When What Goes Up Does Not Come Down - Dealing with Debris

Readers will appreciate that there is international consensus that space activities need to be managed to minimize debris generation and the risk that debris may pose. This consensus is embodied in space debris mitigation guidelines published by organizations such as the International Telecommunication Union (ITU), the Inter-Agency Space Debris Coordination Committee (IADC), and the United Nations. What readers may not be so familiar with is how these guidelines are translated into engineering practice, and that they themselves can contribute to the review of key high level debris mitigation requirements.

The general aim of space debris mitigation measures is to reduce the growth of space debris by ensuring that, "spacecraft and launch vehicle orbital stages are designed, operated and disposed of in a manner that prevents them from generating debris throughout their orbital lifetime" (ISO 24113).

The International Organization for Standardization (ISO) standard ISO 24113:2011 translates these objectives, "into a set of high-level debris mitigation requirements" and practical engineering practice. It sets out the primary space debris mitigation requirements applicable to all elements of unmanned systems launched into, or passing through, near-Earth space, including launch vehicle orbital stages, operating satellites and any objects released as part of normal operations. It defines both Low Earth Orbit (LEO), up to 2,000 km, and Geostationary Earth Orbit (GEO), 35,786 km, as "protected regions."

Processes to enable compliance with these requirements are set out in a series of lower-level implementation standards which cover, for example, guidelines for launch vehicle orbital stages, design and operation guidelines for spacecraft and best practices, data requirements and operational concepts for avoiding collisions among orbiting objects.

Perhaps the most important of the norms within ISO 24113 relates to post-mission disposal. As commented by Hedley Stokes, director at PHS Space Limited, "Disposal is generally regarded as the best way to limit the future increase in the orbital debris population. However, at present a sizable percentage of satellites in LEO do not have adequate provisions for disposal. This is no longer a tenable situation. As a consequence, the widespread adoption of ISO 24113 is now being actively encouraged."

The importance of this standard can be seen by the increasing crowding of LEO through the rapid growth in the number of small satellites in recent years and the imminent arrival of mega-constellations.

ISO 24113 has just reached its first five-year systematic review. The ISO Orbital Debris Working Group (with the catchy reference ISO/TC20/SC14/WG7) is currently working on a new version of ISO 24113.

Since the publication of ISO 24113 in 2011, a number of significant changes have been suggested. These are now being considered by the ISO Orbital Debris Working Group.

ISO 24113 was developed by industry for industry. The five-year review is an opportunity for all stakeholders to confirm that the requirements contained within the standard are achievable and appropriate. Feedback from manufacturers, operators and space agencies is an essential part of that process. As Dr Stokes says "Further comments are welcome, especially from those involved in the large-scale production of satellites."

To ensure that space remains open for business in the long term it is imperative that manufacturers and operators implement debris mitigation measures. ISO 24113 provides a comprehensive set of internationally agreed norms, which have been designed with that objective in mind.

As with other regulatory and licensing agencies, the UK Space Agency consider compliance with ISO 24133 to be a condition of obtaining a UK Outer Space Act license.

Any mandatory measure to mitigate space debris is likely to lead to an increase in the cost of space activities. An international solution to space debris, therefore, can only be achieved after the appropriate national or regional regulations are, as far as possible, harmonized internationally to avoid unfair competition. An international solution must be based on a level playing field. International standards, such as ISO 24113, are therefore vital. However. it is important that such standards are practically implementable and to that end I would encourage interested parties to engage in this review process. VS