UNCONTROLLED RE-ENTRIES OF MASSIVE SPACE OBJECTS
4th International Space Debris Re-entry Workshop ESA/ESOC, Darmstadt, Germany, 28 February – 1 March 2018
• 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
Outline
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
Dry Mass M0 of the re-entering object [kg]
Re-entry 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)
ISTI-CNR uncontrolled re-entry magnitude scale definition
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)
Ec ∼ 10−3
2 ≤ MR < 3 16 (4%) objects Ec ∼ 10−4
1 ≤ MR < 2 376 (84%) objects
Ec < 10−4
0 ≤ MR < 1 55 (12%) objects
MR < 0 1 object MR
M0
[kg] Space Object
2.268 9300 SL-16 (2011-065B) 2.268 9300 SL-23 (2011-001C) 2.268 9300 SL-23 (2011-037D) 2.268 9300 SL-23 (2015-074C) 2.078 6100 DRAGON/FALCON9 (2010-026A) 2.078 6000 CZ-7 (2016-042E) 2.072 6000 CZ-7 (2017-021B) 2.085 5916 PROGRESS-M 27M (2015-024A) 2.053 5668 UARS (1991-063B) 2.041 5502 CZ-2F (2008-047B) 2.041 5502 CZ-2F (2011-053B) 2.041 5502 CZ-2F (2011-063B) 2.041 5502 CZ-2F (2012-032B) 2.04 5500 CZ-2F (2013-029B) 2.04 5500 CZ-2F (2016-057B) 2.04 5500 CZ-2F (2016-061B)
Dry mass M0 of the re-entering object [kg]
Re-entry magnitude MR
All intact objects
Spacecraft Rocket bodies
M0 ≤ 50 MR < 0 1 0 1
50 < M0 ≤ 500 0 ≤ MR < 1 55 (12%) 14 (17%) 41 (11%)
500 < M0 ≤ 5000 1 ≤ MR < 2 376 (84%) 66 (80.5%) 310 (85%)
5000 < M0 ≤ 9300 2 ≤ MR < 3 16 (4%) 2 (2.5%) 14 (4%)
All re-entered intact objects 448 82 366
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)
30 32 24
36 34 33 39
34 34 28
4 4 4 8 6
12 9 7 6 8
34 36 28
44 40
45 48 41 40
36
0
10
20
30
40
50
60
2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Num
ber o
f re-
ente
red
obje
cts
with
mas
s > 5
00 k
g
R/B SC R/B+SC Mass > 500 kg
Observed solar flux F10.7 between January 2008 and January 2018
Average re-entries per year
32 rocket bodies 7 spacecraft 39 intact objects
∼1 intact object every 1-2 weeks
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)
1 1 1 1 1
5
1 1
4
1 1 1
6
2 1 1
4
1
0
2
4
6
8
2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Num
ber o
f re-
ente
red
obje
cts
with
mas
s >
5000
kg
SC R/B R/B+SC
Mass > 5000 kg
Mass ≥ 3900 kg
Space object
INTLDES
Re-entry epoch
Mass [kg]
Inc [deg]
CZ-2F R/B 2008-047B 17/10/2008 5502 42.39 DRAGON/FALCON 9 2010-026A 27/06/2010 6100 34.48 SL-23 R/B 2011-001C 19/03/2011 9300 51.39 SL-23 R/B 2011-037D 08/08/2011 9300 51.38 UARS 1991-063B 24/09/2011 5668 60.35 CZ-2F R/B* 2011-053B 10/10/2011 5500 42.78 CZ-2F R/B 2011-063B 08/11/2011 5502 42.77 SL-16 R/B 2011-065B 22/11/2011 9300 51.42 PHOBOS-GRUNT 2011-065A 15/01/2012 13525 61.73 CZ-2F R/B 2012-032B 26/01/2012 5502 42.77 CZ-2F R/B 2013-029B 21/06/2013 5502 42.77 PROGRESS-M 27M 2015-024A 08/05/2015 7289 64.76 SL-23 R/B 2015-074C 02/01/2016 9300 51.36 CZ-7 R/B 2016-042E 28/07/2016 6000 40.79 CZ-2F R/B* 2016-057B 29/09/2016 5500 42.78 CZ-2F R/B 2016-061B 04/11/2016 5500 42.77 CZ-7 R/B 2017-021B 18/05/2017 6000 42.76
