Analysis of total visual and CCD V-broadband observations of Comet C/1995 O1 (Hale-Bopp): 1995–2001

We developed a general method for determination of water production rates from groundbased visual observations and applied it to Comet Hale–Bopp. Our main objective is to extend the method to include total visual magnitude observations obtained with CCD detector and V filter in the analysis of total visual magnitudes. We compare the CCD V-broadband careful observations of Liller [Liller, W. Pre-perihelion CCD photometry of Comet 1995 O1 (Hale-Bopp). Planet. Space Sci. 45, 1505–1513, 1997; Liller, W. CCD photometry of Comet C/1995 O1 (Hale-Bopp): 1995–2000. Int. Comet Quart. 23(3), 93–97, 2001] with the total visual magnitude observations from experienced international observers found in the International Comet Quarterly (ICQ) archive. A data set of ∼400 CCD observations covering about the same 6 years time span of the ∼12,000 ICQ selected total visual magnitude observations were used in the analysis. A least-square method applied to the water production rates, yields power laws as a function of the heliocentric distances for the pre- and post-perihelion phases. The average dimension of the nucleus as well as its effective active area is determined and compared with values published in the literature.     

Bioelectrochemical degradation of urea at platinized boron doped diamond electrodes for bioregenerative systems

The recovery of potable water from space mission wastewater is critical for the life support and environmental health of crew members in long-term missions. NASA estimates reveal that at manned space missions 1.91 kg/person day of urine is produced, with urea and various salts as its main components. In this research we explore the utilization of urease (EC 3.5.1.5, 15,000 U/g) along with a platinized boron doped diamond electrode (Pt-BDD) to degrade urea. Urea is directly degraded to nitrogen by the in situ utilization of the reaction products as a strategy to increase the amount of clean water in future space expeditions. The biochemical reaction of urease produces ammonia and carbon dioxide from urea. Thereafter, ammonia is electrooxidized at the interface of the Pt-BDD producing molecular nitrogen. The herein presented system has been proven to have 20% urea conversion efficiency. This research has potential applications for future long-term space missions since the reaction byproducts could be used for a biomass subsystem (in situ resource recovery), while generating electricity from the same process.     

DPOD2005: An extension of ITRF2005 for Precise Orbit Determination

For Precise Orbit Determination of altimetry missions, we have computed a data set of DORIS station coordinates defined for specific time intervals called DPOD2005. This terrestrial reference set is an extension of ITRF2005. However, it includes all new DORIS stations and is more reliable, as we disregard stations with large velocity formal errors as they could contaminate POD computations in the near future. About 1/4 of the station coordinates need to be defined as they do not appear in the original ITRF2005 realization. These results were verified with available DORIS and GPS results, as the integrity of DPOD2005 is almost as critical as its accuracy. Besides station coordinates and velocities, we also provide additional information such as periods for which DORIS data should be disregarded for specific DORIS stations, and epochs of coordinate and velocity discontinuities (related to either geophysical events, equipment problem or human intervention). The DPOD model was tested for orbit determination for TOPEX/Poseidon (T/P), Jason-1 and Jason-2. Test results show DPOD2005 offers improvement over the original ITRF2005, improvement that rapidly and significantly increases after 2005. Improvement is also significant for the early T/P cycles indicating improved station velocities in the DPOD2005 model and a more complete station set. Following 2005 the radial accuracy and centering of the ITRF2005-original orbits rapidly degrades due to station loss.     

Composition of solar cosmic rays

Summary The general features of the solar particle composition now seem to be clear. The two most abundant components, protons and helium nuclei, have different velocity spectra, similar, but not exactly identical rigidity spectra, and varying relative abundances. The multiply charged nuclei, on the other hand, appear to have the same spectral shape and relative abundances each time measurements are made, at least in the region from 42 to 135 MeV/nucleon. Further, these relative abundances seem to reflect those of the solar atmosphere insofar as comparison can be made. Electrons are rare, but high energy electrons are not expected to be plentiful due to the probable high rate of energy loss caused by synchrotron radiation at the sun. Energetic neutrons were also not expected in large quantity and have not been observed. Finally, there is positive evidence that very small quantities of deuterons exist, probably in an amount which is about 10^-3 or less of the proton abundance.The experimental data indicate that the propagation phenomenon is not purely rigidity dependent. Although the propagation of solar particles is still not well understood, the development of theories which take into account both the general magnetic field and the inhomogeneities in the field seem to hold some promise of explaining the experimental results. The composition data have also established important restraints which any acceleration theory must satisfy, and thereby contributed greatly to the very difficult problem of determining the acceleration mechanism.The similarity of the relative abundance of the energetic solar particles and the nuclei in the sun's photosphere suggested the possibility of having a new means of estimating the solar neon and helium abundances. This very interesting possibility will have to be explored by further testing of the composition of future solar particle events. Finally, it was seen that the composition was a very strong argument against most stars being the principal source of high energy non-solar cosmic rays, and, therefore, special sources, such as supernovae or possibly quasistellar objects, should be considered as much more likely prospects for the origin of cosmic rays.The results which have been obtained thus far on the composition of solar cosmic rays have indicated that further research in this area of study should be very rewarding and of value to many fields of physics. Further data on the composition and relative, as well as absolute, energy spectra of the various components are needed throughout many events. More experiments also should be performed to determine the properties of the rare components, deuterons, tritons, He³ nuclei, electrons, neutrons, and the heavier nuclei. When these experiments are complete, the knowledge which is needed to aid in answering the solar and astrophysical problems discussed in this review should be at hand.     

