(PCW) satellite system - Agence spatiale canadienne

Canadian Polar Communication and
Weather (PCW) satellite system: New
capabilities for mapping Arctic snow and
ice dynamics from Highly Elliptical Orbit
Alexander P. Trishchenko* and Louis Garand
Environment Canada
and the PCW Science Team
* on secondment from the Canada
Centre for Remote Sensing, NRCan
6th EARSeL Workshop
Cryosphere, Hydrology & Climate interactions
February 7, 2011
University of Berne, Switzerland

Outline
• Why satellite system on Highly Elliptical Orbit (HEO) is
needed ?
• Features of new Polar Communications and Weather
(PCW) satellite system under development in Canada
– Orbital configuration
– Planned imager specs
– Products and services
– Status of the project
• International dimension
Page 2 – February 7, 2011

Why HEO system?
• Polar orbiters have been a workhorse of satellite Earth Observation
for decades, but their ability for repeated imagery is limited by
– a) orbital period (~ 100min)
– b) swath width ( ~ 100km-2500km)
– c) clouds (70% cloud fraction on average) for surface applications
• Geostationary satellites (GEO) can provide nearly continuous
imagery, but not over Polar Regions. Practical limit is

Ice motion from MODIS: Northwest Passage
Page 4 – February 7, 2011

Ice motion from MODIS: Northwest Passage
Source: Yi Luo
Canadian Ice Service
Page 5 – February 7, 2011

Ice motion from MODIS: Hudson Bay
Page 6 – February 7, 2011

Ice motion from MODIS: Hudson Bay
Source: Yi Luo
Canadian Ice Service
Page 7 – February 7, 2011

Refresh rate and spatial coverage are
key requirements
• New generation of GEO imagers (ABI/GOES-R,
FCI/MTG, AHI/Himawari)
– 15 min full disk
– 1-5 min regional subsets
• Cloud tracking => improved wind retrievals
• Improved surface observations due to collecting all
possible clear-sky pixels
• Resolving diurnal cycle of clouds, radiation, snow/ice
cover dynamics
Page 8 – February 7, 2011

Improved clear-sky statistics
due to high temporal frequency
(1-day model data for July 1, 2008)
Start: July 1, 2008 3:00UT
Daily mean cloud fraction :
69% (64%)
Mean cloud fraction after
clear-sky compositing :
(every 15min over 24hrs)
34% (32%)
(50 0 N-90 0 N)
Initial clear-sky mask
Accumulated clear-sky mask after 24hrs
clear
cloud
Page 9 – February 7, 2011

WMO vision for HEO satellite system
• World Meteorological Organization (WMO) in its “Vision
for the Global Observing System (GOS) in 2025”
adopted by the sixty-first session of the WMO Executive
Council (EC-LXI) (WMO, 2009) endorsed the concept of
HEO satellite system to improve Earth observations over
polar latitudes;
• The WMO document recommends operational
implementation of visible (VIS) and infrared (IR) HEO
imagers in order to monitor high latitude phenomena
related to winds, clouds, volcanic ash plumes, sea ice,
snow cover, vegetation properties and wild fires with
sufficient temporal resolution (WMO, 2009).
Page 10 – February 7, 2011

Canadian Polar Communication and Weather (PCW) system
• 2-sat system on HEO orbit to provide continuous Arctic
coverage
– Communication payload
– Meteo payload – provision of multi-spectral imagery with
15-min refresh rate
– Space Weather payload
– Additional payloads possible including atmospheric science
applications
• Anticipated to begin operations in 2017
• Project is in Phase A to be completed at the end of
March 2011. Team is working hard to get approval for
phase B.
Page 11 – February 7, 2011

Highly Elliptical Orbit (HEO)
• HEO is not be eccentric… it is to have high eccentricity
of the orbit to achieve continuous Arctic coverage
Earth’s spin axis
z
Apogee
Equatorial plane
Perigee
Descending node
i
H p =a(1-e)
O
ω
ν
l
H a =a(1+e)
Ω
x
Vernal equinox
y
Ascending node
Satellite spends 2x more time above 45 0 with e≈0.5 relative to circular orbit (e≈0)
3x more time above 45 0 with e≈0.75 relative to circular orbit (e≈0)
Page 12 – February 7, 2011

