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ESA UNCLASSIFIED - For Official Use

Solar Orbiter: 2018-2020 Launch Options Favouring Data Return

J.M. Sánchez Pérez, ESA-ESOC, HSO-GFA

18/06/2015 @ ESTEC

J.M. Sánchez Pérez | ESOC | 18/06/2015 | Slide 2


Introduction

1. Period from September 2018 to December 2020 has been analysed in order to identify launch options for Solar Orbiter considering the maximisation of the data return as a major figure of merit

2. Task is now complete

• A number of possible candidates were analysed

• A set of trajectories has been identified from October 2018 until June 2020 offering better data return than the current CReMA baseline

• Potential downlink improvement from 15% to about 100% possible

• Some launch options provide as well an earlier start of science



On the data return – Downlink index

1. Geometrical index based on the trajectory indicating the capability to downlink data

• It indicates a potential downlink, but real downlink is affected by several S/C & OPS parameters → Simulations by SOC

2. DLindex = Time average of 1/D2, with D distance to the Earth

• But capping the distance to 0.45 AU (limit of bit rate)

• And excluding solar conjunctions periods

3. Dlindex = 1 AU-2 ≈ 2.11 Tbit/year with current comms assumptions



On the data return – Downlink index

2018 October CReMA“Bad” 4:3 Science orbitDL index = 0.73 1/AU2

2018 October A1“Good” 4:3 Science orbitDL index = 1.91 1/AU2

Downlink driven by phasing of the Earth-Sun-Venus GAM geometry

ESV angle = 69°

ESV angle = -21°



Comprehensive launch options search (1)

1. Assumptions and constraints:• Trajectory problem tackled from launch to final 3:2 science orbit

• E(E)VEV, E(E)VVEV and E(E)VEEV transfer options

• Launch from Oct 2018 to Dec 2020 with Earth escape V∞ <= 5.6 km/s

• Up to 3 full revolutions in each transfer leg, 5 during Venus resonances

• 0.27 AU <= Distance to Sun <= 1.57 AU

• Final science orbit in 3:2 resonance with solar inclination 31-35 deg

• Total mission duration <= 10.7 years

• Average data return during science phase >= 2.0 Tbit/year

• Avoid critical superior conjunctions at GAMs (14 out of the last 20 days before a GAM with SES < 3 deg)

• Safe mode blackout periods <= 85 days

2. Over 400 solutions have been found and were further analysed• Many solutions still non compliant with spacecraft constraints (eclipse

duration, Max Sun distance, Safe mode blackout) and/or operational constraints (solar conjunction at GAM)




Cruise duration: from launch until last GAM before perihelion < 0.35 AU




Solutions cluster around same arrival datesVenus can be reached only at given solar longitudes

No good solutions from Jul 2020 to Dec 2020!

Empt

y




More strict Sun distance constraint and cruise duration2 solution clusters: Oct 2018 and Jan-Jun 2020

Only 2 not promising solutions left in 2019




Longer mission not necessarily higher data returnEarth-Venus phasing is critical

Short cruise achieved with low or high max. Sun range only

Empty



Trajectories identified

1. Late 2018• 2018 October CReMA: issue with poor downlink

• 2018 October A1* & D: similar cruise as CReMA and different science phase improving downlink. D has the best downlink

• 2018 October E: different cruise (EVVEV) & early science start, good DL

• 2018 November*: fast EVEV cruise, average downlink

2. 2019 / 2020 February• Options A* and C: short EVEV cruise, average downlink

• Option B: very short EVVEV cruise, excellent downlink, marginal LW

3. 2019 April: longer cruise, average downlink

4. 2019 / 2020 June• Option A*: short EVEV cruise, average DL, maximum Sun range ~1.5 AU

