17 research outputs found
The space coronagraph optical bench (SCoOB): 2. wavefront sensing and control in a vacuum-compatible coronagraph testbed for spaceborne high-contrast imaging technology
The 2020 Decadal Survey on Astronomy and Astrophysics endorsed space-based
high contrast imaging for the detection and characterization of habitable
exoplanets as a key priority for the upcoming decade. To advance the maturity
of starlight suppression techniques in a space-like environment, we are
developing the Space Coronagraph Optical Bench (SCoOB) at the University of
Arizona, a new thermal vacuum (TVAC) testbed based on the Coronagraphic Debris
Exoplanet Exploring Payload (CDEEP), a SmallSat mission concept for high
contrast imaging of circumstellar disks in scattered light. When completed, the
testbed will combine a vector vortex coronagraph (VVC) with a Kilo-C
microelectromechanical systems (MEMS) deformable mirror from Boston
Micromachines Corp (BMC) and a self-coherent camera (SCC) with a goal of raw
contrast surpassing at visible wavelengths. In this proceedings, we
report on our wavefront sensing and control efforts on this testbed in air,
including the as-built performance of the optical system and the implementation
of algorithms for focal-plane wavefront control and digging dark holes (regions
of high contrast in the focal plane) using electric field conjugation (EFC) and
related algorithms.Comment: 7 pages, 5 figures, SPIE Astronomical Telescopes and Instrumentation
202
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
Bright-Moon Sky as a Wide-Field Linear Polarimetric Flat Source for Calibration
Next-generation wide-field optical polarimeters like the Wide-Area Linear
Optical Polarimeters (WALOPs) have a field of view (FoV) of tens of arcminutes.
For efficient and accurate calibration of these instruments, wide-field
polarimetric flat sources will be essential. Currently, no established
wide-field polarimetric standard or flat sources exist. This paper tests the
feasibility of using the polarized sky patches of the size of around ten-by-ten
arcminutes, at a distance of up to 20 degrees from the Moon, on bright-Moon
nights as a wide-field linear polarimetric flat source. We observed 19 patches
of the sky adjacent to the bright-Moon with the RoboPol instrument in the
SDSS-r broadband filter. These were observed on five nights within two days of
the full-Moon across two RoboPol observing seasons. We find that for 18 of the
19 patches, the uniformity in the measured normalized Stokes parameters and
is within 0.2 %, with 12 patches exhibiting uniformity within 0.07 % or
better for both and simultaneously, making them reliable and stable
wide-field linear polarization flats. We demonstrate that the sky on
bright-Moon nights is an excellent wide-field linear polarization flat source.
Various combinations of the normalized Stokes parameters and can be
obtained by choosing suitable locations of the sky patch with respect to the
MoonComment: 8 pages including appendix, 6 figures and 3 tables. Submitted to
Astronomy and Astrophysics for review. Comments are welcom
Starlight-polarization-based tomography of the magnetized ISM: Pasiphae's line-of-sight inversion method
We present the first Bayesian method for tomographic decomposition of the
plane-of-sky orientation of the magnetic field with the use of stellar
polarimetry and distance. This standalone tomographic inversion method presents
an important step forward in reconstructing the magnetized interstellar medium
(ISM) in 3D within dusty regions. We develop a model in which the polarization
signal from the magnetized and dusty ISM is described by thin layers at various
distances. Our modeling makes it possible to infer the mean polarization
(amplitude and orientation) induced by individual dusty clouds and to account
for the turbulence-induced scatter in a generic way. We present a likelihood
function that explicitly accounts for uncertainties in polarization and
parallax. We develop a framework for reconstructing the magnetized ISM through
the maximization of the log-likelihood using a nested sampling method. We test
our Bayesian inversion method on mock data taking into account realistic
uncertainties from and as expected for the optical polarization survey
PASIPHAE according to the currently planned observing strategy. We demonstrate
that our method is effective in recovering the cloud properties as soon as the
polarization induced by a cloud to its background stars is higher than , for the adopted survey exposure time and level of systematic
uncertainty. Our method makes it possible to recover not only the mean
polarization properties but also to characterize the intrinsic scatter, thus
opening ways to characterize ISM turbulence and the magnetic field strength.
Finally, we apply our method to an existing dataset of starlight polarization
with known line-of-sight decomposition, demonstrating agreement with previous
results and an improved quantification of uncertainties in cloud properties.Comment: 28 pages, including 2 appendices, submitted to A&
Approaches to lowering the cost of large space telescopes
New development approaches, including launch vehicles and advances in
sensors, computing, and software, have lowered the cost of entry into space,
and have enabled a revolution in low-cost, high-risk Small Satellite (SmallSat)
missions. To bring about a similar transformation in larger space telescopes,
it is necessary to reconsider the full paradigm of space observatories. Here we
will review the history of space telescope development and cost drivers, and
describe an example conceptual design for a low cost 6.5 m optical telescope to
enable new science when operated in space at room temperature. It uses a
monolithic primary mirror of borosilicate glass, drawing on lessons and tools
from decades of experience with ground-based observatories and instruments, as
well as flagship space missions. It takes advantage, as do large launch
vehicles, of increased computing power and space-worthy commercial electronics
in low-cost active predictive control systems to maintain stability. We will
describe an approach that incorporates science and trade study results that
address driving requirements such as integration and testing costs,
reliability, spacecraft jitter, and wavefront stability in this new
risk-tolerant "LargeSat" context.Comment: Presented at SPIE, Optics+Photonics 2023, Astronomical Optics:
Design, Manufacture, and Test of Space and Ground Systems IV in San Diego,
CA, US
Recommended from our members
Approaches to lowering the cost of large space telescopes
New development approaches, including launch vehicles and advances in sensors, computing, and software, have lowered the cost of entry into space, and have enabled a revolution in low-cost, high-risk Small Satellite (SmallSat) missions. To bring about a similar transformation in larger space telescopes, it is necessary to reconsider the full paradigm of space observatories. Here we will review the history of space telescope development and cost drivers, and describe an example conceptual design for a low cost 6.5 m optical telescope to enable new science when operated in space at room temperature. It uses a monolithic primary mirror of borosilicate glass, drawing on lessons and tools from decades of experience with ground-based observatories and instruments, as well as flagship space missions. It takes advantage, as do large launch vehicles, of increased computing power and space-worthy commercial electronics in low-cost active predictive control systems to maintain stability. We will describe an approach that incorporates science and trade study results that address driving requirements such as integration and testing costs, reliability, spacecraft jitter, and wavefront stability in this new risk-tolerant “LargeSat” context. © 2023 SPIE.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]