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Project Progress

This task focuses on the question of detectability of planets and biosignatures and uses instrument and data simulation models, retrieval techniques, and the amassed spectra of the Virtual Planetary Laboratory to date.

Planet Detection: We developed a new algorithm for planet signal extraction from simulated TPF- I data. The Point Process Algorithm (PPA), uses the prior knowledge that the planets will appear pointlike, and the statistical properties of the planetary system (planets and exo-zodi), modeled within a Bayesian framework. This technique is currently considered the best by the TPF signal extraction group.

We also investigated the limitations on planet detection that would attempt to measure the apparent stellar wobble induced by a planet in a circumstellar disk. Density waves excited by a planet in the circumstellar disk may be an obstacle to the precise measurement of the stellar position required. Our analysis shows that for a 1M_J planet, the Space Interferometry Mission observations will not suffer significant contamination by the disk light.

We have taken sub-millimeter astronomical observations of TPF target stars that show an IR excess in Spitzer data and developed a modeling tool to fit our observations of the circumstellar disks. For Fomalhaut at 350 μm we have discovered structure in the disk that is consistent with gravitational perturbation by an unseen planet.

We have also explored high-precision polarimetry as a means detecting estrasolar terrestrial planets.

Habitability and Biosignature Detection: The combined spectroscopic results to date from several of the VPL activities were used to assess the detectability of planetary characteristics and biosignatures. These spectra were run through instrument simulator models for both the coronographic and interferometric designs of TPF to better understand the detectability of characteristics for planets in our own Solar System and planets around other stars. These spectra have been used to support two TPF instrument concept proposals, and the TPF-C science requirements document.