29 research outputs found
The Observational Effects and Signatures of Tidally Distorted Solid Exoplanets
Our work examines the detectability of tidally distorted solid exoplanets in
synchronous rotation. Previous work has shown that tidally distorted shapes of
close-in gas giants can give rise to radius underestimates and subsequently
density overestimates for those planets. We examine the assumption that such an
effect is too minimal for rocky exoplanets and find that for smaller M Class
stars there may be an observationally significant tidal distortion effect at
very close-in orbits. We quantify the effect for different stellar types and
planetary properties using some basic assumptions. Finally, we develop a simple
analytic expression to test if there are detectable bulge signatures in the
photometry of a system. We find that close in for smaller M Class stars there
may be an observationally significant signature that may manifest itself in
both in-transit bulge signatures and ellipsoidal variations.Comment: 8 pages, 5 figures, accepted for publication in MNRA
Relevance of Tidal Heating on Large TNOs
We examine the relevance of tidal heating for large Trans-Neptunian Objects,
with a focus on its potential to melt and maintain layers of subsurface liquid
water. Depending on their past orbital evolution, tidal heating may be an
important part of the heat budget for a number of discovered and hypothetical
TNO systems and may enable formation of, and increased access to, subsurface
liquid water. Tidal heating induced by the process of despinning is found to be
particularly able to compete with heating due to radionuclide decay in a number
of different scenarios. In cases where radiogenic heating alone may establish
subsurface conditions for liquid water, we focus on the extent by which tidal
activity lifts the depth of such conditions closer to the surface. While it is
common for strong tidal heating and long lived tides to be mutually exclusive,
we find this is not always the case, and highlight when these two traits occur
together.Comment: Submitted to Icaru
Commissioning and performance results of the WFIRST/PISCES integral field spectrograph
The Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies
(PISCES) is a high contrast integral field spectrograph (IFS) whose design was
driven by WFIRST coronagraph instrument requirements. We present commissioning
and operational results using PISCES as a camera on the High Contrast Imaging
Testbed at JPL. PISCES has demonstrated ability to achieve high contrast
spectral retrieval with flight-like data reduction and analysis techniques.Comment: Author's copy - Proceedings of SPIE Volume 10400. Citation to SPIE
proceedings volume will be added when availabl
Simulating the WFIRST coronagraph Integral Field Spectrograph
A primary goal of direct imaging techniques is to spectrally characterize the
atmospheres of planets around other stars at extremely high contrast levels. To
achieve this goal, coronagraphic instruments have favored integral field
spectrographs (IFS) as the science cameras to disperse the entire search area
at once and obtain spectra at each location, since the planet position is not
known a priori. These spectrographs are useful against confusion from speckles
and background objects, and can also help in the speckle subtraction and
wavefront control stages of the coronagraphic observation. We present a
software package, the Coronagraph and Rapid Imaging Spectrograph in Python
(crispy) to simulate the IFS of the WFIRST Coronagraph Instrument (CGI). The
software propagates input science cubes using spatially and spectrally resolved
coronagraphic focal plane cubes, transforms them into IFS detector maps and
ultimately reconstructs the spatio-spectral input scene as a 3D datacube.
Simulated IFS cubes can be used to test data extraction techniques, refine
sensitivity analyses and carry out design trade studies of the flight CGI-IFS
instrument. crispy is a publicly available Python package and can be adapted to
other IFS designs.Comment: 15 page
The IFS for WFIRST CGI: Science Requirements to Design
Direct Imaging of exoplanets using a coronagraph has become a major field of research both on the ground and in space. Key to the science of direct imaging is the spectroscopic capabilities of the instrument, our ability to extract spectra, and measure the abundance of molecular species such as Methane. To take these spectra, the WFIRST coronagraph instrument (CGI) uses an integral field spectrograph (IFS), which encodes the spectrum into a two-dimensional image on the detector. This results in more efficient detection and characterization of targets, and the spectral information is critical to achieving detection limits below the speckle floor of the imager. The CGI IFS operates in two18% bands spanning 600nm to 840nm at a nominal spectral resolution of R50. We present the current science and engineering requirements for the IFS design, the instrument design, anticipated performance, and how the calibration is integrated into the focal plane wavefront control algorithms. We also highlight the role of the Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies (PISCES) at the JPL High Contrast Imaging Testbed to demonstrate performance and validate calibration methodologies for the flight instrument
Flight Integral Field Spectrograph (IFS) Optical Design for WFIRST Coronagraphic Exoplanet Demonstration
Based on the experience from Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies (PISCES) for WFIRST, we have moved to the flight instrument design phase. The specifications for flight IFS have similarities and differences from the prototype. This paper starts with the science and system requirement, discusses a number of critical trade-offs: such as IFS type selection, lenslet array shape and layout versus detector pixel accuracy, how to accommodate the larger Field Of View (FOV) and wider wavelength band for a potential add-on StarShade occulter. Finally, the traditional geometric optical design is also investigated and traded: reflective versus refractive, telecentric versus non-telecentric relay. The relay before the lenslet array controls the chief angle distribution on the lenslet array. Our previous paper has addressed how the relay design combined with lenslet arraypinhole mask can further compress the residual star light and increase the contrast. Finally, a complete phase A IFS optical design is presented
WFIRST CGI Integral Field Spectrograph Performance and Post-Processing in the OS6 Observing Scenario
The WFIRST coronagraph instrument (CGI) will have an integral field spectrograph (IFS) backend to disperse the entire field of view at once and obtain spatially-resolved, low-resolution spectra of the speckles and science scene. The IFS will be key to understanding the spectral nature of the speckles, obtain science spectra of planets and disks, and will be used for broadband wavefront control. In order to characterize, predict, and optimize the performance of the instrument, we present a detailed model of the IFS in the context of the new OS6 observing scenario. The simulation includes spatial, spectral, and temporal variations of the speckle field on the IFS detector plane, which allows us to explore several post-processing methods and assess what gains can be expected. The simulator includes the latest models of the detector behavior when operating in photon-counting mode