Mission success regulations,their effect on ELV launch success and the applicability to regulating commercial human spaceflight

As the human spaceflight industry grows the agencies charged with regulating that industry meet significant challenges. An improvement in launch success would improve the safety for the crew and passengers of a commercial human spaceflight. With respect to ELV launches, NASA's regulations over civil launches are mission success oriented while commercial launches regulated by the FAA-AST, the agency that will also be charged with human spaceflight, takes a more public safety oriented stance. A comparison of the launch success between civil and commercial launches is used to inform the decision on whether or not mission success would be an appropriate regulatory stance for the FAA-AST. The results show that there is no significant difference in launch success between civil and commercial ELV launches. Because of this and because the industry is wary of over regulation, there is indication that a mission success oriented stance might not be appropriate for regulating commercial human spaceflight.     

A multi-disciplinary plan for easier access, management, and analysis of science data

NASA’s COST LESS Team is pursuing strategies to reduce the cost and complexity of planning and executing space missions. The team’s technical goal is to reverse the trend of constructing unique solutions for similar problems. To this end, the team is exploring ways to represent mission functionality in terms of building blocks and is discovering approaches that could accommodate the same building blocks for seemingly disparate activities, such as organizing processed telemetry data, controlling onboard experiments, searching science archives, reducing and presenting information to science users, and supporting educational outreach. Reusable object technology (UOT), a research undertaking by the authors, is showing promise in recognizing similarities in functions which were previously viewed as unique because they appeared in different programs or mission phases. Since UOT is aimed at being implementation independent (i.e. the function performed could be accomplished manually, by an automated process, by a specialized instrument, etc.), no premature judgment for automation or autonomy need be made. In this paper, the authors attempt to strike a balance between theory and reality as they describe UOT, including its beginnings, its underpinning, its utility, and its potential for achieving substantive reductions in cost and complexity for the Agency’s space programs. The authors discuss their collaboration with the Center for EUV Astrophysics, University of California, Berkeley to reduce the cost and complexity of science investigations. Their multi-disciplinary plan incorporates both UOT and a complementary technology introduced in this paper, called interactive archives.     

First results from UVCS/SOHO

We present here the first results obtained by the Ultraviolet Coronagraph Spectrometer (UVCS) operating on board the SOHO satellite. The UVCS started to observe the extended corona at the end of January 1996; it routinely obtains coronal spectra in the 1145 Å – 1287 Å, 984 Å – 1080 Å ranges, and intensity data in the visible continuum. Through the composition of slit images it also produces monocromatic images of the extended corona. The performance of the instrument is excellent and the data obtained up to now are of great interest. We briefly describe preliminary results concerning polar coronal holes, streamers and a coronal mass ejection, in particular: the very large r.m.s. velocities of ions in polar holes (hundreds km/sec for OVI and MgX); the puzzling difference between the HI Ly- image and that in the OVI resonance doublet, for most streamers; the different signatures of the core and external layers of the streamers in the width of the ion lines and in the OVI doublet ratio, indicating larger line-of-sight (l.o.s.) and outflow velocities in the latter.     

线切割放电加工助航空客户飞得更高

过去20年里线切割的切割速度几乎增加了5倍,粗加工的直线切割速度可达600mm2/min;对大多数复杂型腔的加工速度较慢,但也可达到约350mm2/min。通过优化粗加工和精加工的策略,变质层几乎为零,同时没有材料或微观结构的变化,放电脉冲的控制特别是脉冲的持续时间和频率是达到最小损伤的关键因素。     

The Dawn Gravity Investigation at Vesta and Ceres

The objective of the Dawn gravity investigation is to use high precision X-band Doppler tracking and landmark tracking from optical images to measure the gravity fields of Vesta and Ceres to a half-wavelength surface resolution better than 90-km and 300-km, respectively. Depending on the Doppler tracking assumptions, the gravity field will be determined to somewhere between harmonic degrees 15 and 25 for Vesta and about degree 10 for Ceres. The gravity fields together with shape models determined from Dawn??s framing camera constrain models of the interior from the core to the crust. The gravity field is determined jointly with the spin pole location. The second degree harmonics together with assumptions on obliquity or hydrostatic equilibrium may determine the moments of inertia.     

Collisionless Shocks in Partly Ionized Plasma with Cosmic Rays: Microphysics of Non-thermal Components

In this review we discuss some observational aspects and theoretical models of astrophysical collisionless shocks in partly ionized plasma with the presence of non-thermal components. A specific feature of fast strong collisionless shocks is their ability to accelerate energetic particles that can modify the shock upstream flow and form the shock precursors. We discuss the effects of energetic particle acceleration and associated magnetic field amplification and decay in the extended shock precursors on the line and continuum multi-wavelength emission spectra of the shocks. Both Balmer-type and radiative astrophysical shocks are discussed in connection to supernova remnants interacting with partially neutral clouds. Quantitative models described in the review predict a number of observable line-like emission features that can be used to reveal the physical state of the matter in the shock precursors and the character of nonthermal processes in the shocks. Implications of recent progress of gamma-ray observations of supernova remnants in molecular clouds are highlighted.     

