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San Marco 1



San Marco 1 was an Italian flight test of the satellite to furnish data on air density and ionosphere characteristics. The launch vehicle was provided by NASA and was launched with an Italian launch crew.

Spacecraft and Subsystems

The first Italian satellite, San Marco I comprised a heavy cylindrical inner structure surrounded by a lightweight aluminum spherical outer shell, 66 cm in diameter. It had a total mass of 115.2 kg. Four antennas protruded from the equator of the satellite. The outer and inner spheres were connected by a pneumatic caging system. The satellite had black and white longitudinal sections painted on its surface for thermal control. It was spin stabilized and powered by a 12 watt mercury battery (Mallory RM-42R cells) which provided 200 working hours of power.

Communications were via a 0.25 watt crystal controlled transmitter at 136.53 MHz using a pulse-amplitude-modulated / frequency-modulated / phase-modulated (PAM/FM/PM) system for telemetry. Five channels were used, four continuous transmission channels for the atmospheric drag experiment and one sub-commutated channel for housekeeping data and the ionospheric experiment. A 50 milliwatt beacon transmitter with a 136.74 MHz carrier frequency, modulated by the vector sum of the three balance channels, was used for tracking. Ground commands were sent to the spacecraft through a radio frequency link on the 140- to 150- MHz band. The command system consisted of a command receiver, a tone decoder, and a command decoder. The probe carried an air drag experiment consisting of three orthogonal displacement transducers connecting the inner and outer spheres, to measure the atmospheric density at perigee. An ionospheric experiment used a 670 milliwatt, 20.005 MHz transmitter and an extensible 400 cm dipole antenna.

Mission Profile

San Marco I was launched on a U.S. four-stage solid propellant Scout booster from Wallops Island by an all-Italian crew on 15 December 1964. It was put into a 206 km x 820 km orbit, slightly more elliptical than the planned 215 x 680 km orbit, with an inclination of 37.79 degrees and a period of 95 minutes. The spin rate was 3 rpm. The spacecraft did not respond to all commands for the first few days, and it was determined that the spacecraft had a limited receiving range. This was addressed by sending commands at times when San Marco I was in reasonable proximity to a ground station. This limited the ability to turn the satellite off when necessary. This combined with what was thought ot be an open diode in one of the two parallel strings of battery cells resulted in an unanticipated drain on the 200-hour battery. As a power saving measure all long term transmissions from the spacecraft were stopped.

The air-drag experiment operated as planned until 30 December 1964 when tranmissions were terminated to allow the ionospheric experiment to operate. It operated for the scheduled two weeks and was turned off, at this point the batteries were nearly exhausted.

North American Radar Defense (NORAD) observed San Marco 1 reentry at 11:00 UT on 14 September 1965 at an estimated location of 34 N, 173 W. It was later reported that part of a pole piece of the fourth-stage igniter, identified as part of vehicle 137R, was found in Thailand.

Scout Booster

The Scout Booster (S-137) had four stages. The first stage was an Algol IIB, second stage was a Castor I, and the third stage was an Antares II (ABLX-259). The fourth stage was an Altair (ABLX-258) with a fairing and heat shield to protect and hold the satellite for release into orbit.

Alternate Names

  • 00957
  • SM-A
  • San Marco I
  • San Marco-A
  • SanMarco1

Facts in Brief

Launch Date: 1964-12-15
Launch Vehicle: Scout
Launch Site: Wallops Island, United States
Mass: 115.2 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
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