by neufer » Sat Jan 20, 2018 5:03 pm
heehaw wrote:
I have read that Earthshine (the reflected-back-to-us glow of our own planet) is studied spectroscopically, so as to know what the spectrum of a life-bearing planet looks like, for guidance on our examination of the spectra of planets of distant stars.
https://en.wikipedia.org/wiki/Planetshine#Earthshine wrote:
<<Leonardo da Vinci explained the Earthshine phenomenon in the early 16th century when he realized that both Earth and the Moon reflect sunlight at the same time. Light is reflected from the Earth to the Moon and back to the Earth as earthshine.
Earthshine is used to help determine the current albedo of the Earth. The data are used to analyze global cloud cover, a climate factor. Oceans reflect the least amount of light, roughly 10%. Land reflects anywhere from 10–25% of the Sun's light, and clouds reflect around 50%. So, the part of the Earth where it is daytime and from which the Moon is visible determines how bright the Moon's earthshine appears at any given time.
Studies of earthshine can be used to show how the Earth's cloud cover varies over time. Preliminary results show a 6.5% dip in cloud cover between 1985 and 1997 and a corresponding increase between 1997 and 2003. This has implications for climate research, especially with regards to global warming. All clouds contribute to an increased albedo, however some clouds have a net warming effect because they trap more heat than they reflect, while others have a net cooling effect because their increased albedo reflects more radiation than they trap heat. So while the Earth's albedo is measurably increasing, the uncertainty over the amount of heat trapped means the overall effect on global temperature remains unclear.>>
https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory wrote:
<<Deep Space Climate Observatory [DSCOVR] is a NOAA space weather and Earth observation satellite. It was launched by SpaceX on a Falcon 9 launch vehicle on February 11, 2015 from Cape Canaveral. It is in a Lissajous orbit at the Sun-Earth L1 Lagrangian point, 1,500,000 km from Earth, to monitor variable solar wind condition, provide early warning of approaching coronal mass ejections and observe phenomena on Earth including changes in ozone, aerosols, dust and volcanic ash, cloud height, vegetation cover and climate. At this location it has a continuous view of the Sun and of the sunlit side of the Earth. The satellite is orbiting the Sun-Earth L1 point in a six-month period, with a spacecraft-Earth-Sun angle varying from 4 to 15 degrees. It takes full-Earth pictures about every two hours and is able to process them faster than other Earth observation satellites.
DSCOVR started orbiting around L1 by June 8, 2015, just over 100 days after launch. After the spacecraft arrived on site and entered its operational phase, NASA began releasing near-real time images of Earth through the EPIC instrument's website.>>
....................................................................................
National Institute of Standards and Technology Advanced Radiometer (NISTAR) measures irradiance of the sunlit face of the Earth. This data is to be used to study changes in Earth's radiation budget caused by natural and human activities. The radiometer measures in four channels:
- For total radiation in ultraviolet, visible and infrared in range of 0.2-100 µm.
For reflected solar radiation in ultraviolet, visible and near infrared in range of 0.2-4 µm.
For reflected solar radiation in infrared in range of 0.7-4 µm.
For calibration purposes in range of 0.3-1 µm.
[quote="heehaw"]
I have read that Earthshine (the reflected-back-to-us glow of our own planet) is studied spectroscopically, so as to know what the spectrum of a life-bearing planet looks like, for guidance on our examination of the spectra of planets of distant stars.[/quote][quote=" https://en.wikipedia.org/wiki/Planetshine#Earthshine"]
[float=left][img3="[b][color=#0000FF]Leonardo da Vinci's sketch of crescent Moon
with earthshine: part of his Codex Leicester
written between 1506 and 1510[/color][/b]"]https://upload.wikimedia.org/wikipedia/commons/3/30/Leonardo-Earthshine.png[/img3][/float]<<Leonardo da Vinci explained the Earthshine phenomenon in the early 16th century when he realized that both Earth and the Moon reflect sunlight at the same time. Light is reflected from the Earth to the Moon and back to the Earth as earthshine.
Earthshine is used to help determine the current albedo of the Earth. The data are used to analyze global cloud cover, a climate factor. Oceans reflect the least amount of light, roughly 10%. Land reflects anywhere from 10–25% of the Sun's light, and clouds reflect around 50%. So, the part of the Earth where it is daytime and from which the Moon is visible determines how bright the Moon's earthshine appears at any given time. [b][color=#0000FF]Studies of earthshine can be used to show how the Earth's cloud cover varies over time. Preliminary results show a 6.5% dip in cloud cover between 1985 and 1997 and a corresponding increase between 1997 and 2003. This has implications for climate research, especially with regards to global warming.[/color][/b] All clouds contribute to an increased albedo, however some clouds have a net warming effect because they trap more heat than they reflect, while others have a net cooling effect because their increased albedo reflects more radiation than they trap heat. So while the Earth's albedo is measurably increasing, the uncertainty over the amount of heat trapped means the overall effect on global temperature remains unclear.>>[/quote][quote=" https://en.wikipedia.org/wiki/Deep_Space_Climate_Observatory"]
[float=right][img3="[b][color=#0000FF]DSCOVR: the Moon's shadow during the solar eclipse of March 9, 2016
appears as a dark spot moving across the Earth.[/color][/b]"]https://upload.wikimedia.org/wikipedia/commons/c/cb/An_EPIC_Eclipse.gif[/img3][/float]<<Deep Space Climate Observatory [DSCOVR] is a NOAA space weather and Earth observation satellite. It was launched by SpaceX on a Falcon 9 launch vehicle on February 11, 2015 from Cape Canaveral. It is in a Lissajous orbit at the Sun-Earth L1 Lagrangian point, 1,500,000 km from Earth, to monitor variable solar wind condition, provide early warning of approaching coronal mass ejections and observe phenomena on Earth including changes in ozone, aerosols, dust and volcanic ash, cloud height, vegetation cover and climate. At this location it has a continuous view of the Sun and of the sunlit side of the Earth. The satellite is orbiting the Sun-Earth L1 point in a six-month period, with a spacecraft-Earth-Sun angle varying from 4 to 15 degrees. It takes full-Earth pictures about every two hours and is able to process them faster than other Earth observation satellites.
DSCOVR started orbiting around L1 by June 8, 2015, just over 100 days after launch. After the spacecraft arrived on site and entered its operational phase, NASA began releasing near-real time images of Earth through the EPIC instrument's website.>>
....................................................................................
National Institute of Standards and Technology Advanced Radiometer (NISTAR) measures irradiance of the sunlit face of the Earth. This data is to be used to study changes in Earth's radiation budget caused by natural and human activities. The radiometer measures in four channels:
[list][b][color=#0000FF]For total radiation in ultraviolet, visible and infrared in range of 0.2-100 µm.
For reflected solar radiation in ultraviolet, visible and near infrared in range of 0.2-4 µm.
For reflected solar radiation in infrared in range of 0.7-4 µm.
For calibration purposes in range of 0.3-1 µm.[/color][/b][/list][/quote]