300:(HEO), most commonly in the highly specific and crowded GSO/GEO, are too far to make use of the "25-year rule". GSO and GEO require that the orbital plane be almost perfectly equatorial and the altitude be as close to a perfectly circular 35,786 km (22,236 mi), which means that space is limited and satellites cannot be allowed to stay past their useful life. Instead of decelerating for reentry, most satellites at these altitudes accelerate slightly into higher
1067:
389:. The object's orbit can then be projected into the future, estimating where it will be located and the chance it will have a close encounter with another orbiting object. Long-term orbit projections have large error bars due to complicated gravitational effects that gradually perturb the orbit (akin to those of the
331:
is a launch vehicle designed to minimize the effect of its upper stage on space debris. The rocket is composed of two stages, the first of which is suborbital. It reenters within minutes of launch, either intentionally using fuel reserved for stage recovery to land for reuse or is left to continue on
59:
velocity of ~7.8 km/s, two perpendicularly colliding spacecraft would meet at ~12.2 km/s. Almost no known structurally solid materials can withstand such an energetic impact. Most of the satellite would be instantly vaporized by the collision and broken up into myriad pieces ejected at force in all
551:
Collision avoidance maneuvers require significant planning and execution time, which can be an issue if the risk isn't predicted sufficiently in advance. Spacecraft propulsion is often weak, relying on long burns to change their orbits, and the velocity change often requires a meaningful fraction of
559:
to avoid collisions often require roughly 150 second burns and significant disturbances to crew operations because of the mandatory slow reconfiguration of the station's solar panels to avoid damage by propulsion devices. Roughly speaking, the estimated quickest reaction time of the ISS from normal
214:
Several best practices are used to minimize the number of launched objects becoming uncontrollable space debris, varying in technique depending on the object's orbit. Most protective measures ensure that satellites and other artificial objects only remain in their operational orbits for as long as
283:
Satellites at altitudes towards the lower bound of MEO can use the "25-year rule" to decelerate with onboard propulsion so that it will fall out of orbit within 25 years, but this provision is only allowed if satellite operators can prove by statistical analysis that there is less than a 1/10,000
235:
is designed to quickly dispose of itself after launch. The large external tank remains attached to the Space
Shuttle orbiter from liftoff until when it and the orbiter are traveling at just below orbital velocity and have an altitude of approximately 113 km (70 mi), at which point it detaches and
547:
All these occurrences limit strategic options for collision risk reduction in different ways. Very little can prevent the projected collision if both objects don't have control capabilities. If only one of the objects is an operational satellite, it would be the sole contributor to an avoidance
411:
Current avoidance techniques rely on slightly changing the orbit to minimize collision risk and then returning the spacecraft to its previous orbit after the risk event has passed. The exact method used to make orbital adjustments differs based on what controls are available on the spacecraft.
351:(GEO), generally don't have sufficient fuel to de-orbit themselves. GTO trajectories are designed such that the second stage's orbit will naturally decay and reenter the atmosphere after a few months, while stages from missions targeting direct insertion into GEO will remain for a lot longer.
403:, evaluations are made for the risk that any object will traverse within a rectangular region half a mile (1.25 km) above/below and 15 miles (25 km) ahead/behind in orbit and to either side of the spacecraft. This high-risk zone is known as the “pizza box" because of the shape it resembles.
256:
required to decelerate from LEO is small. Most LEO satellites use the last of their remaining onboard station-keeping fuel (used to maintain the satellite's orbit against forces like atmospheric drag that gradually perturb the orbit) to execute de-orbit burns and dispose of themselves.
227:
designed to quickly return from orbit and rocket booster stages which expend their propellant before achieving orbital velocity. Satellites on suborbital trajectories don't usually require any intentional care on the part of the operator to ensure reentry and disposal.
280:(GSO/GEO), and other species) are far from the denser parts of the atmosphere, making full de-orbit burns significantly more impractical. Few satellite designs have sufficient fuel margins to be able to afford such a maneuver at the end of their lives.
