- Email: [email protected]
Geosynchronous region orbital debris modeling with GEO_EVOLVE 2.0
Advances in Space Research 34 (2004) 1166–1170 www.elsevier.com/locate/asr
Geosynchronous region orbital debris modeling with GEO_EVOLVE 2.0 P.H. Krisko a
a,*
, D.T. Hall
b
Lockheed Martin Space Operations, 2400 NASA Road 1, Mail Code C104, Houston, TX 77058, USA b Hernandez Engineering, Inc., 16055 Space Center Blvd. #725, Houston, TX 77058, USA Received 19 October 2002; received in revised form 21 October 2003; accepted 26 October 2003
Abstract GEO_EVOLVE, the NASA/JSC orbital debris simulation model for EarthÕs geosynchronous region, is in the process of being upgraded to version 2.0. The historical period of geosynchronous earth orbit (GEO) growth is mimicked with the addition of a set of updated and expanded launch/breakup files, and two new orbital propagators servicing objects in GEO and geosynchronous transfer orbits (GTO). This results in a GEO_EVOLVE 2.0 generated environment that is comparable with data from the US Space Surveillance Network (SSN) catalog and NASAÕs CDT (CCD Debris Telescope). The slow precession of the node and argument of perigee of objects near GEO has driven the development of a pair-wise collision probability algorithm for use in the projection phase of GEO_EVOLVE 2.0. This module is still in the preliminary testing phase. Ó 2004 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Space debris; Orbital debris modelling; Geosynchronous orbit; modelling with GEO_EVOLVE 2.0
1. Introduction NASAÕs long-term, orbital debris generation and propagation code, GEO_EVOLVE 1.0 was developed in 1999. It is the geosynchronous (GEO) region version of EVOLVE 4.0 (Krisko et al., 2000) and the first attempt by NASA to simulate the GEO environment. The 100-year projected environment of GEO_EVOLVE 1.0 compares well with that of GEODEEM, the Kyoto University model for GEO (Hanada et al., 2001). With no information on the GEO object actual position GEO_EVOLVE 1.0 estimates the probability of a future collision event via a spatial density representation of two objects within a box including the region of orbit crossing. Given the slow precession of the node and argument of perigee in GEO, the method leads to an overestimation of the future collision rate in the GEO region. Still, that collision rate is so small (0.002 per year) so as to be statistically insignificant, in agreement with previous studies (Hechler and Van der Ha, 1981; Martin et al., 2002). *
Corresponding author. Tel.: +1-281-483-4135; +1-281-244-5031. E-mail address: [email protected] (P.H. Krisko).
Three independent developments since 1999 make it reasonable to pursue a meaningful upgrade to GEO_ EVOLVE at this time. The first development is in the recent upgrade of NASAÕs space traffic database files to include, among many other parameters, reliable insertion node, argument of perigee, and mean anomaly of all launched objects from 1957 to 2001. The second includes two new orbital propagation codes that take into account atmospheric drag, solar and lunar gravitational orbital perturbations, solar radiation pressure perturbations, as well as Earth gravity-field zonal ðJ2 J3 ; and J4 Þ and tesseral ðJ2;2 ; J3;1 ; etc:Þ perturbations (in GEO ring only) (Hall, 2001a). Companion to this development is an upgrade of the fragment area-to-mass estimates (Hall, 2001b). Both propagator and area-to-mass values are currently implemented in EVOLVE 4.1 and LEGEND (Opiela and Krisko, 2002; Liou et al., 2001). Inclusion of the tesseral harmonics for objects in the GEO ring allows for the calculation of individual object position at any time in the GEO ring. Thus the two above developments mean that the position and propagation of GEO objects may be compared reliably to their TLE (two-line element set) values. This requires a more restrictive collision probability model. Therefore,
0273-1177/$30 Ó 2004 COSPAR. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2003.10.040
P.H. Krisko, D.T. Hall / Advances in Space Research 34 (2004) 1166–1170
the third development is a collision probability algorithm, which calculates the pair-wise probability of two objects passing through a spherical volume at a snapshot in time. Implementation of the new space traffic database and the orbital propagators has been completed and the comparisons of the resulting GEO_EVOLVE 2.0 historical environment to that of the SSN two line element sets (TLEs) and to the CDT data (Jarvis et al., 2002) are presented here. The collision probability algorithm has been implemented into the GEO_EVOLVE 2.0 structure for testing. That work is ongoing and will not be discussed further in this paper.
