platform technologies for space atmosphere and climate – a
TRANSCRIPT
SPACE Research Centre
SPACE Research Centre
School of Mathematical and Geospatial Sciences
RMIT University, Australia
www.rmit.edu.au/space
Platform Technologies for Space
Atmosphere and Climate – A Project from
the Australian Space Research Program
Robert Norman
SPACE Research Centre
Outline
15-May-2013 ICGPSRO 2013 2
1. Project Overview
2. RMIT University SPACE research centre
3. RMIT RO Capabilities
4. GPS RO for Meteorology in Australian region
5. Tropopause study
6. New Ray Tracing algorithms
7. Conclusion
SPACE Research Centre The RMIT-led ASRP project
• Platform Technologies for Space, Atmosphere and Climate
– $7.5m (~50% cash, $2.85m from Australian government)
– Develop technologies for space research, including space/debris tracking and navigation, weather and climate monitoring, and atmospheric modelling.
– make a significant contribution to our space industry, particularly in the satellite navigation, positioning and tracking; space tracking; meteorological services and space weather; and future planning, design, launch and operation of Australian micro and nano-satellite missions.
• Consortium members
– Prof Kefei Zhang, RMIT University (Leading)
– Prof Peter Teunnisen, CUT (Federation Fellow)
– Prof Chris Rizos, HoS of SSI, UNSW (President of IAG)
– Profs John Le Marshall / Y Kuleshov , Bureau of Meteorology
– Drs Jizhang Sang / Craig Smith, Electro Optic Systems Space System
– Mr Graeme Hopper, GPSat Systems Australia Pty Ltd
– Prof Yue-an Liou, National Central University/Taiwan
– Mr Howard Diamond, World Data Center for Meteorology/NOAA
– Domestic vs international: 6+2
– HE, Gov, Industry: 3(+1)+1(+1)+2
SPACE Research Centre
The SPACE research centre
•SPACE – Satellite Positioning for Atmosphere, Climate
and Environment
•Officially launched on Friday, 19 November 2010 by
–Prof Margaret Gardner – President of RMIT University
–Dr Greg Ayers, CEO and Director of The Australian Bureau of
Meteorology
–Prof Daine Alcorn, Vice President of RMIT – R&I
SPACE Research Centre
RMIT SPACE research Centre
Aims
–The Centre focuses on the development of Platform
Technologies for Space, Atmosphere and Climate, including
new methods, new algorithms and frontier technologies for
satellite positioning, navigation and timing (PNT),
space situation awareness (including space object/debris
monitoring and tracking),
space weather and
climate change modelling.
~25 researchers
SPACE Research Centre
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Project Overview
WP 1 (CUT, GPSat) Ambiguity Resolution, Precise Positioning, Navigation/Guidance
WP 2 (EOSSS, RMIT) Real Time POD Platform Space Tracking
WP 3 (EOSSS, RMIT) Mathematical Modelling of debris environment
Precise Positioning, Navigation & Tracking
WP 5 (RMIT, EOSSS, UNSW, NCU, GPSat) Space-borne platform for atmosphere & space weather
WP 4 (RMIT, UNSW, BoM) Ray tracing, Ionospheric gradients, Multi-path, birefringence, Ionospheric drift and atmospheric winds
Atmosphere and Space Weather
WP 8 (GPSat, RMIT) Space weather events on GNSS
WP 7 (UNSW, CUT, RMIT, EOSSS, GPSat, BoM, NCU) Next generation GNSS, Next generation geo-environmental satellite systems
New Generation Satellite Systems
WP 6 (BoM, RMIT, NCU) Meteorological and Environmental Platforms (Multi-sensor satellite remote sensing for climate and tropical cyclone monitoring)
Weather and Climate
15-May-2013 ICGPSRO 2013
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RMIT RO Capabilities
• GPS Radio Occultation (RO) for Climate monitoring and weather forecasting
– From our research GPS RO data is now used operationally in the BoM Numerical Weather Prediction (NWP) system
• GPS RO to study severe weather events
– Tropical Cyclone analysis
• GPS RO Meteorology – Modeling wet refractivity in the troposphere
• GPS RO quality control and error analysis – Ionospheric correction - Ionospheric residual error analysis – Statistical optimization to improve RO atmosphere profiling
• GPS RO for space weather monitoring
– Detection of Equatorial Plasma Bubbles
• Numerical and Analytical 3-D ray tracing techniques (3D-SMART)
– Simulate GPS RO signal paths.
SPACE Research Centre
RO Observations on Australian Regional
Forecasts
• Study dataset
– Trials conducted using GPS RO profiles from COSMIC, MetOp and GRACE
• Data assimilation
– Into global Australian Community Climate Earth System Simulator
(ACCESS-G)
– 4-D variational assimilation (4DVAR) method to provide forecasts to five
days ahead - assimilate GPS RO refractivity and bending angles
• Results
– the temperature accuracy of these forecasts has been compared to
forecasts generated without the use of the radio occultation data
– The forecasts using radio occultation data have been found to be improved
in the lower, middle and upper troposphere
– The magnitude of the improvement in the Australian region was around 3
points in AC or 8 hours at five days near the surface (MSLP) and in
addition there was clear improvement at standard levels through the
troposphere.
SPACE Research Centre
Tropopause study
9
The lapse rate tropopause (LRT)
The cold point tropopause (CPT) is located at the minimum vertical temperature
SPACE Research Centre
Tropopause study
10
This figure highlights the
radio occultation and
radiosonde CPT
temperatures in six
latitude bands over the
four year period from
2007 to 2011.
