A better understanding of the amplitudes of stellar oscillation modes and surface granulation is essential for improving theories of mode physics and the properties of the outer convection zone of solar-like stars. A proper prediction of these amplitudes is also essential for appraising the detectability of solar-like oscillations for asteroseismic analysis. Comparisons with models, or between different photometric missions, are enabled by applying a bolometric correction, which converts mission-specific amplitudes to their corresponding bolometric (full light) values. We derive the bolometric correction factor for amplitudes of radial oscillation modes and surface granulation as observed by the Kepler, CoRoT, and TESS missions. The calculations are done assuming a stellar spectrum given by a black-body as well as by synthetic spectral flux densities from 1D model atmospheres. We derive a power-law and polynomial relations for the bolometric correction as a function of temperature from the black-body approximation and evaluate the deviations from adopting a more realistic spectrum. Across the full temperature range from 4000 - 7500 K, the amplitudes from TESS are in the black-body approximation predicted to be a factor ~0.83 - 0.84 times those observed by Kepler. We find that using more realistic flux spectra over the black-body approximation can change the bolometric correction by as much as ~30% at the lowest temperatures, but with a change typically within ~5 - 10% around a $T_{\rm eff}$ of 5500 - 6000 K. We find that after $T_{\rm eff}$, the bolometric correction most strongly depends on [M/H], which could have an impact on reported metallicity dependencies of amplitudes reported in the literature.

Bolometric corrections of stellar oscillation amplitudes as observed by the Kepler, CoRoT, and TESS missions

The Transiting Exoplanet Survey Satellite (TESS) is an MIT-led, NASA-funded Explorer-class planet finder launched in April 2018. TESS will carry out a 2-year all-sky survey with the primary goal of detecting small transiting exoplanets around bright and nearby stars. The TESS instrument consists of four wide-field cameras in a stacked configuration, providing a combined field of view of 24  deg  ×   96  deg that spans approximately from the ecliptic plane to the ecliptic pole. In order to achieve the desired photometric precision necessary for the mission, TESS uses the instrument cameras as star trackers during fine-pointing mode to enhance attitude accuracy and stabilization for science operations. We present our approach in quantifying the expected performance of the fine-pointing system and assessing the impact of pointing performance on the overall photometric precision of the mission. First, we describe the operational details of the fine-pointing system with the science instrument being used for star-tracking. Next, we present the testing framework used to quantify the attitude determination performance of the system and the expected attitude knowledge accuracy results, both in coarse-fine pointing hand-off and in nominal fine-pointing conditions. By combining simulations of the instrument and the spacecraft bus, we quantify the closed-loop fine-pointing stability performance of the system in nominal science operations as well as in the case of camera unavailability due to Earth/Moon interference. Finally, we assess the impact of platform pointing stability on the photometric precision of the system using detailed system modeling and discuss the applicability of mitigation techniques to reduce the effect of jitter on TESS science data.

https://www.spiedigitallibrary.org/journals/Journal-of-Astronomical-Telescopes-Instruments-and-Systems/volume-4/issue-4/047001/Fine-pointing-performance-and-corresponding-photometric-precision-of-the-Transiting/10.1117/1.JATIS.4.4.047001.pdf

Fine-pointing performance and corresponding photometric precision of the Transiting Exoplanet Survey Satellite

The Transiting Exoplanet Survey Satellite (TESS) is an Explorer-class mission dedicated to finding planets
around bright, nearby stars so that more detailed follow-up studies can be done. TESS is due to launch in
2017 and careful characterization of the detectors will need to be completed on ground before then to
ensure that the cameras will be within their photometric requirement of 60ppm/hr. TESS will fly MITLincoln
Laboratories CCID-80s as the main scientific detector for its four cameras. They are 100μm deep
depletion devices which have low dark current noise levels and can operate at low light levels at room
temperature. They also each have a frame store region, which reduces smearing during readout and allows
for near continuous integration. This paper describes the hardware and methodology that were developed
for testing and characterizing individual CCID-80s. A dark system with no stimuli was used to measure the
dark current. Fe55 and Cd109 X-ray sources were used to establish gain at low signal levels and its
temperature dependence. An LED system that generates a programmable series of pulses was used in
conjunction with an integrating sphere to measure pixel response non-uniformity (PRNU) and gain at
higher signal levels. The same LED system was used with a pinhole system to evaluate the linearity and
charge conservation capability of the CCID-80s.

Testing and characterization of the TESS CCDs

Thesis: Ph. D. in Space Systems, Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2018.

Fine-pointing system development and photometric precision assessment for the transiting exoplanet survey satellite

The Transiting Exoplanet Survey Satellite, a NASA Explorer-class mission in development, will discover planets around
nearby stars, most notably Earth-like planets with potential for follow up characterization. The all-sky survey requires a
suite of four wide field-of-view cameras with sensitivity across a broad spectrum. Deep depletion CCDs with a silicon
layer of 100 μm thickness serve as the camera detectors, providing enhanced performance in the red wavelengths for
sensitivity to cooler stars. The performance of the camera is critical for the mission objectives, with both the optical
system and the CCD detectors contributing to the realized image quality. Expectations for image quality are studied
using a combination of optical ray tracing in Zemax and simulations in Matlab to account for the interaction of the
incoming photons with the 100 μm silicon layer. The simulations include a probabilistic model to determine the depth of
travel in the silicon before the photons are converted to photo-electrons, and a Monte Carlo approach to charge diffusion.
The charge diffusion model varies with the remaining depth for the photo-electron to traverse and the strength of the
intermediate electric field. The simulations are compared with laboratory measurements acquired by an engineering unit
camera with the TESS optical design and deep depletion CCDs. In this paper we describe the performance simulations
and the corresponding measurements taken with the engineering unit camera, and discuss where the models agree well in
predicted trends and where there are differences compared to observations.

/pdf/the-tess-camera-modeling-and-measurements-with-deep-1mwnym6tve.pdf

The TESS camera: modeling and measurements with deep depletion devices

The Transiting Exoplanet Survey Satellite (TESS) will carry four visible waveband seven-element refractive f/1.4 lenses, each with a 34 degree diagonal field of view. This paper describes the tolerancing, assembly and alignment methods developed during the build of the TESS Risk Reduction Unit optical system. Lens assembly tolerances were derived from a sensitivity analysis using an image quality metric customized for mission performance. The optomechanical design consists of a two-stage lens housing that provides access for active alignment of each lens using a Trioptics OptiCentric measurement system. Thermal stresses and alignment shifts are mitigated by mounting the optics with cast RTV silicone spacers into individually aligned bezels, and custom fixtures were developed to aid in RTV bonding with reduced alignment error. The lens assembly was tested interferometrically over the field of view at room temperature and results were used to successfully predict lens performance and compensator adjustments and detector shim thickness for the -75C operational temperature and pressure.

/pdf/tolerancing-alignment-and-test-of-the-transiting-exoplanet-3xnrcfyfm9.pdf

Tolerancing, alignment and test of the Transiting Exoplanet Survey Satellite (TESS) optical assembly

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The TESS camera: modeling and measurements with deep depletion devices

Tolerancing, alignment and test of the Transiting Exoplanet Survey Satellite (TESS) optical assembly