O3b Explained

O3b MEO
Mission Type:Internet access
Operator:SES Networks
Manufacturer:Thales Alenia Space
Launch Mass:700 kg
Launch Date: (four)
(four)
(four)
(four)
(four)
Orbit Reference:Geocentric orbit
Orbit Regime:Medium Earth orbit
Orbit Periapsis:8063 km
Orbit Period:287.9 minutes
Apsis:gee

O3b is a satellite constellation in Medium Earth orbit (MEO) owned and operated by SES, and designed to provide low-latency broadband connectivity to remote locations for mobile network operators and internet service providers, maritime, aviation, and government and defence. It is often referred to as O3b MEO to distinguish these satellites from SES's forthcoming O3b mPOWER constellation.[1]

O3b originally stood for "other three billion", or the other three billion people at the time that did not have stable internet access, and the constellation was initially built, owned and operated by O3b Networks, which became a wholly owned subsidiary of SES in 2016[2] and ownership and operation of the constellation passed to SES Networks, a division of SES. The O3b MEO constellation began offering service in March 2014.[3]

History

Initially planned to launch in 2010,[4] the first four O3b satellites reached orbit on a Soyuz-2 / Fregat-MT launch vehicle by Arianespace on 25 June 2013.[5] [6] After discovering a hardware defect in the initial satellites, O3b postponed the planned September 2013 launch of four additional satellites so repairs could be made.[7] The second four satellites were launched by the same type of rocket from the Space Center in French Guiana, on 10 July 2014[8] and the O3b system started full commercial service on 1 September 2014.[9]

The third launch of four took place in December 2014, bringing the satellite constellation to 12 satellites.[10] Four years later, four additional satellites were launched on 9 March 2018 on a Soyuz-2.1b rocket from the Centre Spatial Guyanais.[11] In December 2018, Thales Alenia Space said that tests on the final four O3b satellites would be completed by the end of January 2019[12] and the four satellites were successfully launched on 4 April 2019.[13]

In 2010, operators in the Cook Islands,[14] Pakistan[15] and Nigeria[16] were among the first to prebook capacity on the O3b constellation to serve their respective markets.

In 2010, O3b announced the selection of Europe Media Port to be the first provider of Gateway Teleport services for O3b's global network[17] and a contract with Viasat for the production and installation of Ka-band infrastructure.[18]

In July 2014, SES Government Solutions (now SES Space & Defense), a subsidiary of (then O3b investor, now owner) SES, received approval to offer O3b services on their General Services Administration (GSA) schedule allowing SES GS to be the first distribution partner to offer O3b capability directly to the U.S. Government.[19]

In November 2014, MS Quantum of the Seas became the first cruise ship to provide fast internet to guests through O3b Networks. The service is branded "Voom" by its cruise line, Royal Caribbean International and it was subsequently rolled out to every ship in their fleet.[20] [21]

In August 2015, SES subsidiary, SES Government Solutions (now SES Space & Defense) agreed on a one-year contract with US government scientific agency, National Oceanic and Atmospheric Administration (NOAA) to supply O3b services and ground equipment to the National Weather Service Office in American Samoa, expanding NOAA's broadband connectivity outside the continental United States to provide weather, water, and climate data, and forecasts and warnings to American Samoa.[22]

In August 2016, SES Government Solutions (now SES Space & Defense) announced a contract to provide O3b's high throughput, low latency satellite communications for a US Department of Defense end-user. The agreement is for a 365 days-per-year service consisting of a full-duplex symmetric 155 Mbit/s link, gateway access, a transportable 2.4 metre terminal, terrestrial backhaul, and maintenance and installation services, with a latency of under 200 milliseconds per round trip. The contract also provides for additional capacity to meet surge requirements.[23]

In September 2017, SES announced O3b mPOWER, the next generation of MEO satellites to expand the capacity of the existing O3b constellation of (then) 12 satellites. Initially seven O3b mPOWER satellites were ordered from Boeing for launch in 2021 to provide flexible and scalable, low-latency satellite-based networks with terabits of throughput.[24] [25]

In June 2018, the US Department of Defense signed a single-award blanket purchase agreement with SES Government Solutions (now SES Space & Defense) for MEO high throughput, low latency satellite services including managed broadband services, gateway services, and monitoring and control services, to a maximum of US$516.7 million over a five-year period.[26]

