Vanguard 1 (Harvard designation: 1958-Beta 2, COSPAR ID: 1958-002B ) is an American

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

that was the fourth artificial Earth-orbiting satellite to be successfully launched, following

Sputnik 1 Sputnik 1 (, , ''Satellite 1''), sometimes referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program ...

Sputnik 2 Sputnik 2 (, , ''Satellite 2'', or Prosteyshiy Sputnik 2 (PS-2, , ''Simplest Satellite 2'', launched on 3 November 1957, was the second spacecraft launched into Earth orbit, and the first to carry an animal into orbit, a Soviet space dog named ...

, and

Explorer 1 Explorer 1 was the first satellite launched by the United States in 1958 and was part of the U.S. participation in the International Geophysical Year (IGY). The mission followed the first two satellites, both launched by the Soviet Union duri ...

. It was launched 17 March 1958. Vanguard 1 was the first satellite to have solar electric power. Although communications with the satellite were lost in 1964, it remains the oldest man-made object still in orbit, together with the upper stage of its launch vehicle. Vanguard 1 was designed to test the launch capabilities of a three-stage

launch vehicle A launch vehicle is typically a rocket-powered vehicle designed to carry a payload (a crewed spacecraft or satellites) from Earth's surface or lower atmosphere to outer space. The most common form is the ballistic missile-shaped multistage ...

as a part of

Project Vanguard Project Vanguard was a program managed by the United States Navy Naval Research Laboratory (NRL), which intended to launch the first Satellite, artificial satellite into low Earth orbit using a Vanguard (rocket), Vanguard rocket as the launch ...

, and the effects of the

space environment Space environment is a branch of astronautics, aerospace engineering and space physics that seeks to understand and address conditions existing in space that affect the design and operation of spacecraft. A related subject, space weather, deals wit ...

on a satellite and its systems in

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

orbit. It also was used to obtain

geodetic Geodesy or geodetics is the science of measuring and representing the geometry, gravity, and spatial orientation of the Earth in temporally varying 3D. It is called planetary geodesy when studying other astronomical bodies, such as planets ...

measurements through orbit analysis. Vanguard 1, being small and light enough to carry with one hand, was described by the

Soviet Premier The Premier of the Soviet Union () was the head of government of the Union of Soviet Socialist Republics (USSR). From 1923 to 1946, the name of the office was Chairman of the Council of People's Commissars, and from 1946 to 1991 its name was ...

Nikita Khrushchev Nikita Sergeyevich Khrushchev (– 11 September 1971) was the General Secretary of the Communist Party of the Soviet Union, First Secretary of the Communist Party of the Soviet Union from 1953 to 1964 and the Premier of the Soviet Union, Chai ...

, as "the

grapefruit The grapefruit (''Citrus'' × ''paradisi'') is a subtropical citrus tree known for its relatively large, sour to semi-sweet, somewhat bitter fruit. The flesh of the fruit is segmented and varies in color from pale yellow to dark red. Grapefru ...

satellite".

Spacecraft design

The spacecraft is a

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

sphere A sphere (from Ancient Greek, Greek , ) is a surface (mathematics), surface analogous to the circle, a curve. In solid geometry, a sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...

in diameter, with antennas spanning . It contains a 10 mW, 108

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base u ...

transmitter powered by a

mercury battery A mercury battery (also called mercuric oxide battery, mercury cell, button cell, or Ruben-Mallory) is a non-rechargeable electrochemical battery, a primary cell. Mercury batteries use a reaction between mercuric oxide and zinc electrodes in a ...

and a 5 mW, 108.03 MHz transmitter that was powered by six

solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

s mounted on the body of the satellite. Six long

antennas In radio-frequency engineering, an antenna (American English) or aerial (British English) is an electronic device that converts an alternating electric current into radio waves (transmitting), or radio waves into an electric current (receivi ...

, diameter spring-actuated aluminum alloy aerials protrude from the sphere. The transmitters were used primarily for engineering and tracking data, but were also used to determine the

total electron content Total electron content (TEC) is an important descriptive quantity for the ionosphere of the Earth. TEC is the total number of electrons integrated between two points, along a tube of one meter squared cross section, i.e., the electron columnar ...

between the satellite and the ground stations. A backup version of Vanguard 1 is on display at the

Smithsonian National Air and Space Museum The National Air and Space Museum (NASM) of the Smithsonian Institution is a museum in Washington, D.C., in the United States, dedicated to human flight and space exploration. Established in 1946 as the National Air Museum, its main building ...

