View source for WT1190F

{{Short description|Small temporary satellite of Earth that impacted in 2015}}
{{Use dmy dates|date=November 2015}}
{{Infobox planet
| image = WT-reentry-fireball-tight.jpg
| caption = WT1190F entering the atmosphere over Sri Lanka, viewed by the airborne observation team
| name = WT1190F
| discoverer = {{Ubl
 | [[Mount Lemmon Survey]] (G96)
 | [[Catalina Sky Survey]] (703)
 }}
| discovered = {{Ubl
 | 26 October 2009
 | 18 February 2013
 | 29 November 2013
 | 3 October 2015
 }}
| alt_names = {{Hlist
 | 9U01FF6
 | UDA34A3
 | UW8551D
 }}
| mp_category = Distant artificial satellite (before Jun 2009 to 13 November 2015)
| orbit_ref = <ref name=orbitandobs>{{cite web|last1=Gray|first1=Bill|title=Pseudo-MPC for UDA34A3 = UW8551D = WT1190F|url=http://projectpluto.com/temp/mpec9.htm|website=Project Pluto|access-date=23 October 2015}}</ref>
| epoch = 3 October 2015 ([[Julian day|JD]]&nbsp;2457298.5)
| periapsis = {{convert|21222|km|mi|abbr=on}} (0.055&nbsp;[[Lunar distance (astronomy)|LD]]; 3.33&nbsp;[[Earth radius|ER]])
| apoapsis = {{convert|655374|km|mi|abbr=on}} (1.704&nbsp;LD, 102.75&nbsp;ER)
| semimajor = {{convert|338298|km|mi|abbr=on}} (0.880&nbsp;LD, 53.04&nbsp;ER)
| eccentricity = 0.937269
| period = 22.66 days
| mean_anomaly = 6.191°
| inclination = 3.197°
| asc_node = 311.556°
| time_periastron = 2 October 2015 14:39:00 [[Universal Time|UT]]
| arg_peri = 314.044°
| avg_speed = 1.1&nbsp;km/s @ 0.00226&nbsp;AU
| satellite_of = [[Earth]]
| dimensions = {{convert|0.7|to|2|m|ft|sp=us|sigfig=1}}
| density = ~{{cvt|100|kg/m3|g/cm3|disp=out}}<ref name=mpmlinfo>{{cite web|title=WT1190F comes back: ESA NEOCC watching rare reentry|url=https://groups.yahoo.com/neo/groups/mpml/conversations/topics/31398|archive-url=https://archive.today/20151026202327/https://groups.yahoo.com/neo/groups/mpml/conversations/topics/31398|url-status=dead|archive-date=26 October 2015|website=Minor Planet Mailing List|access-date=24 October 2015}}</ref>
| mass = {{convert|250|to|2000|kg|lb|sigfig=2}}
| albedo = >0.1
| magnitude = ~16–23
| abs_magnitude = 31.3
| rotation = 0.75 seconds<ref>[http://www.birtwhistle.org.uk/images/WT1190F_20151113_053428_20_2x2_1A.jpg Peter Birtwhistle]</ref>
|background=#FFC2E0}}
'''WT1190F''' ('''9U01FF6''', '''UDA34A3''', or '''UW8551D''') was a small temporary [[satellite]] of Earth that impacted Earth on 13 November 2015 at 06:18:21.7 (±&nbsp;0.1 seconds) [[Coordinated Universal Time|UTC]].<ref name= Jenniskens >{{cite web |url=http://impact.seti.org/WT1190F-AIAASciTech2016-AIAA-2016-0999.pdf |title=Airborne Observations of an Asteroid Entry for High Fidelity Modeling: Space Debris Object WT1190F |last=Jenniskens |first=Petrus |display-authors=etal |date=8 January 2016 |website=SETI Institute |publisher=[[AIAA]] Science and Technology Forum and Exposition (SciTech 2016) |location=San Diego, CA. |access-date=22 August 2022}}</ref>{{rp|pp=7-8}} It is thought to have been [[space debris]] from the [[trans-lunar injection]] stage of the 1998 [[Lunar Prospector]] mission.<ref>{{cite news |last=Watson |first=Traci |date=13 January 2016|title=Falling space debris traced to 1998 lunar mission |doi=10.1038/nature.2016.19162|url=http://www.nature.com/news/falling-space-debris-traced-to-1998-lunar-mission-1.19162|newspaper=[[Nature (journal)|Nature]]|access-date=18 January 2015}}</ref><ref name="space junk">{{cite news |last=Watson |first=Traci |url=http://www.nature.com/news/incoming-space-junk-a-scientific-opportunity-1.18642 |title=Incoming space junk a scientific opportunity |work=Nature News |date=23 October 2015 |access-date=2015-10-29 }}</ref> It was first discovered on 18 February 2013 by the [[Catalina Sky Survey]].<ref name="mpmlinfo"/><ref name="Gizmag1023">{{cite news |last=Wood |first=Chris |url=http://www.gizmag.com/esa-rocket-reentry-observations/40021/ |title=ESA to study rare rocket body reentry to improve predictive models |work=Gizmag.com |date=2015-10-23 |access-date=2015-10-27 }}</ref> It was then lost, and reacquired on 29 November 2013. It was again discovered on 3 October 2015 by astronomer Rose Garcia with the Catalina Sky Survey 60-inch telescope, and the object was soon identified to be the same as the two objects previously sighted by the team, who have been sharing their data through the [[International Astronomical Union]]'s [[Minor Planet Center]] (MPC).<ref name="ESA prediction">{{Cite web|title = Reentry data will help improve prediction models|url = https://www.esa.int/Space_Safety/Reentry_data_will_help_improve_prediction_models|website = European Space Agency|access-date = 2015-11-02}}</ref> An early orbit calculation showed that it was orbiting Earth in an extremely elliptical orbit, taking it from within the [[Geosynchronous orbit|geosynchronous satellite ring]] to nearly twice the distance of the Moon.<ref name="orbitandobs"/> It was also probably the same object as 9U01FF6, another object on a similar orbit discovered on 26 October 2009.

