so whats happening with EDRS-B?
Europe's satellite laser comms system set to shine
The European Space Agency (ESA) and Airbus Defence and Space are poised to launch the first orbiting component of the European Data Relay System (EDRS), aka the "SpaceDataHighway", described as "the most sophisticated laser communication network ever designed". On 27 January, the EDRS-A node will lift off from Baikonur …
COMMENTS
-
This post has been deleted by its author
-
-
-
-
-
Wednesday 20th January 2016 20:31 GMT Highroads
Re: buy why?
Gold has a low infrared emissivity - that means it won't lose much heat by radiation at the temperatures we are used to. In this case it is probably meant to keep the structure at a very uniform temperature, so that it does not distort too much. Distortion would affect the pointing accuracy to the next satellite.
Gold would also stop the surface corroding but there are better and cheaper ways of doing that. There are space qualified paints or other coatings.
Gold on its own would get rather hot in the sunlight as it absorbs light in the visible and ultraviolet but does not radiate much in the infrared. Usually there would be multiple layers of insulation or MLI blanket over the top of what you see in the picture to protect the system from the cold of space and from the Sun's heat.
-
-
Wednesday 20th January 2016 21:50 GMT Highroads
Re: buy why?
That's right there will be an equilibrium reached for an object in space between the energy absorbed and the heat radiated to the background of space. For a gold surface facing the Sun in low earth orbit and insulated on the back this probably will not be high enough temperature to melt the gold. You can work out the temperatures roughly.
Heat energy radiated to space approx = area *5.67x10^-8* infrared emissivity * (temperature in Kelvin)^4 .
I've simplified the equation here by assuming the background is 0 Kelvin rather than 3 Kelvin.
5.67x10^-8 is approx. the Stefan-Boltzmann constant.
Solar heat input at Earth orbit say 1400 W/m^2
Gold solar absorptance 0.2 -> so 280 W absorbed per m^2
I worked out the temperature to be 705 Kelvin or 430 Celsius.
-
-
-
-
-