12-hr Molniya orbit
• Molniya (12hrs) orbit is considered as a baseline scenario for
Polar Communication and Weather (PCW) satellite system
due to superior imaging conditions over the Arctic;
• Two satellites in 1 orbital plane (6hrs apart) with 63.4 0
inclination, i.e. 4 apogee points: 95 0 W, 175 0 E, 85 0 E, 5 0 W;
• Critical inclination makes apogee location stable
ω&
=
3
4
J
2
n
⎛
⎜
⎝
2
( 1 − e ) 2
• Rate of change for the argument of perigee ≈0
rE
a
⎞
⎟
⎠
2
5
cos
2
i
−
1
Equatorial plane
Descending node
Perigee
Earth’s spin axis
H p =a(1-e)
i
z
O
ω
ν
l
H a =a(1+e)
Ω
y
x
Vernal equinox
Apogee
Ascending node
Page 13 – February 7, 2011

Some feature of Molniya HEO orbit
vs LEO and GEO orbits
Molniya orbit
MODIS
Terra/Aqua
GEO
Satellite ground track pattern is stable (repeatable), but the Local Solar Time
(LST) of apogee point is drifting. This means that VZA-SZA relationship for
each particular point on the Earth surface is time dependent.
Page 14 – February 7, 2011

Location of apogees and coverage for
PCW system
85 0 E
Location of apogees was
selected to maximize land
mass observations at small
viewing zenith angles
(VZA), i.e. looking close to
nadir over land
175 0 E
5 0 W
95 0 W
Page 15 – February 7, 2011

Spatio-temporal coverage from Molniya
Map of coverage (% of time per day)
zonal mean
58 0 N-90 0 N - 100%
above 55 0 N - >95%
Page 16 – February 7, 2011

-4hrs
Temporal Sequence of Earth Views
-3hrs
0hrs
23.7 0 x 23.7 0 19.2 0 x 19.2 0 15.7 0 x 15.7 0
+4hrs
+3hrs
Page 17 – February 7, 2011

Animation of Arctic coverage: July 1, 2008
(CMC model results at 10-km resolution)
R – B6 1.6µm
G – B3 0.87µm
B – B2 0.64µm
Page 18 – February 7, 2011

Harsh ionizing radiation is Molniya orbit
biggest challenge
High energy trapped protons with E>10Mev are the most dangerous
Page 19 – February 7, 2011

How to optimize HEO orbit ?
One needs to increase the
altitude of the orbit when it
crosses the equatorial
plane (i.e. the altitude of
semi-latus rectum), but to
keep semi-major axis
reasonably low to achieve
better spatial resolution
Optimization leads
to orbit parameters
T=16hr
e=0.55
Page 20 – February 7, 2011

Comparison of radiation conditions
between Molniya, GEO and TAP orbits
3-4 order of magnitude smaller flux
of high energy trapped protons
trapped protons flux essentially
vanishes after ≈7mm AL shielding
after ≈9mm AL shielding TAP orbit
becomes similar to GEO
Page 21 – February 7, 2011

16hrs orbit is very good alternative
candidate for PCW
Three APogee (TAP) orbit
Suggested apogees:
95 0 W; 25 0 E, 145 0 E
Page 22 – February 7, 2011

Zonal mean coverage: 12-hr vs 16-hr orbit
Page 23 – February 7, 2011

Viewing Earth from TAP(16-hr) orbit
Animation over 48hr period with 15-min steps
Satellite #1 Satellite #2
Page 24 – February 7, 2011