In September 2019, SES became a Microsoft Azure ExpressRoute services partner to provide dedicated, private network connectivity from sea vessels, aircraft, and industrial or government sites anywhere in the world to the Azure cloud computing service, via both its geostationary satellites and O3b MEO satellites.[27]

In August 2020 SES contracted Boeing to build four O3b mPOWER satellites in addition to the seven ordered in 2017. SpaceX was contracted for additional launches, to make four launches for the whole O3b mPOWER constellation, expected in 2021–2024.[28] [29]

In September 2020, SES and Microsoft announced that SES was the medium Earth orbit connectivity partner for the Microsoft Azure Orbital ground station service that enables network operators to control their satellite operations and capacity from within the Azure cloud computing service. Under their agreement, SES and Microsoft will jointly invest in Azure Orbital ground stations for the MEO and Earth Observation segments, initially in the United States, which will be installed and managed by SES. Also, satellite telemetry, tracking and control systems and data ground stations for the forthcoming O3b mPOWER satellites will be located with Microsoft's Azure edge sites to provide O3b mPOWER customers with "one-hop" access to Azure cloud services.[30] [31]

In October 2020, international charity hospital ships provider, Mercy Ships announced it will be using SES's Signature Maritime connectivity services via O3b satellites to provide remote viewing and diagnosis, and remote training on board the Global Mercy, the world's largest civilian hospital ship.[32]

In February 2021, SES announced two contracts with the US Department of Defense as part of the June 2018 blanket purchase agreement. One is for a portable O3b service to support forward-deployed military personnel[33] and the second to provide O3b mission-critical communications without using a commercial gateway in remote locations in Southwest Asia, managed and controlled from an SES Network Operations Center.[34]

Also in February 2021, SES announced that its Signature Cruise broadband connectivity via O3b will be used on Virgin Voyages' latest ships Scarlet Lady and Valiant Lady to provide passengers with free fast onboard wi-fi internet access.[35]

In June 2021, SES joined the Amazon Web Services Direct Connect Delivery Partner programme, using the O3b constellation (and SES' fleet of geostationary satellites) to provide customers access to AWS cloud-based applications and services from locations around the world with limited or no terrestrial communications, and to provide the cloud provider a backup network if their infrastructure fails.[36]

In August 2021, Microsoft became the first cloud provider customer for O3b, with Microsoft buying managed satellite connectivity services from SES for the Microsoft Azure cloud computing service. Microsoft is initially using the existing first generation O3b satellites, before upgrading to the faster broadband speeds from the forthcoming O3b mPOWER satellites when they come into operation in 2022.[37] (In November 2022, SES announced that the start of the O3b mPOWERservice was delayed until Q3 2023).[38]

In December 2021, SES's wholly owned subsidiary SES Government Solutions (now SES Space & Defense) announced that the US Army has conducted trials of commercial satellite constellations in multiple orbits, including the O3b satellite system, as part of the effort to establish Multi-Domain Operations.[39]

In December 2021, Honeywell, Hughes Network Systems and SES demonstrated multi-orbit high-speed airborne connectivity for military customers using Honeywell's JetWave MCX terminal and a Hughes HM-series modem, and SES satellites in both medium Earth orbit (MEO) and geostationary orbit (GEO). The tests achieved full duplex data rates of more than 40 megabits per second via a number of SES' (GEO) satellites including GovSat-1, and the O3b satellite constellation, with connections moving between GEO/MEO links in under 30 sec.[40]

In May 2022, in conjunction with Kazakhstani mobile network operator, Kcell, SES used the O3b satellite constellation to demonstrate that MEO satellites could be used to provide high-speed 3G and 4G connectivity to remote regions of Kazakhstan for reliable video calling, conferencing and streaming, and web browsing, with a latency five times lower than on the existing platform based on geostationary orbit satellites.[41] [42]

On 16 December 2022, the first two of SES's next generation MEO satellite constellation, O3b mPOWER were successfully launched. The satellites will take approximately six months to reach their designated medium Earth orbit and for commissioning, and the O3b mPower service is expected to begin operations alongside the existing O3b constellation in Q3 2023.[43] The second pair of O3b mPOWER satellites were successfully launched on 28 April 2023, by which time the first pair of satellites had reached medium Earth orbit and were undergoing in-orbit testing.[44]

