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Encyclopedia > Vanguard 2
Vanguard 2
Vanguard 2
Organization: Department of the Navy
Major contractors: Naval Research Laboratory
Mission type: Earth Science
Satellite of: Earth
Launch: February 17, 1959 at 16:05:00 UTC
Launch vehicle: Vanguard rocket
Decay: 300 year orbital lifetime
Mission duration: March 8, 1959 - 19 days
Mass: 23.7 lb (10.8 kg)
NSSDC ID: 1959-001A
Webpage: NASA NSSDC Master Catalog
Orbital elements
Semimajor axis: 8,317.7 km
Eccentricity: .166
Inclination: 32.88°
Orbital period: 125.6 minutes
Apogee: 2,063 mi (3,320 km)
Perigee: 346 mi (557 km)
Orbits: ~190,000 as of July 17, 2004
Radio beacon: Tracking data used to map Earth's shape
Optical scanner: Obtain cloud-cover data


Vanguard 2 Satellite (NASA) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Seal The United States Department of the Navy was established by an Act of Congress on April 30, 1798, to provide administrative and technical support, and civilian leadership to the United States Navy. ... -1... Earth science (also known as geoscience, the geosciences or the Earth Sciences), is an all-embracing term for the sciences related to the planet Earth. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... February 17 is the 48th day of the year in the Gregorian calendar. ... Year 1959 (MCMLIX) was a common year starting on Thursday of the Gregorian calendar. ... ... The Vanguard rocket is the first space launch vehicle of the United States. ... March 8 is the 67th day of the year in the Gregorian Calendar (68th in leap years). ... Year 1959 (MCMLIX) was a common year starting on Thursday of the Gregorian calendar. ... Unsolved problems in physics: What causes anything to have mass? Mass is a property of a physical object that quantifies the amount of matter and energy it is equivalent to. ... The elements of an orbit are the parameters needed to specify that orbit uniquely, given a model of two ideal masses obeying the Newtonian laws of motion and the inverse-square law of gravitational attraction. ... In geometry, the semi-major axis (also semimajor axis) a applies to ellipses and hyperbolas. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... Inclination in general is the angle between a reference plane and another plane or axis of direction. ...

Mission objectives

Vanguard 2 or Vanguard II was an earth-orbiting satellite designed to measure cloud-cover distribution over the daylight portion of its orbit. The spacecraft was a magnesium sphere 20 in (50.8 cm) in diameter. It contained two optical telescopes with two photocells. The sphere was internally gold-plated and externally covered with an aluminum deposit coated with silicon oxide of sufficient thickness to provide thermal control for the instrumentation. Radio communication was provided by a 1 W, 108.03 MHz telemetry transmitter and a 10 mW, 108 MHz beacon transmitter that sent a continuous signal for tracking purposes. A command receiver was used to activate a tape recorder that relayed telescope experiment data to the telemetry transmitter. Both transmitters functioned normally for 19 days. The satellite was spin stabilized at 50 rpm, but telemetry data was poor because of an unsatisfactory orientation of the spin axis. The power supply for the instrumentation was provided by mercury batteries. An Earth observation satellite, ERS 2 For other uses, see Satellite (disambiguation). ... Telemetry is a technology that allows the remote measurement and reporting of information of interest to the system designer or operator. ...

Mission results

Satellite drag atmospheric density

Because of its symmetrical shape, Vanguard 2 was selected by the experimenters for use in determining upper atmospheric densities as a function of altitude, latitude, season, and solar activity. This experiment was not planned prior to launch. Density values near perigee were deduced from sequential observations of the spacecraft position, using optical (Baker-Nunn camera network) and radio and/or radar tracking techniques. This experiment obtained reasonable density values. Vanguard 2 has an expected orbital lifetime of 300 years.

Optical scanner

The optical scanner experiment was designed to obtain cloud-cover data between the equator and 35° to 45° N latitude. As the satellite circled Earth, two photocells located at the focus of two optical telescopes aimed in diametrically opposite directions, measured the intensity of sunlight reflected from clouds (about 80%), from land masses (15 to 20%), and from sea areas (5%). The satellite motion and rotation caused the photocells to scan the earth in successive "lines". Separate solar batteries turned on a recorder only when the earth beneath the satellite was in sunlight and about 50 min of data per orbit were obtained. The measured reflection intensities were stored on tape. Ground stations interrogated the satellite by signaling its command receiver, which caused the entire tape to be played back in 60 s. The tape was then erased and rewound. Experiment equipment functioned normally, but data were poor because of an unsatisfactory satellite spin axis orientation.

See also

Preceded by
Vanguard 1
Project Vanguard
February 17March 8, 1959
Succeeded by
Vanguard 3

  Results from FactBites:
Vanguard (856 words)
Objectives of Project Vanguard were: to develop and procure a satellite-launching vehicle; to place at least one satellite in orbit around the earth during IGY; to accomplish one scientific experiment; and to track flight to demonstrate the satellite actually attained orbit.
Vanguard I completed third year in orbit and was still transmitting.
Vanguard also provided the second stage for the Able, Delta, and Able-Star, as well as the third stage of Scout, pioneering solid-propellant stages used in Polaris and Minuteman.
  More results at FactBites »



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