Project Echo
Navy hangar in Weeksville, North Carolina. | |
Names | ECHO 1 NASA A-11 |
---|---|
Mission type | Communications |
Operator | NASA |
Harvard designation | 1960 Alpha 11 |
COSPAR ID | 1960-009A |
SATCAT no. | 00049 |
Mission duration | 7.75 years (achieved) |
Spacecraft properties | |
Bus | ECHO |
Manufacturer | Bell Labs |
Launch mass | 180 kg (400 lb) |
Dimensions | 30.48 m (100.0 ft) diameter sphere when inflated |
Start of mission | |
Launch date | 12 August 1960, 03:39:43 GMT |
Rocket | Thor DM-19 Delta (Thor 270 / Delta 2) |
Launch site | Cape Canaveral, LC-17A |
Contractor | Douglas Aircraft Company |
End of mission | |
Decay date | 25 May 1968 |
Orbital parameters | |
Reference system | Geocentric orbit |
Regime | Low Earth orbit |
Perigee altitude | 1,524 km (947 mi) |
Apogee altitude | 1,684 km (1,046 mi) |
Inclination | 47.2° |
Period | 118.3 minutes |
Names | NASA A-12 |
---|---|
Mission type | Communications |
Operator | NASA |
COSPAR ID | 1964-004A |
SATCAT no. | 00740 |
Mission duration | 5.5 years (achieved) |
Spacecraft properties | |
Bus | ECHO |
Manufacturer | Bell Labs |
Dimensions | 41 m (135 ft) diameter sphere when inflated |
Start of mission | |
Launch date | 25 January 1964, 13:59:04 GMT |
Rocket | Thor-Agena B (Thor 397 / Agena 6301 / TA-2) |
Launch site | Vandenberg, LC-75-1-1 (SLC-2E) |
Contractor | Douglas Aircraft Company (Thor) Lockheed Martin (Agena) |
End of mission | |
Decay date | 7 June 1969 |
Orbital parameters | |
Reference system | Geocentric orbit |
Regime | Low Earth orbit |
Perigee altitude | 1,029 km (639 mi) |
Apogee altitude | 1,316 km (818 mi) |
Inclination | 81.5° |
Period | 108.95 minutes |
Project Echo was the first passive communications satellite experiment. Each of the two American spacecraft, launched in 1960 and 1964, were metalized balloon satellites acting as passive reflectors of microwave signals. Communication signals were transmitted from one location on Earth and bounced off the surface of the satellite to another Earth location.[1]
The first transmissions using Echo were sent from
Background
The concept of using orbital satellites to relay communications predated space travel, first being advanced by Arthur C. Clarke in 1945. Experiments using the moon as a passive reflecting way station for messages began as early as 1946.[3] With the launching of Sputnik 1, Earth's first artificial satellite, in 1957, interest quickly developed in orbiting communications satellites.
In July 1958, at a US Air Force sponsored meeting on communications satellites, Bell Telephone Laboratories engineer John R. Pierce put forth a presentation on passive satellite relay, describing how a reflective orbiting body could be used to bounce transmissions from one point on the Earth to another. William H. Pickering, director of Jet Propulsion Laboratory (JPL), also attended the conference and suggested that JPL facilities, specifically a 26 m (85 ft) diameter polar-mounted antenna installed near Goldstone Dry Lake in the Mojave Desert, might be used as a ground facility for experiments with such a satellite.[4]
In October 1958, Pierce, along with fellow Bell engineer Rudolf Kompfner, designed an experiment to observe atmospheric refractive effects using reflective balloon satellites. Believing the experiment would advance research toward transoceanic communications via satellites, the two engineers presented a paper advocating for the launch of balloon satellites to be used as passive communications reflectors to the National Symposium on Extended Range and Space Communication on 6 and 7 October 1958.
That same month, the
Objectives
Project Echo was a pathfinder mission with the objective of testing new technologies and preparing for future missions. Spaceflight engineers used Echo to prove new ideas and test limits in aerodynamics, satellite shape and size, construction materials, temperature control and satellite tracking.[6] Echo was designed as an experiment to demonstrate the potential of satellite communications, not to function as a global communications system.
Echo was designed, approved and built with the following objectives:[5]
- Observe and measure the effects of atmospheric drag
- Passively reflect ground based transmissions
- Demonstrate two-way communications
- Demonstrate commitment to the development of an American space program
- Provide precedent for the overflight of other nations by surveillance satellites
All of these objectives were accomplished with Project Echo. Further experiments used the satellite to engage a two-way telephone conversation on 15 August 1960 and to relay a live television transmission in April 1962.
