scispace - formally typeset

Journal ArticleDOI

A LEO satellite postmission disposal study using legend

01 Jul 2005-Acta Astronautica (Pergamon)-Vol. 57, Iss: 2, pp 324-329

AbstractThis paper summarizes results from two postmission disposal (PMD) parametric analyses based on the high fidelity NASA orbital debris evolutionary model LEGEND. The first analysis includes a non-mitigation reference scenario and four test scenarios, where the mission lifetimes of spacecraft are set to 5, 10, 20, and 30 years, respectively, before they are moved to the 25-year decay orbits. The comparison among the five scenarios quantifies how a prolonged spacecraft mission lifetime decreases the effectiveness of the 25-year decay rule in the low Earth orbit region (LEO). The second analysis includes three 25-year decay PMD scenarios where the mission lifetimes of spacecraft are set to 5 years but with disposal success rates set to 50%, 70%, and 90%, respectively. It illustrates how the PMD success rate impacts the long-term debris environment. The conclusion of this paper is that a prolonged spacecraft mission lifetime and a lower PMD success rate can have noticeable negative impact on the debris environment in the long run.

Topics: Space debris (51%)

Summary (1 min read)

Guidelines and Assessment Procedures for

  • Limiting Orbital Debris, recommends placing a spacecraft or upper stage passing through the low Earth orbit regime (LEO, region of space below 2,000 km altitude) in an orbit in which atmospheric drag will limit its lifetime to less than 25 years after the completion of mission4.
  • This postmission disposal practice has been known as the 25-year decay rule.
  • A prolonged spacecraft mission lifetime will certainly decrease the effectiveness of the 25year decay rule.
  • Details of the scenarios and the study results are presented in the following sections.

SPACECRAFT MISSION LIFETIME

  • The spacecraft mission lifetime test cases included a non-mitigation scenario and four PMD test scenarios.
  • Objects with non-zero explosion probabilities were classified, by origin and type, into nine categories.
  • The whole process was repeated until a new orbit that would result in the decay of the vehicle in less than 25 years was reached.
  • An example from the 10-year spacecraft mission lifetime simulation was given in Figure 1 .
  • Note the 25-year rule mitigation scenarios always result in a slightly higher spatial density below 500 km altitude than the environment predicted by the non-mitigation scenario.

PMD SUCCESS RATE

  • The second parametric analysis included a nonmitigation scenario (identical to the one described previously), and three test scenarios where rocket bodies were moved to 25-year decay orbits or LEO storage orbits after launch and spacecraft were moved to 25-year decay orbits or LEO storage orbits after 5 years of mission.
  • Following a procedure similar to that in the previous section, the result for each scenario is based on 30 Monte Carlo runs using LEGEND.
  • The four curves show a clear and expected trend.

LEO PMD

  • If the average operational lifetime of LEO Satellites significantly exceeds five years, an alternative disposal policy could maintain the desired effect of the 25-year decay rule.
  • In other words, the 25-year decay rule would be replaced by a new "30-year-in-orbit" rule.
  • Therefore, the spacecraft would need additional propellant reserves.
  • NlOcm and N1, are the effective numbers of objects, 10 cm and larger and 1 cm and larger, respectively, in LEO.

