22 research outputs found
Laser Guide Star for Large Segmented-Aperture Space Telescopes, Part I: Implications for Terrestrial Exoplanet Detection and Observatory Stability
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 aboard a second spacecraft, formation flying within the telescope
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.Comment: Submitted to A
Design of a Space-Based Laser Guide Star Mission to Enable Ground and Space Telescope Observations of Faint Objects
We present the detailed design of a Laser Guide Star small satellite that would formation fly with a large space observatory or fly with respect to a ground telescope that use adaptive optics (AO) for wavefront sensing and control. Using the CubeSat form factor for the Laser Guide Star small satellite, we develop a 12U system to accommodate a propulsion system. The propulsion system enables the LGS satellite to formation fly near the targets in the telescope boresight and to meet mission requirements on number of targets and duration. We simulate the formation flight at L2 to assess the precision required to enable the wavefront sensing and control during observation. We describe a design reference mission (DRM) for deploying 18 Laser Guide Stars to L2 to assist the Large Ultraviolet, Optical, Infrared Surveyor (LUVOIR). The L2 LGS DRM covers over 250 exoplanet target systems with 5 or more revisits to each system over a 5-year mission using eighteen 12U CubeSats. We present a design reference mission for a laser guide star satellite to geostationary orbit for use with 6.5+ meter ground telescopes with AO to look at HD 50281, HD 180617, and other near-equatorial targets. We assess simulations on the maximum level of thruster noise permitted during the observations to maintain precision formation flying with the observatories
Optical and mechanical design of the extreme AO coronagraphic instrument MagAO-X
Here we review the current optical mechanical design of MagAO-X. The project
is post-PDR and has finished the design phase. The design presented here is the
baseline to which all the optics and mechanics have been fabricated. The
optical/mechanical performance of this novel extreme AO design will be
presented here for the first time. Some highlights of the design are: 1) a
floating, but height stabilized, optical table; 2) a Woofer tweeter (2040
actuator BMC MEMS DM) design where the Woofer can be the current f/16 MagAO ASM
or, more likely, fed by the facility f/11 static secondary to an ALPAO DM97
woofer; 3) 22 very compact optical mounts that have a novel locking clamp for
additional thermal and vibrational stability; 4) A series of four pairs of
super-polished off-axis parabolic (OAP) mirrors with a relatively wide FOV by
matched OAP clocking; 5) an advanced very broadband (0.5-1.7micron) ADC design;
6) A Pyramid (PWFS), and post-coronagraphic LOWFS NCP wavefront sensor; 7) a
vAPP coronagraph for starlight suppression. Currently all the OAPs have just
been delivered, and all the rest of the optics are in the lab. Most of the
major mechanical parts are in the lab or instrument, and alignment of the
optics has occurred for some of the optics (like the PWFS) and most of the
mounts. First light should be in 2019A.Comment: 10 pages, proc. SPIE 10703, Adaptive Optics IV, Austin TX, June 201
The Space Coronagraph Optical Bench (SCoOB): 1. Design and Assembly of a Vacuum-compatible Coronagraph Testbed for Spaceborne High-Contrast Imaging Technology
The development of spaceborne coronagraphic technology is of paramount
importance to the detection of habitable exoplanets in visible light. In space,
coronagraphs are able to bypass the limitations imposed by the atmosphere to
reach deeper contrasts and detect faint companions close to their host star. To
effectively test this technology in a flight-like environment, a high-contrast
imaging testbed must be designed for operation in a thermal vacuum (TVAC)
chamber. A TVAC-compatible high-contrast imaging testbed is undergoing
development at the University of Arizona inspired by a previous mission
concept: The Coronagraphic Debris and Exoplanet Exploring Payload (CDEEP). The
testbed currently operates at visible wavelengths and features a Boston
Micromachines Kilo-C DM for wavefront control. Both a vector vortex coronagraph
and a knife-edge Lyot coronagraph operating mode are under test. The optics
will be mounted to a 1 x 2 meter pneumatically isolated optical bench designed
to operate at 10^-8 torr and achieve raw contrasts of 10^-8 or better. The
validation of our optical surface quality, alignment procedure, and first light
results are presented. We also report on the status of the testbed's
integration in the vaccum chamber.Comment: 14 pages, 9 figure
Three-sided pyramid wavefront sensor. II. Preliminary demonstration on the new CACTI testbed
The next generation of giant ground and space telescopes will have the
light-collecting power to detect and characterize potentially habitable
terrestrial exoplanets using high-contrast imaging for the first time. This
will only be achievable if the performance of Giant Segmented Mirror Telescopes
(GSMTs) extreme adaptive optics (ExAO) systems are optimized to their full
potential. A key component of an ExAO system is the wavefront sensor (WFS),
which measures aberrations from atmospheric turbulence. A common choice in
current and next-generation instruments is the pyramid wavefront sensor (PWFS).
ExAO systems require high spatial and temporal sampling of wavefronts to
optimize performance, and as a result, require large detectors for the WFS. We
present a closed-loop testbed demonstration of a three-sided pyramid wavefront
sensor (3PWFS) as an alternative to the conventional four-sided pyramid
wavefront (4PWFS) sensor for GSMT-ExAO applications on the new Comprehensive
Adaptive Optics and Coronagraph Test Instrument (CACTI). The 3PWFS is less
sensitive to read noise than the 4PWFS because it uses fewer detector pixels.
The 3PWFS has further benefits: a high-quality three-sided pyramid optic is
easier to manufacture than a four-sided pyramid. We detail the design of the
two components of the CACTI system, the adaptive optics simulator and the PWFS
testbed that includes both a 3PWFS and 4PWFS. A preliminary experiment was
performed on CACTI to study the performance of the 3PWFS to the 4PWFS in
varying strengths of turbulence using both the Raw Intensity and Slopes Map
signal processing methods. This experiment was repeated for a modulation radius
of 1.6 lambda/D and 3.25 lambda/D. We found that the performance of the two
wavefront sensors is comparable if modal loop gains are tuned.Comment: 28 Pages, 15 Figures, and 4 Table
HIP 67506 C: MagAO-X Confirmation of a New Low-Mass Stellar Companion to HIP 67506 A
We report the confirmation of HIP 67506 C, a new stellar companion to HIP
67506 A. We previously reported a candidate signal at 2/D (240~mas) in
L in MagAO/Clio imaging using the binary differential imaging
technique. Several additional indirect signals showed that the candidate signal
merited follow-up: significant astrometric acceleration in Gaia DR3,
Hipparcos-Gaia proper motion anomaly, and overluminosity compared to single
main sequence stars. We confirmed the companion, HIP 67506 C, at 0.1" with
MagAO-X in April, 2022. We characterized HIP 67506 C MagAO-X photometry and
astrometry, and estimated spectral type K7-M2; we also re-evaluated HIP 67506 A
in light of the close companion. Additionally we show that a previously
identified 9" companion, HIP 67506 B, is a much further distant unassociated
background star. We also discuss the utility of indirect signposts in
identifying small inner working angle candidate companions.Comment: 10 pages, 9 figures, 4 tables, accepted to MNRA