1) The lectures will examine how changes in the upper atmosphere due to climate change could impact the population of space debris in low Earth orbit. 2) Models predict the atmospheric density at 400km could decrease by 80% by 2095 due to increased CO2, accelerating the natural decay of objects in low orbit. 3) Compliance with guidelines for post-mission disposal of objects can help limit growth of the space debris population, but a strong density trend would remove these benefits and lead to a 50% increase in debris over 100 years.

1. Space Environment
Lecture 18 – Geospace Climate
Impact on space debris (part 1)
Professor Hugh Lewis
SESA3038 Space Environment

2. Overview of lectures 18 & 19
• In the next two lectures we will see the consequences of climate change in
the upper atmosphere on the space debris population in low Earth orbit
– These lectures bridge the topics we have covered this week and those
that are coming in future weeks
– There is *no* detailed introduction to the space debris problem or the
computational models used to investigate it. We will just look at the
results from the computational model DAMAGE applied to two basic
scenarios:
– The effects of a thermospheric density trend on LEO post-mission
disposal and active debris removal
– The effects of a prolonged solar minimum (like the Maunder
minimum from the 1600s) on LEO post-mission disposal and active
debris removal
Space Environment – Geospace Climate

3. Predictions of density changes
(reminder)
WACCM-X model predictions
for the years 2000 and 2095
based on RCP8.5
By the year 2095 atmospheric
density at 400 km altitude could
be at only 20% of the year 2000
level
Space Environment – Geospace Climate

4. Satellite decay (reminder) Space Environment – Geospace Climate
Results from Brown et al., 2019 for RemoveDebris:

5. Impact of trends on space debris Space Environment – Geospace Climate
Inter-Agency Space Debris
Coordination Committee (IADC)
definition:
“Space debris are all man made
objects including fragments and
elements thereof, in Earth orbit
or re-entering the atmosphere,
that are non functional.”

6. Tracked objects 2000-2020 Space Environment – Geospace Climate
https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv24i4.pdf

7. IADC space debris mitigation
guidelines
Space Environment – Geospace Climate
https://www.iadc-home.org/documents_public
Seven mitigation guidelines:
1. Limit debris released during normal operations
2. Minimize potential for post-mission break-ups resulting from stored energy
3. Prevention of on-orbit collisions
4. Minimize the potential for break-ups during operational phases
5. Avoidance of intentional destruction and other harmful activities
6. Post mission disposal: geosynchronous region
7. Post mission disposal: objects passing through the LEO region

8. IADC space debris mitigation
guidelines
Space Environment – Geospace Climate
https://www.iadc-home.org/documents_public
Seven mitigation guidelines:
1. Limit debris released during normal operations
2. Minimize potential for post-mission break-ups resulting from stored energy
3. Prevention of on-orbit collisions
4. Minimize the potential for break-ups during operational phases
5. Avoidance of intentional destruction and other harmful activities
6. Post mission disposal: geosynchronous region
7. Post mission disposal: objects passing through the LEO region

9. Model predictions Space Environment – Geospace Climate
Use Monte Carlo simulation to investigate debris mitigation measures:
E.g. Post-mission disposal in low Earth orbit (LEO)

10. Use Monte Carlo simulation to investigate debris mitigation measures:
E.g. Post-mission disposal in low Earth orbit (LEO)
Model predictions Space Environment – Geospace Climate

11. Benefits of post-mission disposal Space Environment – Geospace Climate
30% compliance
90% compliance

12. Benefits of post-mission disposal Space Environment – Geospace Climate
30% compliance
90% compliance

13. Effects of density trend Space Environment – Geospace Climate
Normal atmospheric
model, no CO2 density
trend
Modified
atmospheric model,
with CO2 density
trend (-2% to -5%
per decade)
90% compliance
90% compliance

14. Effects of density trend Space Environment – Geospace Climate
Normal atmospheric
model, no CO2 density
trend, 30% compliance
with post-mission
disposal guideline
Modified atmospheric
model, with CO2
density trend (-2% to
-5% per decade), 90%
compliance with post-
mission disposal
guideline
30% compliance
90% compliance

15. Effects of density trend Space Environment – Geospace Climate
Normal atmospheric
model, no CO2 density
trend
Modified atmospheric
model, with CO2
density trend (-2% to
-5% per decade)
8,082 objects
90% compliance
90% compliance

16. Effects of density trend Space Environment – Geospace Climate
Normal atmospheric
model, no CO2 density
trend
Modified atmospheric
model, with CO2
density trend (-2% to
-5% per decade)
90% compliance
90% compliance

17. Active debris removal Space Environment – Geospace Climate
Use DAMAGE to explore
the effects of CO2 cooling
on Active Debris Removal:
ADR = 5 removals per year
(commencing 1 January
2020)
MITIGATION = 90% post-
mission disposal compliance
8000
9000
10000
11000
12000
13000
14000
15000
16000
2010 2020 2030 2040 2050 2060 2070 2080
Year
Effective
number
of
objects
(LEO,
>
10
cm)
MITIGATION No Contraction
MITIGATION Contraction
ADR No Contraction
ADR Contraction
ADR10 Contraction
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011JA016482

18. Conclusions Space Environment – Geospace Climate
A density trend of -2% to -5% per decade:
• Removes the benefit of post-mission
disposal:
• The population growth changes from quasi-
stable to non-linear increase
• Average number of objects increases by ~50%
after 100 years (compared with no density trend)
• Increased uncertainty in model MC outputs with
extreme outcomes more likely
• Removes the benefit of active debris
removal:
• Population size after 70 years is greater than the
baseline 90% compliance case when the density
trend is included, even if the debris removal rate
is doubled
Note that recent results (from Brown et al.)
show a density trend of up to -12% per decade