Evolution of the orbital elements for objects with high area-to-mass ratios in geostationary transfer orbits

A new population of uncatalogued objects in geosynchronous Earth orbits (GEO), with a mean motion of about 1 rev/day and eccentricities up to 0.6, has been identified recently. The first observations of this new type of objects were acquired in the framework of the European Space Agency’s (ESA) search for space debris in GEO and the geostationary transfer orbit (GTO) using the ESA 1-m telescope on Tenerife. Earlier studies have postulated that the perturbations due to the solar radiation pressure can lead to such large eccentricities for GEO objects with a high area-to-mass ratio (A/M). The simulations showed that the eccentricities of GEO objects with large A/M exhibit periodic variations with periods of about one year and amplitudes depending on the value of A/M. The findings of these studies could be confirmed by observations from the ESA 1-m telescope on Tenerife.     

Dynamical evolution of high area-to-mass ratio objects in Molniya orbits

For special demands, some notable orbit types have been developed by human, including the Molniya orbits, which have a relatively high eccentricity up to about 0.7, and a period of 12 h. Considering that space debris with high area-to-mass ratio (A/M) has been discovered, such objects may also exist in Molniya orbits due to spacecraft and upper stages fragmentation events. However, there are not sufficient studies of the complex dynamical phenomena of such orbits. These studies can enrich the knowledge about the long-term evolution of these orbits, be helpful to propose uncatalogued objects observation and identification, and also set the protected region as well as active debris removal. In this paper, the characteristics of 2:1 resonance of Molniya satellite orbits are studied. A large set of numerical simulations, including all the relevant perturbations, is carried out to further investigate the main characteristics, and special attention is payed to the dynamical evolution of objects with high A/M, particularly affected by the direct solar radiation pressure. The long-term dynamical evolution of orbital elements, as well as the dependency of lifetime on the A/M value, is discussed.     

Heliotropic dust rings for Earth climate engineering

This paper examines the concept of a Sun-pointing elliptical Earth ring comprised of dust grains to offset global warming. A new family of non-Keplerian periodic orbits, under the effects of solar radiation pressure and the Earth’s J₂ oblateness perturbation, is used to increase the lifetime of the passive cloud of particles and, thus, increase the efficiency of this geoengineering strategy. An analytical model is used to predict the orbit evolution of the dust ring due to solar-radiation pressure and the J₂ effect. The attenuation of the solar radiation can then be calculated from the ring model. In comparison to circular orbits, eccentric orbits yield a more stable environment for small grain sizes and therefore achieve higher efficiencies when the orbit decay of the material is considered. Moreover, the novel orbital dynamics experienced by high area-to-mass ratio objects, influenced by solar radiation pressure and the J₂ effect, ensure the ring will maintain a permanent heliotropic shape, with dust spending the largest portion of time on the Sun facing side of the orbit. It is envisaged that small dust grains can be released from a circular generator orbit with an initial impulse to enter an eccentric orbit with Sun-facing apogee. Finally, a lowest estimate of 1 × 10¹² kg of material is computed as the total mass required to offset the effects of global warming.     

Charge exchange interactions on near-Earth proton radiation for orbit perturbation of high area-to-mass ratio objects

This novel concept expels neutral gas in the presence of geomagnetically-trapped protons in near-Earth orbit. The expelled neutral gas acts to induce charge exchange collisions with the geomagnetically-trapped protons and induce drag on objects which pass through it. The charge exchange collisions between the neutral gas and the geomagnetically-trapped protons create neutrals with similar kinetic energy that are not confined by the geomagnetic field. The charge exchange neutrals are able to collide with orbital objects and perturb their orbits. The delta-v applied by the charge exchange neutral flux is greatest on high area-to-mass objects. Numerical simulation shows charge exchange neutral impacts produce a delta-v on objects on the order of 3.8 x 10⁻¹¹ m/s at a distance of 1 km from the center of the expelled gas in a 1,000 km orbit. The impulse imparted by charge exchange neutral impacts is at least six orders of magnitude smaller than that provided by the induced drag caused by gas expulsion. The localized drag increase can force a majority of small objects into the orbit of the expelled gas cloud, even if that orbit is retrograde to the initial orbit of the objects. This new technique can be applied to the remediation of space debris.     

