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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 NTRS2006

Methodology for Designing Fault-Protection Software

A document describes a methodology for designing fault-protection (FP) software for autonomous spacecraft. The methodology embodies and extends established engineering practices in the technical discipline of Fault Detection, Diagnosis, Mitigation, and Recovery; and has been successfully implemented in the Deep Impact Spacecraft, a NASA Discovery mission. Based on established concepts of Fault Monitors and Responses, this FP methodology extends the notion of Opinion, Symptom, Alarm (aka Fault), and Response with numerous new notions, sub-notions, software constructs, and logic and timing gates. For example, Monitor generates a RawOpinion, which graduates into Opinion, categorized into no-opinion, acceptable, or unacceptable opinion. RaiseSymptom, ForceSymptom, and ClearSymptom govern the establishment and then mapping to an Alarm (aka Fault). Local Response is distinguished from FP System Response. A 1-to-n and n-to- 1 mapping is established among Monitors, Symptoms, and Responses. Responses are categorized by device versus by function. Responses operate in tiers, where the early tiers attempt to resolve the Fault in a localized step-by-step fashion, relegating more system-level response to later tier(s). Recovery actions are gated by epoch recovery timing, enabling strategy, urgency, MaxRetry gate, hardware availability, hazardous versus ordinary fault, and many other priority gates. This methodology is systematic, logical, and uses multiple linked tables, parameter files, and recovery command sequences. The credibility of the FP design is proven via a fault-tree analysis "top-down" approach, and a functional fault-mode-effects-and-analysis via "bottoms-up" approach. Via this process, the mitigation and recovery strategy(s) per Fault Containment Region scope (width versus depth) the FP architecture.

Barltrop, Kevin↗
NASA NTRS2010

Millimeter and Submillimeter Observations of Comet 103P/Hartley 2

The close approach (0.12 AU) of Comet 103P/Hartley 2 to the Earth only S days prior to perihelion provides a unique opportunity to probe the chemical composition of this object. We will employ the Arizona Radio Observatory's Kitt Peak 12m (KPH12M) and the Submillimeter Telescope (SMT) for observations of multiple molecular species and their isotopologs towards the comet. There will also be an attempt to monitor this object during the EPOXI (Extrasolar Planet Observation. and Deep Impact Extended Investigation) flyby mission, which will obtain high resolution infrared spectra, for a comparison of the molecular inventory and a more accurate assessment of the abundances, sources (e.g. jets or cometismals), and chemistry.

Milan, S. N.↗
NASA NTRS2011

Insolation Effects on Lunar Hydrogen: Observation from the LRO LEND and LOLA Instruments

The Moon's polar permanent shadow regions (PSR) have long been considered the unique repository for volatile Hydrogen (H) Largely, this was due to the extreme and persistently cold environment that has been maintained over eons of lunar history. However, recent discoveries indicate that the H picture may be more complex than thc PSR hypothesis suggests. Observations by the Lunar Exploration Neutron Detect (LEND) onboard the Lunar Reconnaissance Orbiter (LRO) indicate some H concentrations lie outside PSR. Similarly, observations from Chandraayan-l's M3 and Deep Impact's EPOXI near infra-red observations indicate diurnal cycling of volatile H in lower latitudes. These results suggest other geophysical phenomena may also play a role in the Lunar Hydrogen budget. In this presentation we review the techniques and results from the recent high latitude analysis and apply similar techniques to equatorial regions. Results from our low latitude analysis will be reported. We discuss interpretations and implications for Lunar Hydrogen studies

McClanahan, T. P.↗
NASA NTRS2011

Temporal and Spatial Aspects of Gas Release During the 2010 Apparition of Comet 103P/Hartley-2

