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NASA NTRS2005

Evolution of Galaxies and the Star Formation Rate in the Infrared

A central goal of extragalactic observational astronomy is to understand how normal galaxies evolve with redshift, and particularly when galaxies formed their stars. While optical and rest-frame UV observations have begun to address these issues, the interpretation of such data is particularly challenging because of the sensitivity to dust obscuration (at optical and UV wavelengths). The absorbed light is re-radiated at IR wavelengths, hence the optimal indicators of the star formation rate (SFR) is at a rest-frame wavelength of approx. 60 microns. The Spitzer Space Telescope mission is revolutionizing the study of the global properties and evolution of galaxies. Spitzer reaches nearly two orders of magnitude more sensitivity than previous IR space missions. This research program is to study the SFR using statistical samples of galaxies in the local universe, at intermediate redshifts, and set the stage for continuing studies up to z=5. The overall research program is divided into three main investigations: A Mid-IR Hubble Atlas and SFR estimators in the local universe, Evolution of the SFR at 0 < z < 1 using pencil beam redshift surveys, and Galaxy formation and evolution at 1 < z < 5. The first papers from Spitzer were published during the last year, including ten refereed journal papers where the PI was first or co-author.

Pahre, Michael A.↗
NASA NTRS2005

A Statistical Analysis of Loop-Top Motion in Solar Limb Flares

Previous studies of hot, thermal solar flare loops imaged with the Ramaty High Energy Solar Spectroscopic Imager (RHESSI) have identified several flares for which the loop top shrinks downward early in the impulsive phase and then expands upward later in the impulsive phase (Sui & Holman 2003; Sui, Holman & Dennis 2004; Veronig et al. 2005). This early downward motion is not predicted by flare models. We study a statistical sample of RHESSI flares to assess how common this evolution is and to better characterize it. In a sample of 88 flares near the solar lin$ that show identifiable loop structure in RHESSI images, 66% (58 flares) showed downward loop-top motion followed by upward motion. We therefore conclude that the early downward motion is a frequent characteristic of flare loops. We obtain the distribution of the timing of the change from downward to upward motion relative to flare start and peak times. We also obtain the distributions of downward and upward speeds.

Holman, Gordon D.↗
NASA NTRS2005

Software Certification and Software Certificate Management Systems

Incremental certification and re-certification of code as it is developed and modified is a prerequisite for applying modem, evolutionary development processes, which are especially relevant for NASA. For example, the Columbia Accident Investigation Board (CAIB) report 121 concluded there is "the need for improved and uniform statistical sampling, audit, and certification processes". Also, re-certification time has been a limiting factor in making changes to Space Shuttle code close to launch time. This is likely to be an even bigger problem with the rapid turnaround required in developing NASA s replacement for the Space Shuttle, the Crew Exploration Vehicle (CEV). Hence, intelligent development processes are needed which place certification at the center of development. If certification tools provide useful information, such as estimated time and effort, they are more likely to be adopted. The ultimate impact of such a tool will be reduced effort and increased reliability.

Denney, Ewen↗
NASA NTRS2010

Weighting Statistical Inputs for Data Used to Support Effective Decision Making During Severe Emergency Weather and Environmental Events

National Aeronautical and Space Administration (NASA) weather and atmospheric environmental organizations are insatiable consumers of geophysical, hydrometeorological and solar weather statistics. The expanding array of internet-worked sensors producing targeted physical measurements has generated an almost factorial explosion of near real-time inputs to topical statistical datasets. Normalizing and value-based parsing of such statistical datasets in support of time-constrained weather and environmental alerts and warnings is essential, even with dedicated high-performance computational capabilities. What are the optimal indicators for advanced decision making? How do we recognize the line between sufficient statistical sampling and excessive, mission destructive sampling ? How do we assure that the normalization and parsing process, when interpolated through numerical models, yields accurate and actionable alerts and warnings? This presentation will address the integrated means and methods to achieve desired outputs for NASA and consumers of its data.