Large catalogued intact objects with mass > 5000 kg 14 rocket bodies (∼4% of large re-entered rocket bodies) 3 spacecraft (∼4% of large re-entered spacecraft) 1-2 intact objects per year
Average re-entries per year
4 rocket bodies < 1 spacecraft 4-5 intact objects
* Used to launch Tiangong-1 * Used to launch Tiangong-2
3
1 1
6
4 3
5 5
9
3
1 1 1 1
3
1 1
7
5
3
6 6
9
3
0
2
4
6
8
10
2008 2009 2010 2011 2012 2013 2014 2015 2016 2017Num
ber o
f re-
ente
red
obje
cts w
ith m
ass >
39
00 k
g
R/B SC R/B+SC
Re-entered mass [2008-2017]
8140 8332 8909 18985 22851 22139 21413 19799
12190 10496
60585 64075 52812
102895
79620 66942
86542
70194
99777
61195
68725 72407 61721
121880
102471 89081
107955
89993
111967
71691
0
20000
40000
60000
80000
100000
120000
140000
2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Re-e
nter
ed m
ass [
kg]
SC R/B R/B+SC
5502 6100
38902
5502 5502
26300
6000 5668
13525
7289
0
10000
20000
30000
40000
50000
2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
Re-e
nter
ed m
ass [
kg] R/B SC
Phobos-Grunt UARS Progress-M 27M
1 SL-16, 2 SL-23, 2 CZ-2F
Mass > 500 kg
Mass > 5000 kg
LARGE M > 50 kg
LARGE M > 500 kg
LARGE M > 5000 kg
No. Mass [kg]
No. Mass [kg] No. Mass [kg]
Rocket bodies
366 754 142 (83%)
324 744 637 (83%)
14 93 808 (78%)
Spacecraft 82 157 098 (17%)
68 153 254 (17%)
3 26 482 (22%)
Intact objects
448 911 240 392 897 891 17 120 290
Orbital inclination of intact objects re-entered between 2008 and 2017
392 intact objects with mass > 500 kg
70 18%
29 7%
0 0%
76 19%
108 28%
19 5%
11 3%
45 11%
14 4%
20 5% > 90°
80°-90°
70°-80°
60°-70°
50°-60°
40°-50°
30°-40°
0
20
40
60
80
100
120DE
LTA
2 R/
BM
OLN
IYA
3-43
DELT
A 2
R/B
CZ-4
B R/
BSL
-8 R
/BSL
-4 R
/BCZ
-2C
R/B
CZ-4
B R/
BSL
-4 R
/BCZ
-4B
R/B
JB-3
BM
OLN
IYA
1-44
MO
LNIY
A 3-
45SL
-8 R
/BSL
-4 R
/BSL
-3 R
/BCO
SMO
S 12
22SL
-4 R
/BSL
-4 R
/BPR
OG
RESS
-M 2
7MM
OLN
IYA
1-42
MO
LNIY
A 1-
92SL
-6 R
/B(1
)SL
-6 R
/B(2
)SL
-6 R
/B(2
)SL
-6 R
/B(2
)RO
SAT
SL-6
R/B
(2)
MO
LNIY
A 3-
46U
ARS
CZ-3
C R/
BSL
-26
R/B
SL-4
R/B
SL-4
R/B
SL-4
R/B
SL-4
R/B
SL-1
2 R/
B(1)
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
ANTA
RES
R/B
SL-4
R/B
ANTA
RES
R/B
SL-2
3 R/
BCZ
-2F
R/B
CZ-2
F R/
BM
OLN
IYA
3-51
DELT
A 2
R/B(
1)CZ
-3A
R/B
DELT
A 4
R/B
CZ-3
B R/
BCZ
-3B
R/B
CZ-3
A R/
BAT
LAS
3A C
ENTA
UR
R/B
ATLA
S 2A
S CE
NTA
UR
R/B
ATLA
S 5
CEN
TAU
R R/
BG
SLV
R/B
CZ-3
C R/
BAR
IAN
E 44
L R/
BAR
IAN
E 44
L R/
BAV
UM
R/B
ARIA
NE
5 R/
B
Orb