Did you find this useful? Give us your feedback

...read more

Content maybe subject to copyright    Report

Source
of
Acquisition
NASA
Johnson
Space
Center
J.-C.
Liou
Lockheed Martin Space Operations,
2400
NASA
Parkway, Mail Code
CI
04,
Houston,
TX
77058,
USA
Email: ier-chvi.liou1
@
isc.nasa.aov
Nicholas
L. Johnson
NASA
Johnson Space Center,
2101
NASA
Parkway, Mail Code
SX,
Houston,
TX
77058,
USA
Em&
nizholas.Liohnson
@
nasa.aov
ABSTRACT
This paper summarizes results from two postmission disposal parametric analyses based
on
the high
fidelity
NASA
orbital debris evolutionary model
LEGEND.
The first analysis includes a
non-
mitigation reference scenario and four test scenarios, where the mission lifetimes of spacecraft are set
to
5,
10,
20, and
30
years, respectively, before they are moved to the 25-year decay orbits. The
comparison among the five scenarios quantifies how a prolonged spacecraft mission lifetime decreases
the effectiveness of the 25-year decay rule in the low
Earth
orbit region. The second analysis includes
three 25-year decay postmission disposal scenarios where the mission lifetimes
of
spacecraft are set to
5
years but with disposal success rates set to
50%,
70%,
and
90%,
respectively. It illustrates how the
postmission disposal success rate impacts the long-term debris environment. The conclusion
of
this
paper is that a prolonged spacecraft mission lifetime and a lower postmission disposal success rate can
have noticeable negative impact on the debris environment in the long run.
INTRODUCTION
Postmission disposal (PMD) has been
recognized as the most effective way to limit
the growth of future orbital debris populations’-
’.
The
1995
NASA
Safety Standard
1740.14,
Guidelines and Assessment Procedures
for
Limiting Orbital Debris,
recommends placing a
spacecraft or upper stage passing through the
low
Earth
orbit regime
(LEO,
region of space
below
2,000
km
altitude) in an orbit in which
atmospheric drag will
limit
its lifetime to less
than 25 years after the completion
of
mission4.
This postmission disposal practice has been
known
as the 25-year decay rule. However, a
prolonged spacecraft mission lifetime will
certainly decrease the effectiveness of the 25-
year decay rule. In addition, the success rate of
PMD has a direct impact on the environment as
well. The objective of the study summarized in
this
paper
is
to quantify how future
LEO
orbital
debris environment responds to different
spacecraft mission lifetimes and different PMD
success rates.
The tool used in
this
study is the
NASA
orbital
debris evolutionary model,
LEGEND’
(a
LEO-
to-GEO &vironment Debris model).
It
is a
high fidelity physical model that is capable of
simulating the historical
as
well as future near
Earth
debris environment. The parametric study
in this paper includes a total of seven test cases
1

based on selected scenarios with different
spacecraft mission lifetimes and with different
PMD success rates. Details of the scenarios and
the study results are presented in the following
sections.
SPACECRAFT
MISSION
LIFETIME
The spacecraft mission lifetime test cases
included a non-mitigation scenario and four
PMD test scenarios. In
all
PMD scenarios
rocket bodies, after launch, were moved to 25-
year decay orbits or to LEO storage orbits
(above 2,000
km
altitude), depending on which
option required the lowest change in velocity
for the maneuvers.
In
the PMD scenarios the
mission lifetimes of spacecraft were set to
5,
10,20, and 30 years, respectively. At the end of
the mission lifetime, each spacecraft was
moved to either the 25-year decay orbit or to a
LEO storage orbit, depending on which option
required the lowest change in velocity for the
maneuvers.
In
most cases, the 25-year decay
orbit was the preferred choice for vehicles
passing through LEO.
Five LEGEND simulations, one for each
scenario, were completed. Each simulation
included
30
Monte Carlo runs with a projection
period of
100
years. Future launch traffic was
simulated by repeating the 1995 to 2002 launch
cycle. The solar 10.7 cm flux used in the orbit
propagator included two components: short
term projection (2003-201
1,
NOAA
Space
Environment Center), and long term projection
(2012-2103). The long-term projection was a
repeat of an average cycle derived from the
Solar Cycles 19-23. Explosion probabilities of
rocket bodies and spacecraft were based on an
analysis of historical explosions between 1988
and 1998. Objects with non-zero explosion
probabilities were classified, by origin and
type, into nine categories. Each category was
assigned a time-dependent explosion
probability for
up
to
10
years (since launch).
Collision probabilities among objects were
calculated based on a fast pair-wise comparison
algorithm6. Only objects
10
cm and larger were
included in collision consideration.
The postmission disposal success rates for the
four mitigation cases were
all
set to 90%. A
simple procedure based on random numbers
was used to determine whether or not
postmission disposal for each vehicle was to be
implemented successfully.
If
it failed, the
vehicle
was
simply left in orbit.
Examples
of
Satellite
PMD
(After
10-year
Mirsion
Lifetime)
zoo0
1330
E
lba)
5
4
irKa
L
-
r
4
1292
i
IMO
I-
e
PW
4ca
Fig.
1:
Examples of spacecraft
PMD
after
10-
year mission lifetime. After their perigee
altitudes were lowered, both vehicles
decayed in 25 years.
The 25-year decay orbit
of
a
vehicle, at the end
of its mission, was determined using a simple
iteration process by reducing its perigee
altitude. The end-of-mission orbit was
propagated forward 'in time for 25 years.
If
the
vehicle decayed, no modifications to its orbit
were made. Otherwise, its perigee altitude was
lowered by
5
km
at a time and the new orbit
was propagated for 25 years. The whole
process was repeated until a new orbit that
would result in the decay of the vehicle in less
than 25 years was reached.
An
example from the 10-year spacecraft
mission lifetime simulation was given in Figure
1.
This
was a spacecraft launched in the year
2000
and
it was repeated in future traffic cycle
every 8 years (only 2008 and 2032 cases
shown). Ten years
after
it was launched in
2008, its perigee altitude was lowered to just
2