1167
2.1. Historical launch/breakup files The upgraded space traffic files, which are implemented in GEO_EVOLVE 2.0, EVOLVE 5.0, and LEGEND, are discussed briefly in Krisko (2002). The launch traffic assigned to GEO_EVOLVE 2.0 is that of the geosynchronous objects and GTO objects with inclinations less than 47°. These are the GTO objects that are most likely to interact with GEO ring objects with finite probability. The verified historical breakups within those regions are listed below. All are considered to be explosive events. 2.2. Orbital propagators: GEOPROP and PROP3D
2. GEO_EVOLVE 2.0 structure Within the GEO_EVOLVE 2.0 structure, launched objects are deposited into their insertion orbits and maneuvered objects are re-orbited within a prescribed time step. Breakup fragments are also deposited via the breakup model as they occur within the time step. All objects are propagated to the next time step. The historical period spans the years 1957 through 2001 and includes the two acknowledged explosive breakups within the GEO band and 12 in GTO. No collision has been confirmed in the GEO region, and it is extremely unlikely that any have occurred. However, the collision probability logic is called within both historical and projection periods. The only distinction between the historical and projection periods, then, is that the historical period deposits known traffic and breakup events and the projection period continually cycles the last eight years of the historical traffic (1994–2001) and proceeds over a predetermined number of Monte Carlo iterations.
GEO_EVOLVE 2.0 calls one of two orbital propagators depending on an objectÕs orbital parameters at the beginning of orbital insertion or maneuver (Liou et al., 2001 and references therein). The GEOPROP propagator is designed to calculate the motion of spacecraft with an orbital period within 10% of that of an object in the GEO ring, i.e., 24 h, and an eccentricity less than 0.1. GEOPROP accounts for solar and lunar gravitational orbital perturbations, solar radiation pressure perturbations, as well as Earth gravityfield zonal ðJ2 ; J3 ; and J4 Þ and tesserral ðJ2;2 ; J3;1 ; etc:Þ perturbations. Because GEOPROP accounts for the motion of Earth-resonant geo-synchronous satellites, it calculates orbital perturbations for all six of the satelliteÕs orbital elements, including changes in the mean anomaly of the object. (see Table 1) In GEO_EVOLVE 2.0 the PROP3D propagator (also used in EVOLVE) addresses the motion of highly eccentric satellites that enter the GEO band at some point in their orbits. PROP3D accounts for the effects of atmospheric drag, solar and lunar gravitation, solar
Table 1 Historical breakups of GTO and GEO intacts processed in GEO_EVOLVE 2.0 Name
International designator (Catalog #)
Type
Event date
Apogee altitude (km)
Perigee altitude (km)
#Debris cataloged/left
Cause
OV2-5 R/B EKRAN2 OCAT R/B AUSSAT/ECS R/B SKYNET 4B,ASTRA 1A R/B INTELSAT 515 R/B GORIZONT 18 Ullage Motor ITALSAT 1 R/B, EUTELSAT 2 F2 TELECOM 2B,INMARSAT 2 R/B COSMOS 2282 Ullage Motor ELEKTRO Ullage Motor RADUGA 33 R/B ASIASAT 3 R/B ARIANE 2 R/B
1968-08 IE (3432) 1977-092A (10365) 1979-104B(11659) 1987-078C (18352) 1988-109C (19689) 1989-006B (19773) 1989-052F(20116) 1991-003C (21057)
GEO GEO GTO GTO GTO GTO GTO GTO
09/21/92 06/25/78 12/24/79 09/87 02/17/98 01/01/01 01/12/93 05/01/96
35,812 35,798 33,140 36,515 35,875 35,720 36,747 30,930
35102 35786 180 245 35 510 258 235
3/3 2/2 13/9 4/2 7/7 6/6 1/0 8/6
Unknown Battery Unknown Unknown Unknown Unknown Propulsion Unknown
1992-021C (21941)
GTO
04/21/93
34,080
235
11/11
Unknown
1994-038F(23174) 1994-069E (23338) 1996-010D (23797) 1997-086D (25129) 1989-006B (19773)
GTO GTO GTO GTO GTO
10/21/95 05/11/95 02/19/96 12/24/97 01/01/01
34,930 35,465 36,505 35,995 35,720
280 155 240 270 510
2/2 1/0 2/1 1/0
Propulsion Propulsion Propulsion Propulsion Propulsion
Information is as listed in the newly upgraded ÔHistory of On-orbit Satellite FragmentationsÕ (Anz-Meador, 2001).