Gardner, Adrian↗
NASA NTRS2013

Estimation of Rain Intensity Spectra over the Continental US Using Ground Radar-Gauge Measurements

A high-resolution surface rainfall product is used to estimate rain characteristics over the continental US as a function of rain intensity. By defining each data at 4-km horizontal resolutions and 1-h temporal resolutions as an individual precipitating/nonprecipitating sample, statistics of rain occurrence and rain volume including their geographical and seasonal variations are documented. Quantitative estimations are also conducted to evaluate the impact of missing light rain events due to satellite sensors' detection capabilities. It is found that statistics of rain characteristics have large seasonal and geographical variations across the continental US. Although heavy rain events (> 10 mm/hr.) only occupy 2.6% of total rain occurrence, they may contribute to 27% of total rain volume. Light rain events (< 1.0 mm/hr.), occurring much more frequently (65%) than heavy rain events, can also make important contributions (15%) to the total rain volume. For minimum detectable rain rates setting at 0.5 and 0.2 mm/hr which are close to sensitivities of the current and future space-borne precipitation radars, there are about 43% and 11% of total rain occurrence below these thresholds, and they respectively represent 7% and 0.8% of total rain volume. For passive microwave sensors with their rain pixel sizes ranging from 14 to 16 km and the minimum detectable rain rates around 1 mm/hr., the missed light rain events may account for 70% of train occurrence and 16% of rain volume. Statistics of rain characteristics are also examined on domains with different temporal and spatial resolutions. Current issues in estimates of rain characteristics from satellite measurements and model outputs are discussed.

Lin, Xin↗
NASA NTRS2013

The Herschel* PEP-HERMES Luminosity Function- I. Probing the Evolution of PACS Selected Galaxies to z approx. equal to 4

We exploit the deep and extended far-IR data sets (at 70, 100 and 160 μm) of the Herschel Guaranteed Time Observation (GTO) PACS Evolutionary Probe (PEP) Survey, in combination with the Herschel Multi-tiered Extragalactic Survey data at 250, 350 and 500 μm, to derive the evolution of the rest-frame 35-, 60-, 90- and total infrared (IR) luminosity functions (LFs) up to z ∼ 4.We detect very strong luminosity evolution for the total IR LF (LIR ∝ (1 + z)(sup 3.55 +/- 0.10) up to z ∼ 2, and ∝ (1 + z)(sup 1.62 +/- 0.51) at 2 less than z less than approximately 4) combined with a density evolution (∝ (1 + z)(sup −0.57 +/- 0.22) up to z ∼ 1 and ∝ (1 + z)(sup −3.92 +/- 0.34) at 1 less than z less than approximately 4). In agreement with previous findings, the IR luminosity density (ρIR) increases steeply to z ∼ 1, then flattens between z ∼ 1 and z ∼ 3 to decrease at z greater than approximately 3. Galaxies with different spectral energy distributions, masses and specific star formation rates (SFRs) evolve in very different ways and this large and deep statistical sample is the first one allowing us to separately study the different evolutionary behaviours of the individual IR populations contributing to ρIR. Galaxies occupying the well-established SFR-stellar mass main sequence (MS) are found to dominate both the total IR LF and ρIR at all redshifts, with the contribution from off-MS sources (≥0.6 dex above MS) being nearly constant (∼20 per cent of the total ρIR) and showing no significant signs of increase with increasing z over the whole 0.8 < z <2.2 range. Sources with mass in the range 10 ≤ log(M/solar mass) ≤ 11 are found to dominate the total IR LF, with more massive galaxies prevailing at the bright end of the high-z (greater than approximately 2) LF. A two-fold evolutionary scheme for IR galaxies is envisaged: on the one hand, a starburst-dominated phase in which the Super Massive Black Holes (SMBH) grows and is obscured by dust (possibly triggered by a major merging event), is followed by an AGN-dominated phase, then evolving towards a local elliptical. On the other hand, moderately star-forming galaxies containing a low-luminosity AGN have various properties suggesting they are good candidates for systems in a transition phase preceding the formation of steady spiral galaxies.