above 400
km.
e new orbit caused the
spacecraft
to
decay in 2043. The same vehicle
launched
in
2032 followed a similar pattern.
The spatial density distribution of
10
cm and
larger objects in LEO at the end of the 100-year
projection is shown in Figure 2. Each curve
represents the average from 30 Monte Carlo
runs. The spatial density distribution at the
beginning of 2003 is also included as the
dashed-curve near the bottom. When compared
with the non-mitigation scenario, the four PMD
cases
all
significantly reduce the growth of
future debris populations. However, there
are
noticeable differences among different
mitigation cases, especially around
800
km,
1,000
km,
and
1,450
km
altitudes. The spatial
density increases with increasing spacecraft
mission lifetime.
LEO Environment
(Objects
210
cm)
2M
303
uy)
5w
aa
xa
Bw
rn
1wo11w12w13~1~~15w1BwlMo1Bwlswlwo
AnIIU&
(h)
Fig. 2: Spatial density distribution of objects
10
cm and larger as a function of altitude at the
end of future projection. The five curves,
from top to bottom, are labeled in the same
order
as
those in the key. The dashed-curve
near the bottom represents the environment
in 2003.
Note the 25-year rule mitigation scenarios
always result in a slightly higher spatial density
below
500
km
altitude than the environment
predicted by the non-mitigation scenario. This
is a direct consequence of moving on-orbit
rocket bodies and spacecraft to the 251year
decay orbits. Even with these increases, the
magnitude of spatial density remains well
below that of most other altitudes.
In
addition,
active collision avoidance procedures ensure no
risk
to
human space flight. The reversed trend
below
500
km
altitude is insignificant when
one evaluates the overall positive impact of
shorter spacecraft mission lifetime
on
the LEO
environment.
The spatial density distribution of
1
cm and
larger objects in
LEO
at the end of 100-year
projection is shown in
Figure
3. Qualitatively,
the trend is similar to that in Figure 2, i.e., a
prolonged spacecraft mission lifetime decreases
the effectiveness of the 25-year decay rule.
Note that for
1
cm debris the spatial density
does not increase below
500
km.
Fig. 3: Spatial density distribution of objects
1
cm and larger as a function of altitude at the
end of future projection. The five curves,
from top to bottom, are labeled in the same
order as those
in
the key. The dashed-curve
near the bottom represents the environment
in 2003.
The effective numbers of objects,
10
cm and
larger and
1
cm and larger, passing through
LEO
are summarized
in
Table
1.
The
effective number is defined as the fractional
time, per orbital period, an object spends
between 200 and
2,000
km
altitudes. When
compared with the non-mitigation scenario
(case
I),
the 5-year spacecraft mission
lifetime PMD scenario effectively reduces
the
LEO
debris populations by more than
3

