The 550-au Mission: a critical discussion |
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| Authors: | S G Turyshev B-G Andersson |
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| Institution: | Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109;Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218 |
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| Abstract: | We have studied the science rationale, goals and requirements for a mission aimed at using the gravitational lensing from the Sun as a way of achieving high angular resolution and high signal amplification. We find that such a mission concept is compromised by several practical problems. Most severe are the effects due to the plasma in the solar atmosphere which cause refraction and scattering of the propagating rays. These effects either limit the frequencies that can be observed to those above ～1 THz, or they move the optical point outwards beyond the vacuum value of ≥550 au. (Thus for observing frequency of 300 GHz the optical point is moved outwards to ～ 680 au.) Density fluctuations in the inner solar atmosphere will further cause random pathlength differences for different rays. The corrections for the radiation from the Sun itself will also be a major challenge at any wavelength used, but could be mitigated with coronographic techniques. Given reasonable constraints on the spacecraft (particularly in terms of size and propulsion), source selection as well as severe navigational constraints further add to the difficulties for a potential mission. Nevertheless, unbiased surveys of small-scale structure on the sky at short wavelengths might be the most promising application of such a mission. |
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| Keywords: | gravitation gravitational lensing space vehicles: instruments telescopes astrometry Sun: general |
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