WT1190F had been orbiting Earth as a temporary satellite (named '''UWAIS''') since mid-2009, if not longer. While it has not been positively identified with any known artificial satellites, its estimated density of 0.1&nbsp;g/cm<sup>3</sup> was much lower than would be expected of a natural object as even water has a density of 1&nbsp;g/cm<sup>3</sup>.  Hence, [[European Space Agency]] astronomers have concluded that the object was likely a fuel tank of some sort.<ref name="mpmlinfo"/><ref name="Gizmag1023"/>

After more observations, astronomers determined that the object would impact Earth on 13 November 2015 at 06:18 UTC (11:48 local time),<ref name="SETI"/> south of [[Sri Lanka]].<ref name="mpmlinfo"/><ref name="Gizmag1023"/> Due to its small size, it was expected that most or all of the object would burn up in the atmosphere before impacting, but would be visible as a bright daytime [[Meteoroid#Fireball|fireball]] if the sky was not badly [[overcast]].<ref name="mpmlinfo"/><ref name="Gizmag1023"/>

A ground-based observational campaign was organized as a possible test for future collision events involving also natural bodies.<ref name="Icarus2017">{{cite journal |last1=Micheli|first1=Marco|last2=Buzzoni|first2=Alberto|last3=Koschny|first3=Detlef|last4=Drolshagen|first4=Gerhard|last5=Perozzi|first5=Ettore|last6=Hainaut|first6=Olivier|last7= Lemmens|first7=Stijn|last8=Altavilla|first8=Giuseppe|last9=Foppiani|first9=Italo
|last10=Nomen|first10=Jaime|last11=Sánchez-Ortiz|first11=Noelia|last12=Marinello|first12=Wladimiro|last13=Pizzetti|first13=Gianpaolo
|last14=Soffiantini|first14=Andrea|last15=Fan|first15=Siwei|last16=Fruehm|first16=Carolin
|date= October 2017|title= The observing campaign on the deep-space debris WT1190F as a test case for short-warning NEO impacts |doi=10.1016/j.icarus.2017.10.006|journal=[[Icarus (journal)|Icarus]] |volume=304|pages=4–8|arxiv=1710.07684|bibcode=2018Icar..304....4M|s2cid=119107218 }}</ref>

