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Echo 1 sits fully inflated at a Navy hangar in Weeksville, North Carolina | |
Operator | NASA |
---|---|
Harvard designation | 1960 Alpha 11 |
COSPAR ID | 1960-009A |
SATCAT no. | 49 |
Spacecraft properties | |
Manufacturer | Bell Labs |
Launch mass | 66 kg (146 lb) |
Dimensions | 30.48 m (100.0 ft) diameter sphere when inflated |
Start of mission | |
Launch date | 03:39:43, August 12, 1960 (UTC) |
Rocket | Thor-Delta |
Launch site | Cape Canaveral AFS SLC-17A |
End of mission | |
Decay date | May 24, 1968 |
Orbital parameters | |
Reference system | Geocentric |
Eccentricity | 0.01002 |
Perigee altitude | 1,524 km (947 mi) |
Apogee altitude | 1,684 km (1,046 mi) |
Inclination | 47.2° |
Period | 118.3 min |
Echo 2 undergoing tensile stress test in a dirigible hangar at Weeksville, North Carolina | |
Operator | NASA |
---|---|
COSPAR ID | 1964-004A |
SATCAT no. | 740 |
Spacecraft properties | |
Manufacturer | Bell Labs |
Dimensions | 41 m (135 ft) diameter sphere when inflated |
Start of mission | |
Launch date | 13:59:04, January 25, 1964 (UTC) |
Rocket | Thor-Agena B |
Launch site | Vandenberg AFB |
End of mission | |
Decay date | June 7, 1969 |
Orbital parameters | |
Reference system | Geocentric |
Eccentricity | 0.01899 |
Perigee altitude | 1,029 km (639 mi) |
Apogee altitude | 1,316 km (818 mi) |
Inclination | 81.5° |
Period | 108.95 min |
Project Echo was the first passive communications satellite experiment. Each of the two American spacecraft, launched in 1960 and 1964, was a metalized balloon satellite acting as a passive reflector of microwave signals. Communication signals were bounced off them from one point on Earth to another.[1]
T. Keith Glennan Shows LBJ Aluminized Mylar Film Used to Make Echo I
Echo 1[edit]
The lego movie 2 video game 1 0 11. NASA's Echo 1 satellite was built by Gilmore Schjeldahl's G.T. Schjeldahl Company in Northfield, Minnesota. The balloon satellite would function as a reflector, not a transceiver; after it was placed in a low Earth orbit, a signal could be sent to it, reflected by its surface, and returned to Earth.[citation needed]
During ground inflation tests, 40,000 pounds (18,000 kg) 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. At launch, the balloon weighed 156.995 pounds (71.212 kg), including 33.34 pounds (15.12 kg) of sublimating powders of two types.[2] According to NASA, 'To keep the sphere inflated in spite of meteorite punctures and skin permeability, a make-up gas system using evaporating liquid or crystals of a subliming solid were [sic] incorporated inside the satellite.'[3] One of the powders weighed 10 pounds (4.5 kg), with a very high vapor pressure; the other had a much lower vapor pressure.[2] Tweet cabinet 2 6 – archive public twitter timelines.
The first attempt to orbit an Echo satellite (also the maiden voyage of the Thor-Delta launch vehicle) miscarried when Echo 1 lifted off from Cape Canaveral's LC-17A on the morning of May 13, 1960. 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.
Echo 1A (commonly referred to as Echo 1) was successfully put into a orbit of 944 to 1,048 miles (1,519 to 1,687 km) by another Thor-Delta,[4][5] and a microwave transmission from the Jet Propulsion Laboratory in Pasadena, California, was relayed by the satellite to Bell Laboratories in Holmdel, New Jersey, on August 12, 1960.[2]
The 30.5-meter (100 ft) diameter balloon was made of 0.5-mil-thick (12.7 μm) biaxially oriented PET film, metalized at a thickness of 0.2 micrometers (0.00787 mils) (a type of film commonly known by the trade name Mylar), and had a total mass of 180 kilograms (397 lb). It was used to redirect transcontinental and intercontinental telephone, radio, and television signals.[2] 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 aided the calculation of atmospheric density and solar pressure, due to its large area-to-mass ratio.[2] During the latter portion of its life, it was used to evaluate the technical feasibility of satellite triangulation.
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.
The spacecraft was nicknamed a 'satelloon' by those involved in the project (a portmanteau combining satellite and balloon).
It was originally expected that Echo 1A would not survive long after its fourth dip into the atmosphere in July 1963, although estimates allowed the possibility that it would continue to orbit until 1964 or beyond.[2] It ended up surviving much longer than expected, and finally reentered Earth's atmosphere and burned up on May 24, 1968.
