FOCAL (spacecraft)
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FOCAL is a proposed space telescope that would use the Sun as a gravity lens. The gravitational lens effect was first derived by Einstein,[1] and the concept of a mission to the solar gravitational lens was first suggested by professor Von Eshleman,[2] and analyzed further by Italian astronomer Claudio Maccone[3] and others.[4]
In order to use the Sun as a gravity lens, it would be necessary to send the telescope to a minimum distance of 550 astronomical units away from the Sun,[3]:4–7 enabling very high signal amplifications: for example, at the 203 GHz wavelength, amplification of 1.3·1015.[5] Maccone suggests that this should be enough to obtain detailed images of the surfaces of extrasolar planets.[6]
Other uses of the mission
Even without using the Sun as the lens, FOCAL could perform various, otherwise impossible measurements: a telescope could be used to measure stellar distances by parallax, which would, using the baseline of 550AU, measure the precise position of every star in the Milky Way,[3]:18 enabling various further scientific discoveries.[3]:18–22 It could also study the interstellar medium,[3]:22 the heliosphere,[3]:27 observe gravitational waves,[3]:25 check for the possible variation of the gravitational constant,[3]:25 observe the cosmic infrared background,[3]:26 characterise interplanetary dust within the Solar system,[3]:27–28 more precisely measure the mass of the Solar system[3]:26 and similar.
Limitations
FOCAL does not require any non-existing technology, however it has various limitations. A space mission of this duration and distance has never been attempted. A gravity lens will bend objects behind it, so that images from the telescope would be difficult to interpret.[5] FOCAL would be able to observe only objects that are right behind the Sun from its point of view, which means that for every observed object a new telescope would have to be made.[3]:33[5]
External links
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References
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Eshleman, Von R., "Gravitational lens of the sun: its potential for observations and communications over interstellar distances," Science, Vol. 205, No. 4411 (1979) pp. 1133-1135.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Turyshev, S. G. and Andersson, B-G., “The 550-AU Mission: a critical discussion”, Mon. Not. R. Astron. Soc. 341, pp. 577–582 (2003).
- ↑ 5.0 5.1 5.2 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