Steven F. Udvar-Hazy Center The Steven F. Udvar-Hazy Center, also called the Udvar-Hazy Center, is the Smithsonian National Air and Space Museum (NASM)'s annex at Dulles International Airport in the Chantilly area of Fairfax County, Virginia. It holds numerous exhibits, ...

Chantilly, Virginia Chantilly is a census-designated place (CDP) in western Fairfax County, Virginia, United States. The population was 24,301 as of the 2020 census. Chantilly is named after an early-19th-century mansion and farm, which in turn took the name of an ...

Mission

On 17 March 1958, the three-stage launch vehicle placed Vanguard into a , 134.27-minute elliptical orbit inclined at 34.25°. Original estimates had the orbit lasting for 2,000 years, but it was discovered that solar

radiation pressure Radiation pressure (also known as light pressure) is mechanical pressure exerted upon a surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of ...

and

atmospheric drag In fluid dynamics, drag, sometimes referred to as fluid resistance, is a force acting opposite to the direction of motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers, two solid surfaces, or b ...

during high levels of solar activity produced significant perturbations in the

perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

height of the satellite, which caused a significant decrease in its expected lifetime to about 240 years. Vanguard 1 transmitted its signals for over six years as it orbited the Earth.

Radio beacon

A 10 mW mercury-battery-powered telemetry transmitter on the 108 MHz band used for

International Geophysical Year The International Geophysical Year (IGY; ), also referred to as the third International Polar Year, was an international scientific project that lasted from 1 July 1957 to 31 December 1958. It marked the end of a long period during the Cold War w ...

(IGY) scientific satellites, and a 5 mW, 108.03 MHz

Minitrack The Minitrack Network was the first U.S. satellite tracking network to become operational, in 1957. It was used to track the flights of Sputnik, Vanguard, Explorer, and other early space efforts. Minitrack was the progenitor of Spacecraft Tracki ...

transmitter powered by six

solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

s were used as part of a radio phase-comparison angle-tracking system. The system transmitted signals through the satellite's six spring-loaded aluminum alloy aerials. Satellite tracking was achieved using these transmitters and Minitrack ground stations situated around the globe. These radio signals were used to determine the

between the satellite and selected ground-receiving stations. The battery-powered transmitter provided internal package temperature for about 16 days and sent tracking signals for 20 days. The solar-cell-powered transmitter operated for more than six years. Signals gradually weakened and were last received at the Minitrack station in

Quito Quito (; ), officially San Francisco de Quito, is the capital city, capital and second-largest city of Ecuador, with an estimated population of 2.8 million in its metropolitan area. It is also the capital of the province of Pichincha Province, P ...

Ecuador Ecuador, officially the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, and the Pacific Ocean on the west. It also includes the Galápagos Province which contain ...

, in May 1964. Since then the spacecraft has been tracked optically from Earth, via

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

Design for atmospheric density measurements

Because of its symmetrical shape, Vanguard 1 was used by experimenters for determining upper atmospheric densities as a function of

altitude Altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum (geodesy), datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometr ...

latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...

season A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's axial tilt, tilted orbit around the Sun. In temperat ...

, and

solar activity Solar phenomena are natural phenomena which occur within the Stellar atmosphere, atmosphere of the Sun. They take many forms, including solar wind, Solar radio emission, radio wave flux, solar flares, coronal mass ejections, Stellar corona#Coron ...

. As the satellite continuously orbited, it would deviate from its predicted positions slightly, accumulating greater and greater shift due to drag of the residual atmosphere. By measuring the rate and timing of orbital shifts, together with the body's drag properties, the relevant atmosphere's parameters could be back-calculated. It was determined that atmospheric pressures, and thus drag and orbital decay, were higher than anticipated, since Earth's upper atmosphere does taper off into space gradually. This experiment was planned extensively prior to launch. Initial

Naval Research Laboratory The United States Naval Research Laboratory (NRL) is the corporate research laboratory for the United States Navy and the United States Marine Corps. Located in Washington, DC, it was founded in 1923 and conducts basic scientific research, appl ...

(NRL) proposals for the project included conical satellite bodies; this eliminated the need for a separate fairing and ejection mechanisms, and their associated weight and failure modes. Radio-tracking would gather data and establish a position. Early in the program, optical tracking (with a

Baker-Nunn camera A Schmidt camera, also referred to as the Schmidt telescope, is a catadioptric Astrophotography, astrophotographic Optical telescope, telescope designed to provide wide Field of view, fields of view with limited Aberration in optical systems, abe ...

network and human spotters) was added. A panel of scientists proposed changing the design to spheres, at least in diameter and hopefully . A sphere would have a constant optical reflection, and constant coefficient of drag, based on size alone, while a cone would have properties that varied with its orientation.