We report measurements of eight primary volatiles (H2O, HCN, CH4, C2H6, CH3OH, C2H2, H2CO, and NH3) and two product species (OH and NH2) in comet lO3P/Hartley-2 using high dispersion infrared spectroscopy. We quantified the long- and short-term behavior of volatile release over a three-month interval that encompassed the comet's close approach to Earth, its perihelion passage, and flyby of the comet by the Deep Impact spacecraft during the EPOXI mission. We present production rates for individual species, their mixing ratios relative to water, and their spatial distributions in the coma on multiple dates. The production rates for water, ethane, HCN, and methanol vary in a manner consistent with independent measures of nucleus rotation, but mixing ratios for HCN, C2H6, & CH3OH are independent of rotational phase. Our results demonstrate that the ensemble average composition of gas released from the nucleus is well defined, and relatively constant over the three-month interval (September 18 through December 1,7). If individual vents vary in composition, enough diverse vents must be active simultaneously to approximate (in sum) the bulk composition of the nucleus. The released primary volatiles exhibit diverse spatial properties which favor the presence of separate polar and apolar ice phases in the nucleus, establish dust and gas release from icy clumps, and from the nucleus, and provide insights into the driver for the cyanogen (CN) polar jet. The spatial distributions of C2H6 & HCN along the near-polar jet (UT 19.5 October) and nearly orthogonal to it (UT 22.5 October) are discussed relative to the origin of CN. The ortho-para ratio (OPR) of water was 2.85 +/- 0.20; the lower bound (2.65) defines T(sub spin) > 32 K. These values are consistent with results returned from ISO in 1997 .

Mumma, M. J.↗
NASA NTRS2011

Centimeter, Millimeter, and Submillimeter Observations of Comet l03P/Hartley 2

The close approach (0.12 AU) of Comet 103P/Hartley 2 to the Earth only 8 days prior to perihelion provided a unique opportunity to probe the chemical composition of this object. Additionally, supporting data was acquired during the EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flyby mission [1], which provided high resolution infrared spectra and images. Observations were conducted from four facilities, contributing to the large ground-based consortium organized in support of the EPOXI mission [2]. The Arizona Radio Observatory's 12m telescope, Kitt Peak, AZ, and Submillimeter telescope, Mt. Graham, AZ, as well as the James Clerk Maxwell Telescope, Mauna Kea, HI and the Greenbank 100m telescope, Greenbank, WV, were employed for this study covering 20 cm, 3 cm, and 0.8-3 mm. Data were obtained, collectively, from 12 October 2010 to 5 November 2010 [3]. HCN, CH3OH, H2CO, HNC, OH, and CS were detected, and upper limits on the abundance of H2S, SO2, c-C3H2, and deuterated isotopologues of HCN, H2CO, and H2O were measured. Upper limits on the D/H ratio derived from DCN gave D/H less than 0.01[3]. Detailed analysis of these data will help constrain the temperature, abundances, variance or periodicity of a given species, and can be compared to results from other comets, as well as support the data obtained from the EPOXI mission. The full analysis and comparison will be presented.

Milam, Stefanie N.↗
NASA NTRS2011

Views from EPOXI: Colors in Our Solar System as an Analog for Extrasolar Planets

The first visible-light studies of Earth-sized extrasolar planets will employ photometry or low-resolution spectroscopy. This work uses EPOCh medium-hand filter photometry between 150 and 950 nm obtained with the Deep Impact (DI) High Resolution Instrument (HRI) of Earth, the Moon, and Mars in addition to previous full-disk observations of the other six solar system planets and Titan to analyze the limitations of using photometric colors to characterize extrasolar planets. We determined that the HRI 350, 550, and 850 nm filters are optimal for distinguishing Earth from the other planets and separating planets to first order based on their atmospheric and surface properties. Detailed conclusions that can be drawn about exoplanet atmospheres simply from a color-color plot are limited due to potentially competing physical processes in the atmosphere. The presence of a Rayleigh scattering atmosphere can be detected by an increase in the 350-550 nm brightness ratio, but the absence of Rayleigh scattering cannot be confirmed due to the existence of atmospheric and surface absorbing species in the UV. Methane and ammonia are the only species responsible for strong absorption in the 850 nm filter in our solar system. The combination of physical processes present on extrasolar planets may differ from those we see locally. Nevertheless, a generation of telescopes capable of collecting such photometric observations can serve a critical role in first-order characterization and constraining the population of Earth-like extrasolar planets.

