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NASA NTRS2020

Design and Performance of the PALM-3000 3.5 kHz Upgrade

PALM-3000 (P3K), the second-generation adaptive optics (AO) instrument for the 5.1 meter Hale telescope atPalomar Observatory, was released as a facility class instrument in October 2011 and has since been used on-skyfor over 600 nights as a workhorse science instrument and testbed for coronagraph and detector development.In late 2019 P3K underwent a significant upgrade to its wavefront sensor (WFS) arm and real-time control(RTC) system to reinforce its position as a state-of-the-art AO facility and extend its faint-end capability forhigh-resolution imaging and precision radial velocity follow-up of Kepler and TESS targets. The main featuresof this upgrade include an EM-CCD WFS camera capable of 3.5 kHz framerates, and an advanced Digital SignalProcessor (DSP) based RTC system to replace the aging GPU based system. Similar to the pre-upgrade system,the Shack-Hartmann wavefront sensor supports multiple pupil sampling modes using a motorized lenslet stage.The default sampling mode with 64×64 subapertures has been re-commissioned on-sky in late 2019, witha successful return to science observations in November 2019. In 64×mode the upgraded system is alreadyachieving K-band Strehl ratios up to 85% on-sky and can lock on natural guide stars as faint as mV=16. A16×16 subaperture mode is scheduled for on-sky commissioning in Fall 2020 and will extend the system’s faintlimit even further. Here we present the design and on-sky re-commissioning results of the upgraded system,dubbed P3K-II.

Vasisht, Gautam↗
NASA NTRS2000

Exploiting the Temperature Dependence of Magnetic Susceptibility to Control Convection in Fundamental Studies of Solidification Phenomena

It is well known that convection is a dominant mass transport mechanism when materials are solidified on Earth's surface. This convection is caused by gradients in density (and therefore gravitational force) that are brought about by gradients in temperature, composition or both. Diffusion of solute is therefore dwarfed by convection and the study of fundamental parameters, such as dendrite tip shape and growth velocity in the absence of convection is nearly impossible. Significant experimental work has therefore been carried out in orbiting laboratories with the intent of minimizing convection by minimizing gravity. One of the best known experiments of this kind is the Isothermal Dendritic Growth Experiment (IDGE), supported by NASA. Naturally such experiments are costly and one objective of the present investigation is to develop an experimental method whereby convection can be- halted, in solidification and other experiments, on the surface. A second objective is to use the method to minimize convection resulting from the residual accelerations suffered by experiments in microgravity. The method to be used to minimize convection relies on the dependence of the magnetic susceptibility of a fluid on temperature or composition (whichever is driving convection). All materials experience a force when placed in a magnetic field gradient. The direction and magnitude of that force depend on the magnetic susceptibility of the material. Consequently the force will vary if the susceptibility varies with temperature or composition. With a magnetic field gradient in the right direction (typically upward) and of the right magnitude, this variation in the magnetic force can be made to exactly cancel the variation in the gravitational force. Expressed another way, normal buoyancy is exactly countered by a "magnetic buoyancy". To demonstrate the principle, a solution of MnC12 in water has been used. First the variation of the susceptibility of this paramagnetic solution with temperature and concentration was measured. Then a "cell", containing this solution and 50mm long by 15mm high by 155mm wide, was placed in a superconducting magnet at Marshall Space Flight Center. The magnetic field was measured at various positions within the bore of the magnet using a Hall effect probe. In this way, a position was found where the magnetic field gradient was predominantly upward; the magnitude of the gradient could then be adjusted by adjusting the current of the magnet. The ends of the cell consisted of machined copper blocks maintained at controlled temperatures by circulating water from constant temperature baths. The walls of the cell were of rectangular section glass tubing so that the cell contents could be seen. Velocities arising from thermal gradients within the cell were measured by particle image velocimetry (PIV). Particles used for this purpose were silver-coated hollow glass spheres of micrometers diameter and nearly the same density as the solution. A central vertical plane of the cell was illuminated by a laser beam passing through a cylindrical lens. Digital images of the particles were captured on a CCD camera and fed to a computer so that frame-to-frame movements of particles traveling with the fluid were captured. These images were employed to compute velocity maps using commercial PIV software. In a typical experiment the cold end of the cell was maintained at 10C and the warm end at 30 C. With no current in the magnet, i.e.- with natural -convection allowed to occur, the fluid was observed to circulate with an average speed of approximately 0.3 millimeters per second. It was visually apparent that this circulation was diminished as the current was increased. At currents of approximately 20A the flow was halted, to within the precision of the PIV measurements. At yet higher currents the convection was reversed with the hotter solution sinking and the cooler solution rising. At 40A this reversed convection had speeds averaging 0.43 millimeters per second. The measurements of susceptibility and density allow an estimate of the field gradient necessary to halt convection in the experiment. That estimate was 7.8T (squared) per meter and the convection was observed to halt in the magnet at a current giving 7.21T (squared) per meter from the magnetic field measurements. Calculations of the flow have been carried out using the computational fluid dynamics software FLUENT and show good agreement with the measurements.