ital i
nclin
atio
n [d
eg]
65 62 60 51 51 51 51
43 43 43 43 43 43 43 42 41 34
010203040506070
PRO
GRE
SS-M
27M
PHO
BOS-
GRU
NT
UAR
SSL
-16
R/B
SL-2
3 R/
BSL
-23
R/B
SL-2
3 R/
BCZ
-2F
R/B
CZ-2
F R/
BCZ
-2F
R/B
CZ-2
F R/
BCZ
-2F
R/B
CZ-2
F R/
BCZ
-7 R
/BCZ
-2F
R/B
CZ-7
R/B
DRAG
ON
/FAL
CON
9
Orb
ital i
nclin
atio
n [d
eg]
17 intact objects with mass > 5000 kg Mass > 500 kg
> 90° 70 18% 80°-90° 29 7% 70°-80° 0 0% 60°-70° 76 19% 50°-60° 108 28% 40°-50° 19 5% 30°-40° 11 3% 20°-30° 45 11% 10°-20° 14 4% 0°-10° 20 5%
Latitude bands overflown by re-entered objects [2008-2017]
0102030405060708090
100
DELT
A 2
R/B
MO
LNIY
A 3-
43DE
LTA
2 R/
BCZ
-4B
R/B
SL-8
R/B
SL-4
R/B
CZ-2
C R/
BCZ
-4B
R/B
SL-4
R/B
CZ-4
B R/
BJB
-3 B
MO
LNIY
A 1-
44M
OLN
IYA
3-45
SL-8
R/B
SL-4
R/B
SL-3
R/B
COSM
OS
1222
SL-4
R/B
SL-4
R/B
PRO
GRE
SS-M
27M
MO
LNIY
A 1-
42M
OLN
IYA
1-92
SL-6
R/B
(1)
SL-6
R/B
(2)
SL-6
R/B
(2)
SL-6
R/B
(2)
ROSA
TSL
-6 R
/B(2
)M
OLN
IYA
3-46
UAR
SCZ
-3C
R/B
SL-2
6 R/
BSL
-4 R
/BSL
-4 R
/BSL
-4 R
/BSL
-4 R
/BSL
-12
R/B(
1)SL
-4 R
/BSL
-4 R
/BSL
-4 R
/BSL
-4 R
/BSL
-4 R
/BSL
-4 R
/BSL
-4 R
/BAN
TARE
S R/
BSL
-4 R
/BAN
TARE
S R/
BSL
-23
R/B
CZ-2
F R/
BCZ
-2F
R/B
MO
LNIY
A 3-
51DE
LTA
2 R/
B(1)
CZ-3
A R/
BDE
LTA
4 R/
BCZ
-3B
R/B
CZ-3
B R/
BCZ
-3A
R/B
ATLA
S 3A
CEN
TAU
R…AT
LAS
2AS
CEN
TAU
R…AT
LAS
5 CE
NTA
UR
R/B
GSL
V R/
BCZ
-3C
R/B
ARIA
NE
44L
R/B
ARIA
NE
44L
R/B
AVU
M R
/BAR
IAN
E 5
R/B
Latit
ude
band
s ove
rflo
wn
[deg
]
> 80° > 70° > 60° > 50° > 40° > 30° > 20° > 10°
24% 25%
45%
72% 77% 80% 91% 95%
392 intact objects with mass > 500 kg
Source: http://www.aerospace.org
34 sightings (27 rocket bodies and 7 spacecraft) out of 373 re-entries of large intact objects (299 rocket bodies and 74 spacecraft) between 2010 and 2017: i.e. in ∼9% of the re-entry events
Moreover, also the re-entry of the Cygnus mass simulator (3800 kg) was sighted in 2013
Sightings [2010-2017]
1 2 1 4
7 8
6
5
2010 2011 2012 20132014 2015 2016 2017
0
20
40
60
80
100
120
SL-4
R/B
DELT
A 2
R/B(
2) (P
AM-D
)
SL-4
R/B
ARIA
NE
44L
R/B
COSM
OS
1484
SL-4
R/B
CZ-4
B R/
B
GO
CE
CZ-3
B R/
B
COSM
OS
1220
SL-4
R/B
COSM
OS
1400
SL-3
R/B
SL-4
R/B
FALC
ON
9 R
/B
CZ-4
B R/
B
SL-4
R/B
SL-6
R/B
(2)
SL-4
R/B
COSM
OS
1315
NFI
RE
SL-4
R/B
SL-4
R/B
SL-2
3 R/
B
CZ-3
B R/
B
JB-3
A
SL-4
R/B
CZ-7
R/B
FALC
ON
9 R
/B
CZ-7
R/B
CZ-4
B R/
B
SL-4
R/B
SL-4
R/B
ANTA
RES
R/B
Orb
ital i
nclin
atio
n [d
eg]
2011
2011
2012
2013
2013
2013
2013
2014
2014
2014
2014
2014
2014
2014
2015
2015
2015
2015
2015
2015
2015
2015
2016
2016
2016
2016
2016
2016
2017
2017
2017
2017
2017 2010
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
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
(1)
Recovered re-entry debris (http://www.aerospace.org/cords/research/reentry-data) 20
09-0
52C
2007
-037
B
2003
-058
C
2011
-001
C
1997
-016
C
2012
-021
C
1975
-077
B
2014
-052
B
2015
-074
C
2016
-050
B
2012
-006
K
2017
-086
D
2010
Mongolia Asia
Malawi Africa
2011 2011 2011
Artigas Uruguay
Baggs Wyoming
USA Mata Roma
Brazil
2012 2013
Buna Texas USA
2013
Ngezi Zimbabwe
Africa
2014 2016 2016 2016 2018
Santa Rita do Pardo Brazil Tuyen Quang
Province Vietnam
Giliraja East Java Indonesia
Oddanchatram India
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.
Puno region Peru
What to expect in 2018? What has already happened?
What is going to happen?
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 of the Chinese space station Tiangong-1, with a launch mass of 8500 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
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°
Physical characteristics of the Zenit-2SB second stage
COSPAR ID 2017-086D Cat. Number 43090
Zenit-2SB second stage
Length 10.4 m
Diameter 3.9 m
Inert mass 8307 kg
Observed orbital decay
The re-entry of the Zenit-2SB second stage Evolution of the ballistic parameter
0.006000.006500.007000.007500.008000.008500.009000.009500.01000
19.7
13.2
10.8 9.2
5.9
4.0
3.0
1.7
1.1
0.3
0.2
Balli
stic
par
amet
er
[m^2
/kg]
Residual lifetime [days]
<B> = 0.00881 m2/kg σ ∼ 7%
11.8 14.4
2.5 -0.1 1.2
-4.8 -8.4
-11.0 -11.9
-4.4 -6.8
-15-10
-505
101520
19.7
13.2
10.8 9.2
5.9
4.0
3.0
1.7
1.1
0.3
0.2
Perc
enta
ge e
rror
on
re
-ent
ry p
redi
ctio
ns [%
]
Residual lifetime [day]
Percentage error affecting the estimate of the residual lifetime Mean prediction error
7.0 6.6
5.7 6.1
6.9
7.9 8.5 8.5
7.7
5.6
6.8
4
5
6
7
8
9
19.7
13.2
10.8 9.2
5.9
4.0
3.0
1.7
1.1
0.3
0.2M
ean
pred
ictio
n er
ror [
%]
Residual lifetime [days]
Orbital predictor SATRAP Atmospheric density model NRLMSISE-00
MACB D=
100 PRED REFRL
REF IN
T TPET T
−= ×
−1
PNRL
n P
PEMPE
N=
= ∑
Value used for the post-event assessment
11 re-entry predictions
A post-event assessment
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)
-5
0
5
10
19.7 13.2 10.8 9.2 5.9 4.0 3.0 1.7 1.1 0.3 0.2Days
with
resp
ect t
o th
e
refe
renc
e re
-ent
ry
epoc
h
Residual lifetime [days]
START COIW END
-0.6
-0.4
-0.2
0
0.2
1.7 1.1 0.3 0.2Residual lifetime [days]
START COIW END
9
11 10
8 9 TLE: 26 January 2018, 05:49 UTC, Residual lifetime = 41h 42m
TLE: 26 January 2018, 21:58 UTC, Residual lifetime = 25h 34m
COIW - 27 January 2018, 20:29 UTC COIW - 27 January 2018, 18:56 UTC
8
The re-entry of the Zenit-2SB second stage
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°
COIW - 27 January 2018, 23:17 UTC COIW - 27 January 2018, 23:11 UTC
The re-entry of the Zenit-2SB second stage