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P.H. Krisko, D.T. Hall / Advances in Space Research 34 (2004) 1166–1170
radiation pressure (including the Earth shadow effect), and EarthÕs gravity-field zonal harmonics J2 ; J3 ; and J4 . It employs atmospheric drag perturbations for an oblate/rotating Jacchia-model atmosphere, along with an upper atmospheric vertical structure with the updated globally-averaged exospheric temperature profile of Hall and Anz-Meador (2001). PROP3D propagates only the first five orbital elements; the change in mean anomaly of an object is not tracked. Instead, the likely mean anomaly over the orbit is randomly selected outside of PROP3D. The nature of this method makes it impossible to compare the GEO_EVOLVE 2.0 generated mean anomaly with that
of a TLE set of an individual GTO satellite. It is unlikely that at any time the position of the object will exactly match that randomly selected in GEO_EVOLVE 2.0.
3. Preliminary historical environment comparison The GEO_EVOLVE 2.0 geosynchronous object historical environment for 1 m and larger cross-section objects on January 1, 2000 is compared with that of the TLE set closest to that date (00003.elm) and to that of NASAÕs CDT for the year 1999. Figs. 1–3 display the three cases, respectively, in the form of right ascension
Fig. 1. GEO_EVOLVE 2.0 environment for Jan. 1, 2000 of the 1 m and larger geosynchronous objects.
Fig. 2. Element set catalog for Jan. 3, 2000 (00003.elm) of geosynchronous objects (80,000 series excluded).
P.H. Krisko, D.T. Hall / Advances in Space Research 34 (2004) 1166–1170
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Fig. 3. CDT data – single observations (last sightings) of correlated targets for the year 1999 (80,000 series excluded).
of the ascending node (RAAN) vs. inclination. The 1 m lower size limit of the GEO_EVOLVE 2.0 results is reasonable in the comparison with these data sets, as it is a general rule-of-thumb that USSPACECOM can routinely catalog objects in the GEO region of that size and the CDT data is of the correlated targets in GEO only. GTO objects are excluded from this comparison given the random mean anomaly in GEO_EVOLVE 2.0. The overall character of the GEO RAAN and inclination precession is matched in all three cases. However, the discrepancies in Figs. 1 and 2 among the low inclination population (less than 1°) and, separately, the high RAAN population (between 270° and 360°) are very likely due to lingering errors in the traffic database file stationkeeping periods. This warrants further investigation. The CDT data in Fig. 3 includes only the single observations (last sightings) of the correlated targets (CTs) for 1999. The ÔsmearÕ in RAAN and inclination in the low RAAN GEO belt of Fig. 3 (as compared to Fig. 2) is dominated by the circular orbit assumptions made in the post-processing phase of the CDT data reduction (K. Jorgensen and K. Jarvis, private communication, 2002).
4. Summary Preliminary historical environment results of GEO_EVOLVE 2.0 match reasonably well with existing datasets. This is a testament to the independent upgrades incorporated into the code, namely, the newly derived space traffic files and the two orbital propaga-
tors, GEOPROP and PROP3D. Tests will continue to determine and correct the sources of any discrepancies, but this initial result bodes well for the continuation of GEO_EVOLVE 2.0 to the projection period. It adds confidence to the proposed method of collision probability analysis (BUBBLE), which is a pair-wise calculation and depends on accurate knowledge of satellite position. Testing of BUBBLE both in and out of GEO_EVOLVE 2.0 will proceed in FY03.
