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.     

Towards Synthesis of Solar Wind and Geomagnetic Scaling Exponents: A Fractional Lévy Motion Model

Mandelbrot introduced the concept of fractals to describe the non-Euclidean shape of many aspects of the natural world. In the time series context, he proposed the use of fractional Brownian motion (fBm) to model non-negligible temporal persistence, the ‘Joseph Effect’; and Lévy flights to quantify large discontinuities, the ‘Noah Effect’. In space physics, both effects are manifested in the intermittency and long-range correlation which are by now well-established features of geomagnetic indices and their solar wind drivers. In order to capture and quantify the Noah and Joseph effects in one compact model, we propose the application of the ‘bridging’ fractional Lévy motion (fLm) to space physics. We perform an initial evaluation of some previous scaling results in this paradigm, and show how fLm can model the previously observed exponents. We suggest some new directions for the future.     

Vertical distribution of disequilibrium species in Jupiter's troposphere

Sources of organic matter and inorganic tracers on Jupiter, including solar UV photolysis, lightning discharges, and convective quenching of hot gases from the lower atmosphere, are reviewed in light of Earth-based and Voyager data with the purpose of predicting the tropospheric steady-state abundances and vertical distributions of HCN, CH₂O, and other species.It is concluded that a steady-state mole fraction of HCN in the Jovian troposphere of only 10^-12 could be maintained by vertical transport of hot gases from the deep atmosphere. The observed HCN abundance (roughly X_HCN = 10^-9) appears to be due to photochemical reactions.After HCN, the most abundant organic disequilibrium species in the troposphere is probably C₂H₆, derived from direct photolysis of CH₄ at high altitudes, with a mole fracton of 10^-10 at the H₂O cloud level. Inorganic tracers of disequilibrium processes are also briefly summarized.     

Post: Polar stratospheric telescope

The tropopause, typically at 16 to 18 km altitude at the lower latitudes, dips to 8 km in the polar regions. This makes the cold, dry and nonturbulent lower stratosphere accessible to tethered aerostats. Tethered aerostats can fly as high as 12 km and are extremely reliable, lasting for many years. In contrast to free-flying balloons, they can stay on station for weeks at a time, and payloads can be safely recovered for maintenance and adjustment and relaunched in a matter of hours. We propose to use such a platform, located first in the Arctic (near Fairbanks, Alaska) and, potentially, later in the Antarctic, to operate a new technology 6-meter, diluted aperture telescope with diffraction-limited performance in the near infrared. Thanks to the low ambient temperature (220 K), thermal emission from the optics is of the same order as that of the zodiacal light in the 2 to 3 micron band. Since this wavelength interval is the darkest part of the zodiacal light spectrum from optical wavelengths to 100 microns, the combination of high resolution images and a very dark sky make it the spectral region of choice for observing the redshifted light from galaxies and clusters of galaxies at moderate to high redshifts.Affiliated to the Astrophysics Division, Space Science Department, European Space Agency     

Development of a high pressure-differential turbine blade cooling system

A convective-film system of high pressure-differential turbine blade cooling is presented. The results of calculating the thermal-hydraulic blade state using the KW3D software are given.     

Lunar Reconnaissance Orbiter (LRO): Observations for Lunar Exploration and Science

