Van Allen Extended Mission Orbit Analysis

9/2014 SWG

T. Sotirelis, F. SiddiqueJHU/APL

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Options

OptionΔV

RBSPA (m/sec)

Fuel Used RBSPA

(kg)

ΔV RBSPB (m/sec)

Fuel Used RBSPB

(kg)

Mission EOL Estimate**

Petal Separation Oct 2015

Petal Separation Oct 2016

Do nothing 0 0 0 0 11/1/2018 4.9° 5.7°

Increase Delta Apogee by 200%* 6.4 2.0 6.4 2.0 7/1/2018 6.4° 10.9°

Decrease RBSPA Perigee to 575 km 9.2 2.9 6.4 2.0 7/1/2018 6.9° 12.4°

Increase Delta Apogee by 300%* 9.6 3.0 9.6 3.0 5/1/2018 7.2° 13.6°

Decrease RBSPA Perigee to 575 km 12.4 3.9 9.6 3.0 5/1/2018 7.6° 15.0°

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• Analysis assumes maneuvers performed June 1, 2015• *Current delta between apogee altitudes is ~140 km• **End of life (EOL) estimates are based on projecting current propellant usage forward. • EOL of spacecraft due to radiation environment is predicted to be 12/1/2019• Perigee altitude reduction already book-kept in the disposal budget, does not affect estimated EOL• Predicted angle between apse lines at nominal mission Q4 exit (Aug 2014) is 2.25 deg• Mission lifetime can be extended by altering disposal scenario

• So far, a scenario adding 50 days has been found

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200% Apse Altitude Change and Decrease Perigee Altitude by 25 km on RBSPA

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NOTE: Due to solar/lunar perturbations, by dropping perigee altitude by 25 km, the range of perigee altitudes will drop from [555,645] km to [495,585] km

Nominal

Decrease Perigee Altitude by 25 km

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Nominal Orbit Increase Delta Apogee 200% on 6/1/2015

A/B Conjunctions: Same MLT: L vs ΔL

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Nominal Orbit Increase Delta Apogee 300% on 6/1/2015

A/B Conjunctions: Same MLT: L vs ΔL

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Nominal OrbitIncrease Delta Apogee 200% & Decrease Perigee A by 25 km on 6/1/2015

A/B Conjunctions: Same MLT: L vs ΔL

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Nominal Orbit Increase Delta Apogee 200% on 6/1/2015

A/B Conjunctions: Same L: L vs ΔMLT

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Nominal OrbitIncrease Delta Apogee 200% & Decrease Perigee A by 25 km on 6/1/2015

A/B Conjunctions: Same L: L vs ΔMLT

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Nominal OrbitIncrease Delta Apogee 200% & Decrease Perigee A by 25 km on 6/1/2015

A/B Conj. ≥30 Minutes: Same L: L vs ΔMLT

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Time Close Together (hours)

Nominal ΔR < 1000 km ΔR < 500 km ΔR < 100 km2015 27.1 3.5 02016 36.7 3.4 02017 19.3 2.5 02018 10.0 1 0

ΔAp 200% PerA -25km

ΔR < 1000 km ΔR < 500 km ΔR < 100 km

2015 19 2.5 02016 8.9 0.9 02017 2.3 0.6 02018 0.8 0.1 0

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Summary

Increasing petal separation will reduce mission lifetime

Close approaches become rarer as the petals separate

Mission lifetime can be extended by altering disposal scenario

What science can be motivated by these scenarios?

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Backup

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Trajectory Status (2014-2016)

             

[Predicted] Lapping Rate Per Quadrant 27-Nov-2013

Q1 2.44

Q2 2.25

Q3 2.52

Q4 2.34

Quadrant Entry/Exit Dates RBSPA RBSPB

Enter Q1 18 Aug 2014 12:00 13 Aug 2014 10:00

Enter Q2 03 Feb 2015 01:00 26 Jan 2015 12:00

Enter Q3 03 Jul 2015 04:00 28 Jun 2015 01:59

Enter Q4 21 Dec 2015 09:00 12 Dec 2015 07:00

Exit Q4 30 May 2016 13:00 20 May 2016 00:00

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Q1Q2

Q3 Q4

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Remaining Usable Propellant Propellant usage based on initial usable propellant = 55.93 kg.

• Usable propellant depicted. For total including residuals, increase by 0.565 kg. As of August 31, 2014: SCA usable = 43.97±0.72 kg. SCB usable = 43.83±0.72 kg.

42434445464748495051525354555657

2012.08.29 2013.01.01 2013.05.06 2013.09.08 2014.01.11 2014.05.16 2014.09.18 2015.01.21

Rem

aini

ng U

sabl

e Pr

opel

lant

[kg]

SC Time [UTC]

Van Allen Probes Remaining Usable Propellant

SCA Remaining Propellant [kg]

SCB Remaining Propellant [kg]

SCA (kg)

SCB (kg)

Total propellants used as of 8/31/14

13.5 13.5

Reserved for Disposal 19 19

Available for extended missions

23.5 23.5

Propellant on-board to extend current operations until ~Nov 2018