Feasible and Affordable Missions for Exoplanet Imaging

The solar gravitational lens (SGL) is characterized by remarkable properties: it offers brightness amplification of up to a factor of ~1e11 [100 billion amplification] (at 1 um) and extreme angular resolution (~1e-10 arcsec). As such, it allows for extraordinary observational capabilities for direct high-resolution imaging and spectroscopy of Earth-like exoplanets.

Above – Artist’s depiction of a possible image from a Solar Gravitational Lens (SGL) telescope.
Credits: Slava Turyshev

A mission to the strong interference region of the SGL (beyond 547.6 AU) carrying a meter-class space telescope with a solar coronagraph would directly image a habitable Earth-like exoplanet within our stellar neighborhood. For an exo-Earth at 30 pc (about 100 light-years), the telescope could measure the brightness of the Einstein ring formed by the exoplanet’s light around the Sun. Even in the presence of the solar corona, the SNR is high enough that in 6 months of integration time one can reconstruct the exoplanet image with ~25 km-scale surface resolution, enough to see surface features and signs of habitability.

The telescope at the lensing point would be looking at a star system on the opposite side of the sun. It would be able to focus on one other star system or perhaps a few that were lined up on the other side of the sun. If the missions are affordable then we would ideally want one space telescope station keeping at each desired gravitational lensing point to observe each solar system. We would then have long term observations and exploration at the 25-kilometer resolution. We would observe all the planets, moons and large asteroids. We would explore the surfaces, oceans and other large features. We would analyze any atmospheres.

There are about 512 or more stars of spectral type “G” (not including white dwarf stellar remnants) are currently believed to be located within 100 light-years or (or 30.7 parsecs) of the sun. There are roughly 2,000 stars at a distance of up to 50 light-years from our Solar System (64 of them are yellow-orange “G” stars like our Sun). As many as 15% of them can have Earth-sized planets in the habitable zone. There are nearly 20,000 stars within 100 light-years.

There are 52 known stars that are within 5.0 parsecs (16.3 light-years) of the Sun. These systems contain a total of 63 stars, of which 50 are red dwarfs, by far the most common type of star in the Milky Way.

There about 80 star systems in the 16-20 light-year distance form the sun.

There are about 50 more star systems in the 20-25 light-year distance from the sun.

There are about 90 star systems in the 25-30 light-year distance from the sun.

Phases I and II of our NIAC Study made three innovations:
(1) proven the feasibility of high-resolution, multipixel imaging of a habitable exoplanet;
(2) devised a swarm architecture for smallsats to explore the interstellar medium;
(3) designed the low-cost solar array propulsion to achieve the exit velocity from the solar system needed for the mission.

While flying along the SGL, our multismallsat architecture concurrently observes the multiple planets/moons of an exosolar system. Such simultaneity of observations reduces integration time, accounts for target’s temporal variability, and “removes the cloud cover”.

Our affordable SGL mission architecture design reduces cost:
1) It cuts the cost of each participant by enabling multiple entities broad choices of funding, building, deploying, operating, analyzing system elements at their choice.
2) It delivers economy of scale in an open architecture designed for mass production to minimize recurring costs.
3) It drives down the total mass (and thereby both NRE/ recurring costs) by using smallsats.
4) It uses realistic-sized solar sails (~16 vanes of 10^3 m^2) to achieve the needed high velocity at perihelion (~150 km/sec).
5) It applies maturing AI technologies for virtually autonomous mission execution eliminating the need for operator-intensive mission management,
(6) It reduces launch costs by relying on “ride-share” opportunities to launch the smallsats, avoiding the costs of large dedicated launchers.

Under a Phase II NIAC program, we determined that much of the foundational technology exists or is in intermediate levels of readiness due to the proliferation of government and commercial smallsat programs. This Phase III proposal will reduce the remaining TRL gaps and mature the SGLF mission concept.
* It will advance our understanding of the SGL-based imaging and spectroscopy of many candidate exoplanets, and define a near term, affordable flight test mission to prove the concept.
* It will refine our understanding of the mission architecture with emphasis on the issues of thermal and stability control during the perihelion acceleration.
* It will employ the system engineering approach successfully applied to many space missions by JPL and Aerospace, and employed by our industry partners, to select the best technologies for long-duration, autonomous operations in deep space and to identify and mitigate mission risks.

This mission is the main way to view a potentially habitable exoplanet in detail.

The SGL mission seeks further insight into the question “Are we alone in the Universe?”

SOURCES- Wikipedia, NASA
Written By Brian Wang, Nextbigfuture.com