by neufer » Sat Oct 16, 2010 1:05 pm
biddie67 wrote:
I can understand how heat could slowly collect when in sunlight, but I don't understand what is generating the heat when there is no sunlight present like when behind the moon or earth from the sun.
Next to the Sun, the Earth & Moon are the main sources of contaminating heat radiation;
one should get as far away from Earth & Moon as possible and then shield from their radiation.
http://en.wikipedia.org/wiki/James_Webb_Space_Telescope wrote:
<<The James Webb Space Telescope's primary scientific mission has four main components:
- * to search for light from the first stars and galaxies which formed in the Universe after the Big Bang,
* to study the formation and evolution of galaxies,
* to understand the formation of stars and planetary systems, and
* to study planetary systems and the origins of life.
Due to a combination of redshift, dust obscuration, and the intrinsically low temperatures of many of the sources to be studied, the JWST must operate at infrared wavelengths, spanning the wavelength range from 0.6 to 28 micrometres. In order to ensure that the observations are not hampered by infrared emission from the telescope and instruments themselves, the entire observatory must be cold. JWST must be well-shielded from the Sun so that it can radiatively cool to roughly 40 K.
To this end, JWST will incorporate a large metalized fan-fold sunshield, which will unfurl to block infrared radiation from the Sun, Earth and Moon. The telescope's location at the Sun-Earth L2 Lagrange point ensures that the Earth and Sun occupy roughly the same relative position in the telescope's view, and thus make the operation of this shield possible.>>
http://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer wrote:
<<Wide-field Infrared Survey Explorer (WISE) is a NASA-funded infrared-wavelength astronomical space telescope launched on 14 December 2009. The 320 million USD mission launched an
Earth-orbiting satellite with a 40 cm diameter infrared telescope, which performed an all-sky astronomical survey with images in the 3 to 25 μm wavelength range, over 10 months. The initial mission length is limited by its hydrogen coolant. In October 2010 WISE
hydrogen coolant and original NASA funding ran out. The proposed WISE warm mission, using remaining functionality, was not approved by NASA.
http://en.wikipedia.org/wiki/Spitzer_Space_Telescope wrote:
<<The Spitzer Space Telescope (SST) is an infrared space observatory launched in 2003. It follows a rather unusual heliocentric orbit trailing and
drifting away from Earth's orbit at approximately 0.1 astronomical unit per year. The primary mirror is 85 centimetres in diameter, f/12 and made of beryllium and was cooled to 5.5 K. The satellite contains three instruments that allowed it to perform imaging and photometry from 3 to 180 micrometers, spectroscopy from 5 to 40 micrometers, and spectrophotometry from 5 to 100 micrometers.
Without liquid helium to cool the telescope to the very cold temperatures needed to operate, most instruments are no longer usable. However, the two shortest wavelength modules of the IRAC camera are still operable with the same sensitivity as before the cryogen was exhausted, and will continue to be used in the Spitzer Warm Mission.>>
http://en.wikipedia.org/wiki/Herschel_Space_Observatory wrote:
<<The Herschel Space Observatory is a space observatory sensitive to the far infrared and submillimetre wavebands. It was carried into orbit in May 2009, reaching
the second Lagrangian point (L2) of the Earth-Sun system, 1,500,000 kilometres from the Earth.
Herschel is charged with four primary areas of investigation:
- * Galaxy formation in the early universe and the evolution of galaxies;
* Star formation and its interaction with the interstellar medium;
* Chemical composition of atmospheres and surfaces of Solar System bodies, including planets, comets and moons;
* Molecular chemistry across the universe.
The mission, formerly titled the Far Infrared and Sub-millimetre Telescope (FIRST), involves the first space observatory to cover the full far infrared and submillimetre waveband. At 3.5 meters wide, its telescope incorporates the largest mirror (made not from glass but from sintered silicon carbide) ever deployed in space. The light is focused onto three instruments with detectors kept at temperatures below 2 K. The instruments are cooled with liquid helium, boiling away in a near vacuum at a temperature of approximately 1.4 K.
The 2,000-litre supply of helium on board the spacecraft will limit its operational lifetime, nonetheless it is expected to be operational for at least 3 years.>>
[quote="biddie67"]
I can understand how heat could slowly collect when in sunlight, but I don't understand what is generating the heat when there is no sunlight present like when behind the moon or earth from the sun.[/quote]
Next to the Sun, the Earth & Moon are the main sources of contaminating heat radiation;
one should get as far away from Earth & Moon as possible and then shield from their radiation.