Crow, Carolyn A.↗
NASA NTRS2011

Earth as an Extrasolar Planet: Earth Model Validation Using EPOXI Earth Observations

The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole disk Earth model simulations used to better under- stand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute s Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model (Tinetti et al., 2006a,b). This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of approx.100 pixels on the visible disk, and four categories of water clouds, which were defined using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to the Earth s lightcurve, absolute brightness, and spectral data, with a root-mean-square error of typically less than 3% for the multiwavelength lightcurves, and residuals of approx.10% for the absolute brightness throughout the visible and NIR spectral range. We extend our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of approx.7%, and temperature errors of less than 1K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be used to simulate Earth s time dependent brightness and spectral properties for wavelengths from the far ultraviolet to the far infrared.brightness

Robinson, Tyler D.↗
NASA NTRS2011

Interplanetary Overlay Network Bundle Protocol Implementation

The Interplanetary Overlay Network (ION) system's BP package, an implementation of the Delay-Tolerant Networking (DTN) Bundle Protocol (BP) and supporting services, has been specifically designed to be suitable for use on deep-space robotic vehicles. Although the ION BP implementation is unique in its use of zero-copy objects for high performance, and in its use of resource-sensitive rate control, it is fully interoperable with other implementations of the BP specification (Internet RFC 5050). The ION BP implementation is built using the same software infrastructure that underlies the implementation of the CCSDS (Consultative Committee for Space Data Systems) File Delivery Protocol (CFDP) built into the flight software of Deep Impact. It is designed to minimize resource consumption, while maximizing operational robustness. For example, no dynamic allocation of system memory is required. Like all the other ION packages, ION's BP implementation is designed to port readily between Linux and Solaris (for easy development and for ground system operations) and VxWorks (for flight systems operations). The exact same source code is exercised in both environments. Initially included in the ION BP implementations are the following: libraries of functions used in constructing bundle forwarders and convergence-layer (CL) input and output adapters; a simple prototype bundle forwarder and associated CL adapters designed to run over an IPbased local area network; administrative tools for managing a simple DTN infrastructure built from these components; a background daemon process that silently destroys bundles whose time-to-live intervals have expired; a library of functions exposed to applications, enabling them to issue and receive data encapsulated in DTN bundles; and some simple applications that can be used for system checkout and benchmarking.

Burleigh, Scott C.↗
NASA NTRS2011

Optical Navigation for the EPOXI Mission

The Deep Impact spacecraft flew by comet Hartley 2 on November 4, 2010 as part of its extended mission called EPOXI. Successful navigation depended critically on the quality and timing of optical navigation data processing, since pictures of the comet provided the most precise comet-relative position of the spacecraft. This paper describes the planning, including the picture timing and pointing; the methods used to determine the center of the comet image in each picture; and the optical navigation results, which provided the necessary information to allow the cameras to accurately target the comet for science imaging at encounter.

small-body mission↗
NASA NTRS2011

Discovery and Mass Measurements of a Cold, 10-Earth Mass Planet and Its Host Star

We present the discovery and mass measurement of the cold, low-mass planet MOA-2009-BLG-266Lb, made with the gravitational microlensing method. This planet has a mass of mp = 10.4 +/- M(Earth) and orbits a star of Mstar = 0.56 +/- 0.09 M(Sun) at a semi-major axis of a = 3.2 + 1.9/-0.5 AU, and an orbital period of 7.6 +7.7/-1.5 yrs. The planet and host star mass measurements are due to the measurement of the microlensing parallax effect. This measurement was primarily due to the orbital motion of the Earth, but the analysis also demonstrates the capability measure micro lensing parallax with the Deep Impact (or EPOXI) spacecraft in a Heliocentric orbit. The planet mass and orbital distance are similar to predictions for the critical core mass needed to accrete a substantial gaseous envelope, and thus may indicate that this planet is a failed gas giant. This and future microlensing detections will test planet formation theory predictions regarding the prevalence and masses of such planets

Barry, Richard K.↗
NASA NTRS2012

Preliminary Crater Retention Ages for an Expanded Inventory of Large Lunar Basins