• Option B: similar to A, but compliant with Rsun <= 1.48 AU

* Trajetories proposed by Dr. Langevin



Downlink Classification

DLindex (AU-2)Core

4:3 or 5:4 orbit

NMP EMP Total science

2018 Oct D 2.43 2.18 1.28 1.89

2020 Feb B 2.42 1.91 1.30 1.72

2018 Oct E 2.09 1.74 1.41 1.55

2017 Jul 1.01 1.43 1.54 1.47

2018 Oct A1 1.60 1.64 1.00 1.42

2017 Jan 1.68 1.34 1.37 1.35

2020 Feb C 0.98 1.40 1.28 1.35

2019 April 0.72 1.20 1.37 1.28

2018 Nov 0.90 1.22 1.29 1.26

2020 Jun A 0.92 1.23 1.29 1.26

2020 Jun B 0.84 1.19 1.30 1.24

2020 Feb A 0.81 1.17 1.29 1.23

2018 Oct CReMA 0.73 0.88 1.36 1.09



Downlink – “Best case”

DLindex (AU-2)Core

4:3 or 5:4 orbit


2018 Oct D 2.43 2.18 1.28 1.89

2020 Feb B 2.42 1.91 1.30 1.72

2018 Oct E 2.09 1.74 1.41 1.55

2017 Jul 1.01 1.43 1.54 1.47

2018 Oct A1 1.60 1.64 1.00 1.42

2017 Jan 1.68 1.34 1.37 1.35

2020 Feb C 0.98 1.40 1.28 1.35

2019 April 0.72 1.20 1.37 1.28

2018 Nov 0.90 1.22 1.29 1.26

2020 Jun A 0.92 1.23 1.29 1.26

2020 Jun B 0.84 1.19 1.30 1.24

2020 Feb A 0.81 1.17 1.29 1.23

2018 Oct CReMA 0.73 0.88 1.36 1.09

1st 5:4 core science orbitDLindex =2.43 AU-2

2nd 4:3 science orbitDLindex =1.89 AU-2



5:4orbit

4:3orbit

Downlink – “Best case”

1st 5:4 core science orbitDLindex =2.43 AU-2


1

2

3

4

5

12 3

1 23

4

5

5

4



Downlink – Excellent science orbits

DLindex (AU-2)Core

4:3 or 5:4 orbit


2018 Oct D 2.43 2.18 1.28 1.89

2020 Feb B 2.42 1.91 1.30 1.72

2018 Oct E 2.09 1.74 1.41 1.55

2017 Jul 1.01 1.43 1.54 1.47

2018 Oct A1 1.60 1.64 1.00 1.42

2017 Jan 1.68 1.34 1.37 1.35

2020 Feb C 0.98 1.40 1.28 1.35

2019 April 0.72 1.20 1.37 1.28

2018 Nov 0.90 1.22 1.29 1.26

2020 Jun A 0.92 1.23 1.29 1.26

2020 Jun B 0.84 1.19 1.30 1.24

2020 Feb A 0.81 1.17 1.29 1.23

2018 Oct CReMA 0.73 0.88 1.36 1.09



Perihelion Radius (AU) Solar inclination (deg)

Evolution of parameters – Late 2018

2018 Nov starts science almost as fast as 2018 Oct E and much higher inclination during NMP. However: < 0.3 AU only at EMP, limited final inclination and average downlink

Trajectories with better downlink have delayed raise of the inclination



Evolution of parameters - 2019&2020

Perihelion Radius (AU) Solar inclination (deg)

Also fast mission with excellent downlink 2020 Feb B lags behind in inclination

2020 Feb A and Jun A start science later at higher inclinations always > 20 deg with average downlink, better than 2018 Oct CReMA, but worse than 2017 Jan or Jul

Other options are intermediate in terms of evolution of orbit parameters



Trajectories identified

1. Late 2018• 2018 October CReMA: issue with poor downlink

• 2018 October A1 & D: similar cruise as CReMA and different science phase improving downlink. D has the best downlink

• 2018 October E: different cruise (EVVEV) & early science start, good DL

• 2018 November: fast EVEV cruise, average downlink

2. 2019 / 2020 February• Options A and C: short EVEV cruise, average downlink

• Option B: very short EVVEV cruise, excellent downlink, marginal LW

3. 2019 April: longer cruise, average downlink and science

4. 2019 / 2020 June• Option A: short EVEV cruise, average DL, maximum Sun distance ~1.5 AU

• Option B: similar to A, but compliant with Rsun <= 1.48 AU

Most promising for late 2018



2018 Oct Option D

• Science phase: 5:4-4:3-3:2-3:2 (inbound)