Satellites

The satellites are deployed in a circular orbit along the equator at an altitude of (medium Earth orbit) at a velocity of approximately, each making 5 orbits a day.[45] Due to problems with a component of the first four satellites launched, three of those four have been placed on standby.[46]

Each satellite is equipped with twelve fully steerable Ka-band antennas (two beams for gateways, ten beams for remotes) that use 4.3 GHz of spectrum (2 × 216 MHz per beam) with a proposed throughput of 1.6 Gbit/s per beam (800 Mbit/s per direction),[47] resulting in a total capacity of 16 Gbit/s per satellite. Each beam's footprint measures in diameter.[48] O3b claims a mouth-to-ear one-way latency of 179 milliseconds for voice communication, and an end-to-end round-trip latency of 140 ms for data services. The maximum throughput per TCP connection is 2.1 Mbit/s.[49] For maritime applications, O3b claims a round-trip latency of 140 ms, and connectivity speeds of over 500 Mbit/s.[50]

The satellites are powered by gallium arsenide solar arrays and lithium-ion batteries[51] and weigh approximately each.[5]

The satellites were constructed by Thales Alenia Space, a division of Thales Group.[52] The first satellite (PFM) was built in the Cannes Mandelieu Space Center, while the rest of the constellation was assembled, integrated and tested in Thales Alenia Space Italy's Roman facilities.

In September 2017, SES announced the next generation of O3b satellites and placed an order for an initial seven from Boeing Satellite Systems using a new satellite platform based on Boeing's 702 line of scalable buses. Expected to launch in 2021, the O3b mPOWER constellation of medium Earth orbit (MEO) satellites for broadband internet services will "be able to deliver anywhere from hundreds of megabits to 10 gigabits to any ship at sea" through 30,000 spot beams. Software-defined routing will direct traffic between the mPOWER MEO satellites and SES' geostationary fleet.[53] In August 2020, SES contracted Boeing to build four additional O3b mPOWER satellites and SpaceX was contracted for an additional two launches, to make four launches for the whole O3b mPOWER constellation in 2022–2024.[54] [55] [56] [57]

List of satellites

NameNORAD IDInt'l CodeLaunch DateLaunch VehiclePeriod (min)
O3B PFM391912013-031D25 June 2013Soyuz ST-B (VS05)287.9
O3B FM2391902013-031C25 June 2013Soyuz ST-B (VS05)287.9
O3B FM3400822014-038D10 July 2014Soyuz ST-B (VS08)287.9
O3B FM4391892013-031B25 June 2013Soyuz ST-B (VS05)287.9
O3B FM5391882013-031A25 June 2013Soyuz ST-B (VS05)287.9
O3B FM6400802014-038B10 July 2014Soyuz ST-B (VS08)287.9
O3B FM7400812014-038C10 July 2014Soyuz ST-B (VS08)287.9
O3B FM8400792014-038A10 July 2014Soyuz ST-B (VS08)287.9
O3B FM9403512014-083D18 December 2014Soyuz ST-B (VS10)287.9
O3B FM10403482014-083A18 December 2014Soyuz ST-B (VS10)287.9
O3B FM11403492014-083B18 December 2014Soyuz ST-B (VS10)287.9
O3B FM12403502014-083C18 December 2014Soyuz ST-B (VS10)287.9
O3B FM13432342018-024D9 March 2018Soyuz ST-B (VS18)287.9
O3B FM14432332018-024C9 March 2018Soyuz ST-B (VS18)287.9
O3B FM15432312018-024A9 March 2018Soyuz ST-B (VS18)287.9
O3B FM16432322018-024B9 March 2018Soyuz ST-B (VS18)287.9
O3B FM17441142019-020C4 April 2019Soyuz ST-B (VS22)287.9
O3B FM18441152019-020D4 April 2019Soyuz ST-B (VS22)287.9
O3B FM19441132019-020B4 April 2019Soyuz ST-B (VS22)287.9
O3B FM20441122019-020A4 April 2019Soyuz ST-B (VS22)287.9
[58]

