# Ultra long baseline space based radio interferometry?

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#### wdobner

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I apologize if this is misplaced, I'm not exactly sure if it'd fall under missions or astronomy. <br /><br />I'm taking a basic astrophysics class, and we recently covered diffraction limited telescope resolution. The resolution of most optical telescopes was given as being in the .01 arcsecond range, while something like the Very Long Baseline Interferometry array operating in the radio range has a resolution of something like 1/1000th of an arcsecond. I know that the HALCA spacecraft was used in conjunction with the VLBI in a highly elliptic orbit with an apogee at 21,000 or so km. If I'm computing 1.22*((lambda)/(diameter of scope)) correctly then that would give a diffraction limited maximum of 1.4x10^-4 arcseconds, assuming it's working with an earth based radio telescope on the opposite side of the earth. That is close to the 10x increase in resolution which the VLBI Space Observation Program claimed, so I hope I'm on the right track. <br /><br />It seems to me that the natural extension of the VSOP program would be to break the radio telescope out of earth orbit and place it in a solar orbit, allowing baselines of millions of kilometers to be used. My first thought was to place two nearly identical radio telescope satellites in orbit at the L4 and L5 LaGrange points. The baseline would be 259.09 million kilometers, and at a wavelength of 2 centimeters I believe this would yield a diffraction limited resolution of 1.942 x 10^-9 arcseconds, 10,000 times better than the VSOP's earth orbiting telescope. Even working with a 1 Au baseline that a single satellite at one Lagrange point combined with the VLBI would provide would yield a diffraction limited resolution of 3.36x10^-8 arcseconds, only about 20 times worse than the two Lagrange satellite combination. At either resolution we'd come close to being able to directly observing the radio interactions between possible supermassive black hole at the galactic core and its accretion disk <br /><br />I know this

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