Herschel↗
NASA NTRS2016

Development of the NASA MCAT Auxiliary Telescope for Orbital Debris Research

The National Aeronautical Space Administration has deployed the Meter Class Autonomous Telescope (MCAT) to Ascension Island with plans for it to become fully operational by summer 2016. This telescope will be providing data in support of research being conducted by the Orbital Debris Program Office at the Johnson Space Center. In addition to the main observatory, a smaller, auxiliary telescope is being deployed to the same location to augment and support observations generated by MCAT. It will provide near-simultaneous photometry and astrometry of debris objects, independent measurements of the seeing conditions, and offload low priority targets from MCAT's observing queue. Its hardware and software designs are presented here The National Aeronautical and Space Administration (NASA) has recently deployed the Meter Class Autonomous Telescope (MCAT) to Ascension Island. MCAT will provide NASA with a dedicated optical sensor for observations of orbital debris with the goal of statistically sampling the orbital and photometric characteristics of the population from low Earth to Geosynchronous orbits. Additionally, a small auxiliary telescope, co-located with MCAT, is being deployed to augment its observations by providing near-simultaneous photometry and astrometry, as well as offloading low priority targets from MCAT's observing queue. It will also serve to provide an independent measurement of the seeing conditions to help monitor the quality of the data being produced by the larger telescope. Comprised of off-the-shelf-components, the MCAT Auxiliary Telescope will have a 16-inch optical tube assembly, Sloan g'r'i'z' and Johnson/Cousins BVRI filters, and a fast tracking mount to help facilitate the tracking of objects in low Earth orbit. Tracking modes and tasking will be similar to MCAT except an emphasis will be placed on observations that provide more accurate initial orbit determination for the objects detected by MCAT. The near-simultaneous observations will also provide the opportunity for multi-filter color information of the debris objects to be obtained. Color information can further distinguish the individual objects within the population and provide insight into the reflectance properties of their surface material. The specific hardware, software, and tasking methodology of the MCAT Auxiliary Telescope is presented here..

Frith, James↗
NASA NTRS2016

Development of the NASA MCAT Auxiliary Telescope for Orbital Debris Research

The National Aeronautical and Space Administration (NASA) has recently deployed the Meter Class Autonomous Telescope (MCAT) to Ascension Island. MCAT will provide NASA with a dedicated optical sensor for observations of orbital debris with the goal of statistically sampling the orbital and photometric characteristics of the population from low Earth to Geosynchronous orbits. Additionally, a small auxiliary telescope, co-located with MCAT, is being deployed to augment its observations by providing near-simultaneous photometry and astrometry, as well as offloading low priority targets from MCAT's observing queue. It will also be available to provide observational measurements to the Space Surveillance Network for the United States Air Force.

Frith, James↗
NASA NTRS2017

Trajectory Dispersed Vehicle Process for Space Launch System

The Space Launch System (SLS) vehicle is part of NASA's deep space exploration plans that includes manned missions to Mars. Manufacturing uncertainties in design parameters are key considerations throughout SLS development as they have significant effects on focus parameters such as lift-off-thrust-to-weight, vehicle payload, maximum dynamic pressure, and compression loads. This presentation discusses how the SLS program captures these uncertainties by utilizing a 3 degree of freedom (DOF) process called Trajectory Dispersed (TD) analysis. This analysis biases nominal trajectories to identify extremes in the design parameters for various potential SLS configurations and missions. This process utilizes a Design of Experiments (DOE) and response surface methodologies (RSM) to statistically sample uncertainties, and develop resulting vehicles using a Maximum Likelihood Estimate (MLE) process for targeting uncertainties bias. These vehicles represent various missions and configurations which are used as key inputs into a variety of analyses in the SLS design process, including 6 DOF dispersions, separation clearances, and engine out failure studies.