Semi-analytical investigations of high area-to-mass ratio geosynchronous space debris including Earth’s shadowing effects

This paper investigates the long-term perturbations of the orbits of geosynchronous space debris influenced by direct radiation pressure including the Earth’s shadowing effects. For this purpose, we propose an extension of our homemade semi-analytical theory [Valk, S., Lemaître, A., Deleflie, F. Semi-analytical theory of mean orbital motion for geosynchronous space debris under gravitational influence. Adv. Space Res., submitted for publication], based on the method developed by Aksnes [Aksnes, K. Short-period and long-period perturbations of a spherical satellite due to direct solar radiation. Celest. Mech. Dyn. Astron. 13, 89–104, 1976] and generalized into a more convenient non-singular formalism. The perturbations accounting for the direct radiation pressure with the Earth’s shadow are computed on a revolution-by-revolution basis, retaining the original osculating Hamiltonian disturbing function. In this framework, we compute the non-singular mean longitude at shadow entry and shadow exit at every orbital revolution in opposition to classical approaches where the singular eccentric anomalies at shadow entry and shadow exit are computed. This new algorithm is developed using non-singular variables. Consequently, it is particularly suitable for both near-circular and near-equatorial orbits as well as orbits which transit periodically around null eccentricities and null inclinations.The algorithm is tested by means of numerical integrations of the equations, averaged over the short periods, including radiation pressure, J₂, the combined Moon and Sun third body attraction as well as the long-term effects of the 1:1 resonance occurring for geosynchronous objects. As an extension of [Valk, S., Lemaître, A., Anselmo, L. Analytical and semi-analytical investigations of geosynchronous space debris with high area-to-mass ratios influenced by solar radiation pressure. Adv. Space Res., doi:10.1016/j.asr.2007.10.025, 2007b], we especially apply our analysis to space debris with area-to-mass as high as 20 m²/kg. This paper provides numerical and semi-analytical investigations leading to a deep understanding of the long-term evolution of the semi-major axis. Finally, these semi-analytical investigations are compared with accurate numerical integrations of the osculating equations of motion over time scales as high as 25 years.     

Intracellular molecular distributions in spacecraft experiments in orbit around Earth

It is possible that the nucleolous inside the cell plays the role of a “gravity receptor”. Furthermore, cells up to 10 μm in diameter can demonstrate some effect due to the redistribution of mitochondria or nucleolous. Effects of gravity should be present in various cell systems where larger objects such as the ribosomes move from cell to cell. In this paper we study the effects of gravity on cells. In particular, we examine the resulting intracellular molecular distribution due to Brownian motion and the ordered distribution of molecules under the action of gravity, where n₀ is the number per unit volume at certain level, and n is the number per unit volume above that level. This is an experiment that takes place at a certain orbital altitude in a spacecraft in orbit around Earth, where the acceleration due to the central field is corrected for the oblateness and also the rotation of the Earth. We found that equatorial circular and elliptical orbits have the highest n/n₀ ratios. This experiment takes place in circular and elliptical orbits, with eccentricities e = 0, 0.1 and involves a bacterial cell at an orbital altitude of 300 km. We found that n/n₀ = 1.00299 and 1.0037 respectively, which is still a 0.6–0.7 % higher than n/n₀ = 0.0996685 calculated on the surface of the Earth. Examining mitochondria in similar orbital experiments we found that equatorial orbits result to higher n/n₀ ratios. In particular, we found that n/n₀ = 8.38119, where an elliptical orbit of eccentricity e = 0.1 results to n/n₀ = 13.8525. Both are high above 100%, signifying the importance of Brownian motion over gravity. Our results are of interest to biomedical applications. Molecular concentrations are important for various processes such as the embryogenesis, positional homeostasis and its relation to cell energy expenditure, cell torque, cell deformation, and more. These results indicate that statistical molecular distributions play an important role for the recognition of a particular environment by the cell, in biological space experiment to come.     

