A solar gravitational lens will be humanity's most powerful telescope (2022)

The most complete plan for this was proposed by JPL's Slava Turyshev and team. It has been selected for Phase III of NASA Innovative Advanced Concepts. [0]

> In 2020, Turyshev presented his idea of Direct Multi-pixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravitational Lens Mission. The lens could reconstruct the exoplanet image with ~25 km-scale surface resolution in 6 months of integration time, enough to see surface features and signs of habitability. His proposal was selected for the Phase III of the NASA Innovative Advanced Concepts. Turyshev proposes to use realistic-sized solar sails (~16 vanes of 10^3 m^2) to achieve the needed high velocity at perihelion (~150 km/sec), reaching 547 AU in 17 years.

> In 2023, a team of scientists led by Turychev proposed the Sundiver concept,[1] whereby a solar sail craft can serve as a modular platform for various instruments and missions, including rendezvous with other Sundivers for resupply, in a variety of different self-sustaining orbits reaching velocities of ~5-10 AU/yr.

Here is an interview with him laying out the entire plan.[2] It is the most interesting interview that I have seen in years, possibly ever.

[0] https://en.wikipedia.org/wiki/Slava_Turyshev#Work

[1] https://www2.mpia-hd.mpg.de/~calj/sundiver.pdf

[2] https://www.youtube.com/watch?v=lqzJewjZUkk

A 6 month integration time is going to generate massive amounts of data. How do they intend to receive all this back from 500 AU away?

The computer onboard likely merges everything into a final image in space?

Orbiting instruments typically transmit raw instruments data blocked into lines or segments that are are each surrounded by checksums.

It might be compressed for transmission, but raw data (warts and all) is king .. once it's "processed" and raw data is discarded .. there's no recovering the raw.

Years later raw data can be reprocessed with new algorithms, faster processes and combined with other sources to create "better" processed images.

Onboard hardware errors (eg: the historic Hubble Telescope erros) can be "corrected" later on the ground with an elaborate backpropagated trandfer function that optimally "fixes" the error, etc.

Data errors (spikes in cell values, glitches from cosmic rays, etc) can be combed out of the raw in post .. if smart people have access to the raw.

Baking processing into on board instrument processing prior to transmission isn't a good procedure.

But this wouldn’t be in orbit; it would be in what NASA calls “deep space”, which relies on the Deep Space Network [1]. The DSN is severely bandwidth constrained, due primarily to a lack of ground antennas. Indeed, for instruments that are located outside Earth’s orbit (e.g. SOHO, which is at Sun-Earth L1 [2]), bandwidth is often a limiting constraint in the design.

My understanding is that some newer instruments do both compress and select data to be downloaded (i.e. prioritizing signal over noise), and that there is more and more consideration of on-board processing for future missions, as well as possibly introducing the capability within DSN itself to prioritize which instruments get bandwidth based on scientific value of their data.

Source: A presentation from people at NASA Heliophysics last week, where this very topic came up.

[1]: < https://www.nasa.gov/communicating-with-missions/dsn/> [2]: < https://science.nasa.gov/mission/soho/>

From the interview linked, it sounds like the current plan doesn't involve the DSN at all: they're effectively out of transmission range past a certain point, and the transmission back is optical, using a big earth or space-based telescope. Which is one of the scary things he mentioned: they're going to be entirely autonomous when collecting the data.