• Cruise: 3.1 years

• 1 perihelion at 0.31 AU in E2-V2 leg

• 9.4 years to is>30°

• Core science orbit:

• 5:4 reached after 3.8 years

• Inclination is low 12.7°, then raises fast

• Superb data return – DLindex 2.43 AU-2

•Excellent data return – DLindex 1.89 AU-2

•Maximum Sun range: 1.448 AU

•Launch window 30 days both Atlas V & A5ECA



2018 Oct Option E

• Very fast cruise: 2.3 years – Type EVVEV

• 2 perihelions at 0.346 AU in E1-V3 leg

• 7.5 years to is>30°, max. is after 9.3 years



• Inclination is low 13.1°, then raises fast


•Very good data return – DLindex 1.55 AU-2

•Max. Sun range: 1.149 AU – No hibernation

•Launch window 30 days Atlas V, 20 d A5ECA

• Science phase: 4:3-3:2-3:2-5:3-3:2 (outbound)



2018 Oct E vs. 2018 Oct DPerihelion Radius (AU) Solar inclination (deg)

Evolution of parameters 2018 Oct. D vs. E

2018 Oct E starts science earlier, goes faster <0.3 AU

2018 Oct E has more science orbits even if last 3:2 is ommited: 20 or 17 vs. 16

Inclination steps are similar, but 2018 Oct E is earlier

2018 Oct D has better downlink and more stable perihelion radius

2

4

3

3

5

3

2

4

3

3

53

1

53

4

3

1

4

3

5

3



Summary – Science Performance

CaseCReMALimits

2018 Oct

CReMA

2018 OctA1

2018 Oct D

2018 Oct E

2018 Nov

2019 April

2020 Feb A

2020 Feb B

2020 Feb C

2020 Jun A

2020 Jun B

+1 year if launched in 2019

Total Duration (y)8.87 – 10.24 9.46 10.46 10.59 10.53 9.43 10.05 9.77 10.57 9.87 9.42 9.46

Cruise duration (y) 2.94 – 3.40

3.17 3.05 3.05 2.26 2.73 3.90 3.07 1.80 2.49 2.72 2.69

1st perih. < 0.3 AU (y)3.50 – 4.67 3.49 4.54 3.92 3.50 5.96 4.25 5.20 2.68 2.87 5.94 2.80

Time to is 30 deg (y) 8.23 8.13 9.58 7.46 7.65 6.97 6.15 8.11 8.03 5.79 7.00

Time to max. solar i (y)7.86 – 9.20 8.44 9.56 9.58 9.57 7.79 8.45 8.22 9.58 8.28 7.86 8.50

NMP+EMP duration (y) 6.28 7.42 7.54 8.28 6.70 6.15 6.69 8.77 7.38 6.70 6.77



Summary – Science Performance

CaseCReMALimits

2018 Oct

CReMA

2018 OctA1

2018 Oct D

2018 Oct E

2018 Nov

2019 April

2020 Feb A

2020 Feb B

2020 Feb C

2020 Jun A

2020 Jun B

Min Sun distance (AU) ≥ 0.280 0.282 0.281 0.290 0.280 0.282 0.282 0.280 0.284 0.283 0.281 0.280

# Perih < 0.3 AU 7 – 12 8 9 12 12 10 11 13 12 12 10 7

Time spent < 0.3 AU (d) 46.5 – 101.6 62 70 52 71 84 64 113 77 56 96 49

# Below 0.4 AU 12 – 16 15 18 16 20 18 16 18 22 23 18 16

Time spent < 0.4 AU (d) 292.8 – 421.4 321 462 404 490 458 424 492 461 462 470 367

Max. solar i (deg) 32.38 - 36.36 32.87 33.43 32.41 32.92(31.3) 30.44 33.17 34.30 33.39