Cowpeas and pinto beans: Performance and yields of candidate space crops in the laboratory biosphere closed ecological system

An experiment utilizing cowpeas (Vigna unguiculata L.), pinto beans (Phaseolus vulgaris L.) and Apogee ultra-dwarf wheat (Triticum sativa L.) was conducted in the soil-based closed ecological facility, Laboratory Biosphere, from February to May 2005. The lighting regime was 13 h light/11 h dark at a light intensity of 960 μmol m⁻² s⁻¹, 45 mol m⁻² day⁻¹ supplied by high-pressure sodium lamps. The pinto beans and cowpeas were grown at two different planting densities. Pinto bean production was 341.5 g dry seed m⁻² (5.42 g m⁻² day⁻¹) and 579.5 dry seed m⁻² (9.20 g m⁻² day⁻¹) at planted densities of 32.5 plants m⁻² and 37.5 plants m⁻², respectively. Cowpea yielded 187.9 g dry seed m⁻² (2.21 g m⁻² day⁻¹) and 348.8 dry seed m⁻² (4.10 g m⁻² day⁻¹) at planted densities of 20.8 plants m⁻² and 27.7 plants m⁻², respectively. The crop was grown at elevated atmospheric carbon dioxide levels, with levels ranging from 300–3000 ppm daily during the majority of the crop cycle. During early stages (first 10 days) of the crop, CO₂ was allowed to rise to 7860 ppm while soil respiration dominated, and then was brought down by plant photosynthesis. CO₂ was injected 27 times during days 29–71 to replenish CO₂ used by the crop during photosynthesis. Temperature regime was 24–28 °C day/deg 20–24 °C night. Pinto bean matured and was harvested 20 days earlier than is typical for this variety, while the cowpea, which had trouble establishing, took 25 days more for harvest than typical for this variety. Productivity and atmospheric dynamic results of these studies contribute toward the design of an envisioned ground-based test bed prototype Mars base.     

3D Imaging of the OH mesospheric emissive layer

A new and original stereo imaging method is introduced to measure the altitude of the OH nightglow layer and provide a 3D perspective map of the altitude of the layer centroid. Near-IR photographs of the OH layer are taken at two sites separated by a 645 km distance. Each photograph is processed in order to provide a satellite view of the layer. When superposed, the two views present a common diamond-shaped area. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a normalized cross-correlation coefficient (NCC). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in July 2006 in Peru. The images were taken simultaneously at Cerro Cosmos (12°09′08.2″ S, 75°33′49.3″ W, altitude 4630 m) close to Huancayo and Cerro Verde Tellolo (16°33′17.6″ S, 71°39′59.4″ W, altitude 2272 m) close to Arequipa. 3D maps of the layer surface were retrieved and compared with pseudo-relief intensity maps of the same region. The mean altitude of the emission barycenter is located at 86.3 km on July 26. Comparable relief wavy features appear in the 3D and intensity maps. It is shown that the vertical amplitude of the wave system varies as exp (Δz/2H) within the altitude range Δz = 83.5–88.0 km, H being the scale height. The oscillatory kinetic energy at the altitude of the OH layer is comprised between 3 × 10⁻⁴ and 5.4 × 10⁻⁴ J/m³, which is 2–3 times smaller than the values derived from partial radio wave at 52°N latitude.     

Validation of B0 and B1 in the IRI 2001 model at low solar activity for Ilorin an equatorial station

A new set of data obtained at low solar activity from Ilorin, Nigeria (geog. latitude 8.5°N, geog longitude, 4.6°E, dip 4.1°S) is used to validate the IRI 2001 model at low solar activity. The results show in general a good agreement between model and observed B0 at night but an over estimation during daytime. The overestimation is greatest during the morning period (0600LT–1000LT). The model prediction for B1 is fairly good at night and during the day. A dependence of B0 on solar zenith angle χ is observed during the daytime. A formulation of the form B0 = A[cos(χ)ⁿ] is therefore proposed. Values of the constants n and A were determined for the period of low solar activity for this station.     

