The History Of Space Junk: When Sputnik I became the first artificial satellite in 1957, it also became the first piece of space junk. The rocket stage that carried it into orbit was the second. These objects were not only the beginning of a new era of space exploration, but also the start of a new challenge: how to monitor and manage the debris that accumulates in space.
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Gabbard diagram is a simple yet useful tool to analyze space object fragmentation. It was developed by John Gabbard, at North American Aerospace Defense Command (NORAD) . It plots the apogee and perigee altitudes of the fragments against their orbital periods. During the breakup/fragmentation, the fragments will gain/loose velocity (ΔV) thus reducing/increasing their orbital energy.
The fragments with increased orbital energy will have higher apogee while those with decreased orbital energy will have lower perigee altitude compared to the parent (fragmented) object, The resulting Gabbard diagram will have an X-shaped distribution (depending upon the fragmentation altitude) with the parent object occupying the center.
The fragments with positive ΔV (higher apogee altitude and same perigee) will be on the right-hand side while those with negative ΔV (lower perigee and apogee).
As the fragment’s loose energy due to atmospheric drag, their position in the Gabbard diagram is pushed towards the bottom left-hand side, until they decay. Moreover, the loss of energy causes their apogee to decreases and the orbits become more circular.
The History Of Space Junk:
The fragments occupying position on the far right-hand (with maximum positive ΔV), will have less decay rate compared to others. Gabbard diagram of Cosmos 1408 fragments with TLE data dated 29- Dec-2021 and 12-Apr-2022.
It can be seen that as the fragments on the left-hand side lost energy due to atmospheric drag, their orbits became relatively circular, merging the two left-hand side arms in the Gabbard diagram for Cosmos 1408.
Threats Due to Space Debris Space debris poses a serious threat to operational satellites which might be damaged or even catastrophically destroyed due to collision. The debris have very high orbital velocity. In LEO orbit it is in the order of 7-8 km/s which gives high momentum approximately ten times the speed of a bullet.
The general rule is that the space debris follows a power law distribution i.e. there are more small sized debris than large debris. With such high speed, even millimetre sized debris can create serious problem for mission operations including the human space flight and robotic missions. It may be noted that debris of size 0.4 mm can penetrate the space suit of astronauts during spacewalk and
threaten the safety of astronauts.
The big tracked objects represent only the tip of the iceberg but most of the mission ending catastrophes are dominated by small (mm to cm sized) debris impacts. The damages caused to space assets due to debris impact.
Major perturbing forces such as atmospheric drag, luni-solar attraction, solar radiation pressure may result in the re-entry of space debris in to Earth’s atmosphere. An object experiences very high aerodynamic load that may cause its structure to break-up during the re-entry. The intense aerothermal heating further causes most of the fragments to ablate, except for those having very high melting point.
Typical break-up of an Automated Transfer Vehicle (ATV). Such surviving objects poses risk to human life, property and environment on surface of the Earth. One such incident is the re-entry of Cosmos 954 in 1978 that scattered radioactive debris over large areas of North Canada.
From the previous discussions, it is evident that space debris poses a risk to space activities. The space debris problem is two-fold, the long-term and the short-term. Historical data shows that the space debris population is increasing and despite decades of efforts to limit the generation of new space debris, there is no sign of any decrease which threatens the long-term sustainability of outer space activities.
For satellite operators, the long-term increase in space object population after thirty to fifty years is not of urgent concern. Their concern is to safeguard their spacecraft over its mission life, which typically is around 5 to 10 years, and hence, they need to address the short-term detrimental effects of space debris. For both cases, accurate debris measurement of space objects is essential.
As we continue to add more and more material to the near-Earth environment, we only increase the potential of more collisions, as more and more fragments are generated. Finally, this may lead to a cascading effect creating a self-sustaining cloud of debris around the Earth. This scenario is known the Kessler Syndrome, after its proponent Kessler, a NASA scientist.