Acknowledgements The authors wish to acknowledge K. Jarvis for the contribution of the CDT data displayed in this paper.
References Anz-Meador, P.D. History of On-orbit Satellite Fragmentations, JSC 29517, Orbital Debris Program Office, July 31 2001. Hall, D.T. Recent enhancements to the EVOLVE orbital propagator. The Orbital Debris Quarterly News 6 (3), 4–5, 2001a. Hall, D.T. Private communication, August 30, 2001b. Hall, D.T., Anz-Meador, P. A solar-flux temperature relationship derived from multiple satellite orbital decay, ESA SP-473, pp. 411– 414, 2001. Hanada, T., Krisko, P., Anz-Meador, P. Consequences of continued growth in the GEO and GEO disposal orbital regimes, in: Space Debris 2000, AAS Science and Technology Series, vol. 103, Rio de Janeiro, pp. 291–304, 2001. Hechler, M., Van der Ha, J.C. Probability of collisions in the geostationary ring. J. Spacecraft Rockets 18 (4), 361–366, 1981. Liou, J.C., Anz-Meador, P.D., Hall, D.T., et al. LEGEND-A LEO to GEO Environment Debris Model, JSC 29711, December 2001.
1170
P.H. Krisko, D.T. Hall / Advances in Space Research 34 (2004) 1166–1170
Jarvis, K.S., Par-Thumm, T.L., Jorgensen, K., et al. CCD Debris Telescope Observations of the Geosynchronous Orbital Debris Environment, Observing Year: 1999, JSC-29712, February 2002. Krisko, P.H., Reynolds, R.C., Bade, A., et al. EVOLVE 4.0 User’s Guide and Handbook, LMSMSS-33020, Houston, April 2000.
Martin, C.E., Stokes, P.H., Walker, R. The long-term evolution of the debris environment in high Earth orbit including the effectiveness of mitigation measures, in: Space Debris 2001, AAS Science and Technology Series, vol. 105, pp. 141–154, 2002. Opiela, J.N., Krisko, P.H. Evaluation of orbital debris mitigation practices using EVOLVE 4.1, in: Space Debris 2001, AAS Science and Technology Series, vol. 105, pp. 209–219, 2002.
Geosynchronous region orbital debris modeling with GEO_EVOLVE 2.0 P.H. Krisko a
a,*
, D.T. Hall
b
Lockheed Martin Space Operations, 2400 NASA Road 1, Mail Code C104, Houston, TX 77058, USA b Hernandez Engineering, Inc., 16055 Space Center Blvd. #725, Houston, TX 77058, USA Received 19 October 2002; received in revised form 21 October 2003; accepted 26 October 2003
Abstract GEO_EVOLVE, the NASA/JSC orbital debris simulation model for EarthÕs geosynchronous region, is in the process of being upgraded to version 2.0. The historical period of geosynchronous earth orbit (GEO) growth is mimicked with the addition of a set of updated and expanded launch/breakup files, and two new orbital propagators servicing objects in GEO and geosynchronous transfer orbits (GTO). This results in a GEO_EVOLVE 2.0 generated environment that is comparable with data from the US Space Surveillance Network (SSN) catalog and NASAÕs CDT (CCD Debris Telescope). The slow precession of the node and argument of perigee of objects near GEO has driven the development of a pair-wise collision probability algorithm for use in the projection phase of GEO_EVOLVE 2.0. This module is still in the preliminary testing phase. Ó 2004 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Space debris; Orbital debris modelling; Geosynchronous orbit; modelling with GEO_EVOLVE 2.0
1. Introduction NASAÕs long-term, orbital debris generation and propagation code, GEO_EVOLVE 1.0 was developed in 1999. It is the geosynchronous (GEO) region version of EVOLVE 4.0 (Krisko et al., 2000) and the first attempt by NASA to simulate the GEO environment. The 100-year projected environment of GEO_EVOLVE 1.0 compares well with that of GEODEEM, the Kyoto University model for GEO (Hanada et al., 2001). With no information on the GEO object actual position GEO_EVOLVE 1.0 estimates the probability of a future collision event via a spatial density representation of two objects within a box including the region of orbit crossing. Given the slow precession of the node and argument of perigee in GEO, the method leads to an overestimation of the future collision rate in the GEO region. Still, that collision rate is so small (0.002 per year) so as to be statistically insignificant, in agreement with previous studies (Hechler and Van der Ha, 1981; Martin et al., 2002). *
Corresponding author. Tel.: +1-281-483-4135; +1-281-244-5031. E-mail address: [email protected] (P.H. Krisko).