half in 2103. This again reaffiis the
general belief that postmission disposal is an
excellent way to limit the growth
of
future
debris populations, primarily by reducing the
number of future collisions.
case
Table
1:
Summary
of
spacecraft mission
lifetime study.
RIB
S/CPMD
Normaliied
No
.
PMD
afterxyear
Nlb,2103
NI~
PMD
SUCCESS
RATE
The second parametric analysis included a non-
mitigation scenario (identical to the one
described previously), and three test scenarios
where rocket bodies were moved to 25-year
decay orbits or LEO storage orbits after launch
and spacecraft were moved to 25-year decay
orbits or LEO storage orbits after 5 years
of
mission. The PMD success rates for the three
test scenarios were set to
90%,
70%,
and
50%,
respectively.
Following a procedure similar to that in the
previous section, the result for each scenario is
based on 30 Monte Carlo runs using
LEGEND.
Figure
4
shows the effective number of objects,
10
cm and larger,
in
LEO
as a function
of
time
during the projection period. The four curves
show a clear and expected trend.
While
PMD
scenarios
all
reduce LEO debris populations in
the future, lower PMD success rate results in
higher debris populations; and the differences
among scenarios increase with time. The
correlation between the PMD success rate and
the effective number of objects in 2103 is close
to a linear relationship. With increasing PMD
success rate, the number of future collisions
decreases.
LEO
PMD
WBs
move
to
2!&y1
decay
orbit.
after
launch,
WCs
move
to
25yr decay
orbits
or
LEO
collection
orbits
aftar
S-yr
2005
mi5
am
20s
m5
mis
2065
m5
2085
2ws
2105
YEW
Fig.
4:
Effective number of objects,
10
cm and
larger, in LEO as a function
of
time. The
four curves, from top
to
bottom, show the
non-mitigation scenario and the three PMD
scenarios with PMD success rates of
50%,
70%,
and
90%,
respectively.
The spatial density distributions of objects, 10
cm and larger, at the end
of
the projection
period are shown in Figure
5.
Similar
distributions for objects
1
cm and larger are
shown in Figure
6.
LEO Environment
(Objects
210
cm)
I.EQI
8
EO8
8sdB
-21W
(PMD
su-s
mW?)
-2103
(PMD
suu~c88s
mte=70?,)
A2103
(PMD
su-s
mte=90%)
5
7.mn
?x
8
8E-m
t
5E.m
4E08
-
,x
3E48
2
E48
Y
E-OB
0
Ex0
2m
Pg
ua
5Gv
600
mo
800
wo
~moi~~12m1~~ua1Mol6001100l6001sw1~
(W
Fig. 5: Spatial density distribution
of
objects
10
cm and larger as a function of altitude at the
end of
future
projection. The
four
curves,
from top to bottom,
are
labeled in the same
order as those in the key. The dashed-curve
near the bottom represents the environment
in 2003.
4

