ORBITALS Phase A Extended Interim Meeting U of A Phase A2 Work Update

ORBITALS Phase A ExtendedInterim Meeting

U of A Phase A2 Work Update

ORBITALS Science Team, University of Alberta

CSA HQ, St. Hubert, 2010/03/17

WP 2.1.1 Launch and Orbit

• Work by Louis Ozeke• New 8 hour period orbit with magnetic

conjunctions to multiple ground segments• Review science return from orbit options for

tomorrows launch/orbit discussion

ORBITALS Mission Orbit Analysis and Science Impact (D2.1.1.1, D2.1.1.3) P1, 2010/02/28

Science Objectives

3.5.1 Primary Science Objective:1. Understand the dynamical variation of outer radiation belt electron flux, including determining the dominant acceleration and loss processes.

3.5.2 Secondary Science Objectives:2. Understand the dynamical behaviour of inner zone and slot region radiation belt particle fluxes.3. Understand the structure of global inner magnetospheric electric and magnetic fields.4. Understand the core ion composition of the outer plasmasphere, plasmapause and plasmatrough regions and its dynamics during storms.

Outer, Inner and Slot Regions

Outer Belt 3 Re – 6 ReInner Belt 1 Re – 2 ReSlot Region 2 Re – 3 ReAll distances are geocentric in the equatorial plane

Orbit Parameters for Candidate Options

Orbit ParameterRaised Perigee

Orbit 375 km Perigee

Orbit 750 km Perigee

Orbit 250 km Perigee

OrbitEpoch 1/1/2013 12:00 1/1/2013 12:00 1/1/2013 12:00 1/1/2013 12:00

Apogee Altitude (km) 33743 (L=6.3) 32835 (L=6.1) 32435 (L=6.1) 35950 (L=6.6)

Perigee Altitude (km) 6627 (L=2.04) 375 (L=1.06) 750 (L=1.12) 250 (L=1.04)Semi-Major Axis (km) 26563 22983 22970.5 24478

Eccentricity 0.51041 0.70617 0.68969 0.72923

Inclination (°) 7 7 7 7

Argument of Perigee (°) 0 0 0 0

RAAN (°) 270 270 270 270

True Anomaly (°) 0 0 0 0

Period (hrs) 11.96

(2 orbits/day)9.63

(5 orbits/2 days)

9.62 (5 orbits/2

days)10.58

(7 orbits/3 days)

Daily Averaged Worst Case Electron and Proton Integral Flux

(AE-8/AP-8 and CRRES ELE/PRO models)

For protons > 50 MeV the flux is more than an order of magnitude greater along the low perigee orbits. The risk of SEU maybe greater at lower perigee.

For electrons the flux is the same for raised & lower perigee orbit options at these energies. Deep dielectric charging risk may not depend on the orbit choice.

ULTIMA Magnetometers (as of 2006)

New 8 hrs period orbit option

• A new orbit option with 3 orbits/day has been examined.

• This orbit option has magnetic conjunctions with different magnetometer arrays at each apogee pass.

• To obtain the 8 hr period the apogee has had to be reduced to ~5.24 Re (radial geocentric distance) for a perigee of 750 km.

• 7.96 hr period (3orbit/day)

• Apogee 27000 km (4.24 Re)

• Perigee 750 km• Incl 7 degs• Dipole tilts of 10

degs & 15 degs give max L-shells of 5.7 & 6.1

• RAAN=240 degs• Argument of perigee=0• True anomaly=0

Magnetic Footprints along the 3 petal orbit(plot shows 20 orbits)

Primary Science Goal Measurement

Need to measure PSD peak radial location L*=5.6 (6.3 Re in the equatorial plane for -100nT Dst).To measure particles at L=6.3 the inclination needs to be at least~10 degs assuming dipole tilt of 15 degs~15 degs assuming a dipole tilt of 10 degs

Results taken from “The energization of relativistic electrons in the outer Van Allen radiation belt” Yue Chen, Geoffrey D. Reeves & Reiner H. W. Friedel, Nature, 2007