512:
which rely on alternative devices for orientation control. At the scale of small objects like CubeSats, forces related to the large relative surface area in proportion to mass become significant. CubeSats are often launched into
41:. The subject includes procedures designed to prevent the accumulation of space debris in orbit, analytical methods for predicting likely collisions, and avoidance procedures to maneuver offending spacecraft away from danger.
493:
to the ISS. This can be initiated by the crew aboard the space station, as an emergency override, in the event of a problem during the docking. This maneuver was demonstrated shortly after the launch of the first ATV,
284:
chance that the atmospheric reentry will cause human injury or property damage. Satellites disposed of in this fashion reenter the atmosphere in an area of the South
Pacific Ocean far from inhabited areas called the
476:
Recent research has developed algorithms to aid collision avoidance efforts within large satellite constellations, although it is unknown whether such research has been implemented in any active constellation
524:
can be used to change orbits slightly to avoid debris collisions by changing the surface area exposed to atmospheric drag, alternating between low-drag and high-drag configurations to control deceleration.
119:
While the number of satellites launched into orbit is relatively low in comparison to the amount of space available in orbit around the Earth, risky near-misses and occasional collisions happen. The
560:
operation is about 5 hours and 20 minutes to account for the ~3 hour setup period of station reconfiguration and the ~2 hours of post-burn lead time to allow the velocity change to take effect.
548:
maneuver, significantly cutting into or entirely using up remaining fuel reserves. The satellite may also have insufficient fuel to complete the maneuver properly, reducing its effectiveness.
420:
NASA uses avoidance maneuvers if the collision risk is identified sufficiently in advance and the risk is high. NASA policy for crewed spacecraft, which all have onboard propulsion, like the
76:
would create off-limits regions in orbit because of risk of collision, and eventually completely block access to space due to the risky ascent through debris-filled orbits during launch.
359:
Most impact risk predictions are calculated using databases of orbiting objects with orbit parameters like position and velocity measured by ground-based observations. The United States
439:
As of August 2020, the ISS has conducted 27 collision avoidance maneuvers since its initial launch in 1999 and is trending upwards with time. The class of debris most dangerous to the
206:
constellations. Each of these systems are planned use tens of thousands of satellites, which will massively increase the total number of satellites and exacerbate space debris issues.
68:
A cascading series of collisions between orbiting satellites and other objects could take place if a critical mass of space debris is allowed to accumulate in Earth orbit, dubbed the
215:
they are functional and controllable. These responsibilities fall on the satellite operator, who is bound by international agreements for how to dispose of orbiting objects.
443:
are those between 1-10 cm. The population of debris in this size range is significant and difficult to track accurately with current methods, meriting further research.
470:. The maneuvers slightly change the orbital trajectory and are usually conducted hours before the risk event to allow the effects of the orbital change to take effect.
37:
inadvertently colliding with other orbiting objects. The most common subject of spacecraft collision avoidance research and development is for human-made satellites in
126:
There are other smaller bits of material in orbit around Earth that could also cause significant damage to satellites. These are relatively small objects such as micro
252:(LEO), with mean altitudes lower than 2000 km (1200 mi). LEO satellites are close to the thicker parts of the atmosphere where safe reentry is practical because the
123:
entirely obliterated both spacecraft and resulted in the creation of an estimated 1,000 new pieces of space debris larger than 10 cm (4 in) and many smaller ones.
393:) and the measurement errors of ground tracking equipment. For these reasons, methods for more precise measurement and estimation are an active field of research.
179:
These objects seem innocuous, but even tiny particles like stray paint flecks can damage spacecraft. Paint flecks caused necessary window replacements after many
473:
When two satellite operators are notified of a potential collision, one or both operators may decide to maneuver their satellite, eg. ESA & SpaceX in 2019.
87:
today are still functional. As of
September 2021, the ESA's Space Debris Office estimates that slightly over half of satellites in space are still operational.
489:
Another use of a collision avoidance maneuver is to abort an automated docking, and such a procedure is built into the software that controls the docking of
236:
follows a ballistic trajectory quickly reentering the atmosphere. Most of the external tank disintegrates due to the heat of reentry, while the orbiter uses
852:
371:
360:
412:
Collision avoidance maneuvers are sometimes also called Debris
Avoidance Maneuvers (DAMs) when the offending object is an article of space debris.