Three independent developments since 1999 make it reasonable to pursue a meaningful upgrade to GEO_ EVOLVE at this time. The first development is in the recent upgrade of NASAÕs space traffic database files to include, among many other parameters, reliable insertion node, argument of perigee, and mean anomaly of all launched objects from 1957 to 2001. The second includes two new orbital propagation codes that take into account atmospheric drag, solar and lunar gravitational orbital perturbations, solar radiation pressure perturbations, as well as Earth gravity-field zonal ðJ2 J3 ; and J4 Þ and tesseral ðJ2;2 ; J3;1 ; etc:Þ perturbations (in GEO ring only) (Hall, 2001a). Companion to this development is an upgrade of the fragment area-to-mass estimates (Hall, 2001b). Both propagator and area-to-mass values are currently implemented in EVOLVE 4.1 and LEGEND (Opiela and Krisko, 2002; Liou et al., 2001). Inclusion of the tesseral harmonics for objects in the GEO ring allows for the calculation of individual object position at any time in the GEO ring. Thus the two above developments mean that the position and propagation of GEO objects may be compared reliably to their TLE (two-line element set) values. This requires a more restrictive collision probability model. Therefore,
0273-1177/$30 Ó 2004 COSPAR. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2003.10.040
P.H. Krisko, D.T. Hall / Advances in Space Research 34 (2004) 1166–1170
the third development is a collision probability algorithm, which calculates the pair-wise probability of two objects passing through a spherical volume at a snapshot in time. Implementation of the new space traffic database and the orbital propagators has been completed and the comparisons of the resulting GEO_EVOLVE 2.0 historical environment to that of the SSN two line element sets (TLEs) and to the CDT data (Jarvis et al., 2002) are presented here. The collision probability algorithm has been implemented into the GEO_EVOLVE 2.0 structure for testing. That work is ongoing and will not be discussed further in this paper.
1167
2.1. Historical launch/breakup files The upgraded space traffic files, which are implemented in GEO_EVOLVE 2.0, EVOLVE 5.0, and LEGEND, are discussed briefly in Krisko (2002). The launch traffic assigned to GEO_EVOLVE 2.0 is that of the geosynchronous objects and GTO objects with inclinations less than 47°. These are the GTO objects that are most likely to interact with GEO ring objects with finite probability. The verified historical breakups within those regions are listed below. All are considered to be explosive events. 2.2. Orbital propagators: GEOPROP and PROP3D
2. GEO_EVOLVE 2.0 structure Within the GEO_EVOLVE 2.0 structure, launched objects are deposited into their insertion orbits and maneuvered objects are re-orbited within a prescribed time step. Breakup fragments are also deposited via the breakup model as they occur within the time step. All objects are propagated to the next time step. The historical period spans the years 1957 through 2001 and includes the two acknowledged explosive breakups within the GEO band and 12 in GTO. No collision has been confirmed in the GEO region, and it is extremely unlikely that any have occurred. However, the collision probability logic is called within both historical and projection periods. The only distinction between the historical and projection periods, then, is that the historical period deposits known traffic and breakup events and the projection period continually cycles the last eight years of the historical traffic (1994–2001) and proceeds over a predetermined number of Monte Carlo iterations.
