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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2000

Proceedings of the Twenty-Fourth Annual Software Engineering Workshop

On December 1 and 2, the Software Engineering Laboratory (SEL), a consortium composed of NASA/Goddard, the University of Maryland, and CSC, held the 24th Software Engineering Workshop (SEW), the last of the millennium. Approximately 240 people attended the 2-day workshop. Day 1 was composed of four sessions: International Influence of the Software Engineering Laboratory; Object Oriented Testing and Reading; Software Process Improvement; and Space Software. For the first session, three internationally known software process experts discussed the influence of the SEL with respect to software engineering research. In the Space Software session, prominent representatives from three different NASA sites- GSFC's Marti Szczur, the Jet Propulsion Laboratory's Rick Doyle, and the Ames Research Center IV&V Facility's Lou Blazy- discussed the future of space software in their respective centers. At the end of the first day, the SEW sponsored a reception at the GSFC Visitors' Center. Day 2 also provided four sessions: Using the Experience Factory; A panel discussion entitled "Software Past, Present, and Future: Views from Government, Industry, and Academia"; Inspections; and COTS. The day started with an excellent talk by CSC's Frank McGarry on "Attaining Level 5 in CMM Process Maturity." Session 2, the panel discussion on software, featured NASA Chief Information Officer Lee Holcomb (Government), our own Jerry Page (Industry), and Mike Evangelist of the National Science Foundation (Academia). Each presented his perspective on the most important developments in software in the past 10 years, in the present, and in the future.

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NASA NTRS2010

ARCADE 2 Observations of Galactic Radio Emission

We use absolutely calibrated data from the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) flight in July 2006 to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index beta_synch = -2.5 +/- 0.1, with free-free emission contributing 0.10 +/- 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc|b| dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of CII emission. Both methods are consistent with a single power-law over the frequency range 22 MHz to 10 GHz, with total Galactic emission towards the north polar cap T_Gal = 0.498 +/- 0.028 K and spectral index beta = -2.55 +/- 0.03 at reference frequency 0.31 GHz. The well calibrated ARCADE 2 maps provide a new test for spinning dust emission, based on the integrated intensity of emission from the Galactic plane instead of cross-correlations with the thermal dust spatial morphology. The Galactic plane intensity measured by ARCADE 2 is fainter than predicted by models without spinning dust, and is consistent with spinning dust contributing 0.4 +/- 0.1 of the Galactic plane emission at 23 GHz.

Kogut, A.↗
NASA NTRS1992

A survey of small-scale extremes in extinction at low Galactic latitudes using IRAS galaxies

Optical CCD and 21 cm H I data are combined here via the Tully-Fisher relation to study the Galactic extinction in the V an I bands over an angular scale of a few arcmin at absolute Galactic latitudes between 2 and 16 deg. Extinctions in V and I bands are found to be linearly correlated with A(I) about 0.58 A(V), with no noticeable environmental dependence and consistent with existing results of Galactic reddening. There is a large scatter in the simple linear relation with csc /b/, confirming the existence of 'holes' and patches at low Galactic latitudes. The mean correlation between Galactic extinction and H I column density over a comparable angular scale is also found to be consistent with those at high latitudes over large angular scales. Correlation is also found between optical extinction and the IRAS 100 micron sky brightness, and this sky brightness is only slightly worse than H I column density as an indicator for optical extinction.

Lu, N. Y.↗
NASA NTRS1991

Hybrid CMS methods with model reduction for assembly of structures

Future on-orbit structures will be designed and built in several stages, each with specific control requirements. Therefore there must be a methodology which can predict the dynamic characteristics of the assembled structure, based on the dynamic characteristics of the subassemblies and their interfaces. The methodology developed by CSC to address this issue is Hybrid Component Mode Synthesis (HCMS). HCMS distinguishes itself from standard component mode synthesis algorithms in the following features: (1) it does not require the subcomponents to have displacement compatible models, which makes it ideal for analyzing the deployment of heterogeneous flexible multibody systems, (2) it incorporates a second-level model reduction scheme at the interface, which makes it much faster than other algorithms and therefore suitable for control purposes, and (3) it does answer specific questions such as 'how does the global fundamental frequency vary if I change the physical parameters of substructure k by a specified amount?'. Because it is based on an energy principle rather than displacement compatibility, this methodology can also help the designer to define an assembly process. Current and future efforts are devoted to applying the HCMS method to design and analyze docking and berthing procedures in orbital construction.

Farhat, Charbel↗
NASA NTRS1997

The SEL Adapts to Meet Changing Times

Since 1976, the Software Engineering Laboratory (SEL) has been dedicated to understanding and improving the way in which one NASA organization, the Flight Dynamics Division (FDD) at Goddard Space Flight Center, develops, maintains, and manages complex flight dynamics systems. It has done this by developing and refining a continual process improvement approach that allows an organization such as the FDD to fine-tune its process for its particular domain. Experimental software engineering and measurement play a significant role in this approach. The SEL is a partnership of NASA Goddard, its major software contractor, Computer Sciences Corporation (CSC), and the University of Maryland's (LTM) Department of Computer Science. The FDD primarily builds software systems that provide ground-based flight dynamics support for scientific satellites. They fall into two sets: ground systems and simulators. Ground systems are midsize systems that average around 250 thousand source lines of code (KSLOC). Ground system development projects typically last 1 - 2 years. Recent systems have been rehosted to workstations from IBM mainframes, and also contain significant new subsystems written in C and C++. The simulators are smaller systems averaging around 60 KSLOC that provide the test data for the ground systems. Simulator development lasts up to 1 year. Most of the simulators have been built in Ada on workstations. The SEL is responsible for the management and continual improvement of the software engineering processes used on these FDD projects.

