Platform Technologies for Space Atmosphere and Climate â€“ A

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


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


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


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


6

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


7

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.


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.


Tropopause study

9

The lapse rate tropopause (LRT)

The cold point tropopause (CPT) is located at the minimum vertical temperature


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.


11

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.


12

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)


13

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.


10-Jun-13 14

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.


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


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.


10-Jun-13 ASSC 2012 17

IRI-2007 (1200LT, Long = 225 deg E)

Winter Summer


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.


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


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


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


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


Thank you

Platform Technologies for Space Atmosphere and Climate â€“ A

Documents

Transcript of Platform Technologies for Space Atmosphere and Climate â€“ A