==Observations==
[[File:Object WT1190F.gif|thumb|left|Bright object in the center is WT1190F as observed by the University of Hawaii 2.2-meter telescope.]]
WT1190F was first discovered by the [[Mount Lemmon Survey]], a participant in the [[Catalina Sky Survey]] [[Near-Earth Object]] surveying program.<ref>{{cite web |url=http://neo.jpl.nasa.gov/programs/catalina.html |archive-url=https://web.archive.org/web/20040114170842/http://neo.jpl.nasa.gov/programs/catalina.html |url-status=dead |archive-date=2004-01-14 |title=Catalina Sky Surveys |publisher=[[NASA]] |date=2013-03-05 |access-date=2015-10-27 }}</ref>  The object was identified with an [[apparent magnitude]] 19.5 on 18 February 2013, and given the temporary designation UDA34A3, but was lost soon after, with an [[observation arc]] of only 5 hours.<ref name="initialtracking">{{cite web|title="Pseudo-MPEC" for UDA34A3 = UW8551D|url=http://www.projectpluto.com/pluto/mpecs/uda.htm|website=Project Pluto|access-date=27 October 2015}}</ref> However, it was again seen by the same survey on 29 November 2013 and given the designation UW8551D and lost again, only being observed for 1 hour 35 minutes.<ref name="initialtracking" />

Most recently, it was recovered on 3 October 2015 and given the designation WT1190F. Its orbit was soon calculated and found to be orbiting Earth, but not with the orbit of any known artificial satellite. The object's orbit was soon connected, allowing more observations to be made, and several [[precovery]] observations have been found of the object, dating back to June 2009.<ref name=epoch2011/>

The type of orbit that WT1190F had was not stable long-term. An object in this type of orbit was likely to impact into Earth or the Moon, or acquire enough [[orbital speed]] to be ejected into orbit around the Sun.<ref name=FAQ/> It was not likely that it had been orbiting Earth for decades.<ref name=FAQ/> In 2011 the orbit had an [[Orbital eccentricity|eccentricity]] of 0.33 and [[perigee]] (closest approach to Earth) of {{convert|248000|km|mi|abbr=on|lk=on}}.<ref name=epoch2011/> It passed about {{convert|22000|km|abbr=on}} from the Moon on 24 May 2012.<ref name=mpec_all/> By 2013 the eccentricity had increased to 0.70 and the perigee decreased to {{convert|105000|km|mi|abbr=on}}.<ref name="initialtracking"/>

{| class="wikitable sortable" style="margin-left: 12px; text-align:center;"
|+ Orbital evolution
! [[Epoch (astronomy)|Epoch]]
! [[Orbital eccentricity|Eccentricity]]
! [[Orbital inclination|Inclination]]
! [[Perigee]]<br />(km)
! [[Apogee]]<br />(km)
|-
| 2011<ref name=epoch2011/> || 0.33 || 59 || 248383 || 495045
|-
| 2013<ref name="initialtracking"/> || 0.70 || 78 || 105639 || 598686
|-
| 2015<ref name=orbitandobs/> || 0.94 || 3 || 21221 || 655374
|}

During WT1190F's orbit, it changed significantly in brightness, from an [[apparent magnitude]] 16 at [[Apsis|perigee]], to magnitude 23 at [[Apsis|apogee]]. It spent most of its time dimmer than magnitude 20.<ref name="orbitandobs"/> This, combined with [[Radiation pressure|solar pressure acceleration]], the [[Yarkovsky effect]], and frequent orbital perturbations by the Moon, made it difficult to precisely predict its orbit and location. About one hour before atmospheric entry, the object had a R magnitude of 13.6,<ref name="DASO537"/>{{refn|Even near apparent magnitude ~13.6 it was about 1000 times too faint to be seen by the naked eye. [[Apparent magnitude#Calculations|Math]]: <math>(\sqrt[5]{100})^{13.6-6}\approx 1000</math>|name=naked|group=lower-alpha}} roughly the brightness of [[Pluto]].