Sure, here are some of the most significant events related to space debris:
|The U.S. Navy intercepted its defunct spy satellite USA-193 on Feb. 20, 2008, sending a trail of debris.
|A woman in Turley, Oklahoma, was struck with a lightweight fragment of charred woven material identified as debris from a Delta 2 booster, which reentered the Earth’s atmosphere on Jan. 22, 1997.
|Several mysterious spheres turned up in Australia in the 1960s. One such titanium sphere was later identified as a tank used for drinking water in the Gemini V spacecraft.
|A secret Soviet-navy satellite called Cosmos 954, which was launched on Sept. 18, 1977, spiraled out of control and reentered over Canada, shedding debris across the frozen ground of the Canadian Arctic.
|On Jan. 21, 2001, a Delta 2 third stage, known as a PAM-D (Payload Assist Module-Delta), reentered the atmosphere over the Middle East.
|Injury from Space Debris
|In 2002, a 6-year-old boy in China became the first person to be injured by direct impact from space debris.
|In 2003, large parts of the Columbia spacecraft reached the ground and entire equipment systems remained intact.
|Japanese Ship Incident
|In 1969, five sailors on a Japanese ship were injured when space debris from what was believed to be a Soviet spacecraft struck the deck of their boat.
|Kosmos 954 Incident
|In 1978, the Soviet reconnaissance satellite Kosmos 954 reentered the atmosphere over northwest Canada and scattered radioactive debris over northern Canada.
|In 1979, portions of Skylab came down over Australia, and several pieces landed in the area around the Shire of Esperance.
Please note that the descriptions are brief and for more detailed information, you can refer to the provided references.
In his 1978 seminal paper , he showed that even without any new launches, such a cascading event can be triggered due to collision among the orbiting objects themselves, the resultant artificial debris belt would severely hinder any future space-based activities. Therefore, various analysis, mitigation and remediation techniques are in place to address the space debris problems.
Space Debris Mitigation
United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) was established in 1959 to govern the exploration and use of outer Space for the benefit of humanity: for peace, security and development. A set of high-level qualitative guidelines for space debris mitigation, having wider acceptance among the global space community was aimed by UN-COPUOS . The space debris mitigation guidelines of IADC  provided the foundation for these guidelines.
The Working Group on Space Debris was established by the Scientific and Technical Subcommittee of the Committee to develop guidelines based on the technical content of IADC space debris mitigation guidelines. It also took into consideration the United Nations treaties and principles on outer space. In 2007.
The subcommittee adopted the Space debris mitigation guidelines on limiting debris released during normal operations, minimising the potential for post-mission break-ups resulting from stored energy, minimising the potential for on-orbit break-ups during operational phases, avoiding intentional destruction and other harmful activities, limiting the long-term presence of spacecraft and launch vehicle in various orbital stages.
In the low-Earth orbit (LEO) region after the end of their mission, limiting the long-term interference of spacecraft and launch vehicle orbital stages with the geosynchronous Earth orbit (GEO) region after the end of their mission and limiting the probability of accidental collision in orbit.
The key rules for post mission disposal are as follows.
- The 25-year rule for LEO as recommended by IADC prescribes that the post-mission orbital life
of a LEO object should be less than 25 years. The 25-year rule is an effective and achievable way to limit the long-term presence of spent upper stage or defunct satellite in LEO .
- For spacecraft or launch vehicle orbital stages operating in the GEO protected region, with either
a permanent or periodic presence, shall be manoeuvred in a controlled manner during the disposal phase to an orbit that lies entirely outside the GEO protected region.
For mitigation of ground casualty risk due to the re-entering objects, the following are recommended:
Re-entry risk mitigation by controlled re-entry:
Controlled re-entry is the ability to ensure re-entry over a pre-determined area. For more massive satellites (mass > 1000 kg), controlled re-entry is to ensure a specified target impact zone outside the habitable area. Controlled re-entry is mandatory if the risk for the ground population is greater than 10-4. Re-entry to be pre-announced to air space (2 days in advance) and naval safety (6 days in advance) authorities for issuing warning messages (NOTAM and NAVAREA).
