Applications of Small Satellites for Defense Space Communication Systems and Technology Development: Pegasus Flight-2 and the Launch of Microsat

DARPA\u27s seven Microsats were placed into orbit on the second flight of the Pegasus. The Microsat program objective is to assess the tactical utility of small, low-cost communications satellites. This paper describes the changes made to the Pegasus since its first flight, provides an overview of the Microsat demonstration program, and outlines the preliminary results of the Pegasus launch. Finally, the near-term Army and Navy demonstration plans for Microsat are discussed

Overview of the SCD1/Pegasus Mission

An overview of the third operational Pegasus mission, carrying the Brazilian Satelite de Coleta de Dados 1 (SCD1) satellite is presented. Developed by INPE, the 250 Ib, spin stabilized satellite will perform real time repeating of environmental data gathered by automatic ground stations throughout Brazil. The target orbit, 405 nm (750 km) at 25 deg inclination, was chosen to provide coverage of the entire Brazilian territory. A review of the SCD1 design, development and testing highlights the effectiveness of lightsat philosophy complemented by pc-based check-out and control equipment. A six month schedule from go-ahead to launch was achieved in spite of delays. Simple and effective hardware and interfaces allowed a straightforward, efficient and relatively short payload integration and test process. Mission planning addressed complex operations, including a cross country ferry flight, ground operations significantly removed from the control room, and a first time east coast Pegasus launch from a new range. A review of the flight results includes flight environments and final Pegasus guidance and performance results

Operating-system support for distributed multimedia

Multimedia applications place new demands upon processors, networks and operating systems. While some network designers, through ATM for example, have considered revolutionary approaches to supporting multimedia, the same cannot be said for operating systems designers. Most work is evolutionary in nature, attempting to identify additional features that can be added to existing systems to support multimedia. Here we describe the Pegasus project's attempt to build an integrated hardware and operating system environment from\ud the ground up specifically targeted towards multimedia

Global crop yield response to extreme heat stress under multiple climate change futures

Extreme heat stress during the crop reproductive period can be critical for crop productivity. Projected changes in the frequency and severity of extreme climatic events are expected to negatively impact crop yields and global food production. This study applies the global crop model PEGASUS to quantify, for the first time at the global scale, impacts of extreme heat stress on maize, spring wheat and soybean yields resulting from 72 climate change scenarios for the 21st century. Our results project maize to face progressively worse impacts under a range of RCPs but spring wheat and soybean to improve globally through to the 2080s due to CO2 fertilization effects, even though parts of the tropic and sub-tropic regions could face substantial yield declines. We find extreme heat stress at anthesis (HSA) by the 2080s (relative to the 1980s) under RCP 8.5, taking into account CO2 fertilization effects, could double global losses of maize yield (ΔY = −12.8 ± 6.7% versus − 7.0 ± 5.3% without HSA), reduce projected gains in spring wheat yield by half (ΔY = 34.3 ± 13.5% versus 72.0 ± 10.9% without HSA) and in soybean yield by a quarter (ΔY = 15.3 ± 26.5% versus 20.4 ± 22.1% without HSA). The range reflects uncertainty due to differences between climate model scenarios; soybean exhibits both positive and negative impacts, maize is generally negative and spring wheat generally positive. Furthermore, when assuming CO2 fertilization effects to be negligible, we observe drastic climate mitigation policy as in RCP 2.6 could avoid more than 80% of the global average yield losses otherwise expected by the 2080s under RCP 8.5. We show large disparities in climate impacts across regions and find extreme heat stress adversely affects major producing regions and lower income countries

Experiments to increase the used Energy with the PEGASUS Railgun

The French-German Research Institute (ISL) has several railguns installed, the largest of these is the PEGASUS accelerator. It is a 6m long, 4x4 cm2 caliber distributed energy supply (DES) railgun. It has a 10 MJ capacitor bank as energy supply attached to it. In the past, this installation was used to accelerate projectiles with a mass of about 300 g to velocities up to 2500 m/s. In the ongoing investigation, it is attempted to accelerate heavier projectiles to velocities above 2000m/s. For this a new type of projectile including a payload section was developed. In this paper the results of the experiments with payload projectiles using a primary energy between 3.8 MJ and 4.8 MJ are discussed.Comment: 6 pages, 11 figures, Submitted to IEEE Transactions on Plasma Science, Special Issue -- Pulsed Power Science & Technology 201

Aircraft Analysis Using the Layered and Extensible Aircraft Performance System (LEAPS)

The Layered and Extensible Aircraft Performance System (LEAPS) is a new air- craft analysis tool being developed by members of the Aeronautics Systems Analysis Branch (ASAB) and the Vehicle Analysis Branch (VAB) at NASA Langley Research Center. LEAPS will enable the analysis of advanced aircraft concepts and architec- tures that include electric and hybrid-electric propulsion systems. The development of LEAPS is motivated by the analysis gaps found in traditional aircraft analysis tools such as the Flight Optimization System (FLOPS). FLOPS has been the tool of choice of the ASAB for over 30 years and has proven to be a reliable analysis tool for conventional aircraft. However, FLOPS is not suitable to analyze the cur- rent unconventional vehicles that are of interest to industry, government agencies, and academia. In contrast, LEAPS is being developed with a flexible architecture that leverages new analysis methodologies that will enable the analysis of unconven- tional aircraft. This paper presents the first complete working version of LEAPS by showing the analysi at include fuel-based and hybrid-electric conceptual aircraft

A Taxonomy of Workflow Management Systems for Grid Computing

With the advent of Grid and application technologies, scientists and engineers are building more and more complex applications to manage and process large data sets, and execute scientific experiments on distributed resources. Such application scenarios require means for composing and executing complex workflows. Therefore, many efforts have been made towards the development of workflow management systems for Grid computing. In this paper, we propose a taxonomy that characterizes and classifies various approaches for building and executing workflows on Grids. We also survey several representative Grid workflow systems developed by various projects world-wide to demonstrate the comprehensiveness of the taxonomy. The taxonomy not only highlights the design and engineering similarities and differences of state-of-the-art in Grid workflow systems, but also identifies the areas that need further research.Comment: 29 pages, 15 figure