Use of medium Earth orbit

O3b MEO is currently the only high-throughput satellite (HTS) system for internet services to use the medium Earth orbit; most other existing and proposed systems use satellites in either geosynchronous orbit (GEO) or low Earth orbit (LEO). Although previous satellite internet services primarily used geosynchronous satellites (SES has four geostationary HTS in orbit – Astra 2E, SES-12, SES-14 and SES-15), demand for increased bandwidth and for lower latency has shifted the focus for HTS to lower orbits.[59] The lower the altitude of the orbit, the closer the satellite is to the Earth and the lower the latency and path losses (enabling lower ground station and satellite power, and costs for the same throughput)[60] The propagation delay for a round-trip internet protocol transmission via a geosynchronous satellite can be over 550 ms, and such latency is the bane of digital connectivity, in particular for automated stock trades, hardcore gaming and Skype video chats.[61] [62] So, many proposed non-geosynchronous satellite internet services have adopted a low Earth orbit of under 2000 km altitude[62] where latency can be as little 40ms,[63] and by 2018 more than 18,000 new LEO satellites had been proposed to launch by 2025.[64]

However, a lower orbit also has drawbacks; satellites move faster relative to the ground and can "see" a smaller area of the Earth, and so for continuous widespread access require a constellation of many satellites, with complex constellation management and tracking by the ground stations.[59] [62] Medium Earth orbit, although higher in altitude than LEO is nevertheless much lower than geosynchronous orbit and so shares many of the advantages of LEO while reducing its drawbacks:[65] [60] [66] [61]

