Debris In Earth Orbit Research Articles

地球低軌道スペースデブリ環境における推移モデル

Study and long-term prediction of orbital debris environment in low Earth orbits are urgent needs for secure human space development and exploration. This paper introduces some results of Low Earth Orbital Debris Environmental Evolutionary Model (LEODEEM) being researched at Kyushu University with collaboration from JAXA for the purpose of discussing problems of space environment conservation. The model calculates LEO debris evolution (less than 2,000 km altitude of perigee) taking into account collisions, and future launch traffic. It becomes possible to predict a long term LEO environment and investigate future mission hazard evaluation by using this model.

Developments in space debris mitigation policy and practices

Since the American Institute of Aeronautics and Astronautics issued the first position paper on space debris 25 years ago, recognition of the threats posed by debris in Earth orbit and the need to act now to protect the future space environment have become widespread. This new awareness has been matched with positive actions by spacecraft and launch vehicle designers, manufacturers, and operators. As a result, a common set of space debris mitigation policies and practices has been forming at both the national and international levels.

Collision risk against space debris in Earth orbits

Opik’s formulae for the probability of collision are applied to the analysis of the collision risk against space debris in Low-Earth Orbit (LEO) and Medium Earth Orbit. The simple analytical formulation of Opik’s theory makes it applicable to complex dynamical systems, such as the interaction of the ISS with the whole debris population in LEO The effect of a fragmentation within a multiplane constellation can also be addressed. The analysis of the evolution of the collision risk in Earth orbit shows the need of effective mitigation measures to limit the growth of the collision risk and of the fragmentation debris in the next century.

Lunar exploration and development—A sustainable model

A long-term goal of space exploration is the development of a lunar settlement that will not only be largely self-sufficient but also contribute to the economy of the Earth–Moon system. Proposals for lunar mining and materials processing developments, as well as tourism-based applications, have appeared in the literature for many years. However, so great are the technical and financial difficulties associated with sustained lunar development that, more than 30 years after the end of the Apollo programme, there have been no practical advances towards this goal. While this may soon be remedied by a series of proposed unmanned orbiters, landers and rovers, the philosophy of lunar exploration and development remains the same as it has for decades: conquer, exploit, and ignore the consequences. By contrasting the well-recognised problems of Earth orbital debris and the barely recognised issue of intentional spacecraft impacts on the lunar surface, this paper illustrates the need for a new model for lunar exploration and development. This new paradigm would assign a value to the lunar environment and provide a balance between protection and exploitation, creating, in effect, a philosophy of sustainable development for the Moon. It is suggested that this new philosophy should be an integral part of any future strategy for lunar colonisation.

Space debris mitigation strategies and practices in geosynchronous transfer orbits

Missions to geosynchronous orbits remain one of the most important elements of space launch traffic, accounting for 40% of all missions to Earth orbit and beyond during the four-year period 2000–2003. The vast majority of these missions leave one or more objects in geosynchronous transfer orbits (GTOs), contributing on a short-term or long-term basis to the space debris population. National and international space debris mitigation guidelines seek to curtail the accumulation of debris in orbits which penetrate the regions of low Earth orbit and of geosynchronous orbit. The orbital lifetime of objects in GTO can be greatly influenced by the initial values of perigee, inclination, and right ascension of the orbital plane, leading to orbital lifetimes of from less than one month to more than 100 years. An examination of the characteristic GTOs employed by launch vehicles from around the world has been conducted. The consequences of using perigees above 300 km and super-synchronous apogees, typically above 40,000 km, have been identified. In addition, the differences in orbital behavior of launch vehicle stages and mission-related debris in GTOs have been investigated. Greater coordination and cooperation between space launch service providers and spacecraft designers and owners could significantly improve overall compliance with guidelines to mitigate the accumulation of debris in Earth orbit.

Detection of Small LEO Debris with Line Detection Method

This paper proposes a new method known as “the line detection method” to detect small pieces of low Earth orbit (LEO) debris. A direction is assumed for the line created by small LEO debris on a CCD image and the values of pixels along that direction are accumulated to improve the signal-to-noise ratio. This method can detect LEO debris that is 30 to 40 times darker than debris that can be detected by usual methods. We tested this method by using the 35-cm telescope and back-illuminated CCD camera at the Mt. Nyukasa Astronomical Observatory. One small piece of LEO debris with a radar cross section of 0.0047 m2 was detected. By using this method, the 1-m telescope and back-illuminated wide-field camera at the Bisei Spaceguard Center (BSGC) are expected to be able to detect LEO debris with a size of a few cm. The line detection method will be used to probe the LEO small debris environment and contribute to solving the space debris problem.

Monitoring the low earth orbit debris environment over an 11-year solar cycle

Orbital debris is a concern for all space faring nations. Prior to 1990, there were no statistically significant measurements of the debris environment for debris sizes below 10 cm diameter. Late in that year, NASA/Johnson Space Center began using the Haystack long range imaging radar to statistically sample the low earth orbit (LEO) debris environment for debris sizes as small as 0.5 cm diameter. These measurements have continued since that date. Models of the LEO debris environment predict a change in the debris flux due to solar activity. High solar activity heats the earth's atmosphere causing it to expand creating an increased atmospheric drag which causes debris to reenter the earth's atmosphere at a higher rate thereby depleting the population at low altitudes. This paper will summarize the Haystack measurements over a complete 11-year solar cycle.