Single Degenerate Models for Type Ia Supernovae: Progenitor’s Evolution and Nucleosynthesis Yields

We review how the single degenerate models for Type Ia supernovae (SNe Ia) works. In the binary star system of a white dwarf (WD) and its non-degenerate companion star, the WD accretes either hydrogen-rich matter or helium and undergoes hydrogen and helium shell-burning. We summarize how the stability and non-linear behavior of such shell-burning depend on the accretion rate and the WD mass and how the WD blows strong wind. We identify the following evolutionary routes for the accreting WD to trigger a thermonuclear explosion. Typically, the accretion rate is quite high in the early stage and gradually decreases as a result of mass transfer. With decreasing rate, the WD evolves as follows: (1) At a rapid accretion phase, the WD increase its mass by stable H burning and blows a strong wind to keep its moderate radius. The wind is strong enough to strip a part of the companion star’s envelope to control the accretion rate and forms circumstellar matter (CSM). If the WD explodes within CSM, it is observed as an “SN Ia-CSM”. (X-rays emitted by the WD are absorbed by CSM.) (2) If the WD continues to accrete at a lower rate, the wind stops and an SN Ia is triggered under steady-stable H shell-burning, which is observed as a super-soft X-ray source: “SN Ia-SSXS”. (3) If the accretion continues at a still lower rate, H shell-burning becomes unstable and many flashes recur. The WD undergoes recurrent nova (RN) whose mass ejection is smaller than the accreted matter. Then the WD evolves to an “SN Ia-RN”. (4) If the companion is a He star (or a He WD), the accretion of He can trigger He and C double detonations at the sub-Chandrasekhar mass or the WD grows to the Chandrasekhar mass while producing a He-wind: “SN Ia-He CSM”. (5) If the accreting WD rotates quite rapidly, the WD mass can exceed the Chandrasekhar mass of the spherical WD, which delays the trigger of an SN Ia. After angular momentum is lost from the WD, the (super-Chandra) WD contracts to become a delayed SN Ia. The companion star has become a He WD and CSM has disappeared: “SN Ia-He WD”. We update nucleosynthesis yields of the carbon deflagration model W7, delayed detonation model WDD2, and the sub-Chandrasekhar mass model to provide some constraints on the yields (such as Mn) from the comparison with the observations. We note the important metallicity effects on ⁵⁸Ni and ⁵⁵Mn.     

Application of mobile-IP to space and aeronautical networks

NASA is interested in applying Mobile Internet Protocol (mobile-IP) technologies to its space and aeronautics programs. In particular, mobile-IP will play a major role in the Advanced Aeronautic Transportation Technology (AATT), the Weather Information Communication (WINCOMM) and the Small Aircraft Transportation System; (SATS) aeronautics programs. This paper describes mobile-IP and mobile-routers-in particular, the features, capabilities, and initial performance of the mobile-router is presented. The application of mobile-router technology to NASA's space and aeronautics programs is also discussed     

Management of transponder resources in mobile satellite systems

Allocation of L-band spectrum for land mobile satellite (MSAT) services in Mobile-WARC-87 paves the way for the introduction of such services in the early 1990s. An overview of the proposed network architecture of the Canadian MSAT network is presented. Management of transponder resources, i.e. power, bandwidth, and spot-beam antennas, which poses a set of unique and significant problems in the design and operation of MSAT networks, is addressed. The three-level hierarchical approach used by the Canadian network is described, and the technical requirements for solving the above problems are identified. The two upper levels employ reconfigurable fixed assignment for allocating transponders to antenna spot beams, and transponder power and bandwidth to different services. The lowest level employs demand assignment and packet multiple access protocols for resource sharing among different subscribers. Uncoupling the resource management problems into manageable portions reduces the complexity and enhances the robustness of the network     

The Mercury Dual Imaging System on the MESSENGER Spacecraft

The Mercury Dual Imaging System (MDIS) on the MESSENGER spacecraft will provide critical measurements tracing Mercury’s origin and evolution. MDIS consists of a monochrome narrow-angle camera (NAC) and a multispectral wide-angle camera (WAC). The NAC is a 1.5° field-of-view (FOV) off-axis reflector, coaligned with the WAC, a four-element refractor with a 10.5° FOV and 12-color filter wheel. The focal plane electronics of each camera are identical and use a 1,024×1,024 Atmel (Thomson) TH7888A charge-coupled device detector. Only one camera operates at a time, allowing them to share a common set of control electronics. The NAC and the WAC are mounted on a pivoting platform that provides a 90° field-of-regard, extending 40° sunward and 50° anti-sunward from the spacecraft +Z-axis—the boresight direction of most of MESSENGER’s instruments. Onboard data compression provides capabilities for pixel binning, remapping of 12-bit data into 8 bits, and lossless or lossy compression. MDIS will acquire four main data sets at Mercury during three flybys and the two-Mercury-solar-day nominal mission: a monochrome global image mosaic at near-zero emission angles and moderate incidence angles, a stereo-complement map at off-nadir geometry and near-identical lighting, multicolor images at low incidence angles, and targeted high-resolution images of key surface features. These data will be used to construct a global image base map, a digital terrain model, global maps of color properties, and mosaics of high-resolution image strips. Analysis of these data will provide information on Mercury’s impact history, tectonic processes, the composition and emplacement history of volcanic materials, and the thickness distribution and compositional variations of crustal materials. This paper summarizes MDIS’s science objectives and technical design, including the common payload design of the MDIS data processing units, as well as detailed results from ground and early flight calibrations and plans for Mercury image products to be generated from MDIS data.