UNCONTROLLED RE-ENTRIES OF MASSIVE SPACE OBJECTS

4th International Space Debris Re-entry Workshop ESA/ESOC, Darmstadt, Germany, 28 February – 1 March 2018 Outline

• Uncontrolled re-entries of massive space objects during the last decade

• The uncontrolled re-entry of the Zenit second stage 2017-086D

• Status and decay time evolution of the Chinese space station Tiangong-1 Premise

 Space hardware re-entries can be of two types

CONTROLLED if the time of re-entry is controlled and the impact of debris is confined to a designated zone UNCONTROLLED if the time of re-entry and ground zone of impact are not controlled

 To characterize in a synthetic way the relevance of uncontrolled re-entries, a re-entry magnitude

ΜR was defined at ISTI-CNR as follows

ΜR = log10 [(dry mass of re-entering object in kg) / 100] + 0.3 ISTI-CNR uncontrolled re-entry magnitude scale definition

Dry Mass M0 of the Re-entry re-entering object [kg] magnitude MR

M0 ≤ 50 MR < 0 50 < M0 ≤ 500 0 ≤ MR < 1 500 < M0 ≤ 5000 1 ≤ MR < 2 5000 < M0 ≤ 50 000 2 ≤ MR < 3 50 000 < M0 ≤ 500 000 3 ≤ MR < 4 500 000 < M0 ≤ 5 000 000 4 ≤ MR < 5

 Sources of data Orbit of re-entered objects: US Space-Track Organization (www.space-track.org) Mass of re-entered objects: ESA’s DISCOS Database (discosweb.esoc.esa.int); Gunter’s Space Page (space.skyrocket.de); Spaceflight101 (spaceflight101.com)

Relevance of uncontrolled re-entries [2008 – 2017]

Large (RCS > 1 m²) catalogued intact objects re-entered into the Earth’s atmosphere during the last decade [2008 – 2017] . 366 rocket bodies (mass between ∼50 kg and ∼9 300 kg, 42 with mass < 500 kg) . 82 spacecraft (mass between ∼57 kg and ∼13 525 kg – launch mass including propellants, 14 with mass < 500 kg)

−3 Ec ∼ 10

0 ≤ MR < 1 55 (12%) objects 2 ≤ MR < 3 −4 16 (4%) objects Ec ∼ 10 −4 Ec < 10 1 ≤ MR < 2 376 (84%) objects

MR < 0 MR M0 Space Object 1 object [kg] 2.268 9300 SL-16 (2011-065B) 2.268 9300 SL-23 (2011-001C) 2.268 9300 SL-23 (2011-037D) Dry mass M0 of the Re-entry All intact Spacecraft Rocket 2.268 9300 SL-23 (2015-074C) 2.078 6100 DRAGON/FALCON9 (2010-026A) re-entering object [kg] magnitude MR objects bodies 2.078 6000 CZ-7 (2016-042E) 2.072 6000 CZ-7 (2017-021B) M0 ≤ 50 MR < 0 1 0 1 2.085 5916 PROGRESS-M 27M (2015-024A) 2.053 5668 UARS (1991-063B) 50 < M0 ≤ 500 0 ≤ MR < 1 55 (12%) 14 (17%) 41 (11%) 2.041 5502 CZ-2F (2008-047B) 2.041 5502 CZ-2F (2011-053B) 500 < M0 ≤ 5000 1 ≤ MR < 2 376 (84%) 66 (80.5%) 310 (85%) 2.041 5502 CZ-2F (2011-063B) 2.041 5502 CZ-2F (2012-032B) 5000 < M0 ≤ 9300 2 ≤ MR < 3 16 (4%) 2 (2.5%) 14 (4%) 2.04 5500 CZ-2F (2013-029B) 2.04 5500 CZ-2F (2016-057B) All re-entered intact objects 448 82 366 2.04 5500 CZ-2F (2016-061B) Re-entry frequency [2008-2017]

Large catalogued intact objects with mass > 500 kg re-entered into the Earth’s atmosphere between 2008 and 2017