Effect of vertical plasma transport on ionospheric F2-region parameters at equatorial latitude

The variability of the F2-layer even during magnetically quiet times are fairly complex owing to the effects of plasma transport. The vertical E × B drift velocities (estimated from simplified electron density continuity equation) were used to investigate the seasonal effects of the vertical ion drifts on the bottomside daytime ionospheric parameters over an equatorial latitude in West Africa, Ibadan, Nigeria (Geographic: 7.4°N, 3.9°E, dip angle: 6°S) using 1 year of ionsonde data during International Geophysical Year (IGY) of 1958, that correspond to a period of high solar activity for quiet conditions. The variation patterns between the changes of the vertical ion drifts and the ionospheric F2-layer parameters, especially; f_oF₂ and h_mF₂ are seen remarkable. On the other hand, we observed strong anti-correlation between vertical drift velocities and h′F in all the seasons. We found no clear trend between N_mF₂ and h_mF₂ variations. The yearly average value of upward daytime drift at 300 km altitude was a little less than the generally reported magnitude of 20 ms⁻¹ for equatorial F-region in published literature, and the largest upward velocity was roughly 32 ms⁻¹. Our results indicate that vertical plasma drifts; ionospheric F2-layer peak height, and the critical frequency of F2-layer appear to be somewhat interconnected.     

A deformation model of flexible,HAMR objects for accurate propagation under perturbations and the self-shadowing effects

A new type of space debris in near geosynchronous orbit (GEO) was recently discovered and later identified as exhibiting unique characteristics associated with high area-to-mass ratio (HAMR) objects, such as high rotation rates and high reflection properties. Observations have shown that this debris type is very sensitive to environmental disturbances, particularly solar radiation pressure, due to the fact that its motion depends on the actual effective area, orientation of that effective area, reflection properties and the area-to-mass ratio of the object is not stable over time. Previous investigations have modelled this type of debris as rigid bodies (constant area-to-mass ratios) or discrete deformed body; however, these simplifications will lead to inaccurate long term orbital predictions. This paper proposes a simple yet reliable model of a thin, deformable membrane based on multibody dynamics. The membrane is modelled as a series of flat plates, connected through joints, representing the flexibility of the membrane itself. The mass of the membrane, albeit low, is taken into account through lump masses at the joints. The attitude and orbital motion of this flexible membrane model is then propagated near GEO to predict its orbital evolution under the perturbations of solar radiation pressure, Earth’s gravity field (J₂), third body gravitational fields (the Sun and Moon) and self-shadowing. These results are then compared to those obtained for two rigid body models (cannonball and flat rigid plate). In addition, Monte Carlo simulations of the flexible model by varying initial attitude and deformation angle (different shape) are investigated and compared with the two rigid models (cannonball and flat rigid plate) over a period of 100?days. The numerical results demonstrate that cannonball and rigid flat plate are not appropriate to capture the true dynamical evolution of these objects, at the cost of increased computational time.     

Tolerance of chufa (Cyperus esculentus L.) plants,representing the higher plant compartment in bioregenerative life support systems,to super-optimal air temperatures

