Project Echo: Difference between revisions
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Echo 2 reentered Earth's atmosphere and burned up on June 7, 1969. NASA abandoned passive communications systems in favor of active satellites following Echo 2. |
Echo 2 reentered Earth's atmosphere and burned up on June 7, 1969. NASA abandoned passive communications systems in favor of active satellites following Echo 2. |
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Echo 2, being even larger than Echo 1A and also orbiting in a near polar orbit, was conspicuously visible to the unaided eye over all of the Earth |
Echo 2, being even larger than Echo 1A and also orbiting in a near polar orbit, was conspicuously visible to the unaided eye over all of the Earth. |
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Of note is that both the Echo 1A and Echo 2 experienced a [[solar sail]] effect due to their large size.<ref>{{Cite web|url=http://science.nasa.gov/headlines/y2008/31jul_solarsails.htm|title=A Brief History of Solar Sails|last=Coulter|first=Dauna|work=[[NASA]]|publisher=[[NASA]]|date=Jumy 31, 2008|accessdate=February 4, 2010}}</ref> |
Of note is that both the Echo 1A and Echo 2 experienced a [[solar sail]] effect due to their large size.<ref>{{Cite web|url=http://science.nasa.gov/headlines/y2008/31jul_solarsails.htm|title=A Brief History of Solar Sails|last=Coulter|first=Dauna|work=[[NASA]]|publisher=[[NASA]]|date=Jumy 31, 2008|accessdate=February 4, 2010}}</ref> |
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Revision as of 17:14, 23 January 2011
Project Echo was NASA's first passive communications satellite experiment. Each spacecraft was designed as a metalized balloon satellite acting as a passive reflector of microwave signals. Communication signals were bounced off of them from one point on Earth to another.[1]
Echo 1
NASA's Echo 1 satellite was built as part of Project Echo by Gilmore Schjeldahl's G.T. Schjeldahl Company in Northfield, MN. The balloon satellite functioned as a reflector, not a transmitter, so that after it was placed in a low Earth orbit (LEO), a signal would be relayed to it, reflected or bounced off of its surface, and then returned to Earth.
Following the failure of the Delta rocket carrying Echo 1 on May 13, 1960, Echo 1A (commonly referred to as just Echo 1) was successfully put into a 944 to 1,048 mi orbit on August 12, 1960.[2][3]
The 30.5-meter (100 ft) diameter balloon was made of 0.5 mils (12.7 μm) thick metalized biaxially oriented PET film ("Mylar") material and it was successfully used to redirect transcontinental and intercontinental telephone, radio, and television signals. The satellite also aided the calculation of atmospheric density and solar pressure due to its large area-to-mass ratio. As its shiny surface was also reflective in the range of visible light, Echo 1A was easily visible to the unaided eye over most of the Earth. It would appear from below one side of the horizon, cross the sky, then disappear below the opposite horizon after crossing the sky, as happens with all low Earth orbit satellites. The spacecraft was nicknamed a 'satelloon' by those involved in the project as a portmanteau of satellite-balloon.
It also had 107.9-MHz beacon transmitters for telemetry purposes, powered by five nickel-cadmium batteries that were charged by 70 solar cells mounted on the balloon. During the latter portion of its life, the spacecraft was used to evaluate the technical feasibility of satellite triangulation. It had a total mass of 180 kg.
Echo 1A reentered Earth's atmosphere and burned up on May 24, 1968.
Echo 2
Echo 2, a 41.1-meter (135 ft) diameter metalized PET film balloon, which was the last balloon satellite launched by Project Echo. It used an improved inflation system to improve the balloon's smoothness and sphericity. It was launched January 25, 1964 on a Thor Agena rocket.
Instrumentation included a beacon telemetry system that provided a tracking signal, monitored spacecraft skin temperature between -120 deg C and +16 deg C, and measured the internal pressure of the spacecraft between 5E-5 mm of mercury and 0.5 mm of mercury, especially during the initial inflation stages. The system consisted of two beacon assemblies powered by solar cell panels and had a minimum power output of 45 mW at 136.02 MHz and 136.17 MHz.[4]
In addition to the passive communications experiments, it was used to investigate the dynamics of large spacecraft and for global geometric geodesy.
Echo 2 reentered Earth's atmosphere and burned up on June 7, 1969. NASA abandoned passive communications systems in favor of active satellites following Echo 2.
Echo 2, being even larger than Echo 1A and also orbiting in a near polar orbit, was conspicuously visible to the unaided eye over all of the Earth.
Of note is that both the Echo 1A and Echo 2 experienced a solar sail effect due to their large size.[5]
Military use
The Echo satellite program also provided the astronomical reference points required to accurately locate the Russian city of Moscow geographically. This improved accuracy was sought by the US military for the purpose of targeting intercontinental ballistic missiles.[6]
Echo I commemoration
The U.S. Post office issued a postage stamp commemorating Project Echo on December 15, 1960.
See also
- Project SCORE – the world's first communications satellite, launched in 1958.
- Courier 1B – the world’s first active repeater satellite, launched in 1960.
- Telstar – the first active, direct relay communications satellite, launched in 1962.
- AO-51, AMSAT-OSCAR 51 (also known as Phase 2E, or ECHO) – an amateur radio communications satellite launched in 2004.
- PAGEOS – a similar balloon satellite project
- Nick D'Alto "The Inflatable Satellite", Invention and Technology Summer 2007, Volume 23, Number 1 pp. 38–43.
- List of communications satellite firsts
- Space exploration
- U.S. space exploration history on U.S. stamps
References
- ^ "Echo 1, 1A, 2 Quicklook". Mission and Spacecraft Library. NASA. Retrieved February 6, 2010.
- ^ Astronautix.com, Echo
- ^ "Echo 1". NASA. Retrieved 13 July 2010.
- ^ "Echo 2". NASA.
- ^ Coulter, Dauna (Jumy 31, 2008). "A Brief History of Solar Sails". NASA. NASA. Retrieved February 4, 2010.
{{cite web}}: Check date values in:|date=(help) - ^ Gray, Mike (1992). Angle of Attack: Harrison Storms and the Race to the Moon. W. W. Norton & Co. pp. 5–6. ISBN 0-393-01892-X.
- Further reading
- Elder, Donald C. (1995). Out from Behind the Eight-Ball: A History of Project Echo. AAS History Series. Vol. 16. Univelt for the American Astronomical Society. ISBN 0-87703-388-9.