Seybert, C. D.↗
NASA NTRS2019

NASA's Orbital Debris Optical Program: ES-MCAT Updated and Upgraded

The 1.3m ES-MCAT telescope (or MCAT for short) now has a proven capability for observing objects from Low- Earth Orbit (LEO) out to Geosynchronous (GEO) orbit, and the ability to run all systems autonomously. A GEO survey, the initial focus for MCAT, will commence in late 2019 to map out the current state of the GEO population as input for the ORbital Debris Engineering Model (ORDEM 4.x). This survey will statistically sample the GEO belt (0 to ~15 deg orbital inclinations) to detect both known and unknown targets. If a break-up occurs, additional surveys of the break-up field can be followed for discovery and investigations of daughter debris fragments from the parent satellite. Discovery can be accomplished by tracking orbits near to and including the parent object’s orbit. Targeted observations of debris can be taken with a suite of broadband filters for characterizing individual objects by ratetracking their known or calculated orbital elements (Two-Line Element sets, TLEs). Several modifications and upgrades have been made to the instrumentation and systems originally installed in 2015 and are reported here. In 2018, MCAT’s primary mirror was recoated with a high-end protected, enhanced silver by the ZeCoat Corporation. The CCD chip was replaced in the Spectral Instruments camera with a broad-band antireflective coated chip. The automated weather systems have been modified from the original system, removing some weather sensors and installing replacements that are better suited to Ascension’s weather and environment. A new 2.5-m ObservaDome replaced the Astrohaven dome on the nearby tower platform that will house an auxiliary 0.4-meter telescope. Finally, in 2019, the Observatory Control System was upgraded to 2.0 which includes additional flexibility for automating data collection and reduction. With these updates completed, MCAT is now well on track to reach Full Operational Capability (FOC) in 2019 for its survey, rate-track, and TLE tracking capabilities.

Lederer, S. M.↗
NASA NTRS1991

Chiron: Evidence for historic cometary activity

The non-asteroidal brightening of (2060) Chiron, first noted by Tholen in 1988 is now ascribed to cometary activity. Photometry since 1988 has revealed a broad surge in brightness that peaked in 1989 about 1.0 mag above the brightness in the mid-1980s. The surge is evidently due to sporatic formation of dust coma, which is itself driven by the presence of extremely volatile ices at or near the surface. CN emission was recently reported. Since Chiron is now nearing perihelion, there is interest in determining whether it has exhibited anomalous brightening in the past, particularly at greater heliocentric distances. Photographic plates dating back to 1895 are known to contain images of Chiron. Using some of these archival material, the initial results are presented for a project to determine Chiron's brightness history over orbital timescales. A particularly homogeneous and high-quality set of plates taken prior to and around the time of Chiron's discovery in Oct. 1977 at the 1.2 m Oschin Schmidt telescope at Mt. Palomar Observatory were examined. Images of Chiron were identified and digitized using a PDS microdensitometer, and images of field stars around Chiron were both similarly digitized and photometrically calibrated using recently acquired B and V band CCD frames. As a result of the present work, eleven new data, including estimated errors, were added between 1969 and 1977. The implications that Chiron can be active at any heliocentric distance in its present orbit suggest that the active volatile is either N2, CH4, or CO, and that a substantial degree of mantling may have developed. Further historical data is presented, the error bars discussed, and possible mechanisms suggested for the observed activity.

