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