. 324 rocket bodies (∼88% of large re-entered rocket bodies) . 68 spacecraft (∼83% of large re-entered spacecraft) R/B SC R/B+SC Mass > 500 kg 60 Average re-entries 48 50 44 45 per year 41 40 39 40 36 36 36 entered entered 40 . 32 rocket bodies - 34 32 34 33 34 34 30 28 28 . 7 spacecraft 30 24 . 39 intact objects 20 12 8 9 7 8 ∼1 intact object 10 4 4 4 6 6 every 1-2 weeks Number of re objects with mass > 500 kg > 500 mass with objects 0 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Observed solar flux F10.7 between January 2008 and January 2018 Re-entry frequency [2008-2017] Large catalogued intact objects with mass ≥ 3900 kg re-entered into the Earth’s atmosphere between 2008 and 2017

. 40 rocket bodies (∼11% of large re-entered rocket bodies) . 4 spacecraft (∼5% of large re-entered spacecraft – For Phobos-Grunt the propellant mass is included) Mass ≥ 3900 kg R/B SC R/B+SC

10 9 9 Average re-entries per 8 7 year

6 6 6

entered - 6 5 5 5 . 4 rocket bodies 4 . < 1 spacecraft 4 3 3 3 3 3 3 3900 kg . 4-5 intact objects 2 1 1 1 1 1 1 1 1

objects with mass > mass with objects 0 Number of re 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Space object INTLDES Re-entry Mass Inc [deg] epoch [kg] CZ-2F R/B 2008-047B 17/10/2008 5502 42.39 Large catalogued intact objects with mass > 5000 kg DRAGON/FALCON 9 2010-026A 27/06/2010 6100 34.48 . ∼ SL-23 R/B 2011-001C 19/03/2011 9300 51.39 14 rocket bodies ( 4% of large re-entered rocket bodies) SL-23 R/B 2011-037D 08/08/2011 9300 51.38 . 3 spacecraft (∼4% of large re-entered spacecraft) UARS 1991-063B 24/09/2011 5668 60.35 CZ-2F R/B* 2011-053B 10/10/2011 5500 42.78 . 1-2 intact objects per year CZ-2F R/B 2011-063B 08/11/2011 5502 42.77 SC R/B R/B+SC SL-16 R/B 2011-065B 22/11/2011 9300 51.42 8 PHOBOS-GRUNT 2011-065A 15/01/2012 13525 61.73 Mass > 5000 kg CZ-2F R/B 2012-032B 42.77 6

26/01/2012 5502 entered entered

CZ-2F R/B 2013-029B 21/06/2013 5502 42.77 - 6 5 PROGRESS-M 27M 2015-024A 08/05/2015 7289 64.76 4 4 SL-23 R/B 2015-074C 02/01/2016 9300 51.36 4 CZ-7 R/B 2016-042E 28/07/2016 6000 40.79 5000 kg 2 CZ-2F R/B* 2016-057B 29/09/2016 5500 42.78 2 1 1 1 1 1 1 1 1 1 1 1 1 1 CZ-2F R/B 2016-061B 04/11/2016 5500 42.77

CZ-7 R/B 2017-021B 18/05/2017 6000 42.76 > objects with mass Number of re 0 * Used to launch Tiangong-1 * Used to launch Tiangong-2 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Re-entered mass [2008-2017]

SC R/B R/B+SC

140000 121880 111967 120000 107955 102895 102471 99777 100000 89081 86542 89993 68725 72407 61721 79620 71691 80000 66942 70194 60585 64075 61195 60000 52812 Mass > 500 kg entered mass [kg]

- 40000 18985 22851 22139 21413 19799 Re 20000 8140 8332 8909 12190 10496 0 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

R/B SC LARGE LARGE LARGE 50000 M > 50 kg M > 500 kg M > 5000 kg 38902 1 SL-16, 2 SL-23, 2 CZ-2F No. Mass No. Mass [kg] No. Mass 40000 [kg] [kg]

30000 Phobos-Grunt 26300 Rocket 366 754 142 324 744 637 14 93 808 bodies (83%) (83%) (78%) UARS Progress-M 27M 20000 Spacecraft 82 157 098 68 153 254 3 26 482 entered mass [kg] 13525 - (17%) (17%) (22%) 7289 Re 10000 5502 6100 5668 5502 5502 6000 Intact 448 911 240 392 897 891 17 120 290 0 objects 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Mass > 5000 kg