Bus, Schelte J.↗
NASA NTRS1986

Astrophysics of brown dwarfs; Proceedings of the Workshop, George Mason University, Fairfax, VA, Oct. 14, 15, 1985

Various reports on theoretical and observational studies of brown dwarfs (BDs) are presented. The topics considered include: astrometric detection of BDs, search for substellar companions to nearby stars using IR imaging, constraints on BD mass function from optical and IR searches, properties of stellar objects near the main sequence mass limit, search for low-mass stellar companions with the HF precision velocity technique, dynamical search for substellar objects, search for BDs in the IRAS data base, deep CCD survey for low mass stars in the disk and halo, the Berkeley search for a faint solar companion, the luminosity function for late M stars, astronomic search for IR dwarfs, and the role of the Space Telescope in the detection of BDs. Also addressed are: theoretical significance of BDs, evolution of super-Jupiters, compositional indicators in IR spectra of BDs, evolution of BDs and the evolutionary status of VB8B, the position of BDs on universal diagrams, theoretical determination of the minimum protostellar mass, Population II BDs and dark halos.

Kafatos, Minas C.↗
NASA NTRS1996

Attitude Accuracy Study for the Earth Observing System (EOS) AM-1 Spacecraft

Earth Observing System (EOS) spacecraft will take measurements of the Earth's clouds, oceans, atmosphere, land, and radiation balance. These EOS spacecraft are part of the National Aeronautics and Space Administration's Mission to Planet Earth, and consist of several series of satellites, with each series specializing in a particular class of observations. This paper focuses on the EOS AM-1 spacecraft, which is the first of three satellites constituting the EOS AM series (morning equatorial crossing) and the initial spacecraft of the EOS program. EOS AM-1 has a stringent onboard attitude knowledge requirement, of 36/41/44 arc seconds (3 sigma) in yaw/roll/pitch, respectively. During normal mission operations, attitude is determined onboard using an extended Kalman sequential filter via measurements from two charge coupled device (CCD) star trackers, one Fine Sun Sensor, and an Inertial Rate Unit. The attitude determination error analysis system (ADEAS) was used to model the spacecraft and mission profile, and in a worst case scenario with only one star tracker in operation, the attitude uncertainty was 9.7/ll.5/12.2 arc seconds (3 sigma) in yaw/roll/pitch. The quoted result assumed the spacecraft was in nominal attitude, using only the 1-rotation per orbit motion of the spacecraft about the pitch axis for calibration of the gyro biases. Deviations from the nominal attitude would show greater attitude uncertainties, unless calibration maneuvers which roll and/or yaw the spacecraft have been performed. This permits computation of the gyro misalignments, and the attitude knowledge requirement would remain satisfied.

Lesikar, James D., II↗
NASA NTRS1986

The distribution of dust in the inner coma of comet IRAS-Araki-Alcock (1983d)

The behavior and characteristics of the inner coma of the Comet IRAS-Araki-Alcock (IAA) were examined for five nights in May 1983 using a ground-based 2.2 m CCD telescope. A highly variable, asymmetric sunward emission was detected, along with a long filamentary structure. The brightness was highest in the sunward direction, with radial brightnesses diminishing more slowly than predicted with a 1/r model. The slow fall-off is attributed to the emission of conglomerate dust grains which fragment while traveling through the inner coma and increase the effective surface area of the dust. Significant day-to-day variations were observed, and the filamentary features were indicative of a centralized region on a mantled nucleus which rotated. The nucleus is estimated to be no more than 17 km in diameter.

Storrs, A. D.↗
NASA NTRS1986

Planetary astronomy

Comets were studied during their relatively quiescent phases at large distances from the sun. This program, has resulted in a variety of CCD images of comets in several visible and near-IR bands selected to sample the continuum, rather than emission features. The most extensive dataset was obtained for P/Halley during January 1985 (plus scattered earlier data), near the time the comet turned on. The data were reduced in a preliminary fashion. Other comets predicted to be relatively inactive (including Neujmin 1 and Arend-Rigaux) were most active than expected. P/Gehrels 3 was also observed.