986:
60:
directions. Because of this, any spacecraft colliding with another object in orbit is likely to be critically damaged or completely destroyed.
223:
Objects launched onto suborbital trajectories will be quickly de-orbited by atmospheric drag. These include things like satellites launched on
910:
260:
The ease of access for de-orbiting LEO satellites at end of life makes it a successful method for controlling the space debris risk in LEO.
580:
during intervals when the vehicle cannot lift off to ensure its trajectory does not take it too close to another object already in space.
399:
conducts orbital projections and assesses collision risk for known objects larger than 4 inches (10 cm). For critical assets like the
316:
launcher designs completely expended their fuel to achieve orbit and left their spent rocket stages in orbit, as in the former Soviet
478:
320:
family of rockets. These upper stages are large artificial satellites, which depending on the orbit can take many years to reenter.
804:"Graveyard Orbits and the Satellite Afterlife | NOAA National Environmental Satellite, Data, and Information Service (NESDIS)"
80:
875:
1110:
186:
Many companies are launching large satellite constellations to provide high-speed communications and internet access from
428:(agreed upon by all international partners) requires planning for avoidance maneuvers if the probability of collision is
339:, the second stage uses remaining fuel to perform a de-orbit burn and disintegrate in the atmosphere. Stages stranded in
344:
556:
425:
400:
232:
1105:
490:
467:
626:
447:
237:
1090:
803:
602:
459:
120:
827:
72:. More collisions would make new smaller fragments which make more collisions and so forth. The resulting
323:
Most modern designs include sufficient fuel margins for de-orbit burns after injecting payload into orbit.
576:(COLA) needs to be performed and approved before launching a satellite. A launch window is said to have a
378:
73:
500:, and subsequently during demonstration approaches to the station which it conducted in late March 2008.
317:
654:
782:
692:
273:
1085:
463:
348:
285:
277:
1072:
916:
440:
390:
340:
269:
462:
may be involved. The ISS can also use the main engines of a docked cargo spacecraft – usually a
367:
in size or larger. Information on smaller articles of space debris is less accurate or unknown.
91:
Estimated quantity figures on human-launched satellites, provided by ESA's Space Debris Office
968:
906:
764:
313:
134:
Estimated quantity figures on space debris estimations, provided by ESA's Space Debris Office
17:
335:
Falcon 9 second stages are dealt with using different techniques depending on the orbit. For
958:
898:
754:
717:
297:
199:
84:
69:
38:
537:
at least one of the offending objects lacks remote control capability due to being defunct
521:
514:
495:
382:
364:
336:
304:
where they will forever remain out of the way of interaction with operational satellites.
301:
249:
224:
187:
56:
1035:
455:
203:
52:
1099:
569:
421:
180:
44:
933:
1080:
533:
Attempts to alleviate potential collisions are complicated by factors including if
451:
920:
902:
890:
446:
These avoidance maneuvers are almost always conducted by the firing of onboard
33:
is the implementation and study of processes minimizing the chance of orbiting
1062:
1010:
853:"launch - What happens to the Falcon 9 second stage after payload separation?"
540:
at least one of the offending objects is a natural satellite, like an asteroid
127:
34:
987:"NASA tweaks space station's position to avoid collision with massive debris"
972:
768:
895:
Proceedings of 2014 IEEE Chinese
Guidance, Navigation and Control Conference
332:
its ballistic trajectory and disintegrate upon reentry into the atmosphere.
363:
maintains a catalog of all known orbiting objects approximately equal to a
759:
742:
741:
Sampaio, J. C.; Wnuk, E.; de Moraes, R. Vilhena; Fernandes, S. S. (2014).
517:, where the atmosphere still provides a small amount of aerodynamic drag.
328:
195:
450:, although some other satellite and spacecraft orientation systems like
432:>1/100,000 and the maneuver wouldn't conflict with mission objectives
509:
253:
248:
The vast majority of artificial satellites and space stations orbit in
963:
946:
889:
Changping, Dang; Bo, Ren; Hong, Yao; Pu, Guo; Wei, Tan (2014-08-08).
