The NASA Innovative Advanced Concepts (NIAC) program recently awarded 25 grants for the development of visionary new technologies. Here we’re going to take a closer look at the following two Phase II awards focused on space astronomy.
Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravity Lens Mission
NASA Jet Propulsion Laboratory
Kilometer Space Telescope (KST)
Each award is worth up to $500,000 for a two-year study. Descriptions of the awards are below.
Direct Multipixel Imaging and Spectroscopy of an Exoplanet
with a Solar Gravity Lens Mission
NASA Jet Propulsion Laboratory
We propose to build upon our Phase I study of a mission to the regions outside our solar system, with the objective of conducting direct high-resolution imaging and spectroscopy of a habitable exoplanet by exploiting optical properties of the solar gravitational lens (SGL). A mission to the focal area of the SGL (which lies beyond 548.7 astronomical unites (AU) on the line connecting the center of the exoplanet and that of our Sun, called the focal line of the SGL) carrying a modest telescope and coronagraph could deliver direct megapixel imaging and high-resolution spectroscopy of a habitable Earth-like exoplanet orbiting a host star at a distance of up to 30 parsec.
The remarkable optical properties of the SGL include major brightness amplification (~1e11 at \lambda=1 um) and extreme angular resolution (~1e-10 arcsec) in a narrow field of view. The entire image of such an exo-Earth is compressed by the SGL into an instantaneous cylinder with a diameter of ~1.3 km in the vicinity of the focal line. Moving outwards while staying within the image, the telescope will take photometric data of the Einstein ring around the Sun formed by the light from the exoplanet and will process the data to reconstruct the image of the exoplanet with a few km-scale resolution of its surface, enough to see its surface features and signs of habitability.
Under a Phase I NIAC program, we evaluated the feasibility of the SGL-based technique for direct imaging and spectroscopy of an exoplanet and, while several practical constraints have been identified, we have not identified any fundamental limitations. We determined that the foundational technology already exists and has high TRL in space missions and applications. Furthermore, the measurements required to demonstrate the feasibility of remote sensing with the SGL are complementary to rotational tomography measurements and ongoing microlensing investigations, so our effort would provide high-value scientific information to other active astrophysics programs.
Under the Phase II program, we will continue to advance our understanding of the SGL-based imaging and spectroscopy, improve on the computational methods developed in Phase I, evaluate specific hardware implementations, and ultimately produce a roadmap for the direct high-resolution sensing of exoplanets. We will refine our understanding of mission architectures and the technology roadmap. To that extent, we will refine the Phase I mission concepts: i) a single probe-class spacecraft, ii) a swarm of small and capable spacecraft, iii) a “string-of-pearls” mission concept using multiple sets of moderate size spacecraft, and will consider other concepts, if identified.
Our main objective for this effort is to study i) how a space mission to the focal region of the SGL may be used to obtain high-resolution direct imaging and spectroscopy of an exoplanet by detecting, tracking, and studying the Einstein ring around the Sun, and ii) how such information could be used to detect signs of life on another planet. We will deliver a list of recommendations on the mission architectures with risk and return trade offs and discuss an enabling technology development program. The resulting mission concept could allow exploration of exoplanets relying on the SGL capabilities decades, if not centuries, earlier than possible with other extant technologies.
Phase II will provide us with a clear understanding of the scientific value of the mission and the trades needed to define the most cost-effective mission design and architecture. If no showstoppers will be identified, we will have all the needed tools and mission rationale to present the SGL imaging mission to the science community for a broader support. As the concept may be the only way to view a potentially habitable exoplanet in detail, it would generate the public interest and enthusiasm that could motivate the needed government and private funding.
Kilometer Space Telescope (KST)
A Kilometer Space Telescope (KST) will provide over three times the diameter and ten times the collecting area of the Arecibo groundbased radio telescope with diffraction-limited performance at optical, infrared, and millimeter wavelengths. This capability is orders of magnitude improvement over the Hubble (HST) and James Webb (JWST) instruments. This Phase 2 NIAC proposal extends Phase 1 technology to measure the optical performance at the meter laboratory scale to predict the performance of a one-kilometer space telescope. Each aspect of the technology, science, development, and mission science will be examined to produce these products:
- Science Requirements
- Lab Measurement of spherical primary optical quality
- Telescope Architectural Trades
- Telescope Design
- Telescope Performance modeling
- Launch and deployment methodology
- Mission Operations
- Science Data Reduction
- Simulated Science data, imagery, and results
- Development and Deployment Plan for KST
- Mission Plan
Dramatic increases in resolution and sensitivity will enable breakthrough science in the discovery and study of terrestrial planets, including spectroscopic search for signatures of life and intelligent life, and the study of some of the very early light emitting objects in the universe.
Unlike other proposed approaches to kilometer class apertures such as interferometers or the Aragoscope, which are all photon starved, the filled aperture KST will be photon rich. A KST would revolutionize astronomy in ways we cannot now imagine. For example, no one predicted that the most stunning images from HST would be of Planetary Nebulae. And HST was only one order of magnitude finer than its predecessors.
We will certainly spend more time in Phase II looking at what might be some of the driving science issues, but for now we simply state that the KST will give us an unparalleled new view of the Universe. Wherever it looks it will make new discoveries. A detailed set of lab experiments will demonstrate the viability of excised portions of spheres as primary mirrors. Optical performance will be measured interferometrically.
We will study both passive and active ways to maintain diffraction-limited performance and to offer both wide field search and narrow filed detailed study modes of operation. The enabling technology also can be used for sun shades for the KST itself, as well as star shades for coronagraphic examination of terrestrial exoplanets.
An early use of this technology could even be to launch star shades for use with JWST. It is possible to deploy structures 100 million times the volume of the launch vehicle payload bay, so in fact a large number of star shades for JWST could be deployed simultaneously, speeding surveys of star planetary systems. As noted in the Phase 1 report, the technology could also be used for large solar sails or habitats.