Chapman, C. R.↗
NASA NTRS1994

The initial mass function for massive stars in the Magellanic Clouds. 2: Interstellar reddening toward 14 OB associations

We have used UBV CCD photometry to determine the interstellar reddening toward 14 OB associations in the Magellanic Clouds. The two reddening-free indices available in the UBV system were used to obtain the reddening estimates. The mean color excesses of the associations range from E(B-V) = 0.01-0.26 mag in the Large Magellanic Cloud (LMC) and from E(B-V) = 0.06-0.25 mag in the Small Magellanic Cloud (SMC). We have modeled the observed scatter in the color excesses of individual stars within the associations and find that statisically significant differential reddening exists in at least some of the associations.

Hill, Robert J.↗
NASA NTRS1993

CCD photometry of 2060 Chiron in 1985 and 1991

CCD photometry of 2060 Chiron from two apparitions, in January 1985 and January 1991, is reported. No evidence is found for a change in the amplitude of Chiron's lightcurve with ecliptic longitude, as would be expected of an object having a high-obliquity rotational axis. An improved value for Chiron's synodic period is reported: 5.917813 +/- 0.000007 hr. No outbursts larger than one-half of one percent were found during the 1991 observations. Secular (yearly) change is due to the gradual dissipation and resupply of material (mainly dust) throughout the coma, while the impulsive (daily) brightenings are probably due to the sudden release of pockets of entrapped volatiles, such as CO2, CN, or possibly H2O.

Marcialis, Robert L.↗
NASA NTRS1986

A data reduction package for multiple object spectroscopy

Experience with fiber-optic spectrometers has demonstrated improvements in observing efficiency for clusters of 30 or more objects that must in turn be matched by data reduction capability increases. The Medusa Automatic Reduction System reduces data generated by multiobject spectrometers in the form of two-dimensional images containing 44 to 66 individual spectra, using both software and hardware improvements to efficiently extract the one-dimensional spectra. Attention is given to the ridge-finding algorithm for automatic location of the spectra in the CCD frame. A simultaneous extraction of calibration frames allows an automatic wavelength calibration routine to determine dispersion curves, and both line measurements and cross-correlation techniques are used to determine galaxy redshifts.

Hill, J. M.↗
DOE OSTI2024

The DarkNESS mission: probing dark matter with a Skipper-CCD satellite observatory

The invention of Skipper-CCDs with sub-electron noise has paved the way for groundbreaking low-threshold dark matter (DM) experiments, such as SENSEI and DAMIC. Conventionally, these experiments are deployed underground to mitigate cosmogenic backgrounds; however, some DM signatures are inaccessible to underground experiments due to attenuation in the Earth’s atmosphere and crust. The DarkNESS mission will deploy an array of Skipper-CCDs on a 6U CubeSat in Low Earth Orbit (LEO) to search for electron recoils from strongly-interacting sub-GeV DM as well as X-ray line signatures from sterile neutrino decay. Using a series of observations from LEO, the DarkNESS mission will set competitive upper limits on the DM-electron scattering cross section and help resolve the experimental conundrum associated with the purported observation of a 3.5 keV X-ray line, potentially produced from sterile neutrino decay. This work will describe the DarkNESS instrument, the technical challenges in operating Skipper-CCDs in the space environment, the scientific objectives of the DarkNESS mission, and the DM parameter space that DarkNESS will probe.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1984

NASA-Texas Planetary Program

Astronomical observations performed at the McDonald Observatory were summarized. Various spectra obtained from Jupiter, Uranus, Saturn, Neptune, Pluto, Titan, Iapetus, and sundry asteroids were described briefly. Spectra taken of various comets using an IDS (Intensified Dissector Scanner) spectrograph on a 2.7 m telescope were reviewed. The Octicon, a linear array of eight 1872-element Reticon arrays that was installed in the 2.7 m coude spectrograph at the observatory, was described. The 2.7 m coude scanner, 2.7 m coude CCD (charge coupled device), and 2.7 m radial velocity spectrometer were mentioned.

Smith, H. J.↗
NASA NTRS1988

Statistical error analysis in CCD time-resolved photometry with applications to variable stars and quasars

Differential photometric time series obtained from CCD frames are tested for intrinsic variability using a newly developed analysis of variance technique. In general, the objects used for differential photometry will not all be of equal magnitude, so the techniques derived here explicitly correct for differences in the measured variances due to photon statistics. Other random-noise terms are also considered. The technique tests for the presence of intrinsic variability without regard to its random or periodic nature. It is then applied to observations of the variable stars ZZ Ceti and US 943 and the active extragalactic objects OQ 530, US 211, US 844, LB 9743, and OJ 287.