324:
191:
508:
Most human-launched satellites without onboard propulsion are small
686:
684:
682:
680:
678:
386:
48:
877:
ESA spacecraft dodges potential collision with
Starlink satellite
130:, remnants of satellite collisions, or small natural satellites.
743:"Resonant Orbital Dynamics in LEO Region: Space Debris in Focus"
435:>1/10,000 and the maneuver wouldn't further endanger the crew
396:
648:
646:
627:"What a mess! Experts ponder space junk problem - USATODAY.com"
934:
Jules Verne demonstrates flawless
Collision Avoidance Maneuver
597:
595:
593:
374:
publishes known parameters for public analysis on the DoD's
55:
being involved in on-orbit collisions. For example, at the
1052:
370:
Once the exact orbit of an object is accurately known, the
891:"The collision avoidance strategy of formation spacecraft"
543:
the risk event isn't predicted with sufficient time to act
375:
296:
Spacecraft orbiting at higher altitudes between LEO and
947:"Spacecraft Collision Avoidance Using Aerodynamic Drag"
828:"Upper stages top list of most dangerous space debris"
783:"The Lifespan of Satellites | European Space Imaging"
568:
Collision avoidance is a concern during spaceflight
268:
Orbits with mean altitudes higher than LEO (such as
945:Omar, Sanny R.; Bevilacqua, Riccardo (2019-12-30).
1053:Interactive debris visualization by stuffin.space
1036:"Mission Status Center - Delta 313 Launch Report"
653:Phillip, Anz-Meador; Shoots, Debi (August 2020).
555:For example, maneuvers commonly conducted by the
552:a complete orbit to produce the required effect.
361:Department of Defense Space Surveillance Network
8:
520:The aerodynamic drag on small satellites in
897:. Yantai, China: IEEE. pp. 1961–1966.
27:Form of collision management in aeronautics
951:Journal of Guidance, Control, and Dynamics
962:
758:
145:Debris objects estimated to be in orbit
132:
89:
589:
1011:"NASA Technical Reports Server (NTRS)"
387:Space Science Data Coordinated Archive
308:Empty rocket stages remaining in orbit
504:Spacecraft without onboard propulsion
79:Very few of all satellites lofted by
7:
747:Mathematical Problems in Engineering
51:) is fast, resulting in significant
693:"Space Debris and Human Spacecraft"
240:to complete its orbital insertion.
416:Spacecraft with onboard propulsion
96:Satellites placed into Earth orbit
25:
142:Events resulting in fragmentation
1065:
857:Space Exploration Stack Exchange
139:Debris objects regularly tracked
655:"Orbital Debris Quarterly News"
574:Collision On Launch Assessment
47:around large bodies (like the
31:Spacecraft collision avoidance
18:Collision On Launch Assessment
1:
603:"Space debris by the numbers"
345:Geostationary transfer orbits
264:Medium Earth orbit and higher
355:Collision prediction methods
691:Garcia, Mark (2015-04-13).
557:International Space Station
491:Automated Transfer Vehicles
426:International Space Station
407:Collision avoidance methods
401:International Space Station
233:Space Shuttle external tank
1127:
903:10.1109/CGNCC.2014.7007479
718:"NASA - The External Tank"
468:Automated Transfer Vehicle
448:Reaction control thrusters
238:Reaction control thrusters
81:human-made launch vehicles
662:NASA Johnson Space Center
564:Effects on launch windows
460:Control moment gyroscopes
144:
141:
138:
1091:Space traffic management
121:2009 satellite collision
631:usatoday30.usatoday.com
219:Suborbital trajectories
210:Risk-mitigation methods
74:positive feedback loop
1111:Satellite collisions
578:COLA blackout period
529:Complicating factors
274:Geosynchronous orbit
1086:Collision avoidance
808:www.nesdis.noaa.gov
760:10.1155/2014/929810
464:Progress spacecraft
349:Geostationary orbit
341:Medium Earth orbits
312:Historically, many
286:spacecraft cemetery
278:Geostationary orbit
270:Medium Earth orbits
135:
92:
1073:Spaceflight portal
1038:. Spaceflight Now.
