The Variety of New Commercial Aircraft Sensors

for Weather, Climate, and Air Quality Applications:

Accuracy and Use

Dr. Rex J. Fleming

SpectraSensors, Inc.

May 16, 2006

• Observational accuracy has not kept pace with advances in computers and modeling/analysis capabilities

• Platforms that move on our planet can potentially make enormous contributions with continuous measurements in space/time.

• If measurements are extremely accurate, then valuable in their own right and make satellite data (conventional or GPS related) more valuable (via Kalman filter, 4DDA,

or other optimization methods)

Time is right for a paradigm shift in observations for atmospheric science

“Accurate” Environmental Data will Escalate in Value over Time

• Weather and climate already impact about 1/7 of a 7 trillion dollar USA economy

• Consider growth in 7 major socioeconomic areas:

Energy: largest single issue for USA and the world Water: fresh water is 2nd largest issue for society Food: average population increase only 1.1%/yr vs 1.7% past 30 yr Transportation: major growth area (aviation impact already huge) Weather impacts: (human health, safety, etc) vs 1.1% pop. growth Climate change (global warming uncertainty vs energy conflict) Construction and other: Population growth 1.1%/year

• Value of “accurate” environmental data will double approximately every 6-8 years in future.

Commercial Aircraft create a paradigm shift in atmosphericobservations – for the benefit of aviation and society

Radiosondes: balloon launchs (2/day) have high vertical resolution; poor space and time resolution (500km, 1/day in many countries);do not serve high space /time requirements of aviation needs

Satellites: global cloud images very useful, but profile data inaccurate; poor vertical resolution on T and q; little information from cloud winds

Commercial aircraft: space/ time coverage from moving platformsprovide unique data blend that helps merges all these data setsinto a unifying whole; winds and water vapor more accurate

15 countries have organized national commercial aircraft programs; 18 more countries have programs in various stages of implementation

The Next Generation Air Transportation System (NGATS) will dependon the aircraft measurements (commercial & possibly general aviation)

This Presentation Covers Three types of Sensors (all same architecture)

2nd generation Water Vapor Sensing System (WVSS-II)

-- WVSS-II (current for commercial jets) in USA and Europe

-- WVSS-III for turboprop a/c and all mobile platforms below 25,000 ft

-- Modified WVSS-II for upper troposphere and stratospheric research (Herriott cell inside; same size, but more expensive)

Mobile Temperature Sensor (MTS) for better temperature from a/c andother mobile platforms

Quantum cascade (QC) lasers for atmospheric trace gases

Emergence of mobile platforms [commercial aircraft (jets and turboprops), helