Results 11 to 20 of about 1,731,322 (198)
ALICE Data Release: A Revaluation of HST-NICMOS Coronagraphic Images [PDF]
The Astronomical Journal, 2018 Abstract The Hubble Space Telescope NICMOS instrument was used from 1997 to 2008 to perform coronagraphic observations of about 400 targets. Most of them were part of surveys looking for substellar companions or resolved circumstellar disks to young nearby stars, making the NICMOS coronagraphic archive a valuable database for exoplanets ...
Hagan, J. Brendan +3 more
core +6 more sources
High contrast imaging wavefront sensor referencing from coronagraphic images [PDF]
Techniques and Instrumentation for Detection of Exoplanets X, 2021 A key challenge of high contrast imaging (HCI) is to differentiate a speckle from an exoplanet signal. The sources of speckles are a combination of atmospheric residuals and aberrations in the non-common path. Those non-common path aberrations (NCPA) are particularly challenging to compensate for as they are not directly measured, and because they ...
Skaf, Nour +13 more
core +7 more sources
Coronagraphic Data Post-processing Using Projections on Instrumental Modes [PDF]
The Astrophysical JournalDirectly observing exoplanets with coronagraphs is impeded by the presence of speckles from aberrations in the optical path, which can be mitigated in hardware with wave front control, as well as in post-processing. This work explores using an instrument
Yinzi Xin +6 more
doaj +2 more sources
Speckle temporal stability in XAO coronagraphic images [PDF]
Astronomy & Astrophysics, 2012 Context. The major source of noise limiting high-contrast imaging is caused by quasi-static speckles. Speckle noise originates from wavefront errors caused by various independent sources, and evolves on different timescales depending on their nature. An understanding of how quasi-static speckles originate from instrumental errors is paramount to the ...
Martinez, P. +3 more
openaire +4 more sources
Parameter Distributions for the Drag‐Based Modeling of CME Propagation
Space Weather, Volume 20, Issue 9, September 2022., 2022 Abstract In recent years, ensemble modeling has been widely employed in space weather to estimate uncertainties in forecasts. We here focus on the ensemble modeling of Coronal Mass Ejections (CME) arrival times and arrival velocities using a drag‐based model, which is well‐suited for this purpose due to its simplicity and low computational cost ...
Gianluca Napoletano +9 more
wiley +1 more source
Space Weather, Volume 20, Issue 7, July 2022., 2022 Abstract The forecasting of the Time‐of‐Arrival (ToA) of coronal mass ejections (CMEs) to Earth does not yet meet most Space Weather users' requirements. The main physical reason is our incomplete understanding of CME propagation in the inner heliosphere.
Evangelos Paouris, Angelos Vourlidas
wiley +1 more source
A Multi‐Purpose Heliophysics L4 Mission
Space Weather, Volume 19, Issue 9, September 2021., 2021 Abstract The Earth‐Sun Lagrangian point 4 is a meta‐stable location at 1 AU from the Sun, 60° ahead of Earth's orbit. It has an uninterrupted view of the solar photosphere centered on W60, the Earth's nominal magnetic field connection to the Sun. Such a mission on its own would serve as a solar remote sensing observatory that would oversee the entire ...
A. Posner +15 more
wiley +1 more source
A Quarter Century of Wind Spacecraft Discoveries
Reviews of Geophysics, Volume 59, Issue 2, June 2021., 2021 Abstract The Wind spacecraft, launched on November 1, 1994, is a critical element in NASA’s Heliophysics System Observatory (HSO)—a fleet of spacecraft created to understand the dynamics of the Sun‐Earth system. The combination of its longevity (>25 years in service), its diverse complement of instrumentation, and high resolution and accurate ...
Lynn B. Wilson III +13 more
wiley +1 more source
CME Magnetic Structure and IMF Preconditioning Affecting SEP Transport
Space Weather, Volume 19, Issue 4, April 2021., 2021 Abstract Coronal mass ejections (CMEs) and solar energetic particles (SEPs) are two phenomena that can cause severe space weather effects throughout the heliosphere. The evolution of CMEs, especially in terms of their magnetic structure, and the configuration of the interplanetary magnetic field (IMF) that influences the transport of SEPs are currently
Erika Palmerio +17 more
wiley +1 more source
Space Weather, Volume 19, Issue 2, February 2020., 2021 Abstract White light images of coronal mass ejections (CMEs) are projections on the plane‐of‐sky (POS). As a result, CME kinematics are subject to projection effects. The error in the true (deprojected) speed of CMEs is one of the main causes of uncertainty to Space Weather forecasts, since all estimates of the CME time‐of‐arrival (ToA) at a certain ...
Evangelos Paouris +3 more
wiley +1 more source