Based on LOLA topography and a new crustal thickness model, the number of candidate lunar basins greater than 300 km in diameter is at least a factor 2 larger than the traditional number based on photogeology alone, and may be as high as 95. Preliminary N(50) crater retention ages for this population of candidate basins shows two distinct peaks. Frey [1] suggested, based on Clementine-era topography (ULCN2005) and a crustal thickness model based on Lunar Prospector data [2], that there could be as many as 98 lunar basins greater than 300 km diameter. Many of the weaker cases have not stood up to recent testing [3,4,5] using LOLA data and a newer crustal thickness model based on Kaguya gravity data and LOLA topography data [6]. As described in companion abstracts [4,5], we have deleted from the earlier inventory 1 more named feature (Sikorsky- Rittenhouse; LOLA data show that its diameter is actually less than 300 km), 11 Quasi-Circular Depressions (QCDs) identified in the ULCN topography, and 11 Circular Thin Areas (CTAs) found in the earlier crustal thickness model [2]. We did this by repeating the scoring exercise originally done in [1] but with the new data [4,5]. Topographic Expression (TE) and Crustal Thickness Expression (CTE) scores were determined for each candidate on a scale of 0 to 5 (5 being a strong, circular signature, 0 for those with no discernible circular topographic or crustal thickness signature). These scores are added together to produce a Summary Score which has a range of 0 to 10. We eliminated all candidates with a Summary Score less than 3, as well as other cases where, for example, the TE went to zero because what looked like a single large circular QCD in the lower resolution ULCN data was in fact a cluster of smaller deep impacts readily apparent in the newer higher resolution LOLA data. This process reduced the original inventory from 98 to 75 candidates.

Frey, H. V.↗
NASA NTRS2012

The Keys to Successful Extended Missions

Many of NASA's successful missions of robotic exploration have gone on to highly productive mission extensions, from Voyager, Magellan, Ulysses, and Galileo, to the Mars Exploration Rovers Spirit and Opportunity, a variety of Mars orbiters, Spitzer, Deep Impact / EPOXI, and Cassini. These missions delivered not only a high science return during their prime science phase, but a wealth of opportunities during their extensions at a low incremental cost to the program. The success of such mission extensions can be traced to demonstration of new and unique science achievable during the extension; reduction in cost without significant increase in risk to spacecraft health; close inclusion of the science community and approval authorities in planning; intelligent design during the development and prime operations phase; and well crafted and conveyed extension proposals. This paper discusses lessons learned collected from a variety of project leaders which can be applied by current and future missions to maximize their chances of approval and success.

mission lifetime↗
NASA NTRS2012

Lessons Learned in the Decommissioning of the Stardust Spacecraft

The Stardust spacecraft completed its prime mission in 2006, returning samples from the coma of comet Wild 2 to earth in the sample return capsule. Still healthy, and in a heliocentric orbit, the Stardust spacecraft was repurposed for a new mission - Stardust NExT. This new mission would take the veteran spacecraft to a 2011 encounter with comet Tempel 1, providing a new look at the comet visited in 2005 by the Deep Impact mission. This extended mission for Stardust would push it to the limits of its fuel reserves, prompting several studies aimed at determining the actual remaining fuel on board. The results were used to plan mission events within the constraints of this dwindling resource. The team tracked fuel consumption and adjusted the mission plans to stay within the fuel budget. This effort intensified toward the end of the mission, when a final assessment showed even less remaining fuel than previously predicted, triggering a delay in the start of comet imaging during the approach phase. The flyby of comet Tempel 1 produced spectacular up close views of this comet, imaging previously seen areas as well as new territory, and providing clear views of the location of the 2005 impact. The spacecraft was decommissioned about a month after the flyby, revealing that the fuel tank was now empty after having flown successfully for 12 years, returned comet dust samples to earth, and flown by an asteroid and two comets.

repurposed spacecrafts↗
NASA NTRS2013

Shape, Density, and Geology of the Nucleus of Comet 103P/Hartley 2

Data from the Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) mission show Comet 103P/Hartley 2 is a bi-lobed, elongated, nearly axially symmetric comet 2.33 km in length. Surface features are primarily small mounds <40 m across, irregularly-shaped smooth areas on the two lobes, and a smooth but variegated region forming a “waist” between the two lobes. Assuming parts of the comet body approach the shape of an equipotential surface, the mean density of Hartley 2 is modeled to be 200–400 kg /cubic m.. Such a mean density suggests mass loss per orbit of >1%. The shape may be the evolutionary product of insolation, sublimation, and temporary deposition of materials controlled by the object’s complex rotation.

