GSCIS-EP-12. June 1, 2012
HEO, LEO, GEO and GSICS
Alexander P. Trishchenko
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GSCIS-EP-12. June 1, 2012
Outline
HEO concept to continuously observe the Arctic
• Objectives and history
• Radiation environment
• Orbital issues
HEO-GEO intercalibration
HEO-LEO intercalibration
Summary
HEO - Highly Elliptical Orbit
PCW – Polar Communication and Weather,
Canadian HEO project
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LEO temporal coverage
GSCIS-EP-12. June 1, 2012
t
t
Number of satellites N to achieve refresh rate t
at latitude circle 
t
t
t
t
t
t
Image from LEO system is obtained as a result
of orbital motion and cross-track scanning
t

cos  sin i
~
N  N ( h,  )
t
where
~
N ( h,  )   2
( R E  h)1.5


h
) sin  ]   
GM arcsin[(1 
RE


h - orbit altitude

th
a
Sw
β – max scan angle
RE – Earth radius
GM – gravitational constant
i – orbit inclination
Trishchenko & Garand, CJRS, 2012.
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GSCIS-EP-12. June 1, 2012
HEO goal - continuous Arctic coverage
2 satellite HEO system can provide continuous
coverage above 600N with VZA <700
• 23(34) LEO (JPSS-like) satellites would be needed to achieve
15(10)-min image refresh rate at 600N,
Zonal mean 2-sat HEO coverage
# of LEO satellites as function of 
at 60o latitude
t
Number of sats
20 min - 17 LEO satellites
15 min - 23 LEO satellites
10 min - 34 LEO satellites
5 min - 68 LEO satellites
LEO satellite orbits are
similar to NOAA/JPSS
100% (i.e. continuous coverage) above 600N
can be achieved from 2-sat HEO system
Trishchenko et al, JTECH, 2011
Trishchenko & Garand, CJRS, 2012.
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GSCIS-EP-12. June 1, 2012
Molniya (12-h) orbit is a popular HEO choice
Harsh ionizing radiation is Molniya’s orbit biggest challenge
How can we solve the radiation problem without affecting HEO goals ?
High energy trapped protons with E>10Mev are the most dangerous
Trishchenko et al, JTECH, 2011
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GSCIS-EP-12. June 1, 2012
Requirements (orbit optimization criteria)
1) Arctic Coverage with 2-sat system:
•
•
•
Altitude distribution of protons at equator
100% above 600N
>95% above 550N
>80% above 500N
2) Radiation Environment
Earth’s spin axis
3) Spatial resolution or altitude range:
Apogee <45,000 km – to maintain reasonable
spatial resolution (25% worse than GEO case)
a(
1+
e)
•
Descending node
4) Orbit maintenance
•
Yellowknife: 62.4422220N, -114.39750E
6) Small ground speed during imaging
period – desirable feature
Trishchenko et al, JTECH, 2011
Equatorial plane
Perigee
y
O

a(
1e)
5) Reception from 1 satellite station is
desirable
i
p=
Stay close to critical inclination to minimize
perigee rotation and orbit maintenance
H
•
Apogee
z
a=
•
•
Avoid trapped energetic protons (>10Mev for
sure, but as much as possible)
As close as possible to GEO
In any circumstance, PCW is a subject to solar
and cosmic particles due to open magnetic lines
in the polar region
H
•

Semi-latus rectum
l

Ascending node
x
Vernal equinox
Rate of change for the argument of perigee
2
3
rE  5 cos 2 i  1

  J 2 n  
2
4
 a  1  e 2 
.
=0, when i=63.40 - critical inclination
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GSCIS-EP-12. June 1, 2012
HEO orbit optimization
Radiation limit
Tundra 24-h
Molniya 12-h
TAP (16-h)
Apogee: 43,500 km
Spatial resolution limit
Three Apogee - TAP
16-h HEO (e=0.55)
as optimal choice
Trishchenko et al, JTECH, 2011
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GSCIS-EP-12. June 1, 2012
Orbit comparison (2-sat constellation)
Molniya (12-h)
Apogee: 39,800 km
TAP (16-h)
Apogee: 43,500 km
850E
250E
50W
1750E
1450E
Tundra (24-h)
Apogee: 48,300 km
Yellowknife
Yk
±4hrs
±5hrs
950W
950W
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GSCIS-EP-12. June 1, 2012
Comparison of zonal mean spatial coverage
16 hr/day of imaging per satellite
Data reception at Yellowknife
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GSCIS-EP-12. June 1, 2012
Satellite altitude for various orbits
Height at 40 N (central US)
TAP: 30,000 km
Molniya: 19,500 km
24-h: 41,200 km
For TAP 95 W apogee
path, data reception at
Yellowknife starts at about 33 N
(height of ~27,000 km,
5.3 h to apogee)
For Molniya, reception starts at
About 45 N (H= ~22,500 km)
4.0 h to apogee
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6h
Earth views from TAP orbit
4h
GSCIS-EP-12. June 1, 2012
2h
0h
14.50
17.90
15.30
26.20
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GSCIS-EP-12. June 1, 2012
Some GEO and HEO (TAP 16-h)
Shaded areas show collocation between GEO and HEO
VZA<50; RAZ<100
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GSCIS-EP-12. June 1, 2012
Some GEO and Molniya (12-h)
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GSCIS-EP-12. June 1, 2012
NPP/Suomi and HEO/TAP(16-h)
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GSCIS-EP-12. June 1, 2012
NPP/Suomi and HEO/Molniya (12-h)
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GSCIS-EP-12. June 1, 2012
Matching pairs TAP & NPP
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GSCIS-EP-12. June 1, 2012
Temporal sequence of matching pairs
TAP & NPP
Collocations between
HEO and NPP can
happen every day
VZA<50, RAZ<100
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GSCIS-EP-12. June 1, 2012
Conclusions
PCW 2-satellite HEO system is significantly more efficient for observing Polar
Regions than constellation of LEO polar orbiters;
17/23/34/68 LEO satellites are required at 600N to provide an imagery updated
every 20/15/10/5 min, respectively. Corresponding numbers in the vicinity of the
North Pole are 5, 7, 10 and 20.
Unique quasi-geostationary capability of HEO system over polar latitudes provides
good opportunity for satellite intercalibration with polar orbiters and some
opportunities with GEO.
References
Trishchenko, A.P., L.Garand, L.D.Trichtchenko, 2011: Three apogee 16-h highly elliptical orbit as optimal choice
for continuous meteorological imaging of Polar Regions. Journal of Atmospheric and Oceanic Technology. Vol.
28(11), pp. 1407-1422.
Trishchenko, A.P., and L. Garand, 2011. Spatial and temporal sampling of Polar Regions from two-satellite
system on Molniya orbit. Journal of Atmospheric and Oceanic Technology, Vol. 28(8), pp. 977-992.
Trishchenko, A.P. and L.Garand, 2012: Observing Polar Regions from space: Advantages of a satellite system
on a highly elliptical orbit versus a constellation of low Earth polar orbiters. Canadian Journal of Remote Sensing.
Vol. 38, No. 1, pp. 12-24.
Acknowledgements
Contributions from Louis Garand (EC) and PCW team are gratefully acknowledged.
SPENVIS tool was used for space environment radiation analysis
MODIS “blue-marble” imagery was used in simulations
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