Orbital inclination of intact objects re-entered between 2008 and 2017

120 392 intact objects

100 with mass > 500 kg

80

60

40 Orbital inclination [deg] inclination Orbital 20

0 UARS JB-3 B ROSAT SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-8 R/B SL-4 R/B SL-3 R/B SL-4 R/B SL-4 R/B SL-8 R/B SL-4 R/B GSLV R/B SL-26 R/B SL-26 SL-23 R/B SL-23 CZ-2F R/B CZ-2F R/B CZ-2F CZ-3C R/B CZ-3C R/B CZ-2C R/B CZ-3B R/B CZ-3B R/B CZ-3B CZ-4B R/B CZ-4B R/B CZ-4B CZ-4B R/B CZ-4B CZ-3A R/B CZ-3A R/B AVUM R/B SL-6 R/B(1) SL-6 R/B(2) SL-6 R/B(2) SL-6 R/B(2) SL-6 R/B(2) SL-6 SL-12 R/B(1) SL-12 DELTA 4 R/B DELTA 2 R/B DELTA 2 R/B ANTARES R/B ANTARES R/B ARIANE 5 R/B COSMOS 1222 MOLNIYA 3-43 MOLNIYA 1-42 MOLNIYA 1-92 MOLNIYA 3-46 MOLNIYA 3-51 MOLNIYA 1-44 MOLNIYA 3-45 DELTA 2 R/B(1) ARIANE 44L R/B ARIANE 44L R/B PROGRESS-M 27M PROGRESS-M

17 intact objects with mass > 5000 kg ATLAS 5 CENTAUR R/B ATLAS 3A CENTAUR R/B Mass > 500 kg ATLAS 2AS CENTAUR R/B 65 70 62 60 60 51 51 51 51 > 90° 70 18% 14 20 45 70 50 43 43 43 43 43 43 43 42 41 80°-90° 29 7% 4% 5% 18% > 90° 40 34 70°-80° 0 0% 11 11% 29 80°-90° 30 60°-70° 76 19% 3% 7% 20 50°-60° 108 28% 19 0 70°-80° 10 40°-50° 19 5% 5% 0% 60°-70°

Orbital inclination [deg] 0 30°-40° 11 3% 50°-60° UARS 20°-30° 45 11% CZ-7 R/B CZ-7 R/B SL-16 R/BSL-16 R/BSL-23 R/BSL-23 R/BSL-23 CZ-2F R/B CZ-2F R/B CZ-2F R/B CZ-2F R/B CZ-2F R/B CZ-2F R/B CZ-2F R/B 10°-20° 14 4% 40°-50° 108 76 0°-10° 20 5% 28% 19% 30°-40° PHOBOS-GRUNT PROGRESS-M 27M DRAGON/FALCON 9 DRAGON/FALCON

Latitude bands overflown by re-entered objects [2008-2017]

] 100 90 deg 80 392 intact objects 70 91% 95% 60 with mass > 500 kg 50 77% 80% 40 72% 30 20 10 45% 0 24% 25% UARS JB-3 B ROSAT SL-8 R/B SL-4 R/B SL-4 R/B SL-8 R/B SL-4 R/B SL-3 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B GSLV R/B SL-26 R/B SL-26 SL-23 R/B SL-23 CZ-2F R/B CZ-2F R/B CZ-2F CZ-3C R/B CZ-2C R/B CZ-3C R/B Latitude bands overflown [ overflown bands Latitude CZ-3B R/B CZ-3B R/B CZ-3B CZ-4B R/B CZ-4B R/B CZ-4B R/B CZ-4B CZ-3A R/B CZ-3A R/B AVUM R/B SL-6 R/B(1) SL-6 R/B(2) SL-6 R/B(2) SL-6 R/B(2) SL-6 R/B(2) SL-6 SL-12 R/B(1) SL-12 DELTA 4 R/B DELTA 2 R/B DELTA 2 R/B ANTARES R/B ANTARES R/B ARIANE 5 R/B COSMOS 1222 MOLNIYA 3-43 MOLNIYA 3-51 MOLNIYA 1-42 MOLNIYA 1-92 MOLNIYA 3-46 MOLNIYA 1-44 MOLNIYA 3-45 DELTA 2 R/B(1) ARIANE 44L R/B ARIANE 44L R/B PROGRESS-M 27M PROGRESS-M ATLAS 3A CENTAUR… ATLAS 2AS CENTAUR…