Plants intended to be included in the photosynthesizing compartment of the bioregenerative life support system (BLSS) need to be studied in terms of both their production parameters under optimal conditions and their tolerance to stress factors that might be caused by emergency situations. The purpose of this study was to investigate tolerance of chufa (Cyperus esculentus L.) plants to the super-optimal air temperature of 45 ± 1 °C as dependent upon PAR (photosynthetically active radiation) intensity and the duration of the exposure to the stress factor. Chufa plants were grown hydroponically, on expanded clay, under artificial light. The nutrient solution was Knop’s mineral medium. Until the plants were 30 days old, they had been grown at 690 μmol m⁻² s⁻¹ PAR and air temperature 25 °C. Thirty-day-old plants were exposed to the temperature 45 °C for 6 h, 20 h, and 44 h at PAR intensities 690 μmol m⁻² s⁻¹ and 1150 μmol m⁻² s⁻¹. The exposure to the damaging air temperature for 44 h at 690 μmol m⁻² s⁻¹ PAR caused irreversible damage to PSA, resulting in leaf mortality. In chufa plants exposed to heat shock treatment at 690 μmol m⁻² s⁻¹ PAR for 6 h and 20 h, respiration exceeded photosynthesis, and CO₂ release in the light was recorded. Functional activity of photosynthetic apparatus, estimated from parameters of pulse-modulated chlorophyll fluorescence in Photosystem 2 (PS 2), decreased 40% to 50%. After the exposure to the stress factor was finished, functional activity of PSA recovered its initial values, and apparent photosynthesis (P_apparent) rate after a 20-h exposure to the stress factor was 2.6 times lower than before the elevation of the temperature. During the first hours of plant exposure to the temperature 45 °C at 1150 μmol m⁻² s⁻¹ PAR, respiration rate was higher than photosynthesis rate, but after 3–4 h of the exposure, photosynthetic processes exceeded oxidative ones and CO₂ absorption in the light was recorded. At the end of the 6-h exposure, P_apparent rate was close to that recorded prior to the exposure, and no significant changes were observed in the functional activity of PSA. At the end of the 20-h exposure, P_apparent rate was close to its initial value, but certain parameters of the functional activity of PSA decreased 25% vs. their initial values. During the repair period, the parameters of external gas exchange recovered their initial values, and parameters of pulse-modulated chlorophyll fluorescence were 20–30% higher than their initial values. Thus, exposure of chufa plants to the damaging temperature of the air for 20 h did not cause any irreversible damage to the photosynthetic apparatus of plants at either 690 μmol m⁻² s⁻¹ or 1150 μmol m⁻² s⁻¹ PAR, and higher PAR intensity during the heat shock treatment enhanced heat tolerance of the plants.     

Variation in the ionospheric propagating factor M(3000)F2 at Ouagadougou,Burkina Faso

We use hourly monthly median values of propagation factor M(3000)F2 data observed at Ouagadougou Ionospheric Observatory (geographic12.4°N, 1.5°W; 5.9^o dip), Burkina Faso (West Africa) during the years Januar1987–December1988 (average F10.7 < 130 × 10⁻²² W/m²/Hz, representative of low solar flux conditions) and for January 1989–December1990 (average F10.7 ? 130 × 10⁻²² W/m²/Hz, representative of high solar epoch) for magnetically quiet conditions to describe local time, seasonal and solar cycle variations of equatorial ionospheric propagation factor M(3000)F2 in the African region. We show that that seasonal trend between solar maximum and solar minimum curves display simple patterns for all seasons and exhibits reasonable disparity with root mean square error (RMSE) of about 0.31, 0.29 and 0.26 for December solstice, June solstice and equinox, respectively. Variability Σ defined by the percentage ratio of the absolute standard deviation to the mean indicates significant dissimilarity for the two solar flux levels. Solar maximum day (10–14 LT) and night (22–02 LT) values show considerable variations than the solar minimum day and night values. We compare our observations with those of the IRI 2007 to validate the prediction capacity of the empirical model. We find that the IRI model tends to underestimate and overestimate the observed values of M(3000)F2, in particular, during June solstice season. There are large discrepancies, mainly during high solar flux equinox and December solstice between dawn and local midnight. On the other hand, IRI provides a slightly better predictions for M(3000)F2 between 0900 and 1500 LT during equinox low and high solar activity and equinox high sunspot number. Our data are of great importance in the area of short-wave telecommunication and ionospheric modeling.     

