Vanguard 1

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Vanguard 1
Vanguard 1.jpg
Mission type Earth science
Operator United States Navy
Harvard designation 1958 Beta 2
SATCAT № 5
Mission duration 20,491 days
Spacecraft properties
Manufacturer NRL
Launch mass 1.47 kilograms (3.2 lb)
Start of mission
Launch date March 17, 1958, 12:15:41 (1958-03-17UTC12:15:41Z) UTC
Rocket Vanguard
Launch site Cape Canaveral LC-18A
End of mission
Last contact May 1964 (1964-06)
Decay date ~240 year orbital lifetime
Orbital parameters
Reference system Geocentric
Regime MEO
Semi-major axis 8,621.86 kilometers (5,357.38 mi)[1]
Eccentricity 0.1850665[1]
Perigee 655 kilometers (407 mi)[1]
Apogee 3,846 kilometers (2,390 mi)[1]
Inclination 34.26 degrees[1]
Period 132.79 minutes[1]
RAAN 329.23 degrees[1]
Argument of perigee 293.07 degrees[1]
Mean anomaly 10.84 degrees[1]
Mean motion 10.84[1]
Epoch 16 April 2014, 17:49:59 UTC[1]
Revolution number 96,062[1]

Vanguard 1 (ID: 1958-Beta 2 [2]) was the fourth artificial Earth orbital satellite launched (after Sputnik 1, Sputnik 2, and Explorer 1), but the first satellite to be solar powered.[3] Although communication with it was lost in 1964, it remains the oldest manmade satellite still in orbit. It was designed to test the launch capabilities of a three-stage launch vehicle as a part of Project Vanguard, and the effects of the environment on a satellite and its systems in Earth orbit. It also was used to obtain geodetic measurements through orbit analysis.

Spacecraft design[edit]

The spacecraft is a 1.47 kg (3.2 lb) aluminum sphere 165 mm (6.4 inches) in diameter. It contains a 10 mW, 108 MHz transmitter powered by a mercury battery and a 5 mW, 108.03 MHz[4] transmitter that was powered by six solar cells mounted on the body of the satellite. Six short antennas protrude from the sphere. The transmitters were used primarily for engineering and tracking data, but were also used to determine the total electron content between the satellite and ground stations. Vanguard also carries two thermistors which measured the interior temperature over sixteen days in order to track the effectiveness of the thermal protection. A backup version of Vanguard 1 is on display at the Smithsonian National Air and Space Museum, Steven F. Udvar-Hazy Center in Chantilly, Virginia.[5]

Mission[edit]

The three stage launch vehicle placed Vanguard into a 654 by 3,969 kilometres (406 mi × 2,466 mi), 134.2 minute elliptical orbit inclined at 34.25 degrees on March 17, 1958. Original estimates had the orbit lasting for 2,000 years, but it was discovered that solar radiation pressure and atmospheric drag during high levels of solar activity produced significant perturbations in the perigee height of the satellite, which caused a significant decrease in its expected lifetime to only about 240 years.[6] The Vanguard 1 transmitted its signals for nearly 7 years as it orbited the earth.[7]

Mission results[edit]

Radio beacon[edit]

A 10 mW transmitter, powered by a mercury battery, on the 108 MHz band used for International Geophysical Year (IGY) scientific satellites, and a 5 mW, 108.03 MHz[8] transmitter powered by six solar cells were used as part of a radio phase-comparison angle-tracking system. The tracking data were used to show that the shape of the Earth has a very slight[9] north-south asymmetry, occasionally described as pear-shaped with the stem at the North Pole. These radio signals were also used to determine the total electron content between the satellite and selected ground-receiving stations. The battery-powered transmitter provided internal package temperature for about sixteen days and sent tracking signals for twenty days. The solar cell powered transmitter operated for more than six years. Signals gradually weakened and were last received at Quito, Ecuador in May 1964 after which the spacecraft was optically tracked from Earth.

Satellite drag atmospheric density[edit]

Because of its symmetrical shape, Vanguard 1 was used by experimenters for use in determining upper atmospheric densities as a function of altitude, latitude, season, and solar activity. As the satellite continuously orbited, it would lag its predicted positions slightly, accumulating greater and greater delay 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.[citation needed]

This experiment was extensively planned prior to launch. Initial Naval Research Laboratory (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 network and human spotters) was added. A panel of scientists proposed changing the design to spheres, at least twenty inches in diameter and hopefully thirty. 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 of the University of Iowa proposed a cylindrical satellite based on his work with rockoons, which became Explorer 1, the first American satellite. The Naval Research Laboratory finally accepted a sphere with a 6.4-inch diameter as a "test vehicle", with a diameter of twenty inches 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.

Since three of the Vanguard satellites are still orbiting in the 2010s, with their drag properties essentially unchanged, they form a baseline data set on the atmosphere of Earth that is 50 years old and counting.[10][11][12]

Post mission[edit]

After the scientific mission ended in 1964, Vanguard 1 became a derelict object—just like the upper stage of the rocket used to launch the satellite had after it finished the delta-v maneuver to place Vanguard 1 in orbit in 1958—and both would continue to orbit Earth for many years. As of September 2013, both objects remain in orbit.[10][13]

50th anniversary[edit]

The Vanguard 1 satellite holds the record for being in space longer than any other man-made object. On March 17, 2008 it logged its 50th year in Earth orbit.

A small group of former NRL and NASA workers had been in communication, 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 March 17, 2008.[14] The meeting concluded with a simulation of the satellite's track as it passed into the orbital area visible from Washington, D.C. (where it is visible from the Earth's surface). The National Academy of Sciences scheduled some seminars to mark the 50th anniversary of the International Geophysical Year, which were the only official observances known.[15]

See also[edit]

References[edit]

  1. ^ a b c d e f g h i j k l "VANGUARD 1 Satellite details 1958-002B NORAD 5". N2YO. 16 April 2014. Retrieved 19 April 2014. 
  2. ^ "U.S. Space Objects Registry". Retrieved 2009-06-25. [dead link]
  3. ^ Vanguard I the World's Oldest Satellite Still in Orbit, accessed September 24, 2007
  4. ^ http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0419878
  5. ^ http://airandspace.si.edu/collections/artifact.cfm?id=A19761019000
  6. ^ "Vanguard 1". NASA. Retrieved 2008-03-25. 
  7. ^ Rosenthal, Alfred. "A record of NASA space missions since 1958". NASA. NASA Technical Reports Server. Retrieved 24 September 2011. 
  8. ^ "Sounds from the First Satellites". AMSAT. 2006-12-15. Retrieved 2008-03-17. 
  9. ^ http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
  10. ^ a b "Vanguard 1 - Satellite Information". Satellite database. Heavens-Above. Retrieved 2013-09-21. 
  11. ^ "Vanguard 2 - Satellite Information". Satellite database. Heavens-Above. Retrieved 2013-09-21. 
  12. ^ "Vanguard 3 - Satellite Information". satellite database. Heavens-Above. Retrieved 2013-09-21. 
  13. ^ "Vanguard 1 Rocket - Satellite Information". Satellite database. Heavens-Above. Retrieved 2013-09-21. 
  14. ^ Vanguard I celebrates 50 years in space
  15. ^ Vanguard Approaches Half A Century In Space, Space Ref Interactive, by Keith Cowing, November 4, 2007