Extrasolar↗
NASA NTRS2013

The Complex Spin State of 103P-Hartley 2: Kinematics and Orientation in Space

We derive the spin state of the nucleus of Comet 103P/Hartley 2, its orientation in space, and its short-term temporal evolution from a mixture of observations taken from the DIXI (Deep Impact Extended Investigation) spacecraft and radar observations. The nucleus is found to spin in an excited long-axis mode (LAM) with its rotational angular momentum per unit mass, M, and rotational energy per unit mass, E, slowly decreasing while the degree of excitation in the spin increases through perihelion passage. M is directed toward (RA, Dec; J2000) = 8+/-+/- 4 deg., 54 +/- 1 deg. (obliquity = 48 +/- 1 deg.). This direction is likely changing, but the change is probably <6 deg. on the sky over the approx. 81.6 days of the DIXI encounter. The magnitudes of M and E at closest approach (JD 2455505.0831866 2011-11-04 13:59:47.310) are 30.0 +/- 0.2 sq. m/s and (1.56 +/- 0.02) X 10(exp -3) sq. m /sq. s respectively. The period of rotation about the instantaneous spin vector, which points in the direction (RA, Dec; J2000) = 300 +/- 3.2deg., 67 +/- 1.3 deg. at the time of closest approach, was 14.1 +/- 0.3 h. The instantaneous spin vector circulates around M, inclined at an average angle of 33.2 +/- 1.3 deg. with an average period of 18.40 +/- 0.13 h at the time of closest approach. The period of roll around the principal axis of minimum inertia (''long'' axis) at that time is 26.72 +/- 0.06 h. The long axis is inclined to M by approx. 81.2 +/- 0.6 deg. on average, slowly decreasing through encounter. We infer that there is a periodic nodding motion of the long axis with half the roll period, i.e., 13.36+/- 0.03 h, with amplitude of 1 again decreasing through encounter. The periodic variability in the circulation and roll rates during a cycle was at the 2% and 10-14% level respectively. During the encounter there was a secular lengthening of the circulation period of the long axis by 1.3 +/- 0.2 min/d, in agreement with ground-based estimates, while the period of roll around the long axis changed by approx. -4.4 min/d at perihelion. M decreased at a rate of 0.038 (sq m/s) per day in a roughly linear fashion. Assuming a bulk density between 230-300 kg/m3 and a total volume for the nucleus of 8.09 X 10(exp 8) cubic m, the net torque acting on the nucleus was in the range 0.8-1.1 X 10(exp 5) kg m(exp 2) /s(exp 2). In order to bring the spacecraft photometric and imaging data into alignment on the direction of M, the directions of the intermediate and short principal axes of inertia had to be adjusted by 33 deg (on the sky) from the values indicated by the shape model with an assumed homogeneous interior. The adjusted direction of the intermediate axis is RA, Dec = 302 deg., -16.5 deg.. The morning and evening terminators in the images are identified, and the variation of the insolation at three regions on the nucleus associated with active areas calculated. The plume of water vapor observed in the inner coma is found to be directed close to the direction of local gravity over the sub-solar region for a range of reasonable bulk densities. The plume does not follow the projected normal to the surface at the sub-solar point.

Comets↗
NASA NTRS2011

EPOXI Trajectory and Maneuver Analyses

The EPOXI mission is a NASA Discovery Mission of Opportunity combining two separate investigations: Extrasolar Planet Observation and Characterization (EPOCh) and Deep Impact eXtended Investigation (DIXI). Both investigations reused the DI instruments and spacecraft that successfully flew by the comet Tempel-1 (4 July 2005). For EPOCh, the goal was to find exoplanets with the high resolution imager, while for DIXI it was to fly by the comet Hartley 2 (4 Nov 2010). This paper documents the navigation experience of the earlier ma-neuver analyses critical for the EPOXI mission including statistical ?V analyses and other useful analyses in designing maneuvers. It also recounts the trajectory design leading up to the final reference trajectory to Hartley 2.

trajectory design↗
NASA NTRS2011

Comet Ephemerides for the EPOXI and Stardust-NExT Flybys

The recently successful flybys of Comet 103P/Hartley 2 by the Deep Impact spacecraft and Comet 9P/Tempel 1 by the Stardust spacecraft each presented different challenges from the perspective of comet ephemeris prediction and spacecraft targeting. Hartley 2 is a small, highly active comet, with nongravitational accelerations that proved very difficult to model, requiring some amount of "cometchasing" by the spacecraft navigators. In contrast, Tempel 1 is a far larger and less active comet. It showed very stable ephemeris behavior and at flyby was within 1-sigma of predictions issued more than a year prior to encounter. This happenstance was fortuitous because the Stardust spacecraft had very little fuel margin available for comet ephemeris errors.

non-gravitational accelerations↗