Raised Perigee Orbit (12 hr orbit)- Once per day apogee conjunctions with Churchill and Alberta line magnetometers- Over an order of magnitude lower flux of > 5-10 MeV protons, reduced risk of SEU- Over 2 orders of magnitude lower flux of > 20 MeV protons, reduced risk of SEU- Inner zone region is missed below altitudes of 1 Re

Lower Perigee Orbit (750 km no main & 375 km with main)- Once per 2 days apogee conjunctions with Churchill & Alberta line

magnetometers- Good coverage of the inner zone at perigee- Increased risk of SEU due to higher flux of > ~10 MeV protons

Lower Apogee Orbit (8 hr orbit) - 3 times per day conjunctions with Church/Alberta, Japanese and European lines- Good coverage of the inner zone at perigee- Reduced coverage of outer zone; poorer conjunctions with GEO satellites.- Increased risk of SEU due to higher flux of > ~10 MeV protons also higher TID- Inclination increase needed

Raised perigee

Apogee conjunctions-Alberta line-Churchill line

Perigee conjunctions-Europe-Japan-poor-Antarctica

375 km perigeemaintenance

Apogee conjunctions-Alberta line-Churchill line-Alaska station-Antarctic-poor

Perigee conjunctions-Europe-Japan

750 km perigee

Apogee conjunctions-Alberta line-poor-Churchill line-Alaska station-Europe-poor-Antarctic-poor

Perigee conjunctions-Europe-Japan

SEU rates detected on 64 Mbit DRAM (COTS) on-board MDS-1 JAXA

Sample time 2.6-5.25 hrs.Er1 & Er2 are two memory slices.Taken from IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 53, NO. 4, AUGUST 2006

Particle flux measurements

• TID is slightly greater than the other orbit options due to greater time spent in the middle of the outer radiation belt at apogee. However TID over 2 years is < 50 krads behind 8 mm of Al so that 100 krad parts may still be used assuming an RDM of 2.

• Worst case electron and proton flux is the same as the other orbit options.• 750 km perigee means measurements of the inner belt are possible.