Cost-effective and robust mitigation of space debris in low earth orbit

For the wide acceptance of space debris mitigation measures throughout government agencies and industry, their cost-effectiveness must be demonstrated. The selected measures must not only be effective at controlling the future growth of the debris population, but they should also aim to minimise the collision risk to spacecraft at a minimal cost of implementation. Furthermore, the selected measures must be sufficiently robust to retain their effectiveness if unexpected increases in space activity were to occur. In this paper, clear criteria are established in order to assess numerous different Low Earth Orbit (LEO) debris mitigation scenarios for their cost-effectiveness and robustness. The ESA DELTA debris model is used to provide long-term debris environment projections for these scenarios as an input to the effectiveness/robustness element. Manoeuvre requirements for the different post-mission disposal scenarios are calculated in order to define the cost-related element. A 25-year post-mission lifetime de-orbit policy, combined with explosion prevention and mission-related object limitation, was found to be the most cost-effective solution to the space debris problem in LEO. This package would also be robust enough to retain its effectiveness even after a significant increase in future launch traffic. It was found that the re-orbiting of space systems above the LEO region would not lead to significant collision activity there over the next century. However, above-LEO disposal should be used sparingly because the disposal region could become unstable after a limited number of localised explosion or collision-induced breakup events due to a lack of air drag to remove the resulting fragments.

In situ debris measurements in MEO/HEO using onboard spacecraft surface inspection system

This paper proposes in situ debris measurements in medium/high earth orbit using an onboard spacecraft surface inspection system. The onboard surface inspection system consists of a small high-resolution CCD camera, data handling and communication subsystems. It can be mounted on many spacecraft and survey impacts on the surfaces of the spacecraft. Once it detects a pit on the surface created by micron-sized debris impact, the system takes the high-resolution image, and then sends the image down to a ground station for further analyses. This type of debris measurements would provide a better and more accurate understanding of the present medium/high earth orbital debris environment because we cannot detect small debris from ground-based sensors. Conceptual design and some experiments are performed to verify the feasibility of this system. Results show that the size of an impacting debris can be estimated, but the velocity of the impacting object is difficult to determine.

Optical observations of the orbital debris environment at NASA

To monitor the orbital debris environment and facilitate orbital debris modeling and forecasting, the Orbital Debris Program Office of the NASA Johnson Space Center operates two principal telescopes: the liquid mirror telescope (LMT) and the charge coupled device debris telescope (CDT). Both telescopes are maintained at the NASA Cloudcroft Observatory, a 15-meter dome at 2761-meter elevation near Cloudcroft, NM. The LMT became operational in October 1996. Approximately 580 hours of digital video data from the LMT have been collected and processed by an automated hardware/software system. Results from 504 hours are presented. This paper also presents the results of a study of the detection sensitivity of the LMT system as well as a new measurement-based model for estimating object size from LMT measurements. The CDT, the other principal component of the optical program, became operational in November 1997. The CDT is currently being used in a statistical survey of catalogued and uncataloguued debris in geosynchronous earth orbit. Approximately 180 nights worth of data have been collected and results from a portion of this data are presented. A new direction for the CDT is to investigate various regions in GEO that would contain debris from hypothesized break-ups.

Updated results on the long-term evolution of the space debris environment

The long-term evolution of artificial debris in earth orbit has been analyzed, taking into account a detailed traffic model, explosions, collisions and the effects of air drag. Several scenarios, most of them implementing mitigation measures discussed at international level, have been simulated over a 200-year time span. Moreover, the sensitivity of the results to different collision model assumptions has been assessed. The simulations confirm the importance of spacecraft and rocket bodies passivation to avoid in-orbit explosions, but the de-orbiting of upper stages is needed as well to curb the debris and collision rate increase and to avert the onset of an exponential growth of artificial objects in the near earth space. The additional removal of end-of-life spacecraft does not improve the outcome dramatically, but may be able to reduce the collision rates in low earth orbit, reversing the historical trend of the last four decades. Of course, the fragmentation models and the simulation assumptions are still affected by a certain degree of uncertainty, but the results of the sensitivity analysis show that our conclusions are consistent and reliable, at least for the first century.

Radar observations of space debris

Our radar monitoring of small Earth-orbiting debris at NASAs Goldstone Tracking Station has been extended to an altitude of 3200 km. Many of the observed particles lie in clusters ; the largest of which appears to be remnants of the West Ford Needles, launched over 3 decades earlier, and originally designed to have reentered the Earths atmosphere long ago.