GEO_EVOLVE 2.0 calls one of two orbital propagators depending on an objectÕs orbital parameters at the beginning of orbital insertion or maneuver (Liou et al., 2001 and references therein). The GEOPROP propagator is designed to calculate the motion of spacecraft with an orbital period within 10% of that of an object in the GEO ring, i.e., 24 h, and an eccentricity less than 0.1. GEOPROP accounts for solar and lunar gravitational orbital perturbations, solar radiation pressure perturbations, as well as Earth gravityfield zonal ðJ2 ; J3 ; and J4 Þ and tesserral ðJ2;2 ; J3;1 ; etc:Þ perturbations. Because GEOPROP accounts for the motion of Earth-resonant geo-synchronous satellites, it calculates orbital perturbations for all six of the satelliteÕs orbital elements, including changes in the mean anomaly of the object. (see Table 1) In GEO_EVOLVE 2.0 the PROP3D propagator (also used in EVOLVE) addresses the motion of highly eccentric satellites that enter the GEO band at some point in their orbits. PROP3D accounts for the effects of atmospheric drag, solar and lunar gravitation, solar
Table 1 Historical breakups of GTO and GEO intacts processed in GEO_EVOLVE 2.0 Name
International designator (Catalog #)
Type
Event date
Apogee altitude (km)
Perigee altitude (km)
#Debris cataloged/left
Cause
OV2-5 R/B EKRAN2 OCAT R/B AUSSAT/ECS R/B SKYNET 4B,ASTRA 1A R/B INTELSAT 515 R/B GORIZONT 18 Ullage Motor ITALSAT 1 R/B, EUTELSAT 2 F2 TELECOM 2B,INMARSAT 2 R/B COSMOS 2282 Ullage Motor ELEKTRO Ullage Motor RADUGA 33 R/B ASIASAT 3 R/B ARIANE 2 R/B
1968-08 IE (3432) 1977-092A (10365) 1979-104B(11659) 1987-078C (18352) 1988-109C (19689) 1989-006B (19773) 1989-052F(20116) 1991-003C (21057)
GEO GEO GTO GTO GTO GTO GTO GTO
09/21/92 06/25/78 12/24/79 09/87 02/17/98 01/01/01 01/12/93 05/01/96
35,812 35,798 33,140 36,515 35,875 35,720 36,747 30,930
35102 35786 180 245 35 510 258 235
3/3 2/2 13/9 4/2 7/7 6/6 1/0 8/6
Unknown Battery Unknown Unknown Unknown Unknown Propulsion Unknown
1992-021C (21941)
GTO
04/21/93
34,080
235
11/11
Unknown
1994-038F(23174) 1994-069E (23338) 1996-010D (23797) 1997-086D (25129) 1989-006B (19773)
GTO GTO GTO GTO GTO
10/21/95 05/11/95 02/19/96 12/24/97 01/01/01
34,930 35,465 36,505 35,995 35,720
280 155 240 270 510
2/2 1/0 2/1 1/0
Propulsion Propulsion Propulsion Propulsion Propulsion
Information is as listed in the newly upgraded ÔHistory of On-orbit Satellite FragmentationsÕ (Anz-Meador, 2001).
1168
P.H. Krisko, D.T. Hall / Advances in Space Research 34 (2004) 1166–1170
radiation pressure (including the Earth shadow effect), and EarthÕs gravity-field zonal harmonics J2 ; J3 ; and J4 . It employs atmospheric drag perturbations for an oblate/rotating Jacchia-model atmosphere, along with an upper atmospheric vertical structure with the updated globally-averaged exospheric temperature profile of Hall and Anz-Meador (2001). PROP3D propagates only the first five orbital elements; the change in mean anomaly of an object is not tracked. Instead, the likely mean anomaly over the orbit is randomly selected outside of PROP3D. The nature of this method makes it impossible to compare the GEO_EVOLVE 2.0 generated mean anomaly with that
of a TLE set of an individual GTO satellite. It is unlikely that at any time the position of the object will exactly match that randomly selected in GEO_EVOLVE 2.0.
3. Preliminary historical environment comparison The GEO_EVOLVE 2.0 geosynchronous object historical environment for 1 m and larger cross-section objects on January 1, 2000 is compared with that of the TLE set closest to that date (00003.elm) and to that of NASAÕs CDT for the year 1999. Figs. 1–3 display the three cases, respectively, in the form of right ascension
Fig. 1. GEO_EVOLVE 2.0 environment for Jan. 1, 2000 of the 1 m and larger geosynchronous objects.
Fig. 2. Element set catalog for Jan. 3, 2000 (00003.elm) of geosynchronous objects (80,000 series excluded).
