George Fox

Arabidopsis homeotic gene APETALA3 ectopic expression: Transcriptional and posttranscriptional regulation determine floral organ identity

APETALA3 (AP3) specifies the development of petals and stamens in the Arabidopsis flower. We constructed a transgenic line, 35S-AP3, that ectopically expresses AP3 under the control of a constitutive promoter. The resulting flowers exhibit a replacement of carpels by stamens and resemble flowers homozygous for the previously described Arabidopsis mutation superman. Although AP3 RNA is detected at high levels throughout the flower and stem in 35S-AP3, AP3 protein is detected at high levels only in the second, third, and fourth floral whorls, demonstrating that AP3 is posttranscriptionally regulated. Ectopic expression of AP3 causes a second floral homeotic gene, PISTILLATA (PI), to function in the fourth whorl of 35S-AP3 flowers. AP3 and PI also activate an AP3 promoter-reporter gene fusion, demonstrating that AP3 positively autoregulates.

NASA technology assessment using real options valuation

We examine the use of real options valuation in the context of prioritizing advanced technologies for NASA funding. Further, we offer a set of computational procedures that quantifies the option value of each technology. Other researchers have applied a real options framework to private sector investments. In the case of NASA investments in advanced technologies, the underlying products, which must be used to justify the investments, are space-related scientific results and discoveries from completed missions to be shared worldwide. As in the private sector, uncertainty plays a significant role in the motivation to use real options in NASA. Uncertainty in NASA technology investments can be classified as development risk and programmatic risk (whether missions using the technology will actually fly). The latter might be called the technology “market risk.” We carried out the approach on a number of planetary exploration technologies. We illustrate the detailed calculations using one of them—lightweight propellant tank technology.

Stochastic Analysis of Constellation Performance and Mass Margins

A new method for analyzing margins in the Constellation program is described and applied to the performance and mass margins for the integrated transportation system returning humans to the lunar surface. The approach treats the Ares-V Earth-departure-stage gross payload-delivery capability and the translunar injection masses of Orion and Altair as random variables. For various vehicle requirements, vehicle control masses, and design reference missions, a Monte Carlo simulation estimate is used to estimate the critical probability that the delivery capability exceeds that injected mass. This critical probability can be used to establish program performance and mass margins and, in conjunction with other measures, to manage vehicle selection and trades at the program level.

Engineering reliability for the NEPTUNE observatory

This paper reviews aspects of engineering for reliability of the proposed NEPTUNE observatory. NEPTUNE has an equipment life requirement of around 30 years, and (because of the local weather) presents limited opportunity for repair. It is necessary to use methods and parts that assure the system are sufficiently reliable and maintainable. Among the factors that influence construction are appropriate parts selection criteria, quality assurance inspections, through testing of hardware, understanding and accommodating the shock environment of deployment and maintenance cycles, assuring that there will not be material compatibility issues, minimizing the risk that software will result in system failure, analyzing the hardware designs to assure that they should still work correctly after 30 years and that failures do not propagate, and tracking all anomalies to make sure they are appropriately resolved.

NASA technology assessment using real options valuation: Regular Paper

This paper investigates alternative approaches to constant rate discounting for calculation of Net Present Value (NPV) in life cycle cost models that are used for engineering trade studies. Alternative approaches are necessary to meet the challenge of equitable intergenerational resource allocation for projects like radioactive waste disposal that have a life cycle that impacts future generations well beyond the 30-year maximum time horizon limit that results from using market-determined interest rates on bonds. This paper reviews the literature on long-term discount models, provides a consistent nomenclature for describing the models, summarizes the theoretical and empirical basis for hyperbolic discounting models, evaluates the research results to date, and provides a recommendation for applying hyperbolic discounting. It also identifies issues with the current U.S. government policy on discounting and the future research necessary to establish an improved foundation for discounting models for long-term projects.

NASA instrument cost/schedule model Hamid Habib-Agahi

NASAs Office of Independent Program and Cost Evaluation (IPCE) has established a number of initiatives to improve its cost and schedule-estimating capabilities.12 One of these initiatives has resulted in the JPL-developed NASA Instrument Cost Model (NICM). NICM is an instrument cost and schedule estimator that contains the following: A system-level cost-estimation tool, a subsystem-level cost-estimation tool, a database of cost and technical parameters of over 140 previously flown NASA remote-sensing and in-situ instruments, a schedule estimator, a set of rules to estimate cost and schedule by life cycle phases (B/C/D), and a novel tool for developing joint probability distributions for cost and schedule risk (Joint Confidence Level (JCL)). This paper describes the development and use of NICM, including the data-normalization processes, data-mining methods (cluster analysis, principal components analysis, regression analysis and bootstrap cross validation), the estimating equations themselves and a demonstration of the NICM tool suite.

Dynamic cost risk estimation and budget misspecification

Cost risk for new technology development is estimated by explicit stochastic processes. Monte Carlo simulation is used to propagate technology development activity budget changes during the technology development cycle.

Latest NASA Instrument Cost Model (NICM): Version VI

The NASA Instrument Cost Model, NICM, is a suite of tools which allow for probabilistic cost estimation of NASAs space-flight instruments at both the system and subsystem level. NICM also includes the ability to perform cost by analogy as well as joint confidence level (JCL) analysis. The latest version of NICM, Version VI, was released in Spring 2014. This paper will focus on the new features released with NICM VI, which include: 1) The NICM-E cost estimating relationship, which is applicable for instruments flying on Explorer-like class missions; 2) The new cluster analysis ability which, alongside the results of the parametric cost estimation for the users instrument, also provides a visualization of the users instruments similarity to previously flown instruments; and 3) includes new cost estimating relationships for in-situ instruments.

A satellite mortality study to support space systems lifetime prediction

Estimating the operational lifetime of satellites and spacecraft is a complex process. Operational lifetime can differ from mission design lifetime for a variety of reasons. Unexpected mortality can occur due to human errors in design and fabrication, to human errors in launch and operations, to random anomalies of hardware and software or even satellite function degradation or technology change, leading to unrealized economic or mission return. This study focuses on data collection of public information using, for the first time, a large, publically available dataset, and preliminary analysis of satellite lifetimes, both operational lifetime and design lifetime. The objective of this study is the illustration of the relationship of design life to actual lifetime for some representative classes of satellites and spacecraft. First, a Weibull and Exponential lifetime analysis comparison is performed on the ratio of mission operating lifetime to design life, accounting for terminated and ongoing missions. Next a Kaplan-Meier survivor function, standard practice for clinical trials analysis, is estimated from operating lifetime. Bootstrap resampling is used to provide uncertainty estimates of selected survival probabilities. This study highlights the need for more detailed databases and engineering reliability models of satellite lifetime that include satellite systems and subsystems, operations procedures and environmental characteristics to support the design of complex, multi-generation, long-lived space systems in Earth orbit.

The use of cluster analysis techniques in space flight project cost risk estimation

Project cost risk is the uncertainty in final project cost, contingent on initial budget, requirements and schedule. For a proposed mission, a dynamic simulation model relying for some of its input on a simple risk elicitation is used to identify and quantify systemic cost risk. In addition, we display in a simple tree the relationship of the new proposed mission to historical missions. The tree is constructed by cluster analysis, a data mining technique for identifying similar objects based on a simple measure of the similarity between two miss ions. The cost history of missions identified by cluster analysis as closest to the proposed mission are used to modify the systemic cost risk. A case study demonstrates this approach to the early evaluation of total cost risk for proposed spaceflight proj ects.