Laser Guide Star for Large Segmented-aperture Space Telescopes. I. Implications for Terrestrial Exoplanet Detection and Observatory Stability

• Published in: The Astronomical journal Vol. 157; no. 1; pp. 36 - 47
• Main Authors: Douglas, E. S., Males, J. R., Clark, J., Guyon, O., Lumbres, J., Marlow, W., Cahoy, K. L.
• Format: Journal Article
• Language: English
• Published: Madison The American Astronomical Society 01.01.2019; IOP Publishing
• Subjects: Apertures; Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BRIGHTNESS; Control stability; DETECTION; Extrasolar planets; Field of view; Formation flying; instrumentation: adaptive optics; instrumentation: high angular resolution; Laser guide stars; LASER RADIATION; Lasers; MIRRORS; NOISE; OPTICS; Planet detection; PLANETS; planets and satellites: detection; RESOLUTION; SATELLITES; SENSORS; SPACE; Space telescopes; SPACE VEHICLES; space vehicles: instruments; Spacecraft; Spacecraft stability; SPECTRA; Star brightness; STARS; TELESCOPES; Terrestrial environments; Terrestrial planets; Vibration; Wave front control; Wave front sensors; Wave fronts
• ISSN: 0004-6256; 1538-3881; 1538-3881
• DOI: 10.3847/1538-3881/aaf385

Precision wavefront control on future segmented-aperture space telescopes presents significant challenges, particularly in the context of high-contrast exoplanet direct imaging. We present a new wavefront control architecture that translates the ground-based artificial guide star concept to space with a laser source on board a second spacecraft, formation flying within the telescope's field of view. We describe the motivating problem of mirror segment motion and develop wavefront sensing requirements as a function of guide star magnitude and segment motion power spectrum. Several sample cases with different values for transmitter power, pointing jitter, and wavelength are presented to illustrate the advantages and challenges of having a non-stellar-magnitude noise limited wavefront sensor for space telescopes. These notional designs allow increased control authority, potentially relaxing spacecraft stability requirements by two orders of magnitude and increasing terrestrial exoplanet discovery space by allowing high-contrast observations of stars of arbitrary brightness.