LEO
Environment
(Objects
21
em)
S
RY
r--
Case
3
Em
B
-
2Em
P
E
0.)
tM6
0
E40
200
300
400
XK)
€.?a 700
BM
€.?a
two
ttcm
t2W
13M
tm1500
tm
tm
tea0
192.3
2wo
Annude
(h)
Fig.
6:
Spatial density distribution of objects
1
cm and larger as a function of altitude at the
end of future projection. The four curves,
from top to bottom, are labeled in the same
order as those in the key. The dashed-curve
near the bottom represents the environment
in 2003
PIM)
Normalized Normalized
pm
successrate Nlh,2103 N1,,2103
Both Figures
5
and
6
illustrate how the
effectiveness of the 25-year rule PMD is
degraded by a lower PMD success rate. Even
the difference between
90%
and
70%
scenarios
is quite significant. The projected
LEO
environment in 2103, normalized to the non-
mitigation scenario, is summarized in Table
2.
The three
PMD
scenarios (cases
II-IV)
all
reduce the
LEO
debris populations by 2103.
However, as the PMD success rate changes
from
90%
to
50%,
the reduction in debris
populations changes from more than half to
only about 25%.
III
IV
yes
70% 0.63
0.58
yes
90%
0.48
0.40
I
II
I
.yes
I
50%
1
0.76
I
0.73
1
The two parametric analyses presented in this
paper quantify
two
important factors in
postmission disposal practices: length of
spacecraft mission lifetime before the 25-year
decay rule is applied and the postmission
disposal success rate. Overall, the results show
that indeed the 25-year decay rule, coupled
with a high PMD success rate, is a very
effective way to limit the growth of future
debris populations in
LEO.
Although the operational lifetime of many LEO
spacecraft are less than five years, some
notable exceptions exist, e.g., Landsats
4
and
5,
SPOT
1,
and HST.
If
the average operational
lifetime of
LEO
Satellites significantly exceeds
five years, an alternative disposal policy could
maintain the desired effect of the 25-year decay
rule. This new policy would decrease the
permissible postmission decay time as the
mission duration increases, such that the sum
remains 30 years, i.e., equivalent to the current
5
plus 25 years. For example, if a spacecraft is
to remain Operational for 12 years, then at the
end of its mission, the vehicle should be placed
in a PMD orbit such that it will decay in 18
years.
In
other words, the 25-year decay rule
would be replaced by a new “30-year-in-orbit”
rule.
A
consequence of
this
“30-year-in-orbit” rule is
that additional propellant might be needed for a
spacecraft with a projected long mission time.
A
longer operational duration would require a
shorter PMD decay orbit in the end which
means a higher velocity change would be
needed for the orbit maneuver.
Therefore, the
spacecraft would need additional propellant
reserves.
Table 2:
Summary
of PMD success rate study.
NlOcm
and
N1,
are the effective numbers of
objects,
10
cm and larger and
1
cm and
larger, respectively, in LEO.
Greater attention to expected satellite mission
times would also be needed. Many satellites
today are launched with “design” lifetimes
which are artificially short for technical and
5

Citations
More filters

Journal ArticleDOI
Abstract: The near-Earth orbital debris population will continue to increase in the future due to ongoing space activities, on-orbit explosions, and accidental collisions among resident space objects. Commonly adopted mitigation measures, such as limiting postmission orbital lifetimes of satellites to less than 25 years, will slow down the population growth, but may be insufficient to stabilize the environment. The nature of the growth, in the low Earth orbit (LEO) region, is further demonstrated by a recent study where no future space launches were conducted in the environment projection simulations. The results indicate that, even with no new launches, the LEO debris population would remain relatively constant for only the next 50 years. Beyond that, the debris population would begin to increase noticeably, due to the production of collisional debris. Therefore, to better limit the growth of future debris population to protect the environment, remediation option, i.e., removing existing large and massive objects from orbit, needs to be considered. This paper does not intend to address the technical or economical issues for active debris removal. Rather, the objective is to provide a sensitivity study to quantify the effectiveness of various remediation options. A removal criterion based upon mass and collision probability is developed to rank objects at the beginning of each projection year. This study includes simulations with removal rates ranging from 2 to 20 objects per year, starting in the year 2020. The outcome of each simulation is analyzed, and compared with others. The summary of the study serves as a general guideline for future debris removal consideration.

184 citations


Journal ArticleDOI
Abstract: Several studies conducted during 1991-2001 demonstrated, with some assumed launch rates, the future unintended growth potential of the Earth satellite population, resulting from random, accidental collisions among resident space objects. In some low Earth orbit (LEO) altitude regimes where the number density of satellites is above a critical spatial density, the production rate of new breakup debris due to collisions would exceed the loss of objects due to orbital decay. A new study has been conducted in the Orbital Debris Program Office at the NASA Lyndon B. Johnson Space Center, using higher fidelity models to evaluate the current debris environment. The study assumed no satellites were launched after December 2005. A total of 150 Monte Carlo runs were carried out and analyzed. Each Monte Carlo run simulated the current debris environment and projected it 200 years into the future. The results indicate that the LEO debris environment has reached a point such that even if no further space launches were conducted, the Earth satellite population would remain relatively constant for only the next 50 years or so. Beyond that, the debris population would begin to increase noticeably, due to the production of collisional debris. Detailed analysis shows that this growth is primarily driven by high collision activities around 900 to 1000 km altitude - the region which has a very high concentration of debris at present. In reality, the satellite population growth in LEO will undoubtedly be worse than this study indicates, since spacecraft and their orbital stages will continue to be launched into space. Postmission disposal of vehicles (e.g., limiting postmission orbital lifetimes to less than 25 years) will help, but will be insufficient to constrain the Earth satellite population. To preserve better the near-Earth environment for future space activities, it might be necessary to remove existing large and massive objects from regions where high collision activities are expected.