441:US Orbital Segment
391:Three-body problem
381:2020-11-17 at the
133:
90:
1106:Orbital maneuvers
1017:. 24 October 2016
964:10.2514/1.G004518
912:978-1-4799-4699-0
177:
176:
117:
116:
102:Still functional
57:Low Earth orbital
39:geocentric orbits
16:(Redirected from
1118:
1075:
1070:
1069:
1068:
1040:
1039:
1032:
1026:
1025:
1023:
1022:
1007:
1001:
1000:
998:
997:
983:
977:
976:
966:
942:
936:
931:
925:
924:
886:
880:
873:
867:
866:
864:
863:
849:
843:
842:
840:
839:
824:
818:
817:
815:
814:
800:
794:
793:
791:
790:
779:
773:
772:
762:
738:
732:
731:
729:
728:
713:
707:
706:
704:
703:
688:
673:
672:
670:
668:
659:
650:
641:
640:
638:
637:
623:
617:
616:
614:
613:
599:
337:Low Earth orbits
302:graveyard orbits
298:High Earth orbit
292:Graveyard orbits
250:Low Earth orbits
225:Sounding rockets
173:>128 million
136:
93:
70:Kessler syndrome
21:
1126:
1125:
1121:
1120:
1119:
1117:
1116:
1115:
1096:
1095:
1071:
1066:
1064:
1061:
1049:
1044:
1043:
1034:
1033:
1029:
1020:
1018:
1009:
1008:
1004:
995:
993:
985:
984:
980:
944:
943:
939:
932:
928:
913:
888:
887:
883:
874:
870:
861:
859:
851:
850:
846:
837:
835:
826:
825:
821:
812:
810:
802:
801:
797:
788:
786:
785:. 11 March 2019
781:
780:
776:
740:
739:
735:
726:
724:
715:
714:
710:
701:
699:
690:
689:
676:
666:
664:
657:
652:
651:
644:
635:
633:
625:
624:
620:
611:
609:
601:
600:
591:
586:
572:. Typically, a
566:
531:
522:Low Earth orbit
515:Low Earth orbit
506:
487:
456:Reaction wheels
418:
409:
383:Wayback Machine
376:space-track.org
357:
310:
294:
266:
246:
244:Low Earth orbit
221:
212:
188:Low Earth orbit
83:that remain in
66:
28:
23:
22:
15:
12:
11:
5:
1124:
1122:
1114:
1113:
1108:
1098:
1097:
1094:
1093:
1088:
1083:
1077:
1076:
1060:
1057:
1056:
1055:
1048:
1047:External links
1045:
1042:
1041:
1027:
1002:
978:
957:(3): 567–573.
937:
926:
911:
881:
868:
844:
819:
795:
774:
733:
708:
674:
642:
618:
588:
587:
585:
582:
570:launch windows
565:
562:
545:
544:
541:
538:
530:
527:
505:
502:
486:
485:Docking aborts
483:
437:
436:
433:
417:
414:
408:
405:
356:
353:
309:
306:
293:
290:
265:
262:
245:
242:
220:
217:
211:
208:
204:Project Kuiper
175:
174:
171:
168:
165:
162:
158:
157:
154:
151:
147:
146:
143:
140:
115:
114:
111:
108:
104:
103:
100:
99:Still in space
97:
65:
62:
53:kinetic energy
26:
24:
14:
13:
10:
9:
6:
4:
3:
2:
1123:
1112:
1109:
1107:
1104:
1103:
1101:
1092:
1089:
1087:
1084:
1082:
1079:
1078:
1074:
1063:
1058:
1054:
1051:
1050:
1046:
1037:
1031:
1028:
1016:
1015:ntrs.nasa.gov
1012:
1006:
1003:
992:
988:
982:
979:
974:
970:
965:
960:
956:
952:
948:
941:
938:
935:
930:
927:
922:
918:
914:
908:
904:
900:
896:
892:
885:
882:
879:
878:
872:
869:
858:
854:
848:
845:
833:
829:
823:
820:
809:
805:
799:
796:
784:
778:
775:
770:
766:
761:
756:
752:
748:
744:
737:
734:
723:
719:
716:Wilson, Jim.
