Jonathan's Space Pages

Catalog of Space Debris Clouds - Introduction

Many of the tracked space debris objects in Earth orbit belong to specific debris clouds - by which I mean that they originate from a single parent object that broke up, and have broadly similar orbital parameters. Some orbital parameters, such as orbital inclination, usually remain relatively constant over decades, so that even objects discovered long after the originating event can often be associated with a specific cloud with high confidence. The Debris Clouds catalog lists these clouds and their characteristic orbital parameters. The catalog has similarities with the classic source on this issue, Nicholas Johnson's History of On-Orbit Satellite Fragmentations, released by the NASA JSC Orbital Debris Program Office (ODPO) and taken over by Philip Anz-Meador after Nick's retirement. At this writing the History is in its 15th edition; it is available at the ODPO website.

The traditional way to represent a debris cloud graphically is the Gabbard diagram (developed by John Gabbard of NORAD in the 1960s), which charts object perigee and apogee versus orbital period. The ODPO document presents these for each event; rather than replicate those, I have chosen to experiment with different representations, described below. The ODPO document also excludes some apparent debris clouds without explanation; the present catalog therefore does not have exactly the same list of clouds.

I consider four main types of debris cloud:

• Case 1: Generic debris clouds which include
  • Residual propellant breakups, when a rocket stage's leftover fuel and oxidizer combine, perhaps years after the stage is abandoned in orbit, resulting in an explosion and destruction of the stage.
  • Propulsion failures, when an attempted rocket burn fails catastrophically.
  • Battery explosions, when stored energy in a spacecraft battery is released destructively
  • Deliberate self-destruct, using an explosive charge on the space object
  • Structural disintegration due to non-propulsion-related overpressure, for example the disruption of an inflated fabric balloon satellite
  • Structural disintegration due to rapid tumbling, sometimes as a result of a stuck thruster
  • Destruction due to the impact of a small debris object or a suborbital antisatellite weapon, where the impacting object does not leave behind its own debris cloud.

  
  All of these cases have a similar result: the parent object is partially or completely destroyed, with smaller or larger amounts of kinetic energy imparted to a range of the resulting debris sending it into a range of different orbits intersecting the original orbit.

  
  

• Case 2: Satellite collision events in which two cataloged orbiting objects collide and generate a dual debris cloud. A collision at orbital velocities results in hypersonic shock waves passing through the two satellites, reducing them to debris almost instantly. The debris clouds from the two shattered satellites then pass through each other retaining the bulk of their original momentum, and you are left with two separate clouds in orbits similar to those of the two original satellites (rather than a single cloud with the velocities isotropized as one might naively expect from experience of low-velocity collisions).

  
  These events are simply treated as two separate clouds in the catalog.

  
  

• Case 3 Extended duration low-energy fragmentation in which debris objects are shed at low relative velocity by a satellite intermittently over many years. These were dubbed `anomalous' events by Johnson and may be due to material degradation of the satellite (for example, deterioration of thermal insulation blankets due to solar ultraviolet exposure). These are included in the catalog as single clouds, but it should be noted that the `event date' given is that of the shedding of the first objects in the cloud (in contrast to the other catalog entries where all the debris objects in the cloud are thought to be created at that one specific time).
• Case 4 Deliberately released objects - in some cases, large numbers of small objects are deliberately released from a satellite or a group of satellites that effectively make a debris cloud. Some such cases are included in the catalog as an aid to identifying newly discovered objects from such `faux debris clouds'.

A fifth case is that of an aerodynamic breakup. As an elliptical orbit satellite approaches reentry, items like solar panels and booms can break off during perigee passages. These breakups don't usually result in large numbers of cataloged debris, and are not included here.