Mission design of a synthetic aperture interferometer system for space exploration of exoplanets


In this project, the array telescope system consists of a collector in the center and four detectors evenly distributed around it. The architecture of the observation scene in orbit is represented. Credit: Space: Science and Technology

The search for extraterrestrial life and the exploration of “another Earth” is an eternal theme for humans and inspires generations of planetary scientists. It not only improves our understanding of the formation and evolution of planets during the formation of a star system, but also helps scientists to study the possible conditions and criteria for the existence of life. Over the past 30 years, scientists have discovered more than 4,000 exoplanets, but exploration still has a long way to go.

Due to the large distance, the search for exoplanets requires high sensitivity and resolution. The space telescope can eliminate interference from the Earth’s atmosphere on observations, and has become a trend in exoplanet exploration. As a next-generation telescope configuration, the array telescope is expected to realize cross-generation of the telescope system so that an Earth-like exoplanet near a Sun-like host star can be detected and characterized by direct imaging.

In a research article recently published in Space: science and technologyXiangyu Li from Beijing Institute of Technology focuses on space-based exoplanet exploration mission and analyzes its scientific background, mission profile, trajectory design method and orbital maintenance technique, which deploys multiple satellites to form a synthetic aperture interferometer system in space to help discover exoplanets.

The author first proposed four array telescope observing applications, which are necessary to search for and characterize habitable exoplanets in neighbors of our solar system (within 65 light years).

  1. High spatial resolution. The star-planet angular distance is better than 0.01 arcsecond at 65 light-years from the Sun.
  2. High contrast. The luminosity of planets and stars differs by at least 7 orders of magnitude in the mid-infrared band.
  3. High sensitivity. The luminosity of the planet in the dominant band of the signal is less than 3 photons/sec/m2.
  4. Wide spectral range. Indirect observation in the near infrared band of 1 to 5 μm and direct observation in the near infrared band of 1 to 13 μm.

Then, the principles of two-element cancellation interferometer and four-element cancellation interferometer were introduced, respectively. Based on the characteristics of observation demands and the principle of interferometry, the general requirements for the array telescope system have been concluded for the design of the trajectory.

Then, the methods of mission orbit selection and transfer trajectory design were proposed. The Sun-Earth halo orbit L2 is selected as the mission orbit for two main reasons. For one thing, the ideal mission orbit should stay away from electromagnetic interference from Earth. On the other hand, a relatively clean dynamic environment is required to reduce the magnitude and frequency of orbit sustaining. Based on the selected periodic orbit, the stable invariant varieties of the periodic orbits were used to find the low energy transfer opportunity. The transfer trajectory was designed using a three-step procedure. First, based on the restricted circular three-body problem, the stable varieties of the target mission orbit at different phase angles were generated, and the branch approaching the Earth was selected. Second, the Poincaré map was selected based on the perigee state constraint. Third, the corresponding manifold that satisfied the height constraint of the parking orbit was chosen as the initial estimate of the transfer trajectory. For the maintenance of the formation configuration around the libration point, the maximum drift error bound constraint existed and the control law based on the tangent targeting method was proposed to maximize the time spent in the bound d error between operations.

Finally, numerical simulations were implemented to validate the effectiveness of the proposed method. Two main results are worth mentioning. In the orbital transfer phase, multiple perigees of the collector were found to reduce the total transfer time to one and a half years, and each transfer needed only a velocity increment of less than 10 m/s to achieve the insertion of the halo orbit. . In the orbit sustaining phase, the spacecraft can satisfy relative position stability constraints at a sustaining frequency of approximately once every two days, with lower overall velocity increments of each spacecraft at 5×10−4 m/s when the error bound is 0.1 m.

Eccentric exoplanet discovered

More information:
Feida Jia et al, Mission Design of an Aperture-Synthetic Interferometer System for Space-Based Exoplanet Exploration, Space: science and technology (2022). DOI: 10.34133/2022/9835234

Provided by Beijing Institute of Technology

Quote: Mission design of an opening-synthetic interferometer system for space-based exoplanet exploration (2022, April 8) retrieved April 8, 2022 from https://phys.org/news/2022-04-mission-aperture-synthetic-interferometer- space-based-exoplanet.html

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