Echo 2[edit]
Echo 2 was a 41.1-meter-diameter (135 ft) balloon satellite, the last launched by Project Echo. A revised inflation system was used for the balloon, to improve its smoothness and sphericity. Echo 2's skin was rigidizable, unlike that of Echo 1A. Therefore, the balloon was capable of maintaining its shape without a constant internal pressure; a long-term supply of inflation gas was not needed, and it could easily survive strikes from micrometeoroids. The balloon was constructed from 'a 0.35 mil (9 µm) thick mylar film sandwiched between two layers of 0.18 mil (4.5 µm) thick aluminum foil and bonded together.'[6] It was inflated to a pressure that caused the metal layers of the laminate to slightly plastically deform, while the polymer was still in the elastic range. This resulted in a rigid and very smooth spherical shell.
Instrumentation included a beacon telemetry system that provided a tracking signal, monitored spacecraft skin temperature between −120 and +16 °C (−184 and 61 °F), and measured the internal pressure of the spacecraft between 0.00005 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.[7]
Echo 2 was launched January 25, 1964, on a Thor Agena rocket. In addition to passive communications experiments, it was used to investigate the dynamics of large spacecraft and for global geometric geodesy. Since it was larger than Echo 1A and orbiting in a near-polar orbit, Echo 2 was conspicuously visible to the unaided eye over all of the Earth. It reentered Earth's atmosphere and burned up on June 7, 1969.
Both Echo 1A and Echo 2 experienced a solar sail effect due to their large size and low mass.[8] Later passive communications satellites, such as OV1-08 PasComSat, solved the problems associated with this by using a grid-sphere design instead of a covered surface. Later yet, NASA abandoned passive communications systems altogether, in favor of active satellites.
Legacy[edit]
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.[9]
The large horn antenna at Holmdel constructed by Bell Labs for the Echo project was later used by Arno Penzias and Robert Woodrow Wilson for their Nobel Prize-winning discovery of the cosmic microwave background radiation.[10]
In popular culture[edit]
On December 15, 1960, the U.S. Post Office issued a postage stamp depicting Echo 1.
Echo 1 stamp – 1960 issue
Gallery[edit]
- Scale prototype of the Echo satellites undergoing a skin stress test on May 1, 1960.
- Holmdel Horn Antenna, constructed for Project Echo, and later used to discover the cosmic microwave background radiation.
- AT&T Bell Labs video about the first voice transmission via satellite and the engineers who conducted the effort.
See also[edit]
- AO-51, AMSAT-OSCAR 51 (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.
- 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
References[edit]
- ^'Echo 1, 1A, 2 Quicklook'. Mission and Spacecraft Library. NASA. Archived from the original on May 27, 2010. Retrieved February 6, 2010.
- ^ abcdefHarrison 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) 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.
- ^NASA/Langley Research Center (NASA-LaRC) (June 29, 1965). 'Static Inflation Test of 135 Ft Satellite In Weeksville, NC'. Internet Archive. Retrieved March 15, 2020.
- ^Astronautix.com, EchoArchived 2008-05-11 at the Wayback Machine
- ^'Echo 1'. NASA. Retrieved 8 October 2015.
- ^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)
- ^'Echo 2'. NASA. Retrieved 2019-01-30.
- ^Coulter, Dauna (31 July 2008). 'A Brief History of Solar Sails'. NASA. NASA. Archived from the original on 28 January 2010. Retrieved 4 February 2010.
- ^Gray, Mike (1992). Angle of Attack: Harrison Storms and the Race to the Moon. W. W. Norton & Co. pp. 5–6. ISBN0-393-01892-X.
- ^'Arno Penzias - Biographical'. nobelprize.org.
Further reading[edit]
- Elder, Donald C. (1995). Out from Behind the Eight-Ball: A History of Project Echo. AAS History Series. 16. Univelt for the American Astronomical Society. ISBN0-87703-388-9.
- Nick D'Alto 'The Inflatable Satellite', Invention and Technology Summer 2007, Volume 23, Number 1 pp. 38–43.
External links[edit]
- A film clip 'Big Bounce, The' is available at the Internet Archive
- A film clip 'Space Triumph. Discoverer Capsule Recovered From Orbit , 1960/08/15 (1960)' is available at the Internet Archive
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Project_Echo&oldid=969426275'
- 2Dependencies
Purpose
If you're not using the on-board audio, you can take advantage of the hardware Pulse Width Modulation capabilities of the Raspberry Pi to control the speed of a small PC fan, based on the system temperature. The fan's status is monitored and logged in Domoticz (and in the syslog). Note that this script is not dependent on Domoticz in any way other than for monitoring. It is launched and runs independently, so that if Domoticz should stop running, for whatever reason, the script will continue to quietly do its thing, keeping your system cool.