Radiation Dose over 2 years Al,

mm

New orbitApogee 4.24Re Perigee 750 km

Raised perigee 375 km perigee 750 km perigee 250 km perigee

CRRES ELE/PRO max dose

AE-8/AP-8 max dose

CRRES ELE/PRO max dose

AE-8/AP-8 max dose

CRRES ELE/PRO max dose

AE-8/AP-8 max dose

CRRES ELE/PRO max dose

AE-8/AP-8 max dose

CRRES ELE/PRO max dose

AE-8/AP-8 max dose

3 2.670E+06 1.005E+06 1.62E+06 5.94E+05 1.75E+06 6.67E+05 1.80E+06 6.87E+05 1.39E+06 5.50E+05

4 6.454E+05 4.071E+05 3.91E+05 2.35E+05 4.28E+05 2.69E+05 4.43E+05 2.77E+05 3.44E+05 2.23E+05

5 2.199E+05 1.734E+051.33E+05 9.66E+04 1.47E+05 1.15E+05 1.53E+05 1.19E+05 1.20E+05 9.61E+04

6 1.064E+05 7.921E+046.33E+04 4.13E+04 7.08E+04 5.36E+04 7.42E+04 5.58E+04 5.87E+04 4.53E+04

7 6.566E+04 4.136E+043.86E+04 1.91E+04 4.33E+04 2.88E+04 4.57E+04 3.03E+04 3.63E+04 2.47E+04

8 4.768E+04

2.607E+04

2.74E+04

1.03E+04

3.12E+04

1.87E+04

3.31E+04

1.98E+04

2.62E+04

1.62E+04

9 3.813E+04 1.977E+042.17E+04 6.75E+03 2.49E+04 1.44E+04 2.65E+04 1.54E+04 2.09E+04 1.26E+04

10 3.212E+04 1.660E+041.69E+04 5.17E+03 2.11E+04 1.22E+04 2.25E+04 1.30E+04 1.77E+04 1.07E+04

12 2.623E+04 1.347E+041.33E+04 3.86E+03 1.76E+04 9.88E+03 1.88E+04 1.06E+04 1.47E+04 8.69E+03

14 2.046E+04 1.167E+048.58E+03 3.21E+03 1.42E+04 8.54E+03 1.51E+04 9.19E+03 1.18E+04 8.69E+03

16 1.850E+04 1.053E+046.79E+03 2.82E+03 1.33E+04 7.69E+03 1.42E+04 8.28E+03 1.10E+04 8.69E+03

18 1.225E+04 9.734E+036.31E+03 2.53E+03 9.09E+03 7.09E+03 9.51E+03 7.64E+03 7.40E+03 8.69E+03

20 8.262E+03 9.009E+035.89E+03 2.29E+03 6.17E+03 6.54E+03 6.28E+03 7.05E+03 4.90E+03 8.69E+03

250 km perigee.

Apogee drifts through all local times in less than 6 months.

What apogee can reach L=5.6*

• L*=5.6 is approximately equal to a dipole L-shell of L=6.3 for a Dst of -100nT

• To reach L=6.3 with the 8 hr period orbit the inclination of the spacecraft needs at least 13 degs assuming a dipole tilt of 11 degs.

• If the dipole tilt is 15 degs (true in the southern hemisphere) then the inclination needs to be at least 10 degs.

Dependence on apogee and perigee of the 8hr period orbit.

• Dropping the perigee down to 375 km means that the apogee can be extended slightly to 27500 km and the 8hrs period is maintained.

• The TID and worst case particle flux are not affected.

• Orbit maintenance is needed at 375 km.

Data still available from the Japanese meridian stations

http://denji102.geo.kyushu-u.ac.jp/denji/obs/cpmn/station/map/russia.gif

L-shell CoverageER102618 ORBITALS Orbit Analysis DRAFT May 16 2008(3)

Orbit Options Low Earth Orbit Spatial Coverage h < 0.5Re (% of Time)

Inner Zone Spatial Coverage

0.5Re < h < 1.5Re (% of Time)

Slot Region Spatial Coverage

1.5Re < h < 3.0Re (% of Time)

Outer Zone Spatial Coverage

3.0Re < h < 6.0Re (% of Time)

Raised Perigee Orbit

0.0 11.2 20.0 68.7

375 km Perigee Orbit with Orbit Maint.

6.4 9.2 17.4 67.0

375 km Perigee Orbit without Orbit Maint.

6.5 9.2 17.6 66.7

750 km Perigee Orbit

6.2 9.6 17.9 66.4

250 km Perigee Orbit

6.0 8.4 15.8 69.7

Meridian Location

Good Conjunction

(ΔLong. < 15°)

Very Good Conjunction

(ΔLong. < 10°)

Excellent Conjunction(ΔLong. < 5°)

Churchill (94°W) 1584 1837 1584

Alberta Line (110°W)

883 945 1036

Europe (20°E) 0 0 0

Japan (138°E) 0 0 0

Churchill (94°W) 1078 1524 1151

Alberta Line (110°W)

666 848 812

Europe (20°E) 228 396 0

Japan (138°E) 0 0 0

Churchill (94°W) 410 451 418

Alberta Line (110°W)

340 296 266

Europe (20°E) 472 498 496

Japan (138°E) 306 309 304

Churchill (94°W) 713 971 1079

Alberta Line (110°W)

459 564 570

Europe (20°E) 724 264 0

Japan (138°E) 0 0 0

Churchill (94°W) 368 385 418

Alberta Line (110°W)

420 421 362

Europe (20°E) 435 432 358

Japan (138°E) 398 378 408250

km

Per

igee

750

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Per

igee

375

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Per

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Rai

sed

Per

igee

375

km

Per

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ER102618 ORBITALS Orbit Analysis DRAFT May 16 2008

Raised perigee typically >30% more conjunctions with the Churchill and Alberta line than lower perigee orbits.

375 km perigeeNo maintenance5 orbits/2 days

Apogee conjunctions-Alberta line-Churchill line-Alaska station-Europe-Antarctic

Perigee conjunctions-Europe-Japan