ROOM
26
Special Report
best-case scenarios we cannot expect 100%
compliance with any set of disposal guidelines. With
more objects being launched to GEO, there will
always be a certain fraction of items that are not de-
orbited prior to their end-of-life. Additionally, there
exists the ever-present danger of debris-on-debris
collisions for objects trapped in the GEO belt.
ADR will be expensive; it will require multiple
launches of many satellites that carry sufficient
fuel to impart the necessary ‘delta-V’ to the
spinning, tumbling debris objects that need to be
removed from the GEO belt. It will also necessitate
the resolution of some thorny legal issues in an
international setting. Thus, ADR is a high-cost,
long lead-time activity. But are there any aspects
of it that might be done cheaper and/or on
shorter timescales?
Certainly characterisation of space objects (an
SSA task) is key to ADR. Before one might attempt
to do anything with a candidate object, one would
want to know as much as possible about that
object. How big is it? At what rate and about what
set of axes does it rotate? What is the area-to-mass
ratio? What surface and thermal properties can be
determined for the object]? These are all questions
that can be answered by ground-based optical
observations using existing technology.
Are there other schemes that might serve as well
as full-blown removal, or act as stopgaps until ADR is
achievable? One idea is ‘just in time’ debris trajectory
adjustment [25]: this scheme involves expelling
compressed cold gas into the orbit of a debris
object to change its course a short time before it is
predicted to collide with another object.
This might be achievable with a few satellites
stationed near the two GEO ‘pinch points’, that
would be called upon as needed. It does not solve
the long-term problem because it does not actually
remove debris but it solves the immediate problem of
preventing collisions. It gets around the ‘probability’
problem by only interacting with objects that are
actually a threat, and it greatly reduces the energy
needed, compared to actually de-orbiting the object.
Another possible first-step could be to attach
small beacons on debris and defunct satellites to
aid in their tracking. It might have similar legal
and political problems to actual ADR but it could
greatly aid in tracking and identifying such objects
and it would be technically much easier.
Therefore, given that ADR will require
international cooperation, technology
development and multiple launches, it is neither
cheap, quick or easy. Yet, if we want to maintain
a sustainable use of the GEO belt, it is something
that will need to be done in the long-term.
Thus, we should continue to investigate ADR, its
derivatives and similar alternatives, though it is
probably unfeasible to begin constructing any
deployable systems for the near future.
What can be done now?
The GEO belt is a shared resource for use by the
human race but continued safe access to this
resource is not assured, chiefly for reasons of our
own making.
Existing and future space debris threatens safe
operations of satellites in this orbital regime. The
space-faring nations whose actions contributed to
the current situation will need to show leadership
regarding actions needed to ameliorate the problem.
The calculated
sub-latitude and sub-
longitude (ground tracks)
for two HAMR objects
observed from Maui,
spanning five days. The
filled circles at zero
degrees latitude represent
the locations of a subset
of the geostationary
satellite [16].