(30.2) 32.85 32.69 31.57

Max. angular rate (deg/d) 7.76 – 8.31 8.137 8.018 7.728 7.820 7.106 7.799 7.484 7.674 7.484 7.323 8.107

|Heliolatitude|>25 deg 6 6 6 11(8) 10 8 13 6

(3) 8 13 9

Heliolatitude>+25 deg (d) 177 174 169 229(137) 147 153 209 188

(90) 118 312 252

Heliolatitude<-25 deg (d) 91 107 90 269(187) 217 232 351 130

(57) 245 196 168

|Heliolat.|>25 deg (d) 268 281 259 498(323) 364 385 560 318

(147) 363 508 420



Summary - Constraints

CaseCReMALimits

2018 Oct

CReMA

2018 OctA1

2018 Oct D

2018 Oct E

2018 Nov

2019 April

2020 Feb A

2020 Feb B

2020 Feb C

2020 Jun A

2020 Jun B

LW Atlas V 411 (d) 30 30 30 30 30 30 29 17 29 30 30

LW Ariane 5 ECA (d) 30 30 30 20 30 2430

(only 2019)

~26(only 2019)

30 (only 2019)

30 30

Max Sun distance (AU)1.186 – 1.478

1.471 1.448 1.448 1.149 1.485 1.128 1.102 1.017 1.110 1.501 1.455

SM Blackouts*: longest (d) ≤ 61.0 46.8 37.9 43.5 64.1 20.3 23.4 52.2 70.1 42.8 37.5 8.0

Conjunctions*: longest (d) ≤ 44.0 14.4 22.2 21.3 25.2 4.0 13.0 30.9 24.0 14.1 3.9 5.7

Longest eclipse - LW (min) ≤ 37.1 28.3 28.3 28.3 26.8 32.0 25.5 26.0 18.8 26.0 34.0 30.8

Longest occultation (min) ≤ 35.1 8.8 6.4 4.8 10.8 0.0 13.9 22.1 17.0 21.9 0.0 0.0

SES angle at Venus (deg) 11.2 13.4 13.5 16.5 21.6 14.9 19.1 13.1 18.9 19.2 15.2

• 2020 Feb B marginal launch window with Atlas V 411

• 2018 Nov and 2020 June A marginally above max. Sun distance constraint

• All other constraints are respected,including OPS constraint to avoid Solar superior conjunction at Venus GAM



Conclusions

• 3 launch options allow fast start of science and excellent downlink improving performance of current CReMA’s best (2017 July)

• Generally very high downlink leads to lower inclinations at start of NMP and a delay in the inclination raise

• Selection process for new baseline in late 2018 – Most promising:

1. 2018 October D favouring downlink

2. 2018 October E favouring fast start of and more science

• Additional trajectories compliant with all mission constraints provide better downlink than CReMA 2018 Oct and give flexibility to launch in different periods from 2019 Feb to 2020 June

• Backup launch options are ensured until 2020 June allowing to accommodate different launch delays

• Selection not considered critical at this point



SPARE SLIDES



2018 Oct CReMA

• Science phase: 1:1-1:1-4:3-3:2-3:2 (inbound)






• Inclination 21.7°

• Poor data return – DLindex 0.73 AU-2

•Overall poor data return – DLindex 1.09 AU-2





2018 Oct Option A1







• Inclination is lower 16.9°

• Good data return – DLindex 1.60 AU-2

•Good overall data return – DLindex 1.42 AU-2

•Poor data return during EMP





2018 November

• Science phase: 4:3-3:2-5:3-5:3* (inbound)

• Very fast cruise: 2.7 years


• However, not possible to reach is>31°



• Inclination is 19.1°

• Average data return – DLindex 0.90 AU-2

•Average data return – DLindex 1.26 AU-2

•Max. Sun range: 1.485 AU – Above constraint




2019 April

• Science phase: 4:3-3:2-3:2-5:3 (outbound)

• Cruise is long: 3.9 years






•Average total data return – DLindex 1.28 AU-2


•Launch window 30 days Atlas V & 24 d A5ECA



2019/2020 February A

• Science phase: 4:3-3:2-5:3-5:3* (outbound)

• Cruise: 3.1 years (4.1 years in 2019)

• 6.2 years to is>30° (7.2 years in 2019)


• 4:3 reached after 3.1 years (4.1 years)

• Inclination is high 21.9°




•Launch window:

• 2019 Atlas V & A5ECA both 30 days

• 2020 Atlas V 29 days



2019/2020 June A

• Science phase: 4:3-3:2-5:3-5:3* (inbound)

• Cruise: 2.7 years (3. 7 years in 2019)