[quote=" http://en.wikipedia.org/wiki/James_Webb_Space_Telescope"]
<<The James Webb Space Telescope's primary scientific mission has four main components:
[list]* to search for light from the first stars and galaxies which formed in the Universe after the Big Bang,
* to study the formation and evolution of galaxies,
* to understand the formation of stars and planetary systems, and
* to study planetary systems and the origins of life.[/list]
Due to a combination of redshift, dust obscuration, and the intrinsically low temperatures of many of the sources to be studied, the JWST must operate at infrared wavelengths, spanning the wavelength range from 0.6 to 28 micrometres. In order to ensure that the observations are not hampered by infrared emission from the telescope and instruments themselves, the entire observatory must be cold. JWST must be well-shielded from the Sun so that it can radiatively cool to roughly 40 K. [b][color=#FF0000]To this end, JWST will incorporate a large metalized fan-fold sunshield, which will unfurl to block infrared radiation from the Sun, Earth and Moon. The telescope's location at the Sun-Earth L2 Lagrange point ensures that the Earth and Sun occupy roughly the same relative position in the telescope's view, and thus make the operation of this shield possible.[/color][/b]>>[/quote]
[quote=" http://en.wikipedia.org/wiki/Wide-field_Infrared_Survey_Explorer"]
<<Wide-field Infrared Survey Explorer (WISE) is a NASA-funded infrared-wavelength astronomical space telescope launched on 14 December 2009. The 320 million USD mission launched an [b][color=#FF00FF]Earth-orbiting satellite[/color][/b] with a 40 cm diameter infrared telescope, which performed an all-sky astronomical survey with images in the 3 to 25 μm wavelength range, over 10 months. The initial mission length is limited by its hydrogen coolant. In October 2010 WISE [b][color=#FF00FF]hydrogen coolant and original NASA funding ran out. The proposed WISE warm mission, using remaining functionality, was not approved by NASA[/color][/b].[/quote]
[quote=" http://en.wikipedia.org/wiki/Spitzer_Space_Telescope"]
<<The Spitzer Space Telescope (SST) is an infrared space observatory launched in 2003. It follows a rather unusual heliocentric orbit trailing and[b][color=#00BF00] drifting away from Earth's orbit at approximately 0.1 astronomical unit per year[/color][/b]. The primary mirror is 85 centimetres in diameter, f/12 and made of beryllium and was cooled to 5.5 K. The satellite contains three instruments that allowed it to perform imaging and photometry from 3 to 180 micrometers, spectroscopy from 5 to 40 micrometers, and spectrophotometry from 5 to 100 micrometers. [b][color=#00BF00]Without liquid helium to cool the telescope to the very cold temperatures needed to operate, most instruments are no longer usable. However, the two shortest wavelength modules of the IRAC camera are still operable with the same sensitivity as before the cryogen was exhausted, and will continue to be used in the Spitzer Warm Mission.[/color][/b]>>[/quote]
[quote=" http://en.wikipedia.org/wiki/Herschel_Space_Observatory"]
<<The Herschel Space Observatory is a space observatory sensitive to the far infrared and submillimetre wavebands. It was carried into orbit in May 2009, reaching [b][color=#0000FF]the second Lagrangian point (L2) of the Earth-Sun system, 1,500,000 kilometres from the Earth[/color][/b].
Herschel is charged with four primary areas of investigation:
[list]* Galaxy formation in the early universe and the evolution of galaxies;
* Star formation and its interaction with the interstellar medium;
* Chemical composition of atmospheres and surfaces of Solar System bodies, including planets, comets and moons;
* Molecular chemistry across the universe.[/list]
The mission, formerly titled the Far Infrared and Sub-millimetre Telescope (FIRST), involves the first space observatory to cover the full far infrared and submillimetre waveband. At 3.5 meters wide, its telescope incorporates the largest mirror (made not from glass but from sintered silicon carbide) ever deployed in space. The light is focused onto three instruments with detectors kept at temperatures below 2 K. The instruments are cooled with liquid helium, boiling away in a near vacuum at a temperature of approximately 1.4 K. [b][color=#0000FF]The 2,000-litre supply of helium on board the spacecraft will limit its operational lifetime, nonetheless it is expected to be operational for at least 3 years.[/color][/b]>>[/quote]