Dependencies
First you'll need to get the PWM activated, which unfortunately isn't as straightforward as one might think; the hardware PWM clock is not initialised at boot, and by default only starts up when the on-board soundcard is in use. There is however an alternative Device Tree Overlay, which activates the hardware PWM clock for general use, see the following guide for how to install it: Using the Raspberry Pi hardware PWM timers. You could of course use a 'soft' PWM instead, but these eat up precious CPU cycles, which seems unnecessary when you just want to change the speed of a fan - so this guide assumes the hardware PWM route.
Once you have installed and activated the pwm-with-clk.dtbo overlay linked to above, you should be able to test the PWM by doing (in a root shell):
Domoticz configuration
To be able to monitor the fan status in Domoticz, you need to create a 'virtual sensor' of the type 'Alert'. Call it 'Fan Status' for example, and make note of its index number (shown on the 'Devices' page in Domoticz).
Hardware
Echo 1 2 – A Powerful Http(s) Service Test Tool For A
If you have access to an oscilloscope, correct functioning of the hardware PWM can be verified by hooking it up to the pin you chose when enabling the overlay (pwm0 defaults to GPIO_18). Otherwise, you can hook up an LED with a small series resistor (270 Ω) between the PWM pin and a GND pin; by modifying the 'duty_cycle' value above you should see the light intensity change. But an output pin on a Raspberry Pi is not powerful enough to directly drive a fan, nor is the voltage sufficient for most PC type fans, which tend to run on 12 V DC (though 5 V varieties also exist). So we will need some external cicuitry to give it a bit more brawn:
Suggested components:
- Q1: any small N-channel MOSFET (e.g. 2N7000/BS170)
- R1: 10 kΩ resistor
- C1: 0.1 uF electrolytic capacitor
- D1: Any small rectifier diode
Nothing too complicated going on there; Q1 will be switched on/off by the PWM signal from the Pi, C1 & D1 smooth out transients, while R1 keeps the MOSFET gate from floating. You can build this on an 8x4 piece of stripboard:
The 'RPM' line is just a straight through connection, in case you want to use a 3-pin fan with tachometer output. You can connect this to an input pin on the RasPi if you want to read it, but you'll need to enable the internal pull-up resistor for it to work (the tachometer output on PC fans is an open collector).
To connect it up, run a wire from the PWM output pin on the Pi (the default is GPIO_18 for pwm0, though you can change this in /boot/config.txt) to the PWM input connector on the stripboard. If your fan is a 12 V model you'll need a separate 12 V power supply, which you connect to the GND and VDC inputs. If it's a 5 V model, you can probably get away with powering it from the 5 V pin on the Pi, provided it has a sufficiently powerful PSU - in this case connect the GND input to one of the ground pins on the Pi, and VDC to the Pi's 5 V pin.
Optionally, if you want to monitor the fan's rotational speed, connect a wire from an input pin on the Pi to the RPM pin on the stripboard, and activate its internal pull-up resistor. Since it's not possible to do this from a Bash script, this functionality is not currently supported by the script featured here. If you want to include RPM monitoring you'll need to install a GPIO library, such as WiringPi, and modify the script to count RPM pulses, and report these to Domoticz in a separate virtual sensor.
Installation instructions
Assuming you have followed the instructions for activating the PWM hardware clock at boot, all you need to do is copy the script below into a new file on your Pi, change the 'fan_idx' to the index of the Domoticz alert sensor you want to use for monitoring, and make it executable:
You can now test the script by running:
Leave the script running, and in another terminal run (for example) 'stress' to load the CPU, causing it to heat up:
![Echo 1 2 – A Powerful Http(s) Service Test Tool Echo 1 2 – A Powerful Http(s) Service Test Tool](https://www.dnsstuff.com/wp-content/uploads/2020/02/nping.png)
You should see the fan start spinning, and after stopping 'stress', eventually stop. You should also see the status of the 'alert' sensor you set up in Domoticz change when the fan status changes. Open the script and edit the temperature breakpoints, and low/high fan-speeds to suit. Note that the fan-speed should never exceed the 'period' value ('period' is the PWM frequency in nanoseconds, so 100000 is 1 kHz), and if you set it too low it may not provide enough energy for the fan to start.
Finally, you probably want to launch this script at boot, and leave it running in the background. On a Systemd Linux distribution (like Raspbian), this is very simple; create a new file in /etc/systemd/system/ called fancontrol.service:
And paste the following into it:
Echo 1 2 – A Powerful Http(s) Service Test Tool Kit
Again, make this executable with:
You then need to tell Systemd about the new service, and enable it to run at boot:
That's all there is to it - you can now try rebooting your system and checking if the fancontrol service is running with:
Script with comments
Link to forum post
There is a topic in the forum if you wish to discuss this script, or if you need help getting it to work: Raspberry Pi hardware PWM fan control and monitoring.
--Lomax (talk) 18:38, 5 February 2017 (CET)
Echo 1 2 – A Powerful Http(s) Service Test Tool Harbor Freight
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