December 05, 2016

Vision of a Asteroid Belt Astronomical Telescope and hypertelescopes

Physics Today has a speculative article that proposes that laser light be used to shape and polish an asteroid to high optical standards. This could create an Asteroid Belt Astronomical Telescope (ABAT).

The Asteroid Belt Astronomical Telescope (ABAT) focuses light from laser-polished asteroids onto dual imaging arrays above and below the solar system; other intense laser pulses maneuver the arrays to different locations, thus allowing ABAT to point at multiple celestial targets. Asteroid ablation residue corralled into a pair of Devil’s Footprints shields the focal regions from solar illumination. (Courtesy of Laura Kim.)

Imagined 10 meter resolution imaging of exoplanet

The imagined angular resolution of exoplanet Gliese 832 c is a factor of 10 000 short of the theoretical limit of 2 × 10^−11 arcsec

Gliese 832 c is the first exoplanet imaged by the Asteroid Belt Astronomical Telescope. This image, with a resolution of 10 meters, was released last month by ABAT, after the telescope’s construction was 1% completed. (Courtesy of Laura Kim.)

An array with elements that share Jupiters orbit would nearly double the effective aperture diameter. Increasing the distance to Neptune and the Kuiper belt would boost resolution further.

Instead of waiting for laser shaping of asteroids, we can start mass production of cubesats with 2 meter mirrors. Deploying these telescopes around the solar system could form a hypertelescope that has the capabilities of the imagined asteroid belt telescope.

The theoretical limit of 2 × 10^−11 arcsec suggests millimeter resolution at 100 light years.

Seth Shostak described a very large optical interferometry space telescope array. Using interferometry to pool data from thousands of small mirrors in space spread out over 100 million miles to image exoplanets 100 light years away down to 2 meter resolution.

At 100 light-years, something the size of a Honda Accord subtends an angle of a half-trillionth of a second of arc. In case that number doesn’t speak to you, it’s roughly the apparent size of a cell nucleus on Pluto, as viewed from Earth.

I think you would have a cube or sphere 1 AU across and that volume would be filled with say 1 million space telescopes. This way every 0.01 AU there is a space telescope and then they get tasked to work with different scopes at different times in order to look at other locations. Each scope would need its own shading devices. so all of the actions are close together And only pivoting is required. 1 billion scopes would mean one every 0.001 AU. etc...

Hypertelescope backgound material

Nextbigfuture has previously covered hypertelescope technology


Hypertelescope paper (11 page pdf)

Flotilllas of satellites are obviously needed for optical arrays in the size range from kilometers to hundreds and thousands of kilometers. Among the possible hypertelescope schemes, those with a concave primary array and focal combiner appeared well suited for space versions with multiple free -flyers . Either spherical ( CARLINA scheme) or paraboloïdal shapes can be considered for the primary array. Early orbital tests are desirable for developing the techniques of formation flying. Our group investigates the design of nano-satellites driven by solar sails, and plans to test them in geostationary orbit . “Gossamer” free -flyers having a mass as low as 100 grams are considered. With a rigid sail of area 0.1 square meter, driving a membrane stellar mirror of comparable size, accelerations can reach 10 microns per square second, providing motions of 5 m in 1000 seconds.

Once control techniques for a flotilla of space mirrors will be mastered, it will perhaps not take many years to expand their size from hundreds of meters to hundreds of kilometers. This is the size needed to obtain well resolved visible images of an exo-Earth within a few parsecs . Simulation 37 have shown that visible “portraits” of such planets can be obtained in 30 mn of exposure, using a 150 km hypertelescope with 150 mirrors of 3 meters.

For ever larger optical arrays, sizes will ultimately be limited by the number of photons received per resel. The, number decreases when exploding an array since it shrinks the celestial resels The Crab pulsar , believed to contain a compact neutron star of visual magnitude 18, requires huge baselines beyond 100,000 km to resolve the 20 km neutron star , but its extreme luminance can provide enough photons per resel through such a highly diluted aperture, with sub -apertures of a few meters . A “Neutron Star Imager” hypertelescope, spanning several hundred thousand kilometers is therefore conceivable. It can be similar to the EED or EEI., but requires primary mirror elements as large as 8 meters to concentrate their focal Airy peaks within a comparable size, so that they be collectible with beam-combiner optics of manageable size.

Laser Driven Hypertelescope
Feasibility of a laser-driven hypertelescope flotilla at L2 (28 page presentation)

• Many small mirrors better than few large ones
• But how small ? Minimum size about 30mm for tolerable beam spread
• 40,000 mirrors of 30mm for same area as JWST ? …. Laser-trapped flotilla ?

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