It is noted that the CPT
temperatures calculated
using these two datasets
are generally consistent.
The largest difference
located at the polar and
southern middle latitude
regions. In other regions,
the differences are quite
small.
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Ray Tracing
The aim of this study is to develop new and improved ray tracing
algorithms
To use the new ray tracing tool to investigate the effects of the ionosphere and atmosphere on GNSS signals.
This is important for improving RO ionosphere and atmosphere retrieval techniques and to improve accuracy in GNSS positioning and navigation.
The focus of this study is on GNSS RO propagation where we use numerical and analytical ray tracing based on geometrical optics to simulate GPS to LEO signal paths.
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Ray Tracing Techniques
There are two main forms of ray tracing and they are:
Numerical ray tracing Generally requires a form of Haselgrove equations where these equations are integrated at each step along the ray path.
Analytical ray tracing
Analytical ray tracing as its name suggests uses explicit equation to represent
the ionosphere and lower atmosphere as well as the ray parameters.
This technique is much quicker than numerical ray tracing, but in the past has
been restricted to much simpler ionospheric models.
We have developed a new 3-D Anaytical ray tracing algorithm (3D-SMART)
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Refractivity in the Ionosphere
The Appleton-Hartree equation which is sometimes referred to as the Appleton-Lassen equation describes the refractive index in the ionosphere.
n is the complex refractive index in the ionosphere
X is proportional to electron density
Y is proportional to magnetic field (y=0, No magnetic field(NF))
Z is proportional to collision frequency
'+' sign represents the "ordinary mode," and
'-' sign represents the "extraordinary mode."
* Collision frequency ignored i.e., Z=0. Dealing with Real refractive index.
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Earth’s Ionosphere
Examples of the vertical layer structure in the ionosphere
The ionosphere is the region from about 60 km to 1500 km in altitude, where
the solar radiance produces a partially ionized plasma of mostly H+ and He+
above 1000 km, O+ from 300 to 500 km and molecular ions (NO+, O2+, N2+)
below 200 km.
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10-Jun-13 ASSC 2012 15
Refractivity in the Stratosphere and
Troposphere
N is typically 310 N-units at sea level
h/H)(0eNN
N - refractivity (N-units)
P - pressure (hPa)
T- temperature (K)
e - partial pressure water vapour (hPa)
n - refractive index
No - refractivity sea level ~310 N-units
h - altitude (km)
H - scale height ~ 7.4 km
SPACE Research Centre
10-Jun-13 ASSC 2012 16
Ray Tracing Program
Traces ray tubes from GPS to LEO satellites
Our ray tube technique involves integrating 18 differential equations simultaneously at each step along the ray path
International Reference Ionosphere (IRI-2007) model
Can trace ordinary (O), extraordinary (X) as well as the no field (NF) ray paths
Program has 2 choices for magnetic model
- Earth centred dipole magnetic field model
- POGO 68/10 magnetic field Legendre model (IRI-2007)
Homing-In capability
Able to trace ray paths and determine group path, phase path, range, height, transmitted and received elevation and azimuth angles as well as the divergent signal strength.
SPACE Research Centre
10-Jun-13 ASSC 2012 17
IRI-2007 (1200LT, Long = 225 deg E)
Winter Summer
SPACE Research Centre
10-Jun-13 ASSC 2012 18
GPS L-Band Propagation
Height versus Refractivity for GPS L1 and L2 frequencies using IRI-2007, with input longitude 225.28º E, latitude 11.85º N, year 2010, day 267 and 1200LT.
perigee Reflection
height
hmF2
The ionosphere is a dispersive medium,
thus the refractivity depends on the
frequency of the propagating wave.
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10-Jun-13 ASSC 2012 19
GPS-LEO propagation
•GPS satellite located at height 20,200 km, -50.0º N, 225.28º E.
•Northward propagation.
•Inputs for the IRI 2007 model were year = 2010, day of year = 267 and 1200LT.
NF – No field
X – extraordinary mode
O – ordinary mode
SS – spherically stratified
50
150
250
350
450
550
650
750
-2 -1 0 1 2
Reflection height - Line of sight height [km]
Refl
ecti
on
heig
ht
[km
]
L2-NF
L2-X
L2-O
L2-SS
0
5
10
15
20
25
30
35
40
45
50
-2 18 38 58 78
Reflection height - Line of sight height [km]
Refl
ecti
on
heig
ht
[km
]
L2-NF
L2-X
L2-O
L2-SS
8.7
8.75
8.8
8.85
8.9
20.2 20.4 20.6 20.8
Reflection height - Line of sight height [km]
Refl
ecti
on
heig
ht
[km
]
L2-NF
L2-X
L2-O
L2-SS
SPACE Research Centre 3D-SMART
-50
-40
-30
-20
-10
0
10
0 10 20 30 40 50 60
La
tera
l D
isp
lac
em
en
t[k
m]
Elevation angle [deg]
ART
NRT
0
10
20
30
40
50
60
70
80
0 10 20 30 40 50
Elevation angle [deg]
La
tera
l D
isp
lac
em
en
t [
km
]
ART
NRT
SPACE Research Centre
Conclusion
•Satellite technologies provide a great platform for
Earth observations and then enhance many studies
such as meteorology, atmosphere and climatology
•We have developed 3-D numerical and analytic ray
tracing algorithms
•The ASRP project offers a great platform and more
exciting opportunities for research and international
collaboration
•We are keen to extend our international collaboration
SPACE Research Centre
Thank you