ALBERT

Description: The successful flight of the Inflatable Reentry Vehicle Experiment (IRVE)-3 has further demonstrated the potential value of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology. This technology development effort is funded by NASA's Space Technology Mission Directorate (STMD) Game Changing Development Program (GCDP). This paper provides an overview of a multi-year HIAD technology development effort, detailing the projects completed to date and the additional testing planned for the future.

Description: Ground magnetic field perturbations recorded by the CANOPUS magnetometer network in the 7 to 13 MLT sector are used to examine how reconfigurations of the dayside polar ionospheric flow take place in response to north-south changes of the IMF. During the 6-h interval in question, IMF Bz oscillates between +/- 7 nT with about a 1-h period. Corresponding variations in the ground magnetic disturbance are observed which we infer are due to changes in ionospheric flow. Cross correlation of the data obtained from two ground stations at 73.5 deg magnetic latitude, but separated by about 2 hours in MLT, shows that changes in the flow are initiated in the prenoon sector (about 10 MLT) and then spread outward toward dawn and dusk with a phase speed of about 5 km/s over the longitude range about 8 to 12 MLT, slowing to about 2 km/s outside this range. Cross correlating the data from these ground stations with IMP 8 IMF Bz records produces a MLT variation in the ground response delay relative to the IMF which is compatible with these deduced phase speeds.

Description: This paper presents a representative example of an enhancement in energetic ion flux associated with the International Sun-Earth Explorer 3 (ISEE 3) spacecraft's encounter with a traveling compression region (TCR). Data from the energetic particle anisotropy spectrometer (EPAS) instrument on ISEE 3 are studied, along with magnetic field data from the vector helium magnetometer. It is concluded that the ion enhancements seen are spatial in nature, thus supporting the idea that TCRs are the lobe signatures of plasmoids moving along the magnetotail, away from earth.

Description: The Ariel 4 satellite was designed to study wave-particle phenomena in the magnetosphere by measuring the electromagnetic wave fields over a wide frequency range and the fluxes and pitch angle distributions of energetic particles. We describe here the results of a preliminary study of the various v.l.f./e.l.f. electromagnetic wave phenomena which are observed. These include man-made signals from v.l.f. transmitters, impulsive noise originating in thunderstorms and emissions arising from magnetospheric energetic charged particles.

Description: Magnetotail observations from the ISEE 3 distant (1983) tail mission taken during the Coordinated Data Analysis Workshop 8 (CDAW 8) A and G events are investigated. The ISEE 3 magnetic field, plasma, and energetic particle measurements taken in these two plasmoids have been analyzed and compared with various equilibrium structures and propagating waves/tail oscillation modes. Results indicate general agreement with either the closed-loop (Hones, 1977) or very small pitch angle flux rope (Hughes and Sibeck, 1987; Birn et al., 1989) models of plasmoid structure and poorer agreement with other hypotheses. Calculations based upon typical plasmoid and tail parameters are presented, indicating that the J and B force associated with the disconnected lobe field lines may be sufficient to accelerate plasmoids up to the speeds observed by ISEE 3. Overall, the energy expended in accelerating the plasmoids down the tail appears comparable to that dissipated in the inner magnetosphere and ionosphere. The study produces strong evidence in favor of the plasmoid model of substorm tail dynamics.

Description: Maintaining contamination certification of multi-mission flight hardware is an innovative approach to controlling mission costs. Methods for assessing ground induced degradation between missions have been employed by the Hubble Space Telescope (HST) Project for the multi-mission (servicing) hardware. By maintaining the cleanliness of the hardware between missions, and by controlling the materials added to the hardware during modification and refurbishment both project funding for contamination recertification and schedule have been significantly reduced. These methods will be discussed and HST hardware data will be presented.