JSpOC decay epoch 27 January 2018, 23:32 UTC ± 1 min 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 after they were notified by local residence»
Sighting
Recovered debris
© Peruvian Air Force / AFP
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
COSPAR ID 2017-031B Cat. Number 42748
C-25 Cryogenic upper stage
Length 13.55m
Diameter 4 m
Inert mass ∼5300 kg
10
100
1000
10000
100000
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
109.
111
9.0
128.
314
0.8
149.
815
9.8
175.
818
2.6
184.
919
0.3
203.
721
2.3
215.
421
9.4
225.
323
3.7
239.
724
4.1
245.
124
6.3
247.
1
Perigee altitude [km] Apogee altitude [km]
First TLE: 5 June 2017, 07:18 UTC 160 × 34918 km; inc: 21.55°
Last TLE: 7 February 2018, 19:17 UTC 101 × 1484 km; inc: 21.42°
Observed orbital decay
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
**Food, food packaging, water and oxygen consumption for 57 astronaut-days: ≈ 303 kg
* Propellant consumption from manoeuvre sequence: ≈ 650 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 March 2016
The autonomous on board attitude control remained, and still is, operational. According to China Manned Space Agency (CMSA): «Its attitude kept stabilized and no anomaly occurred» http://en.cmse.gov.cn/col/col1763/index.html
The attitude is controlled through reaction wheels and reaction control thrusters
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
The attitude control has an indirect effect on the orbit by varying the effective drag cross-section 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
For instance, the net orbital effect of the thrusting occurred on 27 January 2018 corresponded to a ∆V of a few meters per second
Maneuver day B* da dt
a e i ω
January 27 X X X X
February 2 X X X X X
February 11 X X X X X
Significant manoeuvres occurred from 20 January to 18 February 2018
January 27
February 2
February 11
January 27
February 2
February 11
Environmental conditions
Some minor geomagnetic storms (4 < KP ≤ 5)
Quite low solar activity levels
Estimate of the Tiangong-1 ballistic parameter
0.0055
0.0060
0.0065
0.0070
0.0075
0.0080
0.0085
8.47
11.2
1
15.1
6
17.1
6
18.7
7
22.1
5
24.0
8
25.0
9
26.0
2
29.2
7
29.5
7
31.2
6
32.5
0
35.6
2
38.1
2
43.0
8
47.1
4
50.1
3
51.1
2
52.1
2
53.1
7
Balli
stic
par
amet
er [m
²/kg]
Prediction epoch [day of 2018]
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
Forecasting the Tiangong-1 re-entry epoch
80
82
84
86
88
90
92
94
96
98
100
8.47
11.2
1
15.1
6
17.1
6
18.7
7
22.1
5
24.0
8
25.0
9
26.0
2
29.2
7
29.5
7
31.2
6
32.5
0
35.6
2
38.1
2
43.0
8
47.1
4
50.1
3
51.1
2
52.1
2
53.1
7
Nom
inal
re-e
ntry
epo
ch a
t 80
km [d
ay o
f 201
8]
Prediction epoch [day of 2018]
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