Since the beginning of space flight, the collision hazard in Earth orbit has increased as the number of artificial objects orbiting the Earth has grown. Spacecraft performing communications, navigation, scientific, and other missions now share Earth orbit with spent rocket bodies, nonfunctional spacecraft, fragments from spacecraft breakups, and other debris created as a byproduct of space operations. Orbital Debris examines the methods we can use to characterize orbital debris, estimates the magnitude of the debris population, and assesses the hazard that this population poses to spacecraft. Potential methods to protect spacecraft are explored. The report also takes a close look at the projected future growth in the debris population and evaluates approaches to reducing that growth. Orbital Debris offers clear recommendations for targeted research on the debris population, for methods to improve the protection of spacecraft, on methods to reduce the creation of debris in the future, and much more.

Derelict satellites, equipment and other debris orbiting Earth (aka space junk) have been accumulating for many decades and could damage or even possibly destroy satellites and human spacecraft if they collide. During the past 50 years, various National Aeronautics and Space Administration (NASA) communities have contributed significantly to maturing meteoroid and orbital debris (MMOD) programs to their current state. Satellites have been redesigned to protect critical components from MMOD damage by moving critical components from exterior surfaces to deep inside a satellite's structure. Orbits are monitored and altered to minimize the risk of collision with tracked orbital debris. MMOD shielding added to the International Space Station (ISS) protects critical components and astronauts from potentially catastrophic damage that might result from smaller, untracked debris and meteoroid impacts. Limiting Future Collision Risk to Spacecraft: An Assessment of NASA's Meteoroid and Orbital Debris Program examines NASA's efforts to understand the meteoroid and orbital debris environment, identifies what NASA is and is not doing to mitigate the risks posed by this threat, and makes recommendations as to how they can improve their programs. While the report identified many positive aspects of NASA's MMOD programs and efforts including responsible use of resources, it recommends that the agency develop a formal strategic plan that provides the basis for prioritizing the allocation of funds and effort over various MMOD program needs. Other necessary steps include improvements in long-term modeling, better measurements, more regular updates of the debris environmental models, and other actions to better characterize the long-term evolution of the debris environment.

Space-based observations have transformed our understanding of Earth, its environment, the solar system and the universe at large. During past decades, driven by increasingly advanced science questions, space observatories have become more sophisticated and more complex, with costs often growing to billions of dollars. Although these kinds of ever-more-sophisticated missions will continue into the future, small satellites, ranging in mass between 500 kg to 0.1 kg, are gaining momentum as an additional means to address targeted science questions in a rapid, and possibly more affordable, manner. Within the category of small satellites, CubeSats have emerged as a space-platform defined in terms of (10 cm x 10 cm x 10 cm)- sized cubic units of approximately 1.3 kg each called "U's." Historically, CubeSats were developed as training projects to expose students to the challenges of real-world engineering practices and system design. Yet, their use has rapidly spread within academia, industry, and government agencies both nationally and internationally. In particular, CubeSats have caught the attention of parts of the U.S. space science community, which sees this platform, despite its inherent constraints, as a way to affordably access space and perform unique measurements of scientific value. The first science results from such CubeSats have only recently become available; however, questions remain regarding the scientific potential and technological promise of CubeSats in the future. Achieving Science with CubeSats reviews the current state of the scientific potential and technological promise of CubeSats. This report focuses on the platform's promise to obtain high- priority science data, as defined in recent decadal surveys in astronomy and astrophysics, Earth science and applications from space, planetary science, and solar and space physics (heliophysics); the science priorities identified in the 2014 NASA Science Plan; and the potential for CubeSats to advance biology and microgravity research. It provides a list of sample science goals for CubeSats, many of which address targeted science, often in coordination with other spacecraft, or use "sacrificial," or high-risk, orbits that lead to the demise of the satellite after critical data have been collected. Other goals relate to the use of CubeSats as constellations or swarms deploying tens to hundreds of CubeSats that function as one distributed array of measurements.

The 37-year (1961-1998) history of orbital debris concerns. Tracks orbital debris hazard creation, research, observation, experimentation, management, mitigation, protection, and policy. Includes debris-producing, events; U.N. orbital debris treaties, Space Shuttle and space station orbital debris issues; ASAT tests; milestones in theory and modeling; uncontrolled reentries; detection system development; shielding development; geosynchronous debris issues, including reboost policies: returned surfaces studies, seminar papers reports, conferences, and studies; the increasing effect of space activities on astronomy; and growing international awareness of the near-Earth environment.

The future evolution of the debris environment will be forecast on the basis of traffic models and possible hazard mitigation practices. The text shows how large trackable objects will have re-entry pinpointed and predictions made on related risk assessment for possible ground impact. Models will also be described for meteoroids which are also a prevailing risk.