712:
709:
698:
694:
687:
685:
683:
681:
679:
675:
663:
656:
649:
647:
643:
632:
628:
622:
619:
608:
604:
598:
596:
594:
590:
583:
581:
579:
575:
571:
563:
561:
558:
553:
549:
542:
539:
536:
535:
534:
528:
526:
523:
518:
516:
511:
503:
501:
499:
498:
492:
484:
482:
480:
474:
471:
469:
465:
461:
457:
453:
452:Magnetorquers
449:
444:
442:
434:
431:
430:
429:
427:
423:
422:Space Shuttle
415:
413:
406:
404:
402:
398:
394:
392:
388:
384:
380:
377:
373:
368:
366:
362:
354:
352:
350:
346:
342:
338:
333:
330:
326:
321:
319:
315:
307:
305:
303:
299:
291:
289:
287:
281:
279:
275:
271:
263:
261:
258:
255:
251:
243:
241:
239:
234:
229:
226:
218:
216:
209:
207:
205:
201:
197:
193:
189:
184:
182:
181:Space Shuttle
172:
169:
166:
163:
160:
159:
155:
152:
149:
148:
137:
131:
129:
124:
122:
112:
109:
106:
105:
101:
98:
95:
94:
88:
86:
82:
77:
75:
71:
63:
61:
58:
54:
50:
46:
45:Orbital speed
42:
40:
36:
32:
19:
1081:Space debris
1030:
1019:. Retrieved
1014:
1005:
994:. Retrieved
991:nationalpost
990:
981:
954:
950:
940:
929:
894:
884:
876:
871:
860:. Retrieved
856:
847:
836:. Retrieved
834:. 2020-10-13
831:
822:
811:. Retrieved
807:
798:
787:. Retrieved
777:
750:
746:
736:
725:. Retrieved
722:www.nasa.gov
721:
711:
700:. Retrieved
696:
667:November 12,
665:. Retrieved
661:
634:. Retrieved
630:
621:
610:. Retrieved
606:
577:
573:
567:
554:
550:
546:
532:
519:
507:
496:
488:
475:
472:
445:
438:
419:
410:
395:
369:
358:
334:
322:
311:
295:
282:
267:
259:
247:
230:
222:
213:
185:
178:
156:1 mm - 1 cm
125:
118:
78:
67:
43:
30:
29:
607:www.esa.int
497:Jules Verne
385:and NASA's
314:multi-stage
85:Earth orbit
1100:Categories
1021:2020-11-16
996:2020-11-15
862:2020-10-27
838:2020-10-27
813:2020-10-27
789:2020-10-27
727:2020-10-27
702:2020-11-16
636:2020-10-27
612:2021-10-10
584:References
347:(GTO) and
167:>34,000
128:meteoroids
35:spacecraft
973:1533-3884
832:SpaceNews
769:1024-123X
372:DoD's SSN
190:, namely
183:flights.
150:>10 cm
64:Necessity
1059:See also
753:: 1–12.
510:CubeSats
424:and the
379:Archived
365:softball
329:Falcon 9
202:planned
196:Starlink
170:~900,000
343:, like
272:(MEO),
254:Delta-v
164:>500
161:~22,300
153:1-10 cm
113:~4,700
107:~12,070
971:
921:863378
919:
909:
767:
458:, and
325:SpaceX
200:Amazon
192:SpaceX
110:~7,500
917:S2CID
658:(PDF)
318:Zenit
49:Earth
969:ISSN
907:ISBN
765:ISSN
751:2014
697:NASA
669:2020
397:NASA
231:The
198:and
959:doi
899:doi
755:doi
479:GNC
466:or
327:'s
194:'s
1102::
1013:.
989:.
967:.
955:43
953:.
949:.
915:.
905:.
893:.
855:.
830:.
806:.
763:.
749:.
745:.
720:.
695:.
677:^
660:.
645:^
629:.
605:.
592:^
481:.
454:,
288:.
1024:.
999:.
975:.
961::
923:.
901::
865:.
841:.
816:.
792:.
771:.
757::
730:.
705:.
671:.
639:.
615:.
276:/
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.