One dimensional blood flow in a planetocentric orbit

All life on earth is accustomed to the presence of gravity. When gravity is altered, biological processes can go awry. It is of great importance to ensure safety during a spaceflight. Long term exposure to microgravity can trigger detrimental physiological responses in the human body. Fluid redistribution coupled with fluid loss is one of the effects. In particular, in microgravity blood volume is shifted towards the thorax and head. Sympathetic nervous system-induced vasoconstriction is needed to maintain arterial pressure, while venoconstriction limits venous pooling of blood prevents further reductions in venous return of blood to the heart. In this paper, we modify an existing one dimensional blood flow model with the inclusion of the hydrostatic pressure gradient that further depends on the gravitational field modified by the oblateness and rotation of the Earth. We find that the velocity of the blood flow V_B is inversely proportional to the blood specific volume d, also proportional to the oblateness harmonic coefficient J₂, the angular velocity of the Earth ω_E, and finally proportional to an arbitrary constant c. For c = −0.39073 and ξ_H = −0.5 mmHg, all orbits result to less blood flow velocities than that calculated on the surface of the Earth. From all considered orbits, elliptical polar orbit of eccentricity e = 0.2 exhibit the largest flow velocity V_B = 1.031 m/s, followed by the orbits of inclination i = 45°and 0°. The Earth’s oblateness and its rotation contribute a 0.7% difference to the blood flow velocity.     

Properties of the high area-to-mass ratio space debris population at high altitudes

In the framework of its space debris research activities ESA established an optical survey program to study the space debris environment at high altitudes, in particular in the geostationary ring and in the geostationary transfer orbit region. The Astronomical Institute of the University of Bern (AIUB) performs these surveys on behalf of ESA using ESA’s 1-m telescope in Tenerife. Regular observations were started in 1999 and are continued during about 120–140 nights per year. Results from these surveys revealed a substantial amount of space debris at high altitudes in the size range from 0.1 to 1 m. Several space debris populations with different dynamical properties were identified in the geostationary ring. During the searches for debris in the geostationary transfer orbit region a new population of objects in unexpected orbits, where no potential progenitors exist, was found. The orbital periods of these objects are clustered around one revolution per day; the eccentricities, however, are scattered between 0 and 0.6. By following-up some of these objects using the ESA telescope and AIUB’s 1-m telescope in Zimmerwald, Switzerland, it was possible to study the properties of this new population. One spectacular finding from monitoring the orbits over time spans of days to months is the fact that these objects must have extreme area-to-mass ratios, which are by several orders of magnitudes higher than for ‘normal-type’ debris. This in turn supports the hypothesis that the new population actually is debris generated in or near the geostationary ring and which is in orbits with periodically varying eccentricity and inclination due to perturbations by solar radiation pressure. In order to further study the nature of these debris, multi-color and temporal photometry (light curves) were acquired with the Zimmerwald telescope. The light curves show strong variations over short time intervals, including signals typical for specular reflections. Some objects exhibit distinct periodic variations with periods ranging from 10 to several 100 s. All this is indicative for objects with complicated shapes and some highly reflective surfaces.     

Comparing IRI and a regional model with ionosonde measurements in Pakistan

We have used the technique of expansion in Empirical Orthogonal Functions (EOFs) to develop regional models of the critical frequencies of E and F₂ layers (f_oE, f_oF₂), peak height (h_mF₂), and semi-thickness of F₂ layer (Y_mF₂) over Pakistan. In the present study levels of solar activity specified by Smoothed Sunspot Number (R) from 10 to 200 are taken into account. The magnetic dip angle for the model ranges from 30° to 60°. We have compared the regional model and the International Reference Ionosphere (IRI) with measurements of three ionosondes in Pakistan. The model parameters f_oE and f_oF₂ are found overall comparable to the observed hourly median values during daytime at Karachi (geographic latitude = 24.95°N, longitude = 67.13°E, magnetic inclination = 37°), Multan (30.18°N, 71.48°E, 45°) and Islamabad (33.75°N, 73.13°E, 51.5°) during the years 1988, 1996 and 2000. For h_mF₂ the computed values by regional and IRI model for the year 1995 are found close to each other. However, for Y_mF₂the results are better during daytime as compared to nighttime.     