> 80° > 70° > 60° > 50° > 40° > 30° > 20° > 10° ATLAS 5 CENTAUR R/B

Sightings [2010-2017] Source: 2010 2011 2012 2013 http://www.aerospace.org 2014 2015 2016 2017 5 1 2 1 34 sightings (27 rocket bodies and 7 spacecraft) 4 out of 373 re-entries of large intact objects (299 6 rocket bodies and 74 spacecraft) between 2010 and 2017: i.e. in ∼9% of the re-entry events 7 Moreover, also the re-entry of the Cygnus mass 8 simulator (3800 kg) was sighted in 2013

120 ] 2013 2014 2015 2015 2017

deg 100 2013 2014 80 2013 2015 2015 2015 2016 60 2010 2011 2013 2014 2014 2015 2015 2015 2016 2017 2017 2016 2016 2017 2011 2014 40 2017 2014 2014 2016 20

Orbital inclination [ inclination Orbital 2016 2012 0 GOCE NFIRE JB-3 A SL-4 R/B SL-3 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B SL-4 R/B CZ-7 R/B CZ-7 R/B SL-23 R/BSL-23 CZ-4B R/B CZ-3B R/B CZ-4B R/B CZ-3B R/B CZ-4B R/B SL-6 R/B(2) SL-6 ANTARES R/B FALCON 9 R/B 9 FALCON FALCON 9 R/B 9 FALCON COSMOS 1220 COSMOS 1400 COSMOS 1484 COSMOS 1315 ARIANE 44LARIANE R/B DELTA 2 R/B(2) (PAM-D) 2 R/B(2) DELTA Recovered re-entry debris (http://www.aerospace.org/cords/research/reentry-data)

1. A steel propellant tank and 2 titanium pressure spheres – identified as debris from 2nd stage of Delta II 2. Several metal objects - probably debris from 3rd stage of GSLV 3. A titanium rocket-motor casing - identified as debris from 3rd stage of Delta II 4. A metallic sphere - probably a helium pressure tank from 2nd stage of Zenit 3F 5. A metallic sphere - probably a helium pressure tank from 3rd stage of Ariane 4 6. Two metallic spheres - probably helium pressure tanks from 3rd stage of CZ-4B 7. A propellant tank - probably from 2nd stage of a Delta 8. Small cylindrical tanks and a metal ring - probably from the 2nd stage of Falcon 9 9. Two small spherical tanks - probably from the 2nd stage of Zenit 3F 10. A composite overwrapped pressure vessel - identified as a pressure vessel from the 2nd stage of Falcon 9 11. A composite overwrapped pressure vessel - believed to belong to the Vega upper stage AVUM 12. “Several” fuel tanks from the 2nd stage of Zenit 3F

Giliraja Baggs Buna Santa Rita do Pardo East Java Puno region Malawi Wyoming Texas Brazil Indonesia Peru Tuyen Quang Africa USA USA Ngezi Artigas Province Mongolia Mata Roma Zimbabwe Oddanchatram Uruguay Vietnam Asia Brazil Africa India (1)

2010 2011 2011 2011 2012 2013 2013 2014 2016 2016 2016 2018 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 2009-052C 2003-058C 2011-001C 1997-016C 2012-021C 2015-074C 2012-006K 2007-037B 1975-077B 2014-052B 2016-050B 2017-086D

13. Three spherical tanks were found in the Spanish towns of Calasparra, Villavieja and Elda in November 2015 (identified as objects from a Centaur upper stage used to launch the spacecraft USA 200 - 2008-010A - on March 13, 2008) – no TLEs and decay time available

What to expect in 2018?

What has already happened?

Uncontrolled re-entry, on 27 January 2018, of the Zenit-2SB second stage 2017-086D, with an empty mass of 8307 kg

Uncontrolled re-entry, on 8 February 2018, of the C-25 cryogenic upper stage 2017-031B of the GSLV-MK3-D1 launcher, with a dry mass of ∼5300 kg

What is going to happen? Uncontrolled re-entry of the Chinese space station Tiangong-1, with a launch mass of 8500 kg

The re-entry of the Zenit-2SB second stage

The fourth launch, on 26 December 2017, of the Russian-Ukrainian expendable carrier rocket Zenit- 3SLBF (or Zenit-2SB/Fregat-SB) put into orbit the Angola’s first geostationary communication satellite AngoSat-1

