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NASA NTRS2016

The Kepler Science Data Processing Pipeline Source Code Road Map

We give an overview of the operational concepts and architecture of the Kepler Science Processing Pipeline. Designed, developed, operated, and maintained by the Kepler Science Operations Center (SOC) at NASA Ames Research Center, the Science Processing Pipeline is a central element of the Kepler Ground Data System. The SOC consists of an office at Ames Research Center, software development and operations departments, and a data center which hosts the computers required to perform data analysis. The SOC's charter is to analyze stellar photometric data from the Kepler spacecraft and report results to the Kepler Science Office for further analysis. We describe how this is accomplished via the Kepler Science Processing Pipeline, including, the software algorithms. We present the high-performance, parallel computing software modules of the pipeline that perform transit photometry, pixel-level calibration, systematic error correction, attitude determination, stellar target management, and instrument characterization.

Kepler pipeline software↗
NASA NTRS2016

Low order wavefront sensing and control for WFIRST coronagraph

To maintain the required WFIRST Coronagraph starlight suppression performance in a realistic space environment, a low order wavefront sensing and control (LOWFS/C) subsystem is necessary. The LOWFS/C uses the rejected stellar light from coronagraph to sense and suppress the telescope pointing drift and jitter as well as the low order wavefront errors due to changes in thermal loading on the telescope and the rest of the observatory. In this paper we will present an overview of the low order wavefront sensing and control subsystem for the WFIRST Coronagraph and describe the WFIRST Coronagraph LOWFS function, its design, and modeled performance. We will present experimental results on a dedicated LOWFS/C testbed that show that the LOWFS/C subsystem not only can sense pointing errors better than 0.2 mas but has also experimentally demonstrated closed loop pointing error suppression with residuals better than 0.4 mas rms per axis for the vast majority of observatory reaction wheel speeds.

Wilson, Dan↗
NASA NTRS1982

Simplified expressions for the gyrosynchrotron radiation from mildly relativistic, nonthermal and thermal electrons

Simplified expressions are presented for the gyrosynchrotron radiation from mildly relativistic electrons, both for nonthermal (power-law) and for thermal (Maxwellian) distributions. Expressions are given for the emissivity, absorptivity, effective temperature, frequency of peak brightness, and degree of circular polarization. The expressions are designed for the range from about 10 to about 100 of harmonic numbers, 20 to 80 deg of viewing angle, 3 to 7 electron energy spectral index (nonthermal electrons), and 10 to the 8th to 10 to the 9th K in temperature (thermal electrons). This range generally covers the cases of interest for the 10 keV to 1 MeV electrons that are probably important in solar and stellar flares and possibly in other astrophysical situations. The accuracy of these expressions, within the stated range of validity, is generally much better than a factor of 2, while the values of some of the quantities cover up to 15 orders of magnitude. The simplicity of the expressions should make them useful for semiquantitative investigations of models of astrophysical sources

Dulk, G. A.↗
NASA NTRS2006

Instrument Pointing Control System for the Stellar Interferometry Mission - Planet Quest

This paper describes the high precision Instrument Pointing Control System (PCS) for the Stellar Interferometry Mission (SIM) - Planet Quest. The PCS system provides front-end pointing, compensation for spacecraft motion, and feedforward stabilization, which are needed for proper interference. Optical interferometric measurements require very precise pointing (0.03 as, 1-(sigma) radial) for maximizing the interference pattern visibility. This requirement is achieved by fine pointing control of articulating pointing mirrors with feedback from angle tracking cameras. The overall pointing system design concept is presentcd. Functional requirements and an acquisition concept are given. Guide and Science pointing control loops are discussed. Simulation analyses demonstrate the feasibility of the design.

control↗
NASA NTRS2023

Earth/Moon System Star Tracking Sensor for Improved Deep Space Laser Communications