Statham, Tamara↗
NASA NTRS2019

NASA's Orbital Debris Optical Program: MCAT Operational on Ascension

The Orbital Debris Program Office at NASA Johnson Space Center has a long history of an optical observational program. The Meter Class Autonomous Telescope, MCAT, was dedicated to Eugene Stansbery (now also known as ES-MCAT) in 2017. MCAT, a 1.3m DFM telescope, has a proven capability for tracking known objects from Low-Earth Orbits (LEO) out to Geosynchronous (GEO) orbits. Monitoring the population of the GEO belt is accomplished through surveys. A GEO survey statistically samples the GEO belt (0 to ~15 deg orbital inclinations) to detect both correlated and uncorrelated targets. A GEO survey, the initial focus for MCAT, will commence in 2019 to map out the current state of the GEO population as input for the ORbital Debris Engineering Model (ORDEM 4.x). If a break-up occurs, 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 surveying 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 rate-tracking their known or calculated orbital elements (Two-Line Element sets, TLEs). These observations can be used in conjunction with NASA’s Standard Satellite Break-up Model (SSBM). In 2018, MCAT’s primary mirror was realuminized with a high-end protected, enhanced silver ZeCoat and the CCD chip was replaced in the Spectral Instruments camera. With these updates completed, MCAT is now well on track to reach Full Operational Capability (FOC) in 2019 for its survey and rate-track capabilities. A full overview of MCAT’s operational state, capabilities, and mission will be discussed.

Orbital Debris Program↗
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 NTRS2019

The NaK Population: A 2019 Status

The statistical debris measurement campaigns conducted by the Haystack Ultrawideband Satellite Imaging Radar (HUSIR) on behalf of the NASA Orbital Debris Program Office are used to characterize the long-term behavior of the small, low Earth orbit (LEO) orbital debris environment. A long-recognized, unique component of the LEO environment is composed of small Sodium-Potassium (NaK) eutectic nuclear reactor coolant droplets associated with the Soviet Radar Ocean Reconnaissance Satellite (RORSAT) program. Beginning with the flight of Cosmos 1176, RORSAT vehicles would nominally separate their reactor core at end of mission, thereby venting the NaK coolant and producing the NaK droplet population. In this paper, we describe the methodology by which NaK are segregated from the statistically sampled general debris population and their sizes inferred; the current NaK environment; how it has changed over time; and a potential new source of NaK: RORSAT vehicles that did not separate their reactor core by either design or apparent malfunction.

Matney, Mark↗
NASA NTRS2019

Orbital Debris Radar Measurements from the Haystack Ultra-Wideband Satellite Imaging Radar (HUSIR): 2014-2017

For many years, the NASA Orbital Debris Program Office (ODPO) has partnered with the U.S. Department of Defense and the Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL) to collect data on the orbital debris environment using the Haystack radar. These measurements are used to characterize the small debris environment in low Earth orbit (LEO), down to a noise-limited size of approximately 5 mm—depending on altitude. The Haystack radar operated by MIT Lincoln Lab underwent upgrades starting in May 2010, with operations resuming in 2014 as the Haystack Ultra-wideband Satellite Imaging Radar (HUSIR). Hence, the data collected beginning in 2014 represents the first dataset available from this upgraded sensor. HUSIR is the primary source of data used by the ODPO to statistically sample orbital debris in the 5-mm to 10-cm size regime in LEO and is a key source of data to build and validate the NASA Orbital Debris Engineering Model. In this paper, we will present recent results from measurements performed during the US Government fiscal years 2014 – 2017. Using the NASA Size Estimation Model, a method based on laboratory radar measurements of debris, we will compare the size distributions of selected orbital debris populations over this 4-year period and flux measurements of orbital debris greater than 1 cm.