•Max. Sun range: 1.502 AU – Above constraint

•Launch window Atlas V & A5ECA both 30 days



2019/2020 June B


• Cruise: 2.7 years (3. 7 years in 2019)


• 8.2 years to is>31.5° (9.2 years in 2019)



• Inclination is only 12.1°



•Max. Sun range: 1.463 AU

•Launch window Atlas V & A5ECA both 30 days



2019/2020 February B

• Science phase: 5:4-4:3-3:2-5:3 (inbound)

• Very fast cruise: 1.8 years – Type EVVEV (2.8 years in 2019)



• 9.3 years for is>33° (not in 2019)



• Inclination is very low 8.7°


•Excellent total data return – DLindex 1.72 AU-2


•Launch window marginal: only 17 days

• 2020 Atlas V only, 2019 Atlas V & A5ECA



2019/2020 February C

• Variant of Feb A with 5:4 instead 1:1-4:3

• Science phase: 5:4-4:3-3:2-5:3 (outbound)

• Cruise: 2.5 years (3.5 years in 2019)




• Inclination is low 13.9°




•Launch window:

• 2019 Atlas V & A5ECA both 30 days

• 2020 Atlas V 29 days



Data Return – Good NMP case, but …

DLindex (AU-2)Core

4:3 or 5:4 orbit


2018 Oct D 2.43 2.18 1.28 1.89

2020 Feb B 2.42 1.91 1.30 1.72

2018 Oct E 2.09 1.74 1.41 1.55

2017 Jul 1.01 1.43 1.54 1.47

2018 Oct A1 1.60 1.64 1.00 1.42

2017 Jan 1.68 1.34 1.37 1.35

2020 Feb C 0.98 1.40 1.28 1.35

2019 April 0.72 1.20 1.37 1.28

2018 Nov 0.90 1.22 1.29 1.26

2020 Jun A 0.92 1.23 1.29 1.26

2020 Jun B 0.84 1.19 1.30 1.24

2020 Feb A 0.81 1.17 1.29 1.23

2018 Oct CReMA 0.73 0.88 1.36 1.09

1st 4:3core science orbitDLindex =1.60 AU-2




Data Return – … bad EMP

DLindex (AU-2)Core

4:3 or 5:4 orbit


2018 Oct D 2.43 2.18 1.28 1.89

2020 Feb B 2.42 1.91 1.30 1.72

2018 Oct E 2.09 1.74 1.41 1.55

2017 Jul 1.01 1.43 1.54 1.47

2018 Oct A1 1.60 1.64 1.00 1.42

2017 Jan 1.68 1.34 1.37 1.35

2020 Feb C 0.98 1.40 1.28 1.35

2019 April 0.72 1.20 1.37 1.28

2018 Nov 0.90 1.22 1.29 1.26

2020 Jun A 0.92 1.23 1.29 1.26

2020 Jun B 0.84 1.19 1.30 1.24

2020 Feb A 0.81 1.17 1.29 1.23

2018 Oct CReMA 0.73 0.88 1.36 1.09

1st 3:2science orbitDLindex =0.92 AU-2




Data Return – Good EMP

DLindex (AU-2)Core

4:3 or 5:4 orbit


2018 Oct D 2.43 2.18 1.28 1.89

2020 Feb B 2.42 1.91 1.30 1.72

2018 Oct E 2.09 1.74 1.41 1.55

2017 Jul 1.01 1.43 1.54 1.47

2018 Oct A1 1.60 1.64 1.00 1.42

2017 Jan 1.68 1.34 1.37 1.35

2020 Feb C 0.98 1.40 1.28 1.35

2019 April 0.72 1.20 1.37 1.28

2018 Nov 0.90 1.22 1.29 1.26

2020 Jun A 0.92 1.23 1.29 1.26

2020 Jun B 0.84 1.19 1.30 1.24

2020 Feb A 0.81 1.17 1.29 1.23

2018 Oct CReMA 0.73 0.88 1.36 1.09

3:2 science orbit DLindex =1.79 AU-2

5:3 science orbit DLindex =1.05 AU-2

Additional3:2 science orbit DLindex =1.56 AU-2

issue/revision: 1.0 reference: status: for information only esa unclassified - for official use...

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