Howell, Steve B.↗
NASA NTRS1992

Color gradients in cooling flows in clusters of galaxies

U-, b-, V-, and I-band CCD images of 19 centrally dominant galaxies were obtained in cooling-flow clusters (CFDs) and four centrally dominant galaxies in clusters without cooling flows. Photometry through synthetic elliptical apertures was used to determine that many CFDs exhibit color-profile anomalies with respect to the control sample and to gE photometry from the recent literature. The anomalies are stronger and extend to larger galactic radii for higher mass accretion rates (HMARs) as estimated from X-ray observations. At least 11 CFDs with HMARs greater than or approximately equal to 70 solar masses/yr have blue color-profile anomalies that extend radially 5-20 kpc. Some CFDs with smaller HMARs have milder anomalies extending only less than or approximately equal to 5 kpc. The prevalence of color anomalies suggests that star formation which includes massive blue stars occurs continuously for a substantial fraction of the Hubble time, or in frequent episodes.

Mcnamara, Brian R.↗
NASA NTRS1992

The chronology of the formation of the Galaxy

Recent advances in our understanding of horizontal-branch (HB) stars and in precision CCD photometry make it possible to establish a chronology of the formation of the Galaxy from the fossil record. The Lee et al. HB evolutionary models and the inferred age-metallicity relation of the Galactic globular-cluster system are now strengthened by many pieces of supporting evidence. This provides valuable information regarding the formation chronology of the halo and disk. Moreover, there is strong evidence from RR Lyrae stars that the radial variation in HB morphology observed in the halo continues to the very center of the Galaxy, which suggests that the formation of the bulge and halo was an inside-out process. These two crucial pieces of information are combined to extend the Searle and Zinn picture of halo formation to include the formation of the bulge and disk. The emerging picture is consistent with the idea that galaxies formed as clusters and mergers of many small gas-rich subsystems, rather than by the rapid collapse of single large protogalactic clouds.

Lee, Young-Wook↗
NASA NTRS2002

Compact Video Microscope Imaging System Implemented in Colloid Studies

Long description Photographs showing fiber-optic light source, microscope and charge-coupled discharge (CCD) camera head connected to camera body, CCD camera body feeding data to image acquisition board in PC, and Cartesian robot controlled via PC board. The Compact Microscope Imaging System (CMIS) is a diagnostic tool with intelligent controls for use in space, industrial, medical, and security applications. CMIS can be used in situ with a minimum amount of user intervention. This system can scan, find areas of interest in, focus on, and acquire images automatically. Many multiple-cell experiments require microscopy for in situ observations; this is feasible only with compact microscope systems. CMIS is a miniature machine vision system that combines intelligent image processing with remote control. The software also has a user-friendly interface, which can be used independently of the hardware for further post-experiment analysis. CMIS has been successfully developed in the SML Laboratory at the NASA Glenn Research Center and adapted for use for colloid studies and is available for telescience experiments. The main innovations this year are an improved interface, optimized algorithms, and the ability to control conventional full-sized microscopes in addition to compact microscopes. The CMIS software-hardware interface is being integrated into our SML Analysis package, which will be a robust general-purpose image-processing package that can handle over 100 space and industrial applications.

McDowell, Mark↗
NASA NTRS1987

Rapid variability of the R Coronae Australis reflection nebula NGC 6729

Measurable changes in the surface brightness of the reflection nebula associated with R CrA occur over intervals as short as 24 hours. These and other more extreme variations are demonstrated with CCD images obtained over a 23-day period March 10 to April 2, 1984. During this time span R CrA brightened by 1.3 mag. The alterations in the appearance of the nebula NGC 6729 are apparently caused by the shadowing effects of clouds which are very close to the star, probably well within 1 Au. The spectrum of R CrA may itself vary slightly from night to night, and these changes are echoed by the surrounding nebula with an observable time delay. A photograph showing the complicated filamentary structure in NGC 6729 is reproduced and the relation between the reflection nebula and its illuminating star is discussed.

Graham, J. A.↗