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Vanguard 3



Vanguard 3 (1959 Eta 1) was launched at 05:20:07 UT (12:20:07 a.m. EST) on 18 September 1959 by a Vanguard rocket from the Eastern Test Range of the Atlantic Missile Range at Cape Canaveral into a geocentric orbit. The objectives of the flight were to measure the Earth's magnetic field, the solar X-ray radiation and its effects on the Earth's atmosphere, the near-earth micrometeoroid environment, and the drag effects and density of the upper atmosphere. Instrumentation included a proton magnetometer, X-ray ionization chambers, radio transmitters, and various micrometeoroid detectors. The data obtained provided a comprehensive survey of the Earth's magnetic field over the area covered, defined the lower edge of the Van Allen radiation belt, and provided a count of micrometeoroid impacts. Vanguard 3 has an expected orbital lifetime of roughly 300 yr. from launch.

Mission Profile

Vanguard 3 was launched on 18 September 1959 at 05:20:07 UT from Cape Canaveral and was injected at 05:29:49 into a 33.35 degree inclination Earth orbit with a perigee altitude of 512 km, apogee of 3750 km, and an orbital period of 130 minutes. The third stage was purposely left attached to the satellite in order to produce a long tumble period to avoid corrections to the magnetometer that would be necessary with a rapidly rotating satellite. Perigee remained on the nightside throughout the mission. All experiments functioned normally. The batteries lasted for 85 days, until 11 December 1959, at which time all communication with the spacecraft ceased. It was still tracked optically for the atmospheric drag experiment.

Spacecraft and Subsystems

The Vanguard 3 satellite was a 50.8 cm (20 inch) diameter sphere with a 66 cm (26 inch) conical boom on top. The lower three-fourths of the sphere was silicon-monoxide-coated magnesium and the upper fourth and the conical extension were made of fiberglass (glass fiber phenolic resin). Mass of the satellite was approximately 23.7 kg (52.25 lbs. wt.), the total mass of the orbiting spacecraft with the 19.2 kg third stage casing attached was 42.9 kg.

Power was provided by specially built Yardley Silvercels (AgZn chemical batteries) with non-magnetic lugs, designed to last approximately 3 months. The batteries were held in a pressurized can mounted in the lower two-thirds of the sphere. The can also contained a smaller cylinder, in its top center, which held the electronics for the x-ray, peak memory, temperature measurements, micrometeorite detector, and data encoder, topped by the 30 mW, 108.00 MHz mini track beacon transmitter. Another cylinder, mounted on top of the pressurized compartment, held the magnetometer instrumentation package and electronics, and the command receiver and 80 mW, 108.03 MHz transmitter and electronics for burst telemetry for the magnetometer.

A tape recorder was used to store data for playback during ground station passes. Four spring loaded aerials extended from the equator of the sphere at 90 degree intervals. A small solar cell and cadmium sulfide cell were also mounted on the sphere wall near the equator to study the longevity of solar cells in space. The magnetometer sensor head was mounted at the end of the conical boom. The sphere was spin-stabilized and had passive thermal control. It had no engines for thrust or attitude control.

Launch Vehicle

Vanguard was the designation used for both the launch vehicle and the satellite. The first stage of the three-stage Vanguard Test vehicle was powered by a GE X-405 28,000 pound (~125,000 N) thrust liquid rocket engine, propelled by 7200 kg of kerosene (RP-1) and liquid oxygen, with helium pressurant. It also held 152 kg of hydrogen peroxide. It was finless, 13.4 m (44 ft.) tall, 1.14 m (45 in.) in diameter, and had a launch mass of approximately 8090 kg (17,800 lbs. wt.).

The second stage was a 5.8 m (19 ft.) high, 0.8 m (31.5 in.) diameter Aerojet-General AJ-10 liquid engine burning 1520 kg (3350 lbs) Unsymmetrical Dimethylhydrazine (UDMH) and White Inhibited Fuming Nitric Acid (WIFNA) with a helium pressurant tank. It produced a thrust of 7340 pounds (~32,600 N) and had a launch mass of approximately 1990 kg (4390 lbs. wt.). This stage contained the complete guidance and control system.

The third stage, Allegheny Ballistics Laboratory X-248, used for Vanguard 3 was different than for the previous Vanguards. As before, it used solid propellant and had a similar shape (1.5 m high by 0.8 m in diameter), but both the case and nozzle were made of glass-reinforced plastic instead of steel. This had the advantage of minimizing the affect on the magnetometer. The motor case without fuel had a mass of 19.2 kg (42.3 lb wt). The total fueled mass was 227 kg (500 lbs. wt.).

The total height of the vehicle with the satellite fairing was about 21.9 meters (72 feet). The payload capacity was 11.3 kg (25 lbs.) to a 555 km (345 mi.) Earth orbit. A nominal launch would have the first stage firing for 144 seconds, bringing the rocket to an altitude of 58 km (36 mi), followed by the second stage burn of 120 seconds to 480 km (300 mi), whereupon the third stage would bring the satellite to orbit.

Alternate Names

  • 00020
  • 1959 Eta 1
  • Magne-Ray
  • Vanguard TV4 Backup
  • Vanguard3

Facts in Brief

Launch Date: 1959-09-18
Launch Vehicle: Vanguard
Launch Site: Cape Canaveral, United States
Mass: 42.9 kg

Funding Agency

  • 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. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. John W. TownsendProject ManagerNASA Goddard Space Flight Center
Dr. James P. HeppnerProject ScientistNASA Goddard Space Flight Center

Selected References

  • Zadunaisky, P. E., and B. Miller, Elements of the orbit of the satellite 1959 Eta (Vanguard 3) during the first year after launching, SAO, SR-71, Cambridge, MA, July 1961.
  • Green, C. M., Vanguard - a history, NASA, SP-4202, Wash., DC, 1970.

Other Sources of Vanguard Information

Vanguard, a History - NASA document SP-4202 online

Vanguard 3 Flight Backup Model.

Vanguard 3 Flight Backup Model.

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