PCW Imager Specifications
Band
No.
subgroup
Wavelength
(microns)
Heritage
Priority
GSD (km)
Goal Max
Main applications
1
VNIR
0.45-0.49
ABI, FDHSI
1
0.5 1.5
Surface, clouds, aerosols
2
0.59-0.69
ABI, FDHSI
1
0.5 1.5
Wind, clouds, ice mapping
3
0.704-0.714
MERIS-09
2
0.5 1.5
Water quality, chlorophyll
4
0.85-0.89
ABI, FDHSI
1
0.5 1.5
Wind, aerosols, vegetation
5
SWIR
1.04 – 1.06
SGLI SW1
2
1.0 3.0
Snow grain and clouds
6
1.37-1.39
ABI, FDHSI
2
1.0 3.0
Cirrus detection
7
1.58-1.64
ABI, FDHSI
1
0.5 1.5
Snow-cloud distinction, ice cover
8
2.22-2.28
ABI, FDHSI
1
1.0 3.0
Aerosol, smoke, cloud phase
9
MWIR
3.80-4.00
ABI, FDHSI
1
2.0 3.0
Fog, fires, ice/cloud separation, wind, cld.phase
10
5.77-6.60
ABI, FDHSI
1
2.0 3.0
Wind, high level humidity
11
6.75-7.15
ABI, MTSAT
1
2.0 3.0
Wind, mid level humidity
12
7.24-7.44
ABI, FDHSI
1
2.0 3.0
Wind, low level humidity
13
LWIR
8.30-8.70
ABI, FDHSI
1
2.0 3.0
Total water, cloud phase
14
9.42-9.80
ABI, FDHSI
2
2.0 3.0
Total ozone
15
10.1-10.6
ABI, FDHSI
2
2.0 3.0
Cloud, surface, cirrus
16
10.8-11.6
ABI, HIRS
1
2.0 3.0
Cloud, SST, ash
17
11.8-12.8
ABI, FDHSI
1
2.0 3.0
Ash, SST
18
LIRCO2
13.0-13.6
ABI, FDHSI
1
2.0 3.0
Cloud height
19
13.5-13.8
MODIS,HIRS
2
2.0 6.0
Cloud height, low level temperature
20
13.8-14.1
MODIS,HIRS
2
2.0 6.0
Cloud height, mid level temperature
21
14.1-14.4
MODIS,HIRS Page 25 – February 2 7, 2011 2.0 6.0
Cloud height, high level temperature

Snow grain size
1.04-1.06µm channel was selected: Band 5
Page 26 – February 7, 2011

Angular sampling from Molniya HEO
SZA-VZA sampling VZA-RAZ sampling
Orbit precession around direction to the Sun: 1.14deg/day.
Complete cycle is ~ 10.5 month (360 deg)
Rich angular sampling from HEO Molniya orbit => better observations of angular
anisotropy of the Earth radiation field than for polar orbiters and GEO
Page 27 – February 7, 2011

Preliminary list of products from PCW
CATEGORY
PRODUCT
Repeat
Cycle
Latency
COMMENT
Imagery
Level 1C imagery
Level 2 imagery
15 min
15 min
15 min
30 min
Calibrated, mapped to standard grid (15 min
refresh)
Composite of 2 satellites
AMV: Atmospheric Motion
Vectors
1 hour
1 hour
Latency is w.r.t. oldest image of triplets/duos
used for tracking
Cloud mask
15 min
30 min
Important for direct assimilation of radiances
Priority 1 - Near Real
Time Level 2
products derived
from Level 1C
Cloud height, amount,
emissivity, temperature
Volcanic ash height (optical
depth)
15 min
15 min
30 min
30 min
Important for AMV
When active. Done at Dorval volcanic ash
advisory center. Could develop a SO 2
product
as well.
Fog and surface visibility
15 min
30 min
Forest fires. Hot spots
3 hours
1 hour
Product elaborated either, at CFS and/or
another governmental entity
Page 28 – February 7, 2011

Preliminary list of products from PCW
CATEGORY
PRODUCT
Repeat
Cycle
Latency
COMMENT
Snow/ice mapping (cover
and depth)
6 hours
6hours
Derived from 15 min. Resolution 2 km. May
include snow grain size.
SST: sea surface
temperature
1 hour
2 hours
Resolution 4 km
Priority 2 - Level 2/3
(see note below)
LST: land surface
temperature
Surface albedo
1 hour
6 hours
2 hours
6 hours
Resolution 4 km
Resolution 10 km. Could be done at another
governmental entity
Aerosol optical depth
3 hours
6 hours
Resolution 10 km
Atmospheric stability index
1 hour
1 hour
Resolution 10 km
Aircraft icing threat
1 hour
15 min
Resolution 10 km
Total ozone
1 hour
1 hour
Resolution 10 km
Page 29 – February 7, 2011