The Lunar Reconnaissance Orbiter (LRO) was implemented to facilitate scientific and engineering-driven mapping of the lunar surface at new spatial scales and with new remote sensing methods, identify safe landing sites, search for in situ resources, and measure the space radiation environment. After its successful launch on June 18, 2009, the LRO spacecraft and instruments were activated and calibrated in an eccentric polar lunar orbit until September 15, when LRO was moved to a circular polar orbit with a mean altitude of 50 km. LRO will operate for at least one year to support the goals of NASA’s Exploration Systems Mission Directorate (ESMD), and for at least two years of extended operations for additional lunar science measurements supported by NASA’s Science Mission Directorate (SMD). LRO carries six instruments with associated science and exploration investigations, and a telecommunications/radar technology demonstration. The LRO instruments are: Cosmic Ray Telescope for the Effects of Radiation (CRaTER), Diviner Lunar Radiometer Experiment (DLRE), Lyman-Alpha Mapping Project (LAMP), Lunar Exploration Neutron Detector (LEND), Lunar Orbiter Laser Altimeter (LOLA), and Lunar Reconnaissance Orbiter Camera (LROC). The technology demonstration is a compact, dual-frequency, hybrid polarity synthetic aperture radar instrument (Mini-RF). LRO observations also support the Lunar Crater Observation and Sensing Satellite (LCROSS), the lunar impact mission that was co-manifested with LRO on the Atlas V (401) launch vehicle. This paper describes the LRO objectives and measurements that support exploration of the Moon and that address the science objectives outlined by the National Academy of Science’s report on the Scientific Context for Exploration of the Moon (SCEM). We also describe data accessibility by the science and exploration community.     

The Dawn Ion Propulsion System

Dawn??s ion propulsion system (IPS) is the most advanced propulsion system ever built for a deep-space mission. Aside from the Mars gravity assist it provides all of the post-launch ??V required for the mission including the heliocentric transfer to Vesta, orbit capture at Vesta, transfer to various Vesta science orbits, escape from Vesta, the heliocentric transfer to Ceres, orbit capture at Ceres, and transfer to the different Ceres science orbits. The ion propulsion system provides a total ??V of nearly 11 km/s, comparable to the ??V provided by the 3-stage launch vehicle, and a total impulse of 1.2×10⁷ N?s.     

Assessment of gas temperature fluctuations in the GTE combustion chamber exit section at generalizing experimental data on fuel combustion efficiency

It is suggested that gas composition at every point of the combustion chamber exit section be characterized by the temperature values T _i (“ideal” temperature) corresponding to the local values of the air-to-fuel coefficient α _i under complete fuel combustion (ν _comb ≈ 1). It is assumed that the values of T _i are distributed over the exit section area (gas mass) linearly and the values of T _imax and T _imin can be determined by the experimental data on the gas temperature fields in the combustion chambers. The distribution of temperatures T _i is used when it is necessary to generalize the experimental data on fuel combustion efficiency in GTE combustion chambers.     

The James Webb Space Telescope

The James Webb Space Telescope (JWST) is a large (6.6 m), cold (<50 K), infrared (IR)-optimized space observatory that will be launched early in the next decade into orbit around the second Earth–Sun Lagrange point. The observatory will have four instruments: a near-IR camera, a near-IR multiobject spectrograph, and a tunable filter imager will cover the wavelength range, 0.6 < ; < 5.0 μ m, while the mid-IR instrument will do both imaging and spectroscopy from 5.0 < ; < 29 μ m.The JWST science goals are divided into four themes. The key objective of The End of the Dark Ages: First Light and Reionization theme is to identify the first luminous sources to form and to determine the ionization history of the early universe. The key objective of The Assembly of Galaxies theme is to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present day. The key objective of The Birth of Stars and Protoplanetary Systems theme is to unravel the birth and early evolution of stars, from infall on to dust-enshrouded protostars to the genesis of planetary systems. The key objective of the Planetary Systems and the Origins of Life theme is to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for the origins of life in those systems. Within these themes and objectives, we have derived representative astronomical observations.To enable these observations, JWST consists of a telescope, an instrument package, a spacecraft, and a sunshield. The telescope consists of 18 beryllium segments, some of which are deployed. The segments will be brought into optical alignment on-orbit through a process of periodic wavefront sensing and control. The instrument package contains the four science instruments and a fine guidance sensor. The spacecraft provides pointing, orbit maintenance, and communications. The sunshield provides passive thermal control. The JWST operations plan is based on that used for previous space observatories, and the majority of JWST observing time will be allocated to the international astronomical community through annual peer-reviewed proposal opportunities.