Murray, James↗
NASA NTRS2019

Recent Results from the Goldstone Orbital Debris Radar: 2016-2017

Since 1993, the NASA Orbital Debris Program Office has used the Goldstone Orbital Debris Radar (Goldstone) to sample statistically the orbital debris environment. Due to the sensitivity of this radar, which can detect an approximately 3 mm-diameter conducting sphere at 1,000 km, it has filled an important role in the characterization of the sub-centimeter-sized orbital debris population. Through the years, the capabilities of this system have increased – recent updates include increased receiver bandwidth and a change in the bi-static observation geometry – both of which enhance the radar’s ability to estimate orbital parameters. In 2016, dual polarization capability was added, making this the first year where both right- and left-hand circularly polarized information was available from this sensor. This additional polarization information may enable better characterization of sub-centimeter-sized particles in low Earth orbit, particularly since the receiver triggers on reflected energy from both left- and right-handed circular polarizations independently. In this paper, we present measurements and results derived from data taken during the calendar years (CY) 2016-2017 by Goldstone and compare this dataset to measurements taken by the Haystack Ultra-wideband Satellite Imaging Radar (HUSIR) during a similar timeframe.

Murray, James↗
NASA NTRS2019

NASA’s Orbital Debris JAO/ES-MCAT Optical Telescope Facility on Ascension Island

The NASA Orbital Debris Program Office has a long-standing optical program begun over three and a half decades ago in 1984, designed to observe the Earth-orbiting environment with optical telescopes. Photometrically calibrated optical data provides a statistical sample for input to NASA models of the debris population for understanding the current and future debris environment around the Earth. Tracked objects and orbits allow for analysis of break-up events. Both known (correlated target in the SSN catalogue, or CT) and unknown (uncorrelated target, or UCT) objects are of interest to better understand how to protect current spacecraft and design more robust future operational satellites, and advise on how policies and practices can lead to protecting the environment itself for future generations. In 2015, a joint NASA JSC – Air Force Research Labs (AFRL) project culminated in the installation of the 1.3-meter Eugene Stansbery Meter Class Autonomous Telescope, ES-MCAT (a.k.a. MCAT) on Ascension Island. This DFM Engineering designed telescope provides nearly five-times greater light-collecting power than its predecessor, the 0.6-m MODEST telescope, and faster tracking capabilities by both the telescope and the 7-m ObservaDome. This allows for all orbital regimes to be easily within reach, ranging from low Earth to geosynchronous orbits. Extensive testing and commissioning activities of this custom system led to successfully reaching Initial Operational Capability in 2018, and the facility is currently on track to reach Full Operational Capability. The John Africano Observatory (JAO) comprises the primary 1.3-m ES-MCAT facility, the adjacent tower platform with a 0.4-m telescope, a sophisticated suite of weather instruments, and custom software by Euclid Research for autonomously running the entire system, including monitoring the weather and hardware, tasking all components, and collecting, processing, and analyzing the data. The mission of JAO and MCAT will be discussed, including survey and tracking tasking, a full discussion of data calibration, and both optics and weather-dependent performance.

