Analysis of the flight dynamics of the Solar Maximum Mission (SMM) off-sun scientific pointing

Algorithms are presented which were created and implemented by the Goddard Space Flight Center's (GSFC's) Solar Maximum Mission (SMM) attitude operations team to support large-angle spacecraft pointing at scientific objectives. The mission objective of the post-repair SMM satellite was to study solar phenomena. However, because the scientific instruments, such as the Coronagraph/Polarimeter (CP) and the Hard X ray Burst Spectrometer (HXRBS), were able to view objects other than the Sun, attitude operations support for attitude pointing at large angles from the nominal solar-pointing attitudes was required. Subsequently, attitude support for SMM was provided for scientific objectives such as Comet Halley, Supernova 1987A, Cygnus X-1, and the Crab Nebula. In addition, the analysis was extended to include the reverse problem, computing the right ascension and declination of a body given the off-Sun angles. This analysis led to the computation of the orbits of seven new solar comets seen in the field-of-view (FOV) of the CP. The activities necessary to meet these large-angle attitude-pointing sequences, such as slew sequence planning, viewing-period prediction, and tracking-bias computation are described. Analysis is presented for the computation of maneuvers and pointing parameters relative to the SMM-unique, Sun-centered reference frame. Finally, science data and independent attitude solutions are used to evaluate the large-angle pointing performance

Fixed-head star tracker magnitude calibration on the solar maximum mission

The sensitivity of the fixed-head star trackers (FHSTs) on the Solar Maximum Mission (SMM) is defined as the accuracy of the electronic response to the magnitude of a star in the sensor field-of-view, which is measured as intensity in volts. To identify stars during attitude determination and control processes, a transformation equation is required to convert from star intensity in volts to units of magnitude and vice versa. To maintain high accuracy standards, this transformation is calibrated frequently. A sensitivity index is defined as the observed intensity in volts divided by the predicted intensity in volts; thus, the sensitivity index is a measure of the accuracy of the calibration. Using the sensitivity index, analysis is presented that compares the strengths and weaknesses of two possible transformation equations. The effect on the transformation equations of variables, such as position in the sensor field-of-view, star color, and star magnitude, is investigated. In addition, results are given that evaluate the aging process of each sensor. The results in this work can be used by future missions as an aid to employing data from star cameras as effectively as possible

Micromechanical Properties of Injection-Molded Starch–Wood Particle Composites

The micromechanical properties of injection molded starch–wood particle composites were investigated as a function of particle content and humidity conditions. The composite materials were characterized by scanning electron microscopy and X-ray diffraction methods. The microhardness of the composites was shown to increase notably with the concentration of the wood particles. In addition,creep behavior under the indenter and temperature dependence were evaluated in terms of the independent contribution of the starch matrix and the wood microparticles to the hardness value. The influence of drying time on the density and weight uptake of the injection-molded composites was highlighted. The results revealed the role of the mechanism of water evaporation, showing that the dependence of water uptake and temperature was greater for the starch–wood composites than for the pure starch sample. Experiments performed during the drying process at 70°C indicated that the wood in the starch composites did not prevent water loss from the samples.Peer reviewe

Integrating acoustics engineering and soundscape design for an urban park: a case study

A new urban park is proposed in the centre of Stockton-on-Tees, England. One of the design’s features is the incorporation of a road, which will be converted from dual to single carriageway. How will the road traffic noise affect the soundscape for the users of the various parks spaces? A combination of traditional methods such as noise propagation modelling and newly developed soundscape assessment and analysis tools were used to answer this question. This approach was able to identify the biggest acoustic risks for the current design, and propose potential improvements for the sonic environment. The challenges encountered with this novel practical application of the soundscape method in a commercial context are discussed

Flexible bimetal and piezoelectric based thermal to electrical energy converters

cited By 4International audienceA new approach to thermal energy harvesting is presented in this paper. The devices we fabricate are composed of thermal bimetals and piezoelectric membranes. Bimetals that show a snapping behavior when heated are used. When brought to a predetermined temperature, a bimetal snaps abruptly from one position to another. In this step a thermal to mechanical conversion takes place. The provided mechanical energy is then converted into electricity by a piezoelectric membrane. When shocked by the bimetal, the piezoelectric material provides voltage pulses that can be recovered with the help of an energy harvesting circuit. With this approach we have managed to build thin devices that are assembled into matrixes on a flexible substrate, and work at temperatures close to ambient. The key point of their functioning is their intrinsic ability to keep a high temperature gradient when heated and thus work without a heat sink. This is a substantial advantage over the thermal harvesters based on Seebeck effect that need a bulky heat sink for optimal performance. Pulse frequencies of 2.4 Hz have been reached, with an electrical energy per pulse up to 31 μJ. The mechanical energy per cycle delivered by a bimetal is bigger and can reach 770 μJ for a 3 °C temperature difference operation. These results have been obtained while cooling with ambient air, without a heat sink. The main characteristics of our devices and ways to improve the performance are discussed in this paper. © 2014 Elsevier B.V