173 citations


Journal ArticleDOI
Abstract: In the last decade, space debris modelling studies have suggested that the long-term low Earth orbit (LEO) debris population will continue to grow even with the widespread adoption of mitigation measures recommended by the Inter-Agency Space Debris Coordination Committee. More recently, studies have shown that it is possible to prevent the expected growth of debris in LEO with the additional removal of a small number of selected debris objects, through a process of active debris removal (ADR). In order to constrain the many degrees of freedom within these studies, some reasonable assumptions were made concerning parameters describing future launch, explosion, solar and mitigation activities. There remains uncertainty about how the values of these parameters will change in the future. As a result, the effectiveness of ADR has only been established and quantified for a narrow range of possible future cases. There is, therefore, a need to broaden the values of these parameters to investigate further the potential benefits of ADR. A study was completed to model and quantify the influence of four key parameters describing launch and explosion rates, the magnitude of solar activity and the level of post-mission disposal compliance on the effectiveness of ADR to reduce the LEO debris population. Each parameter's value was drawn from a realistic range, based upon historical data of the last 50 years and, in the case of post-mission disposal, a current estimate of the level of compliance and a second optimistic value. Using the University of Southampton's Debris Analysis and Monitoring Architecture to the Geosynchronous Environment (DAMAGE) model, the influence of each parameter was modelled in Monte Carlo projections of the ≥5 cm LEO debris environment from 2009 to 2209. In addition, two ADR rates were investigated: five and ten removals per year. The results showed an increase in the variance of the size of the LEO population at the 2209 epoch compared with previous ADR modelling studies. In some cases, the number of LEO debris objects in the population varied by a factor greater than ten. Ten removals per year were not sufficient to prevent the long-term growth of the population in some cases, whilst ADR was not required to prevent population growth in others.

43 citations


Cites background from "A LEO satellite postmission disposa..."

  • ...The effectiveness of PMD has been well demonstrated [6,7,10,16]....

    [...]

  • ...Several previous modelling studies [16-19] have shown that adjusting the values of these parameters, such as increasing or decreasing launch rates or modifying solar cycle projections, can significantly influence the size of the future debris population....

    [...]


Journal ArticleDOI
TL;DR: Estimates of damage generated by past and future space activities can be used to help determine one-time legacy fees and fees on future activities, which can deter future debris generation, compensate operational spacecraft that are destroyed in future collisions, and partially fund research and development into space debris mitigation technologies.
Abstract: We model the orbital debris environment by a set of differential equations with parameter values that capture many of the complexities of existing three-dimensional simulation models. We compute the probability that a spacecraft gets destroyed in a collision during its operational lifetime, and then define the sustainable risk level as the maximum of this probability over all future time. Focusing on the 900- to 1000-km altitude region, which is the most congested portion of low Earth orbit, we find that – despite the initial rise in the level of fragments – the sustainable risk remains below 10 - 3 if there is high (>98%) compliance to the existing 25-year postmission deorbiting guideline. We quantify the damage (via the number of future destroyed operational spacecraft) generated by past and future space activities. We estimate that the 2007 FengYun 1C antisatellite weapon test represents ≈ 1 % of the legacy damage due to space objects having a characteristic size of ⩾ 10 cm, and causes the same damage as failing to deorbit 2.6 spacecraft after their operational life. Although the political and economic issues are daunting, these damage estimates can be used to help determine one-time legacy fees and fees on future activities (including deorbit noncompliance), which can deter future debris generation, compensate operational spacecraft that are destroyed in future collisions, and partially fund research and development into space debris mitigation technologies. Our results need to be confirmed with a high-fidelity three-dimensional model before they can provide the basis for any major decisions made by the space community.