=== Impact ===
WT1190F made [[atmospheric entry]] at {{convert|11|km/s|mph|abbr=off|sp=us}}.<ref name="esa20151030"/> Whatever was left from the re-entry was calculated to have fallen into the ocean about {{convert|100|km|mi}} from [[Galle]], [[Sri Lanka]].<ref name="ESA prediction"/> The closest approach to Galle occurred during atmospheric flight when the object had an altitude of 45{{Spaces}}km and a distance of 51{{Spaces}}km.<ref name=mpec_gal/> For observers in [[Colombo]], Sri Lanka, the object started out{{Clarify|date=November 2019}} 30 degrees above the horizon coming in from slightly south of due west.<ref name=mpec7/> Its mass was not sufficient to cause any risk to the area, but the event still produced a bright fireball. Scientists wanted to study WT1190F to better understand the trajectory and atmospheric entry of satellites, debris, and small asteroids from translunar orbit.<ref name=UAE>{{cite web|last1=Al-Ashi|first1=Sameh|title=UAE sponsors airborne campaign to observe November 13 entry of space debris WT1190F|url=http://www.astronomycenter.net/events/2015/11/03/wt1190f?l=en|website=IAC|date=4 November 2015|access-date=8 November 2015}}</ref><ref name="ESA prediction"/> The International Astronomical Center (IAC) and the [[United Arab Emirates Space Agency]] utilized a [[Gulfstream 450]] jet to study the re-entry from above the clouds and haze.<ref name=UAE/> The airborne observation team successfully captured the re-entry on video.<ref name="SETI"/><ref name=UT20151113>{{cite web|last1=King|first1=Bob|title=Spectacular Breakup of WT1190F Seen by Airborne Astronomers|url=http://www.universetoday.com/123400/spectacular-breakup-of-wt1190f-seen-by-airborne-astronomers/|website=[[Universe Today]]|date=13 November 2015|access-date=13 November 2015}}</ref>

{| class="wikitable sortable right" style="margin-left: 12px; text-align:center;"
|+ Impact approach<ref>[https://archive.today/20151119013612/http://www.minorplanetcenter.net/iau/artsats/artsats.html The Distant Artificial Satellites Observation Page]</ref>
! Date
! [[apparent magnitude|vmag]]
! Distance<br />(km)
! Velocity<br />wrt Earth<br />(km/s)<ref>[https://ssd.jpl.nasa.gov/horizons/app.html#/ Ephemeris]</ref>
|-
| 05 || 20.8 || 602399 || 0.2
|-
| 08 || 20.5 || 524608 || 0.5
|-
| 10 || 20.0 || 420800 || 0.8
|-
| 11 || 19.6 || 345999 || 1.0
|-
| 12 || 19.0 || 246196 || 1.4
|-
| 13 || 17.1 || 89914 || 2.8
|-
| Impact || ~ –6<ref>[http://www.amsmeteors.org/fireballs/faqf/#3 Can you see fireballs in daylight, and will a fireball leave a trail?]</ref> || 0 || 11.3
|}

===Airborne observations ===
[[File:G450 Wt1190f 1.jpg|thumb|left|Gulfstream 450 business jet rented for the mission]]

The International Astronomical Center (IAC) and the [[United Arab Emirates Space Agency]] observed WT1190F as it fell towards the Earth. The IAC chartered a [[Gulfstream 450]] jet to bring researchers such as [[Peter Jenniskens]] to the area of WT1190F's impact, at a high altitude, to view the event over clouds or haze.<ref name=UAE/> The Next TC3 Consortium Asteroid Detection and Early Warning team narrowed the atmospheric entry time to ±&nbsp;1.3 seconds.<ref name="SETI"/>

Observers on the ground could not see the fireball because of rain, but the plane was able to find an opening in the clouds. The fireball was a bright [[naked eye]] object. [[Astronomical spectroscopy|Spectroscopic]] data was acquired to determine what the object was made of,<ref name="SETI"/> and the results published.{{r|Jenniskens|p=9}}
{{clear}}

==See also==
*[[List of reentering space debris]]

===Impacts by known objects===
*[[2008 TC3|2008 TC<sub>3</sub>]]
*[[2014 AA]]
*[[2018 LA]]
*[[2019 MO]]

===Previous temporary satellites===
*{{mpl|2006 RH|120}}
*[[6Q0B44E]]
*[[J002E3]]