See also

Notes and References

  1. https://www.ses.com/our-coverage/o3b-meo O3b MEO
  2. http://www.businesswire.com/news/home/20160801005941/en/SES-Completes-Acquisition-100-O3b-Networks SES Completes Acquisition of 100% of O3b Networks
  3. 1407.2521. Revisiting elliptical satellite orbits to enhance the O3b constellation. Journal of the British Interplanetary Society. 67. 3. 110–118. 2014. Wood. Lloyd. Lou. Yuxuan. Olusola. Opeoluwa . 2014JBIS...67..110W.
  4. http://o3bnetworks.com/media-centre/press-releases/2009/global-broadband-solution
  5. Web site: Soyuz Flight VS05 with four O3b networks satellites. Arianespace. 25 June 2013. 27 October 2020.
  6. Web site: O3b's Satellites Launch Successfully. O3b. 25 June 2013. 28 October 2020. https://web.archive.org/web/20140521125821/http://www.o3bnetworks.com/additional-pages/blog/o3b's-satellites-launch-successfully. 21 May 2014. dead.
  7. https://archive.today/20140520150216/http://www.spacenews.com/article/satellite-telecom/37953delayed-o3b-satellites-should-be-ready-for-march-launch Delayed O3b Satellites Should be Ready for March Launch
  8. Web site: O3b Networks going operational with state-of-the-art satellite constellation to serve the other 3 billion. 29 July 2014. https://web.archive.org/web/20140730013147/http://www.o3bnetworks.com/3222. 30 July 2014. dead.
  9. Web site: O3b Successfully Launches Four More Satellites to Complete }} Constellation ]. Satellite Markets & Research . 18 December 2014 . 28 October 2020.
  10. https://spaceflightnow.com/2014/12/19/third-quartet-of-satellites-launched-for-o3b-networks/ Third quartet of satellites launched for O3b Networks
  11. https://www.nasaspaceflight.com/2018/03/arianespace-soyuz-st-b-latest-o3b-launch/ Arianespace Soyuz ST-B launches latest O3b satellites
  12. https://advanced-television.com/2018/12/19/thales-readies-4-satellites-for-o3b/ Thales readies 4 satellites for O3b
  13. https://www.space.com/arianespace-soyuz-launches-4-ses-satellites.html Four New Satellites Ride Into Space To Join Growing SES Constellation
  14. http://www.o3bnetworks.com/media-centre/press-releases/2010/o3b-networks-and-telecom-cook-islands-sign-long-term-agreement-on-bandwidth-provision-for-internet-connectivity
  15. http://o3bnetworks.com/media-centre/press-releases/2010/pak-datacom-limited-signs-exclusive-national-capacity-agreement-with-o3b-networks-to-deploy-high-speed-internet-to-pakistan
  16. http://www.o3bnetworks.com/media-centre/press-releases/2010/o3b-networks-signs-deal-with-netcom,-nigeria-to-provide-fast-and-reliable-connectivity-to-ships-and-offshore-platforms
  17. http://www.o3bnetworks.com/media-centre/press-releases/2010/o3b-selects-europe-media-port-(emp)-as-its-first-gateway-teleport-operator-for-new-high-capacity-data-network
  18. https://spacenews.com/mark-rigolle-chief-executive-officer-o3b-networks/ Interview with Mark Rigolle, Chief Executive Officer, O3B Networks
  19. SES. 29 July 2014 . SES Receives Approval from GSA to Sell O3b Services. 28 October 2020.
  20. http://www.cntraveler.com/stories/2014-11-21/royal-caribbean-quantum-of-the-seas-smart-ship-technology Royal Caribbean's Quantum of the Seas Wows with Smart Ship Technology
  21. http://www.royalcaribbeanblog.com/2016/04/29/royal-caribbean-add-high-speed-internet-every-ship-the-fleet-may-1st Royal Caribbean to add high speed internet to every ship in the fleet by May 1st
  22. SES. 17 August 2015. NOAA Signs First U.S. Government Deal With SES for O3b High Throughput Solution. 28 October 2020.
  23. http://www.finanznachrichten.de/nachrichten-2016-08/38422099-ses-government-solutions-to-provide-the-us-government-with-a-high-performance-network-004.htm SES Government Solutions to Provide the US Government with a High-Performance Network
  24. SES opens new era in global connectivity with O3b mPOWER. SES. 11 September 2017. 27 December 2022.
  25. https://spaceflightnow.com/2017/09/12/ses-orders-seven-satellites-from-boeing-to-help-meet-growing-broadband-demand/ SES orders seven satellites from Boeing to help meet growing broadband demand
  26. https://militaryembedded.com/comms/satellites/dod-signs-five-year-bpa-with-ses-for-medium-earth-orbit-satellite-services DoD signs five-year BPA with SES for medium Earth orbit satellite services
  27. https://advanced-television.com/2019/09/09/ses-extends-reach-of-microsoft-azure-expressroute/ SES extends reach of Microsoft Azure ExpressRoute
  28. Boeing to Build Four Additional 702X Satellites for SES's O3b mPOWER Fleet. Boeing . 7 August 2020 . 27 January 2023.
  29. https://spacenews.com/ses-taps-spacex-for-two-additional-falcon-9-launches/ SES taps SpaceX for two additional Falcon 9 launches
  30. https://azure.microsoft.com/en-us/blog/introducing-azure-orbital-process-satellite-data-at-cloudscale/ Introducing Azure Orbital: Process satellite data at cloud-scale
  31. SES Becomes Microsoft Azure Orbital Founding Connectivity Partner. 22 September 2020. 30 October 2020.
  32. https://www.satellitetoday.com/mobility/2020/10/16/ses-provides-connectivity-services-for-mercy-ships/ SES Provides Connectivity Services for Mercy Ships