36 citations


Journal ArticleDOI
Abstract: Orbit manoeuvre of low Earth orbiting (LEO) debris using ground-based lasers has been proposed as a cost-effective means to avoid debris collisions. This requires the orbit of the debris object to be determined and predicted accurately so that the laser beam can be locked on the debris without the loss of valuable laser operation time. This paper presents the method and results of a short-term accurate LEO (

29 citations


Cites background from "A LEO satellite postmission disposa..."

  • ...Mitigation measures such as post mission disposal have been shown in simulation studies to reduce growth rate of the debris environment (Liou and Johnson, 2005), however, these measures alone are insufficient to reverse the collisional cascading phenomenon (Liou and Johnson, 2009)....

    [...]


References
More filters

Journal ArticleDOI
Abstract: A new orbital debris evolutionary model is being developed by the NASA Orbital Debris Program Office at Johnson Space Center. LEGEND, a LEO-to-GEO Environment Debris model, is capable of reproducing the historical debris environment as well as performing future debris environment projection. The model covers the near Earth space between 200 and 40,000 km altitude and outputs debris distributions in one-dimensional (altitude), two-dimensional (altitude, latitude), and three-dimensional (altitude, latitude, longitude) formats. LEGEND is a three-year (2001–2003) project. The historical part of the model has been completed and the future projection part is being developed/tested. The model utilizes a recently updated historical satellite launch database, two efficient and accurate propagators, and a new NASA satellite breakup model. This paper summarizes the justifications for building a full-scale three-dimensional debris evolutionary model, the overall model structure, and several key components of the model. Preliminary model predictions of debris distributions in the Low Earth Orbit (LEO), Medium Earth Orbit (MEO), and Geosynchronous Earth Orbit (GEO) regions are presented.

103 citations


Journal ArticleDOI
Abstract: In a continuing effort to limit future space debris generation, the NASA Policy Directive 8710.3 was issued in May 1997. It requires all NASA-sponsored programs to conduct formal assessments in accordance with NASA Safety Standard 1740.14 to quantify the potential to generate debris and to consider debris mitigation options. Recent improvements to the NASA long-term debris environment model, EVOLVE 4.0, allow for a reassessment of the effects of NASA Safety Standard mitigation measures on the projected debris environment. The NASA Safety Standard guidelines requiring the passivation of upper stages and spacecraft through depletion of on-board energy sources, and the post-mission disposal of satellites may be studied with EVOLVE 4.0. In this paper, we present the results of a set of parametric EVOLVE 4.0 studies. We set our test matrix to include a draconian level of explosion suppression, i.e. , passivation in future launches, and post-mission disposal decay time periods ranging from 100 years to 25 years. The post-mission disposal options are initiated at a time 10 years in the future. It is confirmed that explosion suppression alone effects only a minor change in the long-term environment. Post-mission disposal implementation is required to significantly reduce it. But complications arise for the longer tested post-mission disposal lifetime. The enhanced dwell time at low altitudes (the dominant manned spacecraft region of Earth orbits) increases the likelihood that a collision will occur there compared to the lower post-mission disposal lifetime of 25 years.

18 citations



Journal ArticleDOI
Abstract: Relativistic electron beam accelerators (5 MeV, 0.1 A) can now be flown on spacecraft. Injection from low-Earth-orbit into the atmosphere makes it possible to perform active perturbation experiments in the 40–60 km altitude range. These include modification of the atmospheric electric potential structure over thunderstorm regions and the possible stimulation of high-altitude-lightning, as well as studies of relativistic electron precipitation effects on chemical reaction paths. In this paper, the initial stage of the beam injection process is simulated by a fully electromagnetic and relativistic Particle-in-Cell (PIC) code. The self-consistent implementation of electric charging of a spacecraft structure in an electromagnetic code is demonstrated, and beam propagation dynamics is explored for a range of beam to ambient plasma densities. It is shown that the combined effects of ambient plasma and beam self-fields may allow propagation in the ion-focused regime and that this regime primarily is expected for relativistic beams.

5 citations