Analytical solution for continuous-time Kalman tracking filterswith colored measurement noise in frequency domain

New expressions are given for analytical solutions to the steady-state Kalman gains of the two-state exponentially correlated velocity (ECV) and the three-state exponentially correlated acceleration (ECA) tracking filters with position measurements by using spectral factorization method. The measurement colored noise model is characterized by a correlation time 1/λ. The vehicle oscillations such as wind-induced-bending is also considered in the modeling of the system which leads to the most generalized state transition matrix     

SPOT-2 and TOPEX/Poseidon precise orbit determination from DORIS doppler tracking

The French earth observation satellite SPOT-2 has served as a testbed for precise orbit determination from DORIS doppler tracking in anticipation of the TOPEX/Poseidon mission. Using the most up-to-data gravity field model, JGM-2, a radial orbit accuracy of about 2–9 cm was achieved, with an rms of fit of the tracking data of about 0.64 mm/s. Furthermore, it was found that the coordinates of the ground stations can be determined with an accuracy of the order of 2–5 cm after removal of common rotations, and translations.

Using a slightly different model for atmospheric drag, but the same gravity model, precise orbits of TOPEX/Poseidon from DORIS tracking data were determined with a radial orbit accuracy of the order of 4–5 cm, which is far within the 13 cm mission requirement. This conclusion is based on the analysis of 1-day overlap of successive 11-day orbits, and the comparisons with orbits computed from satellite laser tracking (SLR) and from the combination of SLR and DORIS tracking. Results indicate a consistency between the different orbits of 1–4 cm, 4–20 cm, and 6–13 cm in the radial, cross-track, and along-track directions, respectively. The residual rms is about 4–5 cm for SLR data and 0.56 mm/s for DORIS tracking. These numbers are roughly twice as large as the system noise levels, reflecting the fact that there are still some modeling errors left.     

Issues of exploration: human health and wellbeing during a mission to Mars.

Today, the tools are in our hands to enable us to travel away from our home planet and become citizens of the solar system. Even now, we are seriously beginning to develop the robust infrastructure that will make the 21st century the Century of Space Travel. But this bold step must be taken with due concern for the health, safety and wellbeing of future space explorers. Our long experience with space biomedical research convinces us that, if we are to deal effectively with the medical and biomedical issues of exploration, then dramatic and bold steps are also necessary in this field. We can no longer treat the human body as if it were composed of muscles, bones, heart and brain acting independently. Instead, we must lead the effort to develop a fully integrated view of the body, with all parts connected and fully interacting in a realistic way. This paper will present the status of current (2000) plans by the National Space Biomedical Research Institute to initiate research in this area of integrative physiology and medicine. Specifically, three example projects are discussed as potential stepping stones towards the ultimate goal of producing a digital human. These projects relate to developing a functional model of the human musculoskeletal system and the heart.     

Hermes vehicle

The presence of Europe in the future developments of spatial programs, which are foreseen, for the 1990s and further, needs the availability of vehicles, modules and all related technologies adapted to operational use of low earth orbit station.The manned HERMES vehicle shall be part of the in-orbit infrastructure realized either in the European context or in cooperation between Europe and the United States.The main mission for this vehicle will be to run a shuttle with the station that means transport and change of the crews, its safe return in abort condition and cargo transport of consumable and experimental equipment.Secondary missions could be servicing on automatic platform, making autonomous scientific experiments. Lastly, the vehicle, by means of its on-board propulsion capability, could be used to accomplish in-orbit tow and assembly missions.Studies which are undertaken now about the vehicle are devoted to the aerodynamic shape (research of a compromise between aerothermic and overall fitting), the system (functional architecture, ground and flight configuration); further works dealing with technology are presently on hand in the field of thermal protection, aerodynamics, power generation with a high massic yield.     

A space radiation transport method development.

Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from the preliminary design concepts to the final design. In particular, we will discuss the progress towards a full three-dimensional and computationally efficient deterministic code for which the current HZETRN evaluates the lowest-order asymptotic term. HZETRN is the first deterministic solution to the Boltzmann equation allowing field mapping within the International Space Station (ISS) in tens of minutes using standard finite element method (FEM) geometry common to engineering design practice enabling development of integrated multidisciplinary design optimization methods. A single ray trace in ISS FEM geometry requires 14 ms and severely limits application of Monte Carlo methods to such engineering models. A potential means of improving the Monte Carlo efficiency in coupling to spacecraft geometry is given in terms of re-configurable computing and could be utilized in the final design as verification of the deterministic method optimized design.