Habitable Zones & Global Climate

From Direct Measurement Of The Universe's Expansion History To Characterization Of Nearby Habitable Planet Candidates

By Keith Cowing
November 14, 2021
Filed under
From Direct Measurement Of The Universe's Expansion History To Characterization Of Nearby Habitable Planet Candidates
High-dispersion spectrograph design optimized for the (a)(b) short (305 - 500 nm) and (c)(d) long (463 - 660 nm) channels. A dichroic mirror between the field stop and the collimator lens, which is not shown in this diagram, divides a beam into two in terms of the wavelength. The color of the ray indicates a different grating order: 29, 23, and 18 grating orders for the blue, green, and orange rays in the short channel and 35, 29, and 25 grating orders in the long one, respectively. Each beam has a field of view of 4 λ D in radius. The entrance beam with 3 mm diameter was divided into five without any densification. The footprint on the plane 1 after the Bowen-Walraven type image slicer was used is shown in the left upper panel of (b).

The direct measurement of the Universe’s expansion history and the search for terrestrial planets in habitable zones around solar-type stars require extremely high-precision radial velocity measures over a decade.

This study proposes an approach for enabling high-precision radial velocity measurements from space. The concept presents a combination of a high-dispersion densified pupil spectrograph and a novel telescope line-of-sight monitor. The precision of the radial velocity measurements is determined by combining the spectrophotometric accuracy and the quality of the absorption lines in the recorded spectrum. Therefore, a highly dispersive densified pupil spectrograph proposed to perform stable spectroscopy can be utilized for high-precision radial velocity measures. A concept involving the telescope line-of-sight monitor is developed to minimize the change of the telescope line-of-sight over a decade.

This monitor allows the precise measurement of a long-term telescope drift without any significant impact on the Airy disk when the densified pupil spectra are recorded. We analytically derive the uncertainty of the radial velocity measurements, which is caused by the residual offset of the line-of-sights at two epochs. We find that the error could be reduced down to approximately 1 cm/s, and the precision will be limited by another factor (e.g., wavelength calibration uncertainty). A combination of the high precision spectrophotometry and the high spectral resolving power could open a n

ew path toward the characterization of nearby non-transiting habitable planet candidates orbiting late-type stars. We present two simple and compact high-dispersed densified pupil spectrograph designs for the cosmology and exoplanet sciences.

Densified pupil spectrograph as high-precision radial velocimetry: From direct measurement of the Universe’s expansion history to characterization of nearby habitable planet candidates

Taro Matsuo, Thomas P. Greene, Mahdi Qezlou, Simeon Bird, Kiyotomo Ichiki, Yuka Fujii, Tomoyasu Yamamuro

Comments: 37 pages, 18 figures, Accepted for publication in the Astronomical Journal
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2111.06766 [astro-ph.IM] (or arXiv:2111.06766v1 [astro-ph.IM] for this version)
Submission history
From: Taro Matsuo
[v1] Fri, 12 Nov 2021 15:23:31 UTC (23,227 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