The goal of this research is to improve deep space communication links by exploring a new concept in stellar navigation that uses images of the Earth/Moon system to obtain precise pointing information so that the laser signal from the satellite can be directed at the ground station with unprecedented accuracy. Currently, the concept for satellite pointing relies on a dual axis star tracker that compares images of the celestial sphere to a star catalog to obtain a 3-axis orientation solution. Most star trackers are designed with a wide field of view (required to obtain enough bright starts to achieve a navigational fix) and only provide reliable pitch and yaw estimates thus necessitating the use of a second star tracker looking at an axis perpendicular to the first one to obtain an accurate estimate of the roll of the spacecraft. In the new concept the optical design will be modified to ensure that both the Earth and the Moon will be within a narrow field of view centered on Earth relative to the field of view of most star tracking systems. Because of the proximity of the bodies, it is possible to obtain highly accurate estimates of the pitch, yaw and roll of the spacecraft relative to the Earth/Moon system. The new tracker will allow for accurate 3-axis control of the spacecraft from a single tracker thus allowing the second star tracker, which would normally be pointed in a direction perpendicular to the one pointed at earth, to obtain the spacecraft roll estimate. This wide field star tracker facilitates functions like the initial satellite pointing during the acquisition phase of establishing the laser communication link or solving the lost in space problem should the system need to be reset. This new design will be tested in simulation and compared for 3-axis pointing accuracy against a standard commercial star tracker.

Star tracker↗
NASA NTRS1990

Image motion compensation for the Ultraviolet Imaging Telescope

On August 12, 1990, the Space Shuttle Columbia will carry the ASTRO-1 Spacelab payload into low earth orbit for a ten day mission. This mission will carry out ultraviolet and X-ray observations to study supernovas, galaxies, and other stellar objects. The Ultraviolet Imaging Telescope (UIT) is one of a cluster of three ultraviolet telescopes mounted on the shuttle-attached three-axis Instrument Pointing System (IPS). Shuttle disturbances such as astronaut crew motion, orbiter thruster firings, and other payload dynamic disturbances induce sufficient errors on the IPS which exceed the UIT jitter requirements. To meet the specified science objectives, an Image Motion Compensation System was designed and implemented for the ASTRO mission. This paper describes the UIT Image Motion Compensation system design and the performance improvements to be derived through use of this system.

Bauer, Frank H.↗
NASA NTRS2012

Mining the HST Treasury: The ASTRAL Reference Spectra for Evolved M Stars

The "Advanced Spectral Library (ASTRAL) Project: Cool Stars" (PI = T. Ayres) is an HST Cycle 18 Treasury Program designed to collect a definitive set of representative, high-resolution (R greater than 100,000) and high signal/noise (S/N greater than 100) UV spectra of eight F-M evolved cool stars. These extremely high-quality STIS UV echelle spectra are available from the HST archive and through the University of Colorado (http://casa.colorado.edu/~ayres/ASTRAL/) portal and will enable investigations of a broad range of problems -- stellar, interstellar. and beyond -- for many years. In this current paper, we concentrate on producing a roadrnap to the very rich spectra of the two evolved M stars in the sample, the M3.4 giant Gamma Crucis (GaCrux) and the M2Iab supergiant Alpha Orionis (Betelgeuse) and illustrate the huge increase in coverage and quality that these spectra provide over that previously available from IUE and earlier HST observations. These roadmaps will facilitate the study of the spectra, outer atmospheres, and winds of not only these stars. but also numerous other cool, low-gravity stars and make a very interesting comparison to the already-available atlases of the K2III giant Arcturus.

Carpenter, K. G.↗
NASA NTRS1985

A practical scheduling algorithm for Shuttle-based astronomy missions

In the Astro mission series (initial flight planned for March, 1986), the Shuttle will be used as a dedicated stellar astronomy observatory. A modified Spacelab pallet is to be used for the Astro payload, which will consist of three ultraviolet (UV) telescopes and a wide field camera mounted together on a single gimbal mount called the Inertial Pointing System (IPS). Three flights of 7-10 days duration are to be made with the same payload at intervals of 8-9 months. Previous experience has shown that changes in design requirements are inevitable, and the evolution of operational concepts will effect changes in scheduling algorithm software. For these reasons, the design goals of the Astron algorithm and its family of auxiliary software modules have been related to functional modularity, constraint flexibility, user friendliness, and 'light' input requirements. Attention is given to hardware characteristics, environmental constraints, the basic criteria function, 'Cinderella' logic, counters and constraints, and scheduling trends.

Guffin, O. T.↗
NASA NTRS1989

The Allegheny Observatory search for planetary systems

The accomplishments of the observatory's search for planetary systems are summarized. Among these were the construction, implementation, and regular use of the Multichannel Astrometric Photometer (MAP), and the design, fabrication and use of the second largest refractor objective built since 1950. The MAP parallax and planetary observing programs are described. Various developments concerning alternate solid state photodetectors and telescope instrumentation are summarized. The extreme accuracy of the system is described in relation to a study of the position and velocity of the members of the open cluster Upgren 1. The binary star system stringently tests the theory of stellar evolution since it is composed of an evolved giant F5 III and a subgiant F5 IV star. A study that attempts to measure the luminosities, surface temperatures, and masses of these stars is discussed.

