ISO 16164:2015 focuses on the post-mission disposal of spacecraft operating in, or crossing, Low Earth Orbit (LEO). The disposal of orbital launch stages operating in, or crossing, LEO is not dealt with in this International Standard.
Post-mission disposal of an Earth-orbiting spacecraft broadly means removing the spacecraft from its operational orbit after the end of mission, manoeuvring it to a region of space where it is less likely to interfere or collide with other operational spacecraft or with orbital debris and passivating.
For a spacecraft operating in, or crossing LEO, there are six disposal options that might be used to ensure its compliance with orbital debris mitigation requirements (as stated in ISO 24113). In order of preference, these are the following:
a) retrieving it and performing a controlled re-entry to recover it safely on the Earth;
b) manoeuvring it in a controlled manner into a targeted re-entry with a well-defined impact footprint on the surface of the Earth to limit the possibility of human casualty;
c) manoeuvring it in a controlled manner to an orbit that has a decay lifetime short enough to meet all orbital debris mitigation requirements;
d) augmenting its orbital decay by deploying a device so that the remaining orbital lifetime is short enough to meet all orbital debris mitigation requirements;
e) allowing its orbit to decay naturally, given that all orbital debris mitigation requirements will be met without the need for a disposal manoeuvre or other action;
f) manoeuvring it in a controlled manner to an orbit with a perigee altitude sufficiently above the LEO protected region (i.e. a graveyard orbit) that long-term perturbation forces do not cause it to re-enter the LEO protected region within 100 years.
ISO 16164:2015 specifies requirements for the following:
a) planning for disposal and passivation of spacecraft operating in LEO to ensure that final disposal is sufficiently characterized and that adequate propellant will be reserved for any propulsive manoeuvre required,
b) selecting a disposal orbit where the spacecraft will re-enter the Earth's atmosphere within the next 25-years, or where the spacecraft will not re-enter the protected region within the next 100-years, and
c) estimating, prior to launch, a 90 % or better probability of successfully executing the disposal manoeuvre.
Techniques for planning and executing space hardware disposal are provided that reflect current internationally accepted guidelines and consider current operational procedures and best practices.