Lederer, S. M.↗
NASA NTRS2020

Recent Radar Observations of the Sub-Centimeter Orbital Debris Environment

The NASA Orbital Debris Program Office (ODPO) has conducted radar observations of the orbital debris environment since the early 1990’s to provide measurement data that supports orbital debris models and risk mitigation activities in support of NASA mission objectives. Orbital debris radar observations are a unique mode for radar operation, employing a fixed beam configuration to statistically sample the environment. An advantage of conducting operations in this fashion is that it enables observations of smaller classes of orbital debris than would otherwise be available from the same sensor operating in a traditional tracking mode. Orbital debris-mode radar observations are used to fill in the gaps, which exist in the currently available data from the Space Surveillance Network (SSN), on small size orbital debris populations that represent significant risk to NASA programs. These gaps have typically covered orbital debris with characteristic sizes less than approximately 10 cm down to approximately 3 mm in low Earth orbit (LEO) – depending upon the altitude and sensor configuration. The value of orbital debris radar measurements lies in the ability to extract partial orbital element information about orbital debris in the centimeter to several millimeter size regimes in low Earth orbit – which are not available from other measurement sources. This paper will discuss observations of this smaller class of orbital debris observed in recent years from the radars at the MIT Haystack Observatory in Westford, Massachusetts, and the Goldstone Solar System Radar near Barstow, California. The former radar is able to observe orbital debris down to approximately 5 mm, and the latter, orbital debris with characteristic sizes near 3 mm – at altitudes less than 1000 km. The characteristics and inferences about the current LEO orbital debris environment, and the different subpopulations that are identifiable in the observations are highlighted.

Kennedy, Timothy↗
NASA NTRS2018

Wall-Resolved Large-Eddy Simulations of Transonic Shock-Induced Flow Separation

Wall-resolved large-eddy simulations of shock-induced flow separation over an axisymmet- ric bump for a Mach number of 0.875 and a chord-based Reynolds number of 2.763 million are performed. The incoming boundary layer has a momentum-thickness Reynolds number of 6600 at 1.5 chords upstream of the bump. The calculations, which employ up to 24 billion grid points, simulate the experimental model of Bachalo and Johnson (AIAA Journal, Vol. 24, No. 3, 1986), except that the tunnel walls are ignored and free air is assumed. The effects of domain span and grid resolution are examined along with the main flowfield features. The predicted shock position as well as separation and reattachment locations agree well with the experiment. Grid convergence is observed in the attached region well upstream of separation. Two-point azimuthal correlations suggest that a span of at least 20 degrees is needed in the attached region, while a 120-degree span might be barely large enough in the separated region. Computed root-mean-square surface pressure fluctuations at the shock foot reach about 5 percent of ambient pressure and the level at reattachment location drops to about half of the primary peak. Simulations reveal evidence of the low-frequency shock unsteadiness; however, a much longer statistical sample is needed to investigate this phenomenon.

Uzun, Ali↗
NASA NTRS2020

Simple, Compact, High-Resolution Monochromatic X-Ray Source for Characterization of X-Ray Calorimeter Arrays

X-ray calorimeters routinely achieve very high spectral resolution, typically a few eV full width at half maximum (FWHM). Measurements of calorimeter line shapes are usually dominated by the natural linewidth of most laboratory calibration sources. This compounds the data acquisition time necessary to statistically sample the instrumental line broadening and can add systematic uncertainty if the intrinsic line shape of the source is not well known. To address these issues, we have built a simple, compact monochromatic x-ray source using channel cut crystals. A commercial x-ray tube illuminates a pair of channel cut crystals that are aligned in a dispersive configuration to select the Kα1 line of the x-ray tube anode material. The entire device, including the x-ray tube, can be easily hand-carried by one person and may be positioned manually or using a mechanical translation stage. The output monochromatic beam provides a collimated image of the anode spot with magnification of unity in the dispersion direction (typically 100 μm–200 μm for the x-ray tubes used here) and is unfocused in the cross-dispersion direction so that the source image in the detector plane appears as a line. We measured output count rates as high as 10 count/s/pixel for the Hitomi soft x-ray spectrometer, which had 819 μm square pixels. We implemented different monochromator designs for energies of 5.4 keV (one design) and 8.0 keV (two designs), which have effective theoretical FWHM energy resolution of 0.125 eV, 0.197 eV, and 0.086 eV, respectively; these are well-suited for optimal calibration measurements of state-of-the art x-ray calorimeters. We measured an upper limit for the energy resolution of our Cr Kα1 monochromator of 0.7 eV FWHM at 5.4 keV, consistent with the theoretical prediction of 0.125 eV.

M A Leutenegger↗