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Author Topic: What are the fuel implications of herschel and planck in the L2 orbit?  (Read 1948 times)

lyner

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The two new telescopes are bound for Lagrange point L2. The L2 Lagrange point is referred to as an unstable point as the telescopes will eventually drift away.
Some details are here: http://map.gsfc.nasa.gov/mission/observatory_l2.html.
The two telescopes will need occasional course corrections to keep them in the region. Could this limit the usable lifetime of the telescopes? Does anyone have an idea of the amount of energy likely to be needed?
What are the advantages of L2 as opposed to a large radius circular Polar orbit around Earth?


 

Offline syhprum

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Quote from

http://www.alphagalileo.org/ViewItem.aspx?ItemId=57639&CultureCode=en

"Without regular trajectory corrections, they would naturally drift off into a useless orbit about the Sun or Earth, with the rate of drift increasing with time," says Gienger. The trade-off, however, is that the L2 location provides an almost perfect vantage point from which to conduct both missions' scientific observations, which depend on maintaining a clear view of the universe while minimising influence from the Earth or Sun's gravity, heat or radiation.

To keep the experiments operational at low temperatures it is required to carry a large quantity of liquid Helium, presumably locating the space craft at L2 where it is shielded from the Sun by the Earth reduces the coolant load that more than compensates for the fuel required to maintain station.   
« Last Edit: 18/05/2009 18:33:55 by syhprum »
 

lyner

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If it's shielded from the Sun then they can't use solar cells either, presumably. Tough, uh?
 

lyner

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Not that the eclipse region is very big - so where is the shielding effect? It's an interesting notion that the Earth can 'shield' from gravity.
 

Offline syhprum

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That an interesting point Herschel requires 1KW to operate which must presumably come from Solar cells as you say the eclipse area is small.
Although the presence of the Earth distorts the gravitational field from the sun there is of course no shielding (this has been ruled out both by experiment and theory).
"a clear view of the universe while minimising influence from the Earth or Sun's gravity, heat or radiation."

http://herschel.esac.esa.int/overview.shtml

Here is a good picture of Herschel as you see the reverse side of the Sunshield is covered in Solar cells.
« Last Edit: 19/05/2009 09:48:40 by syhprum »
 

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