Preliminary list of climate products from PCW
CATEGORY
Priority 2 - Level 3
climate essential
variables – Not
elaborated at
EC Dorval
Archive Products
PRODUCT
NDVI: Normalized Difference
Vegetation Index
FPAR
LAI: Leaf Area Index
Radiative fluxes
Land surface emissivity
Repeat
Cycle
1 day
1 day
1 day
1 hour
1 day
Latency
Resolution 4km
Levels 0, 1C and 2 are archived forever at CMC, and Level 1B for 5 years. In addition rotating archive of
Level 0 at ground receiving station.
Note :Level 2 products are retrievals made from Level 1C. Level 3 products defined at a coarser resolution. Surface parameters
are only available in clear air (mask =0) or when the sun angle allows. In areas devoid of observations, the pixels are either
left blank or replaced by a previously obtained value.
1 day
1 day
1 day
1 day
1 day
COMMENT
Resolution 1 km
Fraction of Absorbed Photosynthetically
Active Radiation. Resolution 1 km
Resolution 2 km
Resolution 10 km (SW, LW at surface and
TOA)
Page 30 – February 7, 2011

PCW Mission development in Phase A
Lead
Canadian Space Agency
Partners
Environment Canada
Dept National Defense
User and Science Team (U&ST):
Environment Canada (EC),
Dept. of National Defense (DND),
Natural Resources Canada,
Canadian Coast Guard,
Transport Canada, NavCanada,
Dept. of Indian and Northern Affairs,
Gov. of Nunavut
And other gov. agencies
International Section of U&ST
URD
Industrial Team:
MDA (prime),
Com Dev,
ABB Bomem,
Magellan/Bristol Aerospace,
ADVANTECH,
SED,
TELESAT
Page 31 – February 7, 2011

International Engagement
• NOAA, NASA, EUMETSAT, FMI, SHMI, ESA, ECMWF
participation in International section of User & Science Team
• NOAA
– Contributions to PCW to be explored through EC-NOAA
MOU, and Canada-US Agreement on space technology.
• Russia Arktika Mission
– liaison through WMO Focus Group on HEO and bi-laterally
– agreement in principle to coordinated missions – e.g., orbital
configuration, imaging frequency, etc
Page 32 – February 7, 2011

Conclusions
• HEO satellite system offers unique opportunity for continuous observations
of polar regions and snow/ice dynamics;
• Canada is planning to launch the Polar Communication and Weather
(PCW) 2-sat system with operations beginning around 2017;
• Phase A has been extended until the end of March 2011. Team is working
hard to move project into Phase B;
• 21 channel imager with spatial resolution from 0.5km to 2km will provide
continuous observations over the Arctic with refresh rate 15minutes;
• The set of operational products and Essential Climate Variables (ECVs) will
be produced to be compatible with NOAA GOES-R ABI + some extras;
• Observations from HEO orbit provide very rich geometry that should lead to
improving the quality of atmospheric and surface products;
• PCW data will be included as part of Global Space-Based Inter-Calibration
System (GSICS) to ensure the quality of data products.
• Proxy data are available for at 35km (globally) and 10km (Arctic) and 15min
time steps for July 1, 2008:
– ftp server: depot.cmc.ec.gc.ca; directory: upload/cmdd/pcw/.
– Login as anonymous user
Page 33 – February 7, 2011

References
• Kidder, S.Q. and T.H.Vonder Haar, 1990: On the use of satellites in
Molniya orbits for meteorological observation of middle and high
latitudes. J. Atm. Oceanic Tech., 7, 517-522
• Trishchenko, A.P., and L.Garand, 2011: Spatial and temporal
sampling of Polar Regions from two-satellite system on Molniya
orbit. J. Atmos. Oceanic Tech., 45pp. In press.
• 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 . J. Atmos. Oceanic Tech.,
to be submitted.
• WMO, 2009: WMO vision for the GOS in 2025. WMO (CM-9)/Doc. 8
(14.I.2009). Port of Spain. Trinidad and Tobago. 19pp. [Available at:
http://www.wmo.int/pages/prog/sat/meetings/documents/cm9_Doc_
08_GOSVision2025.pdf]
Page 34 – February 7, 2011