Liquid metal mirror for optical measurements of orbital debris

A telescope employing a liquid metal (mercury) mirror that is three meters in diameter was developed for the purpose of measuring the population of small orbital debris. The telescope is installed at a 9,000 ft site in the mountains of New Mexico at a latitude of 32.98 degrees, and has completed final optical performance tests. A Ford 2048 × 2048 CCD detector is used at the image plane. With this detector, the limiting stellar magnitude of the telescope was measured to be 23 at a S/N of about 3, with a nominal full width, half maximum for stellar images of 1.3 arcsec. Safety problems with toxic mercury vapor were minimal at operating temperatures below 60 F, greatly simplifying operations with the mirror. Performance of the telescope for debris at geosynchronous orbit (GEO) altitudes is estimated to be in the range 5 to 10 cm using the existing CCD detector. However, at its present location in New Mexico, the telescope cannot be used for detection of debris in the GEO region, since it cannot see debris with inclinations below 32 degrees. Performance of the telescope for debris in low earth orbit depends on the kind of detector that is used. Efforts were made to use the CCD detector for fast-moving low earth orbit debris by reading out the detector at the same rate and in the same direction as the debris object crosses the field of view of the telescope. In this mode, the telescope was capable of detecting debris as small as 3 centimeters at 900 km altitude. However, this mode is very inefficient, since debris moving in other directions is not detected. Observations have also been done using an intensified CCD video camera as the detector. The limiting detectable size for this detector was about 4 centimeters at 500 km, and 7 centimeters at 1000 km. A design was developed for the optimum detector for fast-moving debris in low earth orbit based on currently available technology. This is a 1024×1024 element CCD detector operating at 200 frames per second, with pixels binned to 16×16. This detector should be capable of detecting 1 cm debris at 500 km and 1.5 cm debris at 1000 km. New data processing algorithms will be required to process the data stream from this detector.

Long term Evolution of Earth Orbiting Debris

AbstractThe space environment is presently dominated by man-made debris, for particles larger than 1 mg. A comprehensive survey of the debris population from 1 mg to the larger sizes in view of the recent data from radar and optical observations, and from the analysis of materials retrived from space is given.A brief description of the major source and sink mechanisms acting on the debris population is given, along with a very short introduction to the two models for the long term evolution developed by the group in Pisa in the last years.The results of the long term evolution analysis are presented in some detail. A likely scenario of the future space activities leads to a large growth of mmsize particles due to several catastrophic collisions. The simulation highlights the necessity of more realistic explosion models, since the current ones overestimate the 10 cm-sized fragments.An enlarged version of this paper can be found at the CNUCE Spaceflight Dynamics Group Web site: http://apollo.cnuce.cnr.it/~rossi/homerossi.html.

The long-term implications of operating satellite constellations in the low earth orbit debris environment

DRA's Integrated Debris Evolution Suite (IDES) model is used in this study to predict the future evolution of the orbital debris environment for two distinct scenarios. For the first case, a pre-generated background debris population for 1995 and ‘business as usual’ future launch/explosion rates are used as input to the model. IDES then employs its collision event prediction algorithm to simulate evolution from 1996 to 2020 as a baseline. The second scenario uses the same initial conditions and future trends, but in addition, a large constellation is introduced into the simulation process from year 1998 onwards. The additional contribution of the constellation to the temporal variation of key environment/population parameters is presented; including enhancement from any long-term collision coupling effects.

Collisional evolution of the Earth's orbital debris cloud

We have developed a numerical algorithm to model the future collisional evolution of the low‐orbiting Earth debris population, accounting for both the wide spectrum of masses (or sizes) of the orbiting objects, and their different altitudes, which result in a variable efficiency of the drag‐induced decay. The evolution process has been assumed to be caused by a number of source and sink mechanisms, such as launches, explosions, atmospheric drag, and mutual collisions. The collisional outcomes have been described through a semiempirical model for the fragment mass distributions, consistent with the available experimental evidence. A runaway exponential growth of collision fragments is always found in our model. Although its timing and pace are sensitive to some poorly known parameters, fairly plausible parameter choices predict that the runaway growth will occur within the next century, starting in the crowded shells between 700 and 1000 km of altitude and, somewhat later, between 1400 and 1500 km. The runaway growth is delayed until a few centuries in the future only if the catastrophic breakup threshold in specific impact energy for orbiting objects exceeds that for natural rocky bodies by at least a factor of 10. Our simulations show that the sensitivity of the results to future launch and/or deorbiting and removal policies is rather weak, so that drastic measures will need to be taken soon in order to significantly avoid or delay a catastrophic outcome.

Development of concepts for detection and characterisation of debris in Earth orbit using passive optical instruments

There is a need for improved knowledge of the space-debris environment, in the millimetre and centimetre debris-size range. A study on passive optical instruments for observation of space debris concludes that useful data can be acquired using either ground-based or space-based systems.

Future collisional evolution of Earth-orbiting debris

Earth-orbiting objects can undergo high-velocity mutual collisions which affect their size distribution by generating swarms of fragments, playing the role of potential new projectiles. We are developing a model which simulates this collisional evolution process by integrating a set of 150 coupled, nonlinear, first-order differential equations which include various source and sink terms. Some preliminary results are illustrated, showing that on the long term the impact process can cause a catastrophic decrease of the spacecraft population, in particular in the shell between 700 and 1000 km altitudes.

Is the space environment at risk?

The huge potential of space for science, exploration and peaceful applications could be jeopardized by debris in Earth orbit, and by an extraterrestrial arms race.