Ground stations
Two ground stations were used for testing Project Echo. The Goldstone facility located at Goldstone Dry Lake in the Mojave Desert, California and the Crawford Hill facility located at Holmdel, New Jersey. Both sites used separate antennas for transmitting and receiving. West-to-east transmissions were sent from Goldstone by a 26 m (85 ft) dish antenna built for Project Echo by JPL. The signals were received at Crawford Hill by a 6 × 6 m (20 × 20 ft) aperture horn-reflector antenna. Horn antennas were known to have low-noise properties. A transmission frequency of 2390 megahertz was selected, as this was the planned frequency band for future satellite experiments. East-to-west transmissions were sent from Crawford Hill using a 18 m (59 ft) diameter parabolic antenna and received at Goldstone using the existing Pioneer program antenna. A transmission frequency of 960.05 megahertz was used for westbound communications because the JPL receiver was already tuned to this frequency from the Pioneer lunar program.[5]
Satellite acquisition and tracking were accomplished by three methods: optical, digital slave, and automatic radar. Optical tracking was the easiest method but could only be used at night when the Sun illuminated the satellite. Broad and narrow field telescopes with a television camera were mounted to the structure of the antenna at each site. The camera images were displayed to a servo operator who would control the position of the antenna to track the satellite. When optical tracking could not be used, a computer system called digital slave could acquire and track Echo. Digital slave worked by receiving primary tracking data from the NASA Minitrack network of stations. The computer would then issue antenna-pointing commands to control the antenna. The third tracking method was a continuous-wave radar subsystem. Radar was not suitable for acquisition of the satellite, but once Echo was acquired by optical, or digital slave, radar signals could be used to automatically maintain tracking.[5]
Spacecraft
The Echo spacecraft (Echo 1, Echo 1A, and Echo 2) were large thin skinned spheres that were inflated in orbit after leaving the atmosphere. These balloon satellites were approximately 30 m (98 ft) in diameter with a thin skin made of Mylar (a trade name for stretched polyethylene terephthalate or BoPET), and were built by Gilmore Schjeldahl's G.T. Schjeldahl Company in Northfield, Minnesota. The satellites functioned as a reflector, not a transceiver; after being placed in low Earth orbit, signals could be sent from a ground station, reflected by its surface, and returned to Earth.[7]
As its shiny surface was also reflective in the range of visible light, Echo was easily visible to the unaided eye over most of the Earth. The spacecraft was nicknamed a "satelloon" by those involved in the project (a
Echo 1
Echo 1 was 30 m (98 ft) in diameter, had a non-rigid skin made of 12.7 μm (0.00050 in)-thick Mylar, and had a total mass of 180 kg (400 lb), weighing 71 kg (157 lb) at launch. During ground inflation tests, 18,000 kg (40,000 lb) of air were needed to fill the balloon, but while in orbit, several pounds of gas were all that was required to fill the sphere. To address the problem of meteorite punctures and keep the sphere inflated, Echo 1 included a 15.12 kg (33.3 lb) make-up gas system using two types of sublimating powders – 9.1 kg (20 lb) of anthraquinone and 4.6 kg (10 lb) of benzoic acid.[9] It also had 107.9 MHz telemetry beacons, powered by five nickel-cadmium batteries that were charged by 70 solar cells mounted on the balloon. The spacecraft was useful to the calculation of atmospheric density and solar pressure, due to its large area-to-mass ratio.[8]
Echo 2
Echo 2 was a 41.1 m (135 ft)-diameter balloon satellite, the last launched by Project Echo. A revised inflation system was used for the balloon, to improve its smoothness and
Flights
Five suborbital ballistic tests to determine whether the launch, deploy, and expansion mechanisms would work were flown using the Shotput test vehicle, a three-stage rocket.[12] The first Shotput flew at 5:40 pm on 27 October 1959. Shotput 1 successfully delivered the Echo prototype to the desired altitude, but a small amount of residual gas in the folds of the balloon violently expanded, bursting the test article. People up and down the Atlantic coast witnessed what looked like distant fireworks as thousands of pieces of shredded Mylar reflected sunlight in a display that lasted for about 10 minutes.[6] Four more Shotput tests were flown on 16 January, 27 February, 1 April, and 31 May 1960.[13]
On 13 May 1960, the first attempt to orbit an Echo satellite was made. The mission, which was also the maiden voyage of the Thor-Delta launch vehicle, failed before deployment of the payload. Echo 1 lifted off from Cape Canaveral's LC-17A, and the Thor stage performed properly, but during the coasting phase, the attitude control jets on the unproven Delta stage failed to ignite, sending the payload into the Atlantic Ocean instead of into orbit.
On 12 August 1960, Echo 1A (commonly referred to as Echo 1) was successfully put into an orbit of 944 to 1,048 mi (1,519 to 1,687 km) by another Thor-Delta. It ended up surviving much longer than expected, and finally reentered Earth's atmosphere and burned up on 24 May 1968.