Design for Demise:
To avoid the risk of human casualty from a spacecraft component, the re-entry should not pose a risk to more than 10-4 of the ground population. The components of the spacecraft shall be designed to demise during re-entry. A trade-off between survivability and structural stability to absorb launch stresses shall be ensured.
Space weather is mainly governed by various solar phenomena and their interactions with Earth’s magnetosphere, ionosphere and thermosphere. It has a significant impact on the behaviour and dynamics of space debris. The major space weather events are driven by solar particle events due to coronal mass ejections, solar flares, trapped radiation and galactic cosmic rays.
Depicts particle and energy flux in solar wind and coronal mass ejections reaching the Earth’s environment. Solar radiation storms associated with CME and flares have a high density of high energy particles, protons and electrons that pervade the near-Earth environment. Geomagnetic storms are disturbances in the Earth’s magnetosphere, caused by strong variations in the speed, density, and magnetic properties of the solar wind.
Such storms increase the atmospheric drag and also affect satellite electronics, navigation, and radio systems. They result in increased radiation hazards to astronauts and affect the satellites and radio systems. Radio blackouts are caused by solar flares and produce enhanced electron density which primarily affects the high frequency communication and cause GPS outages. Variations in atmospheric density directly impact the drag experienced by space debris in low Earth orbit (LEO).
During periods of heightened solar activity, the atmosphere expands, leading to increased drag on objects. Consequently, the orbital decay accelerates, causing objects to re-enter the Earth’s
atmosphere more rapidly than anticipated.
The impact of space weather on a spacecraft. When Solar Energetic particles (SEP) interact with space debris, they induce electrostatic charging and modify the orbital trajectories of debris objects. SEPs can degrade the performance of on-board sensors and instruments, including those used for debris tracking and avoidance.
Space weather events can compromise the structural integrity of spacecraft and satellites, rendering them more susceptible to impacts from micrometeoroids and space debris. Out of 49 satellites launched in the batch 40 of them re-entered the atmosphere because of a geomagnetic storm.
Natural Objects and Micrometeoroids:
The solar system consists of eight planets, numerous planetary satellites, asteroids, comets,
meteoroids and other icy planets along with the interplanetary medium of highly tenuous gas and dust.
Asteroids are rocky remnants of the early formation of our solar system. Ranging in size from a few meters to hundreds of kilometers, these celestial bodies orbit the Sun. They are mostly found in the asteroid belt between the orbits of Mars and Jupiter.
As their orbits are perturbed due to various forces, some of the asteroids cross the Earth’s orbit and may even impact the Earth. The asteroids with a perihelion distance of less than 1.3 AU are termed Near Earth Asteroid (NEA).
Potentially Hazardous Asteroids (PHA) are the bigger NEAs with a size of more than 140m and having orbits that pass within 7.5 million km from Earth. The actual probability of impact with orbiting spacecraft is very small.
Comets are composed of icy materials and dust. They are formed in the outer regions of the solar nebula and are mostly found in the Kuiper Belt and Oort cloud regions. They have a highly elliptical orbit around the Sun. When a comet approaches the Sun, the heat causes the ice to vaporize, creating a glowing coma and a characteristic tail forms due to the radiation pressure from the Sun. \
A second tail known as the ion tail or the gas tail also forms due to the ionization of gas by high energy solar particles. Cometary debris can also pose a risk to spacecraft, particularly due to the release of gas and the potential for fragmentation.
Micrometeoroids are tiny, solid particles that travel through space at high velocities. They can range in size from 10 micrometres to 2 millimetres, and their origin can vary from asteroid collisions to the fragmentation of comets. They burn up when they enter a planet’s atmosphere. Micrometeoroids are not called space debris because they are not human-made. Micrometeoroids pose a significant hazard to spacecraft due to their immense spacecraft due to their immense speed and the potential damage they can inflict upon impact.
micrometeoroids measuring a fraction of a millimetre can breach protective layers, damaging
sensitive equipment or puncturing the fuel tank of a spacecraft. The comprehensive knowledge of the components that make up the space environment as discussed in this section forms the basis of