P.H. Krisko, D.T. Hall / Advances in Space Research 34 (2004) 1166–1170
1169
Fig. 3. CDT data – single observations (last sightings) of correlated targets for the year 1999 (80,000 series excluded).
of the ascending node (RAAN) vs. inclination. The 1 m lower size limit of the GEO_EVOLVE 2.0 results is reasonable in the comparison with these data sets, as it is a general rule-of-thumb that USSPACECOM can routinely catalog objects in the GEO region of that size and the CDT data is of the correlated targets in GEO only. GTO objects are excluded from this comparison given the random mean anomaly in GEO_EVOLVE 2.0. The overall character of the GEO RAAN and inclination precession is matched in all three cases. However, the discrepancies in Figs. 1 and 2 among the low inclination population (less than 1°) and, separately, the high RAAN population (between 270° and 360°) are very likely due to lingering errors in the traffic database file stationkeeping periods. This warrants further investigation. The CDT data in Fig. 3 includes only the single observations (last sightings) of the correlated targets (CTs) for 1999. The ÔsmearÕ in RAAN and inclination in the low RAAN GEO belt of Fig. 3 (as compared to Fig. 2) is dominated by the circular orbit assumptions made in the post-processing phase of the CDT data reduction (K. Jorgensen and K. Jarvis, private communication, 2002).
4. Summary Preliminary historical environment results of GEO_EVOLVE 2.0 match reasonably well with existing datasets. This is a testament to the independent upgrades incorporated into the code, namely, the newly derived space traffic files and the two orbital propaga-
tors, GEOPROP and PROP3D. Tests will continue to determine and correct the sources of any discrepancies, but this initial result bodes well for the continuation of GEO_EVOLVE 2.0 to the projection period. It adds confidence to the proposed method of collision probability analysis (BUBBLE), which is a pair-wise calculation and depends on accurate knowledge of satellite position. Testing of BUBBLE both in and out of GEO_EVOLVE 2.0 will proceed in FY03.
Acknowledgements The authors wish to acknowledge K. Jarvis for the contribution of the CDT data displayed in this paper.
References Anz-Meador, P.D. History of On-orbit Satellite Fragmentations, JSC 29517, Orbital Debris Program Office, July 31 2001. Hall, D.T. Recent enhancements to the EVOLVE orbital propagator. The Orbital Debris Quarterly News 6 (3), 4–5, 2001a. Hall, D.T. Private communication, August 30, 2001b. Hall, D.T., Anz-Meador, P. A solar-flux temperature relationship derived from multiple satellite orbital decay, ESA SP-473, pp. 411– 414, 2001. Hanada, T., Krisko, P., Anz-Meador, P. Consequences of continued growth in the GEO and GEO disposal orbital regimes, in: Space Debris 2000, AAS Science and Technology Series, vol. 103, Rio de Janeiro, pp. 291–304, 2001. Hechler, M., Van der Ha, J.C. Probability of collisions in the geostationary ring. J. Spacecraft Rockets 18 (4), 361–366, 1981. Liou, J.C., Anz-Meador, P.D., Hall, D.T., et al. LEGEND-A LEO to GEO Environment Debris Model, JSC 29711, December 2001.
1170
P.H. Krisko, D.T. Hall / Advances in Space Research 34 (2004) 1166–1170
Jarvis, K.S., Par-Thumm, T.L., Jorgensen, K., et al. CCD Debris Telescope Observations of the Geosynchronous Orbital Debris Environment, Observing Year: 1999, JSC-29712, February 2002. Krisko, P.H., Reynolds, R.C., Bade, A., et al. EVOLVE 4.0 User’s Guide and Handbook, LMSMSS-33020, Houston, April 2000.
Martin, C.E., Stokes, P.H., Walker, R. The long-term evolution of the debris environment in high Earth orbit including the effectiveness of mitigation measures, in: Space Debris 2001, AAS Science and Technology Series, vol. 105, pp. 141–154, 2002. Opiela, J.N., Krisko, P.H. Evaluation of orbital debris mitigation practices using EVOLVE 4.1, in: Space Debris 2001, AAS Science and Technology Series, vol. 105, pp. 209–219, 2002.