  33. https://www.satellitetoday.com/government-military/2021/02/19/ses-government-solutions-wins-us-dod-maritime-deal-for-o3b/ Wins US DoD Maritime Deal for O3b
  34. https://www.satellitetoday.com/broadcasting/2021/02/22/ses-wins-slew-of-european-public-broadcast-deals/ SES Wins Slew of European Public Broadcast Deals
  35. https://www.rivieramm.com/news-content-hub/virgin-invests-in-high-speed-satellite-communications-63804 Virgin invests in high-speed satellite communications
  36. https://spacenews.com/ses-strengthens-amazon-web-services-cloud-partnership/ SES strengthens Amazon Web Services cloud partnership
  37. https://spacenews.com/o3b-mpower-get-first-cloud-customer-on-track-for-launch-even-as-covid-19-issues-loom/ O3b mPOWER get first cloud customer, on track for launch even as COVID-19 issues loom
  38. https://spacenews.com/o3b-mpower-flexibility/ SES eagerly awaiting the flexibility O3b mPower promises
  39. https://www.satellitetoday.com/government-military/2021/12/07/us-army-uses-ses-meo-technology-in-multi-orbit-tests/ US Army Uses SES MEO Technology in Multi-Orbit Tests
  40. https://www.satellitetoday.com/government-military/2021/12/20/honeywell-ses-and-hughes-demonstrate-meo-to-geo-satellite-switching-for-military-customers/ Honeywell, SES, and Hughes Demonstrate MEO to GEO Satellite Switching for Military Customers
  41. https://www.commsupdate.com/articles/2022/05/26/kcell-ses-demo-o3b-satellite-enabled-remote-mobile-services/ Kcell, SES demo O3b satellite-enabled remote mobile services
  42. SES. 25 May 2022 . Kcell and SES Successfully Demonstrate Cellular Network connectivity in Kazakhstan. 30 May 2022.
  43. https://spacenews.com/spacex-launches-first-pair-of-o3b-mpower-satellites/ SpaceX launches first pair of O3b mPower satellites
  44. https://spacenews.com/spacex-launches-second-set-of-o3b-mpower-satellites/ SpaceX launches second pair of O3b mPower satellites
  45. Web site: iDirect's Interoperability with O3b's MEO Satellite System. 2008. 31 January 2013 . https://web.archive.org/web/20140811010152/http://www.idirect.net/Company/Press-Room/Press-Releases/2008/Release-358.aspx. 11 August 2014. dead.
  46. Web site: O3B NETWORKS SATELLITES. 13 November 2019.
  47. Web site: O3b Networks Presentation. O3b Networks. presentation. 23 February 2009. 9 January 2013.
  48. Web site: O3b website – Our technology. 9 January 2013. O3b Networks. https://web.archive.org/web/20150317220715/http://www.o3bnetworks.com/o3b-advantage/our-technology. 17 March 2015. dead.
  49. Web site: Why Latency Matters to Mobile Backhaul. O3b Networks and Sofrecom. 18 April 2013 . dead. https://web.archive.org/web/20131118044646/http://o3bnetworks.com/media/45606/o3b_latency_mobile%20backhaul_130417.pdf. 18 November 2013.
  50. Web site: O3b Maritime. O3b Networks. 18 June 2012. dead. https://web.archive.org/web/20121024025342/http://o3bnetworks.com/media/60982/o3b_maritime_brochure.pdf. 24 October 2012.
  51. Web site: O3b Networks: Space Vehicle. dead. https://web.archive.org/web/20090219201829/http://o3bnetworks.com/spacevehicle.html. 19 February 2009.
  52. Web site: O3b Networks: Advantage. dead . https://web.archive.org/web/20110303154852/http://www.o3bnetworks.com/Advantages/advantages.html. 3 March 2011.
  53. http://spacenews.com/ses-building-a-10-terabit-o3b-mpower-constellation/ SES building a 10-terabit O3b "mPOWER" constellation
  54. Boeing to Build Four Additional 702X Satellites for SES's O3b mPOWER Fleet. Boeing. 7 August 2020. 20 August 2020.
  55. https://spacenews.com/ses-taps-spacex-for-two-additional-falcon-9-launches/ SES taps SpaceX for two additional Falcon 9 launches
  56. https://www.satellitetoday.com/launch/2021/12/30/top-satellite-launches-to-watch-in-2022/ Top Satellite Launches to Watch in 2022
  57. Web site: 4 November 2021 . SES YTD 2021 Results . 27 January 2022 . . 4.
  58. Web site: O3B Networks satellites. www.n2yo.com. 14 November 2019.
  59. https://www.mckinsey.com/industries/aerospace-and-defense/our-insights/large-leo-satellite-constellations-will-it-be-different-this-time Large LEO satellite constellations: Will it be different this time?
  60. https://www.satelliteevolutiongroup.com/articles/LEO-Constellations&Tracking.pdf LEO constellations and tracking challenges
  61. https://www.telesat.com/wp-content/uploads/2020/07/Real-Time-Latency-Rethinking-Remote-Networks.pdf Real-Time Latency: Rethinking Remote Networks
  62. https://spacenews.com/divining-what-the-stars-hold-in-store-for-broadband-megaconstellations/ LEO and MEO broadband constellations mega source of consternation
  63. https://www.omniaccess.com/leo/ Low Earth Orbit satellites, improving latency
  64. http://www.satnews.com/story.php?number=257303683 NSR Reports China's Ambitious Constellation of 300 Small Satellites in LEO
  65. http://www.ing.unisannio.it/labtlc/ghidini/LEO-MEO-GEO.pdf Satellites: LEO, MEO & GEO
  66. http://interactive.satellitetoday.com/via/march-2019/the-gravity-of-space-debris/ The Gravity of Space Debris