James Van Allen James Alfred Van Allen (September 7, 1914August 9, 2006) was an American space physicist at the University of Iowa. He was instrumental in establishing the field of magnetospheric research in space. The Van Allen radiation belts were named af ...

of the

University of Iowa The University of Iowa (U of I, UIowa, or Iowa) is a public university, public research university in Iowa City, Iowa, United States. Founded in 1847, it is the oldest and largest university in the state. The University of Iowa is organized int ...

proposed a cylindrical satellite based on his work with

rockoon A rockoon (from ''rocket'' and ''balloon'') is a sounding rocket that, rather than being lit immediately while still on the ground, is first carried into the upper atmosphere by a gas-filled balloon, then separated from the balloon and ignited. ...

s, which became

, the first American satellite. The Naval Research Laboratory finally accepted a sphere with a of diameter as a "Test Vehicle", with a diameter of set for the follow-on satellites. The weight savings, from reduced size as well as decreased instrumentation in the early satellites, was considered to be acceptable. As Vanguard 1,

Vanguard 2 Vanguard 2 (or Vanguard 2E before launch) is an Earth-orbiting satellite launched 17 February 1959 at 15:55:02 GMT, aboard a Vanguard SLV-4 rocket as part of the United States Navy's Project Vanguard. The satellite was designed to measure clou ...

, and Vanguard 3 are still orbiting with their drag properties essentially unchanged, they form a baseline data set on the

atmosphere of Earth The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather ...

that is over 60 years old and continuing.

After the mission

After its scientific mission ended in 1964, Vanguard 1 became a

derelict Derelict may refer to: Law * Derelict, property that has been abandoned or deserted ** Derelict (maritime), property which has been abandoned and deserted at sea without any hope of recovery Arts, entertainment, and media Music * "Dead Man's Ch ...

object Object may refer to: General meanings * Object (philosophy), a thing, being, or concept ** Object (abstract), an object which does not exist at any particular time or place ** Physical object, an identifiable collection of matter * Goal, an a ...

– as did the upper stage of the launch rocket, after it finished the

delta-v Delta-''v'' (also known as "change in velocity"), symbolized as and pronounced , as used in spacecraft flight dynamics, is a measure of the impulse per unit of spacecraft mass that is needed to perform a maneuver such as launching from or l ...

maneuver to place Vanguard 1 in orbit in 1958. Both objects remain in orbit. Vanguard 1 was projected to remain aloft for up to 2,000 years, but solar radiation pressure and atmospheric drag perturbations during periods of high solar activity affected its perigee, reducing its lifetime, and now it is expected to burn up in the atmosphere in about 240 years, sometime in the late 22nd century. As space travel becomes routine, and especially when its re-entry date draws near, some have suggested that the satellite might be retrieved as a valued artifact of early space exploration.

50th anniversary

The Vanguard 1 satellite and upper launch stage hold the record for being in space longer than any other human-made object, and as such have traveled farther over the Earth's surface than any other human-made object. A small group of former

NRL The National Rugby League (also known as the NRL Telstra Premiership for sponsorship reasons) is a professional rugby league competition in Oceania which contains clubs from New South Wales, Queensland, Victoria (state), Victoria, the Austral ...

and

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

workers had been in communication with one another, and a number of government agencies were asked to commemorate the event. The Naval Research Laboratory commemorated the event with a day-long meeting at NRL on 17 March 2008. The meeting concluded with a simulation of the satellite's track as it passed into the orbital area visible from

Washington, D.C. Washington, D.C., formally the District of Columbia and commonly known as Washington or D.C., is the capital city and federal district of the United States. The city is on the Potomac River, across from Virginia, and shares land borders with ...

, (where it is visible from the Earth's surface). The

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...

scheduled seminars to mark the 50th anniversary of the

.Vanguard Approaches Half A Century In Space
SpaceRef Interactive, by Keith Cowing, November 4, 2007

References

External links

''United States Space Program Progress 1958''
discusses Vanguard 1 and other American space launches in 1958 at YouTube {{Orbital launches in 1958 Spacecraft launched in 1958 1958 in the United States Project Vanguard Derelict satellites orbiting Earth Gravimetry satellites Atmospheric sounding satellites Geospace monitoring satellites