Gatewood, George D.↗
NASA NTRS2016

eXTP: Enhanced X-Ray Timing and Polarimetry Mission

eXTP is a science mission designed to study the state of matter under extreme conditions of density, gravity and magnetism. Primary goals are the determination of the equation of state of matter at supra-nuclear density, the measurement of QED effects in highly magnetized star, and the study of accretion in the strong-field regime of gravity. Primary targets include isolated and binary neutron stars, strong magnetic field systems like magnetars, and stellar-mass and supermassive black holes. The mission carries a unique and unprecedented suite of state-of-the-art scientific instruments enabling for the first time ever the simultaneous spectral-timing-polarimetry studies of cosmic sources in the energy range from 0.5-30 keV (and beyond). Key elements of the payload are: the Spectroscopic Focusing Array (SFA) - a set of 11 X-ray optics for a total effective area of approx. 0.9 m(exp. 2) and 0.6 m(exp. 2) at 2 keV and 6 keV respectively, equipped with Silicon Drift Detectors offering less than 180 eV spectral resolution; the Large Area Detector (LAD) - a deployable set of 640 Silicon Drift Detectors, for a total effective area of approx. 3.4 m(exp. 2), between 6 and 10 keV, and spectral resolution better than 250 eV; the Polarimetry Focusing Array (PFA) - a set of 2 X-ray telescope, for a total effective area of 250 cm(exp. 2) at 2 keV, equipped with imaging gas pixel photoelectric polarimeters; the Wide Field Monitor (WFM) - a set of 3 coded mask wide field units, equipped with position-sensitive Silicon Drift Detectors, each covering a 90 degrees x 90 degrees field of view. The eXTP international consortium includes major institutions of the Chinese Academy of Sciences and Universities in China, as well as major institutions in several European countries and the United States. The predecessor of eXTP, the XTP mission concept, has been selected and funded as one of the so-called background missions in the Strategic Priority Space Science Program of the Chinese Academy of Sciences since 2011. The strong European participation has significantly enhanced the scientific capabilities of eXTP. The planned launch date of the mission is earlier than 2025.

X-ray astronomy↗
NASA NTRS1996

The Response of the BATSE LADs to Radiation From the Crab Nebula and Plans for Radioactivity Studies on Space Station

The Burst And Transient Source Experiment (BATSE) onboard the Compton Gamma-Ray Observatory (CGRO) was designed to measure X-rays and gamma rays with energies from about 50 keV to above 2 MeV. As with many scientific investigations, the success of the original experiment lead to additional areas of research interest. In the case of BATSE the ability to observe the radiation from sources down to about 20 keV became readily apparent. This lead to a continuing program of measuring the spectrum of radiation from stellar objects at these lower energies. One of these, the Crab Nebula, has a very steady radiation flux and, thus, has become a "standard candle" for such measurements. The Large Area Detectors (LADS) on BATSE contain a 1.27-cm thick, 25.4-cm radius NaI(Tl) detector behind a 6.35-mm thick polystyrene Charged Particle Detector (CPD) used to "veto" charged particles signals. The detectors have been calibrated with a series of gamma and X-ray sources and the results carefully simulated with a Monte Carlo code. In the calibration process the computer simulation accounts for scattering from material in the counting room as well as the BATSE structure. For an orbiting detector, scattering from the entire spacecraft must be modeled as well as for all covering material over the detectors. Five years after CGRO was launched on April 5, 1991, a large body of observational data has been taken of the Crab Nebula. The technique used for these observations, and for many other X-ray sources, is Earth occultation. From the perspective of the spacecraft, the Earth occults most stellar objects once in orbit, i.e., the signal is lost as the source sets and is regained as the source rises. A careful analysis of the continuing signals from all sources measured allows for an accurate measurement of the spectrum of a given source. An analysis of this data from the Crab has indicated that the LADs are very responsive at energies as low as 20 keV-at energies below the range of calibration. While the model accounts for many of the interactions of the photons with the detectors, the observation of nonstatistical deviations at low energy and at small angles has suggested a need to recalibrate at energies where the attenuation effects are increasing exponentially.