After separating from the Fregat upper stage, the Zenit-2SB second stage began its orbital decay, only subjected to natural perturbations, from an initial orbit of ∼162 × 566 km in altitude and inclination of 51.37°

COSPAR ID 2017-086D Cat. Number 43090

Observed orbital decay

Zenit-2SB second stage Length 10.4 m Physical characteristics of the Zenit-2SB second stage Diameter 3.9 m Inert mass 8307 kg

The re-entry of the Zenit-2SB second stage

Orbital predictor Evolution of the ballistic parameter SATRAP 0.01000 Value used for

Atmospheric density 0.00950 C A B = D the post-event model 0.00900 M assessment NRLMSISE-00 0.00850

[m^2/kg] 0.00800 0.00750 = 0.00881 m2/kg

. 11 re-entry parameter Ballistic 0.00700 σ ∼ 7% predictions 0.00650 . A post-event 0.00600 9.2 5.9 4.0 3.0 1.7 1.1 0.3 0.2

assessment 19.7 13.2 10.8 Residual lifetime [days] Percentage error affecting the estimate of Mean prediction error the residual lifetime NP PE = RL TTPRED− REF MPE ∑ PERL =100 × n=1 N P

TTREF− IN 9 8.5 8.5

20 7.9 7.7 15 8 7.0 6.9 10 14.4 6.8 11.8 7 6.6 5 6.1 5.7 5.6 0 6 2.5 -0.1 1.2 -5 5 -4.4 entry [%] predictions entry -4.8 - Percentage errorPercentage on -10 -6.8

re -8.4 4 -15 -11.0 -11.9 [%] error Mean prediction 9.2 5.9 4.0 3.0 1.7 1.1 0.3 0.2 19.7 13.2 10.8 9.2 5.9 4.0 3.0 1.7 1.1 0.3 0.2 19.7 13.2 10.8 Residual lifetime [day] Residual lifetime [days]

The re-entry of the Zenit-2SB second stage Re-entry uncertainty windows Residual lifetime ± 30% - re-entry predictions 1-7 Residual lifetime ± 20% - re-entry predictions 8-11 & post-event assessment Reference re-entry epoch: 27 January 2018, 23:32 UTC (JSpOC post-event assessment)

START COIW END START COIW END 10 0.2

0

entry entry 5 - 11 -0.2 10 0 epoch -0.4 9

reference re -5 -0.6 8 19.7 13.2 10.8 9.2 5.9 4.0 3.0 1.7 1.1 0.3 0.2 1.7 1.1 0.3 0.2 Days with respect to the the to respect with Days Residual lifetime [days] Residual lifetime [days]

COIW - 27 January 2018, 18:56 UTC COIW - 27 January 2018, 20:29 UTC

8 9 TLE: 26 January 2018, 05:49 UTC, Residual lifetime = 41h 42m TLE: 26 January 2018, 21:58 UTC, Residual lifetime = 25h 34m

The re-entry of the Zenit-2SB second stage

COIW - 27 January 2018, 23:11 UTC COIW - 27 January 2018, 23:17 UTC

10 11

TLE: 27 January 2018, 15:31 UTC, Residual lifetime = 8h 1m TLE: 27 January 2018, 19:52 UTC, Residual lifetime = 3h 40m

Post-event assessment

TLE: 27 January 2018, 19:52 UTC

B = 0.0077 m2/kg

Nominal re-entry epoch 27 January 2018, 23:32 UTC

Re-entry window: ±0.03 days ± 43m12s

Latitude: -8.38°

Longitude: 285.01°

The re-entry of the Zenit-2SB second stage

Sighting

JSpOC decay epoch Recovered 27 January 2018, 23:32 UTC ± 1 min debris Lat: -9.2° Lon: 285.7°

Source: Aerospace Corporation

 «This object was sighted re-entering on 27 January 2018 at 23:32 UTC over Pucallpa, Peru»

 «Several fuel tanks were recovered by the Peruvian Air Force near the Puno region of Peru © Peruvian Air Force / AFP after they were notified by local residence»

Re-entry of the C-25 cryogenic upper stage The Indian Geosynchronous Satellite Launch Vehicle Mark III D1 (GSLV-MK3-D1) was used to launch the experimental Indian geostationary communication satellite GSAT-19 on 5 June 2017

