Echo satellite
Encyclopedia
Project Echo was the first passive communications satellite
experiment. Each of the two American spacecraft was 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.
NASA
's Echo 1 satellite was built by Gilmore Schjeldahl
's G.T. Schjeldahl Company in Northfield, Minnesota
. The balloon satellite functioned as a reflector, not a transmitter, so that after it was placed in a low Earth orbit, a signal would be sent 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 put successfully into a 944 to 1,048 mi orbit by another Thor-Delta and a microwave transmission from the Jet Propulsion Laboratory in Pasadena, California was received at Bell Laboratories in Homdel, New Jersey on August 12, 1960.
The 30.5-meter (100 ft) diameter balloon was made of 0.5 mil thick metalized biaxially oriented PET film
("Mylar") material, and it was 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 was 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.
In addition to the passive communications experiments, it was used to investigate the dynamics of large spacecraft and for global geometric geodesy
.
Echo 2, being 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 reentered Earth's atmosphere and burned up on June 7, 1969. NASA abandoned passive communications systems in favor of active satellites following Echo 2.
Of note is that both the Echo 1A and Echo 2 experienced a solar sail
effect due to their large size and low mass.
Project Echo on December 15, 1960.
Communications satellite
A communications satellite is an artificial satellite stationed in space for the purpose of telecommunications...
experiment. Each of the two American spacecraft was a metalized balloon satellite
Balloon satellite
A balloon satellite is a satellite that is inflated with gas after it has been put into orbit.-List of Balloon Satellites:...
acting as a passive reflector
Reflection (physics)
Reflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...
of microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
signals. Communication signals were bounced off of them from one point on Earth to another.
Echo 1
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Echo 1 satellite was built by Gilmore Schjeldahl
Gilmore Schjeldahl
Gilmore Tilmen Schjeldahl was an American businessman and inventor in plastics, adhesives, and circuitry. He was awarded 16 US patents and may be best known for inventing the plastic-lined airsickness bag....
's G.T. Schjeldahl Company in Northfield, Minnesota
Northfield, Minnesota
As of the census of 2000, there were 17,147 people, 4,909 households, and 3,210 families residing in the city. The population density was 2,452.2 people per square mile . There were 5,119 housing units at an average density of 732.1 per square mile...
. The balloon satellite functioned as a reflector, not a transmitter, so that after it was placed in a low Earth orbit, a signal would be sent to it, reflected or bounced off of its surface, and then returned to Earth.
Following the failure of the Delta rocket
Delta rocket
Delta is a versatile family of expendable launch systems that has provided space launch capability in the United States since 1960. There have been more than 300 Delta rockets launched, with a 95 percent success rate. Two Delta launch systems – Delta II and Delta IV – are in active use...
carrying Echo 1 on May 13, 1960, Echo 1A (commonly referred to as just Echo 1) was put successfully into a 944 to 1,048 mi orbit by another Thor-Delta and a microwave transmission from the Jet Propulsion Laboratory in Pasadena, California was received at Bell Laboratories in Homdel, New Jersey on August 12, 1960.
The 30.5-meter (100 ft) diameter balloon was made of 0.5 mil thick metalized biaxially oriented PET film
PET film (biaxially oriented)
BoPET is a polyester film made from stretched polyethylene terephthalate and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aroma barrier properties and electrical insulation.A variety of companies manufacture boPET and other...
("Mylar") material, and it was used to redirect transcontinental and intercontinental telephone
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
, radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
, and television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
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
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.
In addition to the passive communications experiments, it was used to investigate the dynamics of large spacecraft and for global geometric geodesy
Geodesy
Geodesy , also named geodetics, a branch of earth sciences, is the scientific discipline that deals with the measurement and representation of the Earth, including its gravitational field, in a three-dimensional time-varying space. Geodesists also study geodynamical phenomena such as crustal...
.
Echo 2, being 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 reentered Earth's atmosphere and burned up on June 7, 1969. NASA abandoned passive communications systems in favor of active satellites following Echo 2.
Of note is that both the Echo 1A and Echo 2 experienced a solar sail
Solar sail
Solar sails are a form of spacecraft propulsion using the radiation pressure of light from a star or laser to push enormous ultra-thin mirrors to high speeds....
effect due to their large size and low mass.
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.Echo I commemoration
The U.S. Post office issued a postage stamp commemoratingU.S. space exploration history on U.S. stamps
With the advent of unmanned and manned space flight a whole new era of American history had presented itself. Keeping with the tradition of honoring the country's history on the face of U.S. postage stamps, the U.S. Post Office began honoring the various events with its commemorative postage stamp...
Project Echo on December 15, 1960.
See also
- List of communications satellite firsts
- Project SCOREProject SCOREProject SCORE was the world’s first communications satellite. Launched aboard an Atlas rocket on December 18, 1958, SCORE provided a first test of a communications relay system in space, as well as the first successful use of the Atlas as a launch vehicle...
– world's first communications satellite, launched in 1958. - Courier 1BCourier 1BCourier 1B was the world's first active repeater satellite after launch on 4 October 1960. Courier was built by the Palo Alto, California–based Western Development Labs division of Philco, previously known as Army Fort Monmouth Laboratories and now the Space Systems/Loral division of Loral Space &...
– world’s first active repeater satellite, launched in 1960. - TelstarTelstarTelstar is the name of various communications satellites, including the first such satellite to relay television signals.The first two Telstar satellites were experimental and nearly identical. Telstar 1 was launched on top of a Thor-Delta rocket on July 10, 1962...
– first active, direct relay communications satellite, launched in 1962. - AO-51AO-51AO-51 is the in-orbit name designation of a LEO amateur radio microsatellite of the OSCAR series; formerly known as ECHO. It was launched on June 29, 2004 from Baikonur Cosmodrome, Kazakhstan on a Dnepr launch vehicle...
, AMSAT-OSCAROSCAROSCAR is an acronym for Orbiting Satellite Carrying Amateur Radio. OSCAR series satellites use amateur radio frequencies to facilitate communication between amateur radio stations. These satellites can be used for free by licensed amateur radio operators for voice and data communications...
51 (also known as Phase 2E, or ECHO) – an amateur radio communications satellite launched in 2004. - PAGEOSPAGEOSPAGEOS was a balloon satellite which was launched by the NASA in June 1966. Pageos had a diameter of exactly , consisted of a thick mylar plastic film coated with vapour deposited aluminium enclosing a volume of and was used for the Weltnetz der Satellitentriangulation -- a global cooperation...
– a similar balloon satellite project - U.S. space exploration history on U.S. stampsU.S. space exploration history on U.S. stampsWith the advent of unmanned and manned space flight a whole new era of American history had presented itself. Keeping with the tradition of honoring the country's history on the face of U.S. postage stamps, the U.S. Post Office began honoring the various events with its commemorative postage stamp...
Further reading
- Nick D'Alto "The Inflatable Satellite", Invention and Technology Summer 2007, Volume 23, Number 1 pp. 38–43.