Description: The Earth Observing System (EOS) AM-1 spacecraft for NASA's Mission to Planet Earth is scheduled to be launched on an Atlas IIAS vehicle in June of 1998. One concern is that the instruments on the EOS spacecraft are sensitive to the shock-induced vibration produced when the spacecraft separates from the launch vehicle. By employing unique statistical analysis to the available ground test shock data, the NASA Lewis Research Center found that shock-induced vibrations would not be as great as the previously specified levels of Lockheed Martin. The EOS pyroshock separation testing, which was completed in 1997, produced a large quantity of accelerometer data to characterize the shock response levels at the launch vehicle/spacecraft interface. Thirteen pyroshock separation firings of the EOS and payload adapter configuration yielded 78 total measurements at the interface. The multiple firings were necessary to qualify the newly developed Lockheed Martin six-hardpoint separation system. Because of the unusually large amount of data acquired, Lewis developed a statistical methodology to predict the maximum expected shock levels at the interface between the EOS spacecraft and the launch vehicle. Then, this methodology, which is based on six shear plate accelerometer measurements per test firing at the spacecraft/launch vehicle interface, was used to determine the shock endurance specification for EOS. Each pyroshock separation test of the EOS spacecraft simulator produced its own set of interface accelerometer data. Probability distributions, histograms, the median, and higher order moments (skew and kurtosis) were analyzed. The data were found to be lognormally distributed, which is consistent with NASA pyroshock standards. Each set of lognormally transformed test data produced was analyzed to determine if the data should be combined statistically. Statistical testing of the data's standard deviations and means (F and t testing, respectively) determined if data sets were significantly different at a 95-percent confidence level. If two data sets were found to be significantly different, these families of data were not combined for statistical purposes. This methodology produced three separate statistical data families of shear plate data. For each population, a P99.1/50 (probability/confidence) per-separation-nut firing level was calculated. By using the binomial distribution, Lewis researchers determined that this pernut firing level was equivalent to a P95/50 per-flight confidence level. The overall envelope of the per-flight P95/50 levels led to Lewis' recommended EOS interface shock endurance specification. A similar methodology was used to develop Lewis' recommended EOS mission assurance levels. The available test data for the EOS mission are significantly larger than for a normal mission, thus increasing the confidence level in the calculated expected shock environment. Lewis significantly affected the EOS mission by properly employing statistical analysis to the data. This analysis prevented a costly requalification of the spacecraft's instruments, which otherwise would have been exposed to significantly higher test levels.

Description: A survey of theoretical and experimental research on the origin and characteristics of low-frequency hydromagnetic (HM) waves in the magnetosphere is presented, with a focus on advances in theory made in the last ten years. Basic wave theory and a collisionless plasma theory are applied to the magnetosphere as a HM system. Continuous energy sources are considered, such as the Kelvin-Helmholtz instability, the ring-current plasma, and drift instabilities. Other topics discussed include the theory of inhomogeneous HM waves, signal behavior in atmosphere and ionosphere, Alfven waves and ionosphere-magnetosphere coupling, Pi2 signals, damping, pulsating aurora, heavy-ion scattering, and standing waves in high-speed flows (like the wake phenomena caused on Jupiter by the passing of Io, observed by Voyager 1).

Description: Direct measurements of the spatial extent of the resonant hydromagnetic waves associated with Pc 4 and 5 magnetic pulsations made by the closely spaced ISEE 1 and 2 satellites are presented together with ISEE 1 determinations of the harmonic of the resonant waves. The use of two satellites in similar orbits, which makes it possible to distinguish between spatial and temporal features, has shown the resonant region widths to extend over about 0.2 to 1.6 L shells for three events detected on the dayside between L = 4 and L = 7. The two events for which plasma density data was available occurred at plasma density gradients in the vicinity of the plasmapause. The standing wave harmonic was determined by the combination of two techniques: the comparison of the observed wave period with that predicted by standing wave theory, and the comparison of the phases of the observed wave electric and magnetic field. The two events analyzed are found to be second harmonic oscillations, suggesting internal generation in the magnetosphere by a bounce resonant mechanism.

Description: System albedo, an important climatological and environmental parameter, is considered. Some of the problems and assumptions involved in evaluating albedo from satellite data are discussed. Clear-sky and cloud albedos over the United Kingdom and parts of northwest Europe are treated. Consideration is given to the spectral, temporal, and spatial variations and the effect of averaging. The implications of these results for those using and archiving albedo values and for future monitoring of system albedo are discussed. Normalization is of especial importance since this correction alters many albedo values. The pronounced difference in spectral albedo of the two visible channels reemphasizes the problem of attempting to calculate integrated albedo values from meteorological satellite data. The assumption of isotropic reflection is seen to be invalid, hindering the computation of accurate albedo values.