After releasing the spacecraft, the upper stage remained passive in a geosynchronous transfer orbit Observed COSPAR ID Perigee altitude [km] Apogee altitude [km] orbital decay 2017-031B 100000 Cat. Number 42748 10000 First TLE: 5 June 2017, 07:18 UTC 160 × 34918 km; inc: 21.55° 1000 C-25 Cryogenic upper stage Last TLE: 7 February 2018, 19:17 UTC 101 × 1484 km; inc: 21.42° Length 13.55m 100

Diameter 4 m 10 0.0 10.9 21.0 26.8 35.2 43.5 48.5 56.0 60.6 66.4 79.3 86.0 93.4 Inert mass ∼5300 kg 109.1 119.0 128.3 140.8 149.8 159.8 175.8 182.6 184.9 190.3 203.7 212.3 215.4 219.4 225.3 233.7 239.7 244.1 245.1 246.3 247.1

JSpOC decay epoch 8 February 2018, 11:30 UTC ± 180 min Lat: 21.1° Lon: 341.9° Sub-satellite ground tracks corresponding to the last JSpOC re-entry uncertainty window

The Chinese space station Tiangong-1

Tiangong-1, launched on 29 September 2011, was the first Chinese space station, used both as human tended laboratory and target for testing orbital rendezvous and docking

Launch mass 8506 kg Propellant at launch 1000 kg Consumables at launch ≈ 350 kg Current propellant* ≈ 350 kg MMH ≈ 120 kg N2O4 ≈ 230 kg Current consumables** ≈ 50 kg Current mass# ≈ 7550 kg Dry mass ≈ 7150 kg

* Propellant consumption from manoeuvre sequence: ≈ 650 kg **Food, food packaging, water and oxygen consumption for 57 astronaut-days: ≈ 303 kg # Comparable to the launch mass of Progress-M 27M (7289 kg)

Status of Tiangong-1 The ground control of the space station was lost on 16 Significant manoeuvres occurred from 20 January to 18 February 2018 March 2016 Maneuver day B* da a e i ω dt The autonomous on board attitude control remained, January 27 X X X X and still is, operational. According to China Manned Space Agency (CMSA): «Its attitude kept stabilized and February 2 X X X X X no anomaly occurred» February 11 X X X X X http://en.cmse.gov.cn/col/col1763/index.html

The attitude is controlled through reaction wheels and February 11 reaction control thrusters February 2 Probably , the solar panels are kept pointed towards the Sun to guarantee the power supply needed to keep the station alive, and the body is aligned along the velocity vector February 11 The attitude control has an indirect effect on the orbit . by varying the effective drag cross-section January 27 . by producing a net ∆V when the reaction control thrusters are activated

As an example, possible recent thrusting periods were identified in the TLEs of January 27, February 2 and February 11 February 2

January 27 For instance, the net orbital effect of the thrusting occurred on 27 January 2018 corresponded to a ∆V of a few meters per second

Environmental conditions

Quite low solar activity levels

Some minor geomagnetic storms

(4 < KP ≤ 5)

Estimate of the Tiangong-1 ballistic parameter

NRL-B -50/60 GOST-B-50/60 NRL-B-30 GOST-B-30 NRL-B-20 GOST-B-20 NRL-B-10 GOST-B-10 0.0085

0.0080

0.0075

0.0070

0.0065 Ballistic parameter [m²/kg] parameter Ballistic 0.0060

0.0055 8.47 11.21 15.16 17.16 18.77 22.15 24.08 25.09 26.02 29.27 29.57 31.26 32.50 35.62 38.12 43.08 47.14 50.13 51.12 52.12 53.17 Prediction epoch [day of 2018]

Forecasting the Tiangong-1 re-entry epoch

NRL-B -50/60 GOST-B-50/60 NRL-B-30 GOST-B-30 NRL-B-20 GOST-B-20 NRL-B-10 GOST-B-10 100

98

96

94

92

90

88 entry epochentryatof 80 km 2018] [day

- 86

84

Nominal re Nominal 82

80 8.47 11.21 15.16 17.16 18.77 22.15 24.08 25.09 26.02 29.27 29.57 31.26 32.50 35.62 38.12 43.08 47.14 50.13 51.12 52.12 53.17

Prediction epoch [day of 2018]