On 25 January 1964, Echo 2 was launched on a
Both Echo 1A and Echo 2 experienced a
Legacy
Project Echo facilitated the first successful satellite transmission and first two way communications between the JPL Goldstone facility and Bell Telephone Laboratories facility in Holmdel, New Jersey. Other groups participated in experiments including the
The Echo satellite program also provided the astronomical reference points required to accurately locate Moscow. This improved accuracy was sought by the U.S. military for the purpose of targeting intercontinental ballistic missiles.[16]
The
On 15 December 1960, the U.S. Post Office issued a postage stamp depicting Echo 1.
Gallery
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Scale prototype of the Echo satellites undergoing a skin stress test on 1 May 1960.
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Echo 1
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AT&T Bell Labs video about the first voice transmission via satellite and the engineers who conducted the effort.
See also
- OSCAR51 (also known as Phase 2E, or ECHO) – an amateur radio communications satellite launched in 2004
- Courier 1B – world's first active repeater satellite, launched in 1960
- List of communications satellite firsts
- PAGEOS – a similar balloon satellite project
- Project SCORE– world's first communications satellite, launched in 1958
- Telstar – first active, direct relay communications satellite, launched in 1962
- TransHab, a subsequent expandable spacecraft technology project pursued by NASA
- U.S. space exploration history on U.S. stamps
- Norman L. Crabill
References
- ^ "Echo 1, 1A, 2". Mission and Spacecraft Library. NASA. Archived from the original on 27 May 2010. Retrieved 6 February 2010. This article incorporates text from this source, which is in the public domain.
- ^ a b Astronautix.com, Echo Archived 2008-05-11 at the Wayback Machine
- ^ Butrica, Andrew J. (1996). To See the Unseen: A History of Planetary Radar Astronomy. NASA. Archived from the original on 23 August 2007. This article incorporates text from this source, which is in the public domain.
- ^ Marsh, Allison (12 November 2020). "When a Giant Mylar Balloon Was the Coolest Thing in Space". IEEE Spectrum. Retrieved 10 February 2021.
- ^ .
- ^ .
- ^ NASA/Langley Research Center (NASA-LaRC) (29 June 1965). "Static Inflation Test of 135 ft Satellite In Weeksville, North Carolina". Internet Archive. Retrieved 15 March 2020.
- ^ a b c d Harrison M. Jones; I. I. Shapiro; P. E. Zadunaisky (1961). H. C. Van De Hulst, C. De Jager and A. F. Moore (ed.). "Solar Radiation Pressure Effects, Gas Leakage Rates, and Air Densities Inferred From the Orbit Of Echo I". Space Research II, Proceedings of the Second International Space Science Symposium, Florence, April 10–14, 1961. North-Holland Publishing Company-Amsterdam.
The observed variations of the Echo orbit - due primarily to the effects of the pressure of sunlight - are in excellent agreement with our theoretical results. The perigee altitude has an oscillation of large amplitude (approximately equal to 600 km (370 mi)) and long period (approximately equal to 300 days), which has a decisive influence on the lifetime of Echo I. Our present best estimate is that the balloon will perish in the summer of 1963.
- ^ Davis and Tanimoto. "Mechanical Development of Antenna Systems" (PDF). NASA JPL. Retrieved 8 January 2022.
- ^ Staugaitis, C. & Kobren, L. "Mechanical And Physical Properties of the Echo II Metal-Polymer Laminate (NASA TN D-3409)", NASA Goddard Space Flight Center (1966) This article incorporates text from this source, which is in the public domain.
- ^ "Echo 2". NASA. Retrieved 30 January 2019. This article incorporates text from this source, which is in the public domain.
- ^ "Shotput". Gunter's Space Page. Retrieved 21 March 2024.
- ^ "Shotput". Astronautix. Archived from the original on 28 December 2016. Retrieved 27 February 2021.
- ^ "Echo 1". NASA. Retrieved 8 October 2015. This article incorporates text from this source, which is in the public domain.
- ^ Coulter, Dauna (31 July 2008). "A Brief History of Solar Sails". NASA. Archived from the original on 28 January 2010. Retrieved 4 February 2010. This article incorporates text from this source, which is in the public domain.
- ISBN 0-393-01892-X.
- ^ "Arno Penzias - Biographical". nobelprize.org.
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 ISBN 0-87703-388-9.
- Nick D'Alto "The Inflatable Satellite", Invention and Technology Summer 2007, Volume 23, Number 1, pp. 38–43
External links
- A film clip "Big Bounce, The" is available for viewing at the Internet Archive
- A film clip "Space Triumph. Discoverer Capsule Recovered From Orbit, 15 August 1960" is available for viewing at the Internet Archive