The TOLIMAN mission will fly a low-cost space telescope designed and led from the University of Sydney. Its primary science targets an audacious outcome in planetary astrophysics: an exhaustive search for temperateorbit rocky planets around either star in the Alpha Centauri AB binary, our nearest neighbour star system. By performing narrow-angle astrometric monitoring of the binary at extreme precision, any exoplanets betray their presence by gravitationally, engraving a tell-tale perturbation on the orbit. Recovery of this challenging signal, only of order micro-arcseconds of deflection, is normally thought to require a large (meter-class) instrument. By implementing significant innovations optical and signal encoding architecture, the TOLIMAN space telescope aims to recover such signals with a telescope aperture of only a 12.5cm. Here we describe the key features of the mission: its optics, signal encoding and the 16U CubeSat spacecraft bus in which the science payload is housed - all of which are now under construction. With science operations forecast on a timescale of a year, TOLIMAN aims to determine if the Sun’s nearest neighbour hosts a potential planetary stepping stone into the galaxy. Success would lay down a visionary challenge for futuristic high speed probe technologies capable of traversing the interstellar voids.
We describe the requirements and associated technology development plan for the communications data link from low mass interstellar probes. This work is motivated by several proposed deep space and interstellar missions with an emphasis on the Breakthrough Starshot project. The Starshot project is an effort to send the first low mass interstellar probes to nearby star systems and transmit back scientific data acquired during system transit within the time scale of a human lifetime. The about 104-fold increase in distance to nearby stars compared to the outer planets of our solar system requires a new form of propulsion to reach speeds of approximately 20% of the speed of light. The proposed use of a low mass sailcraft places strong constraints on the mass and power for the Starshot communications system. We compare the communications systems in current and upcoming solar system probes, New Horizons and Psyche, against the requirements for Starshot and define Figures of Merit for the communications capability in terms of data downlink rate multiplied by distance squared per unit mass. We describe current and future technology developments required for the on-board transmitter (signal generation, signal distribution, and beamforming) and for the near-Earth communications receiver (low-cost large aperture telescopes, high resolution spectrometers, and single photon counting detectors). We also describe a roadmap for technology development to meet the goals for future interstellar communications.
One of the main design considerations of the Large Binocular Telescope (LBT) was the goal to resolve the habitable zones (HZs) of the nearest stars at mid-infrared wavelengths around 10 μm. The LBT Interferometer (LBTI) makes use of the telescope’s two 8.4m mirrors on a common mount and their 22.7m edge-to-edge separation for sensitive, high-angular resolution observations at thermal-infrared wavelengths. In addition to adaptive optics imaging using the two mirrors separately, the instrument enables nulling and Fizeau imaging interferometry exploiting the full resolving power of the LBT. The LBTI team has successfully completed the Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS), for which we used nulling-interferometry to search for exozodiacal dust, and we are continuing the characterization of the detected systems. Here, we describe a new program to exploit the LBTI’s Fizeau imaging interferometric capabilities for a deep imaging search for low-mass, HZ planets around a small sample of particularly suitable, nearby stars. We also review the LBTI’s current status relevant to the proposed project to demonstrate the instrument is ready for such a large project.
We present the concept of using an orbiting laser as a coherent optical reference to phase a several kilometer diameter array of ground-based lasers designed to accelerate interstellar nano-spacecraft to 20% light-speed using laser propulsion. We investigate the geometrical and temporal constraints for the initial case of the target star Proxima b in the Alpha Centauri system using a laser ground site in the southern hemisphere. Based on these constraints, we detail requirements for the mission architecture for an orbiting laser to be used as an optical reference. We then present two orbits that can meet all given requirements and represent a range of engagement times and days between engagements. We also present a range of orbits with periods from 3 to 4 days and engagement times from 660 to 800 s. If desired, the orbit can be matched to the sidereal day, so each orbit period, the beacon can align with the ground station and the same target star without maneuvers. A discussion of the tradeoff between the Earth-based site latitude, time on engagement, and days between engagements is presented.
The TOLIMAN space telescope is a low-cost, agile mission concept dedicated to astrometric detection of exoplanets in the near-solar environment, and particularly targeting the Alpha Cen system. Although successful discovery technologies are now populating exoplanetary catalogs into the thousands, contemporary astronomy is still poorly equipped to answer the basic question of whether there are any rocky planets orbiting any particular star system. Toliman will make a first study of stars within 10 PC of the sun by deploying an innovative optical and signal encoding architecture that leverages the most promising technology to deliver data on this critical stellar sample: high precision astrometric monitoring. Here we present results from the Foundational Mission Study, jointly funded by the Breakthrough Prize Foundation and the University of Sydney which has translated innovative underlying design principles into error budgets and potential spacecraft systems designs.
By adding a dedicated coronagraph, ESO in collaboration with the Breakthrough Initiatives, modifies the Very Large Telescope mid-IR imager (VISIR) to further boost the high dynamic range imaging capability this instru- ment has. After the VISIR upgrade in 2012, where coronagraphic masks were first added to VISIR, it became evident that coronagraphy at a ground-based 8m-class telescope critically needs adaptive optics, even at wavelengths as long as 10μm. For VISIR, a work-horse observatory facility instrument in normal operations, this is ”easiest” achieved by bringing VISIR as a visiting instrument to the ESO-VLT-UT4 having an adaptive M2. This “visit” enables a meaningful search for Earth-like planets in the habitable zone around both α-Cen1,2. Meaningful here means, achieving a contrast of ≈ 10-6 within ≈ 0.8arcsec from the star while maintaining basically the normal sensitivity of VISIR. This should allow to detect a planet twice the diameter of Earth. Key components will be a diffractive coronagraphic mask, the annular groove phase mask (AGPM), optimized for the most sensitive spectral band-pass in the N-band, complemented by a sophisticated apodizer at the level of the Lyot stop. For VISIR noise filtering based on fast chopping is required. A novel internal chopper system will be integrated into the cryostat. This chopper is based on the standard technique from early radio astronomy, conceived by the microwave pioneer Robert Dicke in 1946, which was instrumental for the discovery of the 3K radio background.
We have fabricated a diamond-turned low-mass version of a toroidal mirror which is a key element for a spaceborne
visible-light heliospheric imager. This mirror's virtual image of roughly a hemisphere of sky is viewed by a conventional
photometric camera. The optical system views close to the edge of an external protective baffle and does not protrude
from the protected volume. The sky-brightness dynamic range and background-light rejection requires minimal wideangle
scattering from the mirror surface. We describe the manufacturing process for this mirror, and present preliminary
laboratory measurements of its wide-angle scattering characteristics.
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