindrical center post and central drum connected by three orthogonal strain gauge elements to the thin-walled spun aluminum outer shell. It had black and white longitudinal sections painted on its surface for thermal control. It was spin stabilized at under 6 rpm.

A 5-m dipole antenna was extended along the spin axis only when the beacon experiment was turned on. The beacon experiment used a 670 mW HF (20.005 MHz) transmitter. Four 48-cm telemetry and command antennas extended symmetrically outward from the satellite equator. The satellite was powered by four mercury battery packs, and rough measures of satellite attitude were provided by six solar cell sensors. The PAM/FM/PM telemetry system employed redundant transmitters.

San Marco 2 was launched by an Italian crew on 26 April 1967 at 10:06 UT. Launch was on a solid-propellant four-stage Scout booster from a platform anchored in Formosa Bay in the Indian Ocean, five km off the coast of Kenya at 2.56 deg. S latitude. It was put into an initial 218.8 x 748.7 km altitude orbit with a period of 94.28 minutes and an inclination of 2.892 degrees. By 30 May, the orbit had evolved to 210 x 683 km altitude. On 26 June, the beacon experiment was turned on and operated for 3 weeks, with a total of 170 passes over the Nairobi receiving station measured. The satellite performed as expected until August 5, 1967. By August 14, power had decreased so that satellite command was no longer possible. Reentry occurred on October 14, 1967, during orbit 2680.

The Scout booster (S-153C) comprised an Algol IIB first stage, a Castor II second stage, an Antares II third stage, and an FW-4 fourth stage.

Alternate Names

  • 02761
  • SM-B
  • San Marco II
  • San Marco-B
  • SanMarco2

Facts in Brief

Launch Date: 1967-04-26
Launch Vehicle: Scout
Launch Site: San Marco Platform, Kenya
Mass: 129.3 kg

Funding Agencies

  • National Research Council-Italian Space Commission (Italy)
  • NASA-Office of Space Science Applications (United States)


  • Space Physics
  • Earth Science

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. Dieter K. Bilitza



NameRoleOriginal AffiliationE-mail
Mr. Anthony J. CaporaleProject ManagerNASA Goddard Space Flight
Dr. Robert F. FellowsProgram ScientistNASA Headquarters
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