Laird, C. E.↗
NASA NTRS1989

Solar and stellar coronal plasmas

Progress in observational, theoretical, and radio studies of coronal plasmas is summarized. Specifically work completed in the area of solar and stellar magnetic fields, related photospheric phenomena and the relationships between magnetism, rotation, coronal and chromospheric emission in solar-like stars is described. Also outlined are theoretical studies carried out in the following areas, among others: (1) neutral beams as the dominant energy transport mechanism in two ribbon-flares; (2) magneto hydrodynamic and circuit models for filament eruptions; and (3) studies of radio emission mechanisms in transient events. Finally, radio observations designed for coronal activity studies of the sun and of solar-type coronae are described. A bibliography of publications and talks is provided along with reprints of selected articles.

Golub, Leon↗
NASA NTRS2002

Kepler Mission: A Discovery-Class Mission Designed to Determine the Frequency of Earth-Size and Larger Planets Around Solar-Like Stars

The first step in discovering the extent of life in our galaxy is to determine the number of terrestrial planets in the habitable zone (HZ). The Kepler Mission is designed around a 0.95 in aperture Schmidt-type telescope with an array of 42 CCDs designed to continuously monitor the brightness of 100,000 solar-like stars to detect the transits of Earth-size and larger planets. The photometer is scheduled to be launched into heliocentric orbit in 2007. Measurements of the depth and repetition time of transits provide the size of the planet relative to the star and its orbital period. When combined with ground-based spectroscopy of these stars to fix the stellar parameters, the true planet radius and orbit scale, hence the position relative to the HZ are determined. These spectra are also used to discover the relationships between the characteristics of planets and the stars they orbit. In particular, the association of planet size and occurrence frequency with stellar mass and metallicity will be investigated. At the end of the four year mission, hundreds of terrestrial planets should be discovered in and near the HZ of their stars if such planets are common. Extending the mission to six years doubles the expected number of Earth-size planets in the HZ. A null result would imply that terrestrial planets in the HZ occur in less than 1% of the stars and that life might be quite rare. Based on the results of the current Doppler-velocity discoveries, detection of a thousand giant planets is expected. Information on their albedos and densities of those giants showing transits will be obtained.

William Borucki↗
NASA NTRS2002

Kepler Mission: A Wide-FOV Photometer Designed to Determine the Frequency of Earth-Size and Larger Planets Around Solar-like stars

The first step in discovering the extent of life in our galaxy is to determine the number of terrestrial planets in the habitable zone (HZ). The Kepler Mission is designed around a 0.95 m aperture Schmidt-type telescope with an array of 42 CCDs designed to continuously monitor the brightness of 100,000 solar-like stars to detect the transits of Earth-size and larger planets. The photometer is scheduled to be launched into heliocentric orbit in 2007. Measurements of the depth and repetition time of transits provide the size of the planet relative to the star and its orbital period. When combined with ground-based spectroscopy of these stars to fix the stellar parameters, the true planet radius and orbit scale, hence the position relative to the HZ are determined. These spectra are also used to discover the relationships between the characteristics of planets and the stars they orbit. In particular, the association of planet size and occurrence frequency with stellar mass and metallicity will be investigated. At the end of the four year mission, hundreds of terrestrial planets should be discovered in and near the HZ of their stars if such planets are common. A null result would imply that terrestrial planets in the HZ occur in less than 1% of the stars and that life might be quite rare. Based on the results of the current doppler-velocity discoveries, detection of a thousand giant planets is expected. Information on their albedos and densities of those giants showing transits will be obtained.

Borucki, William↗
NASA NTRS2016

A Broadband X-Ray Imaging Spectroscopy with High-Angular Resolution: the FORCE Mission