Solar cycle and latitude dependence of high-beta suprathermal plasma conditions in interplanetary space between 1.3 and 5.4 AU

The analysis of energetic particles and magnetic field measurements from the Ulysses spacecraft has shown that in a series of events, the energy density contained in the suprathermal tail particle distribution is comparable to or larger than that of the magnetic field, creating conditions of high-beta plasma. In this work we analyze periods of high-beta suprathermal plasma occurrences (β_ep > 1) in interplanetary space, using the ratio (β_ep) of the energetic particle (20 keV to ∼5 MeV) and magnetic field energy densities from measurements covering the entire Ulysses mission lifetime (1990–2009) in order to reveal new or to reconfirm some recently defined interesting characteristics. The main key-results of the work are summarized as follows: (i) we verify that high-beta events are detected within well identified regions corresponding mainly to the vicinity of shock surfaces and magnetic structures, and associated with energetic particle intensity enhancements due to (a) reacceleration at shock-fronts and (b) unusually large magnetic field depressions. (ii) We define three considerable features for the high-beta events, concentrated on the next points: (a) there is an appreciable solar-activity influence on the high-beta events, during the maximum and middle solar-cycle phase, (b) the annual peak magnitude and the number of occurrences of high events are well correlated with the sunspot number, (c) the high-beta suprathermal plasma events present a spatial distribution in heliographic latitudes (HL) up to ∼±80°, and a specific important concentration on the low (−25° ? HL < −6°, 6° < HL ? 25°) and median (−45° ? HL < −25°, 25° < HL ? 45°) latitudes. We also reconfirm by a statistical analysis the results of Marhavilas and Sarris (2011), that the high-beta suprathermal plasma (β_ep > 1) events are characterized by a very large parameter β_ep (up to 1732.5), a great total duration (406 days) and a large percentage of the Ulysses-mission lifetime (which is equal to 6.34% of the total duration with usable measurements, and 11.3% of the duration in presence of suprathermal particles events).     

Effects of mineral nutrition conditions on heat tolerance of chufa (Сyperus esculentus L.) plant communities to super optimal air temperatures in the BTLSS

The use of mineralized human wastes as a basis for nutrient solutions will increase the degree of material closure of bio-technical human life support systems. As stress tolerance of plants is determined, among other factors, by the conditions under which they have been grown before exposure to a stressor, the purpose of the study is to investigate the level of tolerance of chufa (Cyperus esculentus L.) plant communities grown in solutions based on mineralized human wastes to a damaging air temperature, 45 °C. Experiments were performed with 30-day-old chufa plant communities grown hydroponically, on expanded clay aggregate, under artificial light, at 690 μmol m⁻² s⁻¹ PAR and at a temperature of 25 °C. Plants were grown in Knop’s solution and solutions based on human wastes mineralized according to Yu.A. Kudenko’s method, which contained nitrogen either as ammonium and urea or as nitrates. The heat shock treatment lasted 20 h at 690 and 1150 μmol m⁻² s⁻¹ PAR. Chufa heat tolerance was evaluated based on parameters of CO₂ gas exchange, the state of its photosynthetic apparatus (PSA), and intensity of peroxidation of leaf lipids. Chufa plants grown in the solutions based on mineralized human wastes that contained ammonium and urea had lower heat tolerance than plants grown in standard mineral solutions. Heat tolerance of the plants grown in the solutions based on mineralized human wastes that mainly contained nitrate nitrogen was insignificantly different from the heat tolerance of the plants grown in standard mineral solutions. A PAR intensity increase from 690 μmol m⁻² s⁻¹ to 1150 μmol m⁻² s⁻¹ enhanced heat tolerance of chufa plant communities, irrespective of the conditions of mineral nutrition under which they had been grown.     

Active debris removal of multiple priority targets

Today’s space debris environment shows major concentrations of objects within distinct orbital regions for nearly all size regimes. The most critical region is found at orbital altitudes near 800 km with high declinations. Within this region many satellites are operated in so called sun-synchronous orbits (SSO). Among those, there are Earth observation, communication and weather satellites. Due to the orbital geometry in SSO, head-on encounters with relative velocities of about 15 km/s are most probable and would thus result in highly energetic collisions, which are often referred to as catastrophic collisions, leading to the complete fragmentation of the participating objects. So called feedback collisions can then be triggered by the newly generated fragments, thus leading to a further population increase in the affected orbital region. This effect is known as the Kessler syndrome.