Pajerski, Rose S.↗
NASA NTRS1994

Morphology of the interstellar cooling lines detected by COBE

The Far-Infrared Absolute Spectrophotometer (FIRAS) on the COBE satellite has conducted an unbiased survey of the far-infrared emission from our Galaxy. The first results of this survey were reported by Wright et al. (1991). We report the results of new analyses of this spectral survey, which includes emission lines from 158 micrometer C(+), 122 and 205 micrometer N(+), 370 and 609 micrometer C(0), and CO J = 2 goes to 1 through J = 5 goes to 4. We report the morphological distribution along the Galactic plane (b = 0 deg) of the spectral line emission, and the high Galactic latitude intensities of the C(+) and 205 micrometer N(+) emission. In the Galactic plane the 205 micrometer line of N(+) generally follows the 158 micrometer C(+) line distribution, but the intensities scale as I(N(+) 205 micrometer) varies as I(C(+) 158 micrometer)(exp 1.5) toward the inner Galaxy. The high Galactic latitude intensity of the 158 micrometer fine-structure transition from C(+) is I(C(+) 158 micrometer) = (1.43 +/- 0.12) x 10(exp -6) csc (absolute value of b) ergs/sq cm s sr for absolute value of b greater than 15 deg, and it decreases more rapidly than the far-infrared intensity with increasing Galactic latitude. C(+) and neutral atomic hydrogen emission are closely correlated with a C(+) cooling rate of (2.65 +/- 0.15) x 10(exp -26) ergs/s. We conclude that this emission arises almost entirely from the cold neutral medium. The high Galactic latitude intensity of the 205 micrometer fine-structure transition from N(+) is I(N(+) 205 micrometer) = (4 +/- 1) x 10(exp -8) csc (absolute value of b) ergs/((sq cm)(s)(sr)) arising entirely from the warm ionized medium. We estimate the total ionizing photon rate in the Galaxy to be phi = 3.5 x 10(exp 53) ionizing photons per second, based on the 205 micrometer N(+) transition.

Bennett, C. L.↗
NASA NTRS1997

The Goddard High Resolution Spectrograph Scientific Support Contract

In 1988, Computer Sciences Corporation (CSC) was selected as the Goddard High Resolution Spectrograph (GHRS) Scientific Support Contractor (SSC). This was to have been a few months before the launch of NASA's first Great Observatory, the Hubble Space Telescope (HST). As one of five scientific instruments on HST, the GHRS was designed to obtain spectra in the 1050-3300 A ultraviolet wavelength region with a resolving power, lambda/Delta(lambda) , of up to 100,000 and relative photometric accuracy to 1%. It was built by Ball AeroSpace Systems Group under the guidance of the GHRS Investigation Definition Team (IDT), comprised of 16 scientists from the US and Canada. After launch, the IDT was to perform the initial instrument calibration and execute a broad scientific program during a five-year Guaranteed Time Observation (GTO) period. After a year's delay, the launch of HST occurred in April 1990, and CSC participated in the in-orbit calibration and first four years of GTO observations with the IDT. The HST primary mirror suffered from spherical aberration, which reduced the spatial and spectral resolution of Large Science Aperture (LSA) observations and decreased the throughput of the Small Science Aperture (SSA) by a factor of two. Periodic problems with the Side 1 carrousel electronics and anomalies with the low-voltage power supply finally resulted in a suspension of the use of Side 1 less than two years after launch. At the outset, the GHRS SSC task involved work in four areas: 1) to manage and operate the GHRS Data Analysis Facility (DAF); 2) to support the second Servicing Mission Observatory Verification (SMOV) program, as well as perform system engineering analysis of the GHRS as nesessary; 3) to assist the GHRS IDT with their scientific research programs, particularly the GSFC members of the team, and 4) to provide administrative and logistic support for GHRS public information and educational activities.

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NASA NTRS1991

Systems engineering studies of on-orbit assembly operation

While the practice of construction has a long history, the underlying theory of construction is relatively young. Very little has been documented as to techniques of logistic support, construction planning, construction scheduling, construction testing, and inspection. The lack of 'systems approaches' to construction processes is certainly one of the most serious roadblocks to the construction of space structures. System engineering research efforts at CSC are aimed at developing concepts and tools which contribute to a systems theory of space construction. The research is also aimed at providing means for trade-offs of design parameters for other research areas in CSC. Systems engineering activity at CSC has divided space construction into the areas of orbital assembly, lunar base construction, interplanetary transport vehicle construction, and Mars base construction. A brief summary of recent results is given. Several models for 'launch-on-time' were developed. Launch-on-time is a critical concept to the assembly of such Earth-orbiting structures as the Space Station Freedom, and to planetary orbiters such as the Mars transfer vehicle. CSC has developed a launch vehicle selection model which uses linear programming to find optimal combinations of launch vehicles of various sizes (Atlas, Titan, Shuttles, HLLV's) to support SEI missions. Recently, the Center developed a cost trade-off model for studying on orbit assembly logistics. With this model it was determined that the most effective size of the HLLV would be in the range of 120 to 200 metric tons to LEO, which is consistent with the choices of General Stafford's Synthesis Group Report. A second-generation Dynamic Construction Activities Model ('DYCAM') process model has been under development, based on our past results in interruptability and our initial DYCAM model. This second-generation model is built on the paradigm of knowledge-based expert systems. It is aimed at providing answers to two questions: (1) what are some necessary or sufficient conditions for judging conceptual designs of spacecraft?, and (2) can a methodology be formulated such that these conditions may be used to provide computer-aided tools for evaluating conceptual designs and planning for space assembly sequences? Early simulation results indicate that the DYCAM model has a clear ability to emulate and simulate human orbital construction processes.

Morgenthaler, George W.↗