We are proposing FORCE (Focusing On Relativistic universe and Cosmic Evolution) as a future Japan-lead X-ray observatory to be launched in the mid 2020s. Hitomi (ASTRO-H) possesses a suite of sensitive instruments enabling the highest energy-resolution spectroscopy in soft X-ray band, a broadband X-ray imaging spectroscopy in soft and hard X-ray bands, and further high energy coverage up to soft gamma-ray band. FORCE is the direct successor to the broadband X-ray imaging spectroscopy aspect of Hitomi (ASTRO-H) with significantly higher angular resolution. The current design of FORCE defines energy band pass of 1-80 keV with angular resolution of <15" in half-power diameter, achieving a 10 times higher sensitivity above 10 keV compared to any previous missions with simultaneous soft X-ray coverage. Our primary scientific objective is to trace the cosmic formation history by searching for "missing black holes" in various mass-scales: "buried supermassive black holes (SMBHs)" (> 10(exp 4) Stellar Mass) residing in the center of galaxies in a cosmological distance, "intermediate-mass black holes" (10(exp 2)-(10(exp 4) Stellar Mass) acting as the possible seeds from which SMBHs grow, and "orphan stellar-mass black holes" (< 10(exp 2) Stellar Mass) without companion in our Galaxy. In addition to these missing BHs, hunting for the nature of relativistic particles at various astrophysical shocks is also in our scope, utilizing the broadband X-ray coverage with high angular-resolution. FORCE are going to open a new era in these fields. The satellite is proposed to be launched with the Epsilon vehicle that is a Japanese current solid-fuel rocket. FORCE carries three identical pairs of Super-mirror and wide-band X-ray detector. The focal length is currently planned to be 10 m. The silicon mirror with multi-layer coating is our primary choice to achieve lightweight, good angular optics. The detector is a descendant of hard X-ray imager onboard Hitomi (ASTRO-H) replacing its silicon strip detector with SOI-CMOS silicon pixel detector, allowing an extension of the low energy threshold down to 1 keV or even less.

Hard X-ray↗
NASA NTRS2014

Performance of an Achromatic Focal Plane Mask for Exoplanet Imaging Coronagraphy

Coronagraph technology combined with wavefront control is close to achieving the contrast and inner working angle requirements in the lab necessary to observe the faint signal of an Earth-like exoplanet in monochromatic light. An important remaining technological challenge is to achieve high contrast in broadband light. Coronagraph bandwidth is largely limited by chromaticity of the focal plane mask, which is responsible for blocking the stellar PSF. The size of a stellar PSF scales linearly with wavelength; ideally, the size of the focal plane mask would also scale with wavelength. A conventional hard-edge focal plane mask has a fixed size, normally sized for the longest wavelength in the observational band to avoid starlight leakage. The conventional mask is oversized for shorter wavelengths and blocks useful discovery space. Recently we presented a solution to the size chromaticity challenge with a focal plane mask designed to scale its effective size with wavelength. In this paper, we analyze performance of the achromatic size-scaling focal plane mask within a Phase Induced Amplitude Apodization (PIAA) coronagraph. We present results from wavefront control around the achromatic focal plane mask, and demonstrate the size-scaling effect of the mask with wavelength. The edge of the dark zone, and therefore the inner working angle of the coronagraph, scale with wavelength. The achromatic mask enables operation in a wider band of wavelengths compared with a conventional hard-edge occulter.

Focal Plane Mask↗
NASA NTRS1998

Scientific Issues Addressed by the Kepler Mission

The Kepler Mission uses a wide field-of-view telescope to photometrically monitor 100,000 main-sequence stars for evidence of planetary transits. Because of the large number of stars monitored and because the mission is designed with a precision (0.002%) sufficient to readily recognize Earth-size planets transiting solar-like stars, several hundred Earth-size planets should be found. Based on the the Dopper velocity observations that find 2% of the main-sequence stars have Jupiter-size planets in short-period orbits, the Kepler mission is also expected to detect about 2000 giant planets. Several questions about the association of planet types and stellar characteristics can be investigated. For example; Are small planets found when Jupiter-mass planets are also present in inner orbits? What is the frequency of small planets compared to Jupiter-mass planets? What is the frequency and distribution of planets intermediate in size and mass to that of Earth and Jupiter? What correlations exist between planet size, distribution, and frequency with the characteristics of the stars they orbit? A comparison between model predictions and observation should be a useful step in evolving better models of planetary system formation and help put the formation of our Solar System in perspective.

Bourcki, W. J.↗
NASA NTRS1973

Conical focusing crystal spectrometers for cosmic X-ray astronomy

A crystal spectrometer for rocket and satellite experiments is described. Parallel X rays from a stellar object are reflected at constant angle by Bragg crystals arranged around the sector of a cone so that a single wavelength is brought to a focus onto the axis of the cone. The aberrations produced when this array is tilted to change the wavelength are considered. It is shown that these are minimized by moving cone and detector in a nearly theta to two-theta motion and by using a small-angle sector. In a specific design for a satellite instrument using LiF crystal to observe a spectral region including the iron lines at 1.9 A, a spectral resolution of 3 mA over a spectral range of 1.6-2.1 A can be obtained, with the cosmic-ray background rate, and hence the time to detect a weak line decreased by a factor 80 compared to a flat crystal spectrometer. Examples of performance for a low energy rocket experiment are also given.

Woodgate, B. E.↗