==Notes==
{{Notelist}}

==References==
{{Reflist|30em|
| refs =

<ref name=FAQ>[http://projectpluto.com/temp/wt1190f.htm WT1190F FAQs]{{Snd}} Bill Gray</ref>

<ref name=epoch2011>{{cite web
|last1=Gray |first1=Bill
|title=Pseudo-MPEC for UDA34A3 = UW8551D = WT1190F
|url=http://www.projectpluto.com/temp/mpec11.htm
|website=Project Pluto
|date=30 October 2015
|access-date=8 November 2015}}</ref>

<ref name=mpec_all>{{cite web
|last1=Gray |first1=Bill
|title=Pseudo-MPEC for UDA34A3 = UW8551D = WT1190F
|url=http://projectpluto.com/temp/mpec_all.htm
|website=Project Pluto
|date=5 November 2015
|access-date=8 November 2015}}</ref>

<ref name="esa20151030">{{cite web
|title=ESA SPONSORS WT1190F OBSERVATIONS
|publisher=esa blog
|url=http://blogs.esa.int/rocketscience/2015/10/30/esa-sponsors-wt1190f-observations/
|date=30 October 2015
|access-date=2015-11-10}}</ref>

<ref name="SETI">{{cite web
|title=Rapid Response to the next Small Asteroid Impact
|publisher=[[SETI Institute]]
|url=http://impact.seti.org/
|access-date=2015-11-10}}</ref>

<ref name=mpec_gal>{{cite web
|last1=Gray |first1=Bill
|title=Ephemerides for (Gal) Galle, Sri Lanka
|url=http://www.projectpluto.com/temp/mpec_gal.htm#eph
|archive-url=https://web.archive.org/web/20151115055636/http://www.projectpluto.com/temp/mpec_gal.htm#eph
|url-status=dead
|archive-date=15 November 2015
|website=Project Pluto
|date=11 November 2015
|access-date=12 November 2015}}
</ref>

<ref name=mpec7>{{cite web
|last1=Gray |first1=Bill
|title=Ephemerides for (Col) Colombo, Sri Lanka
|url=http://www.projectpluto.com/temp/mpec7.htm#eph
|website=Project Pluto
|date=13 November 2015
|access-date=12 November 2015}}</ref>

<ref name="DASO537">{{cite web
|title=DASO Circular No. 537
|publisher=[[Minor Planet Center]]
|date=13 November 2015
|url=http://www.minorplanetcenter.net/iau/DASO/000000/DASO_000537.txt|archive-url=https://web.archive.org/web/20151120033003/http://www.minorplanetcenter.net/iau/DASO/000000/DASO_000537.txt|url-status=dead|archive-date=20 November 2015}}</ref>

}}

==External links==
{{wikimedia|collapsible=true|wikt=no|b=no|d=Q21210774|v=no|voy=no|s=no|q=no|n=no|c=Category:WT1190F}}
* [http://www.slate.com/blogs/bad_astronomy/2015/10/27/wt1190f_rocket_booster_will_re_enter_on_november_13_2015.html A Piece of Cosmic Debris Will Hit Earth on Nov. 13]{{Snd}} [[Phil Plait]]
* [http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&sstr=WT1190F Ephemeris]{{Snd}} [[JPL Horizons On-Line Ephemeris System]]
* [http://projectpluto.com/temp/wt1190f.htm WT1190F FAQs]{{Snd}} Bill Gray
* [http://impact.seti.org/WT1190F-widefield-Jenniskens.mp4 MP4 video of approximately how the fireball would have looked to the naked eye]{{Snd}} [[Peter Jenniskens]]
* [https://docslib.org/tags/WT1190F/ WT1190F]{{Snd}} Collection of articles from docslib.org

{{2015 in space}}
{{Modern impact events}}

[[Category:Astronomical objects discovered in 2015|20151003]]
[[Category:Astronomical objects discovered in 2013|20130218]]
[[Category:Claimed moons of Earth]]
[[Category:Space debris]]
[[Category:Modern Earth impact events]]
[[Category:2015 in Sri Lanka|20151113]]
[[Category:2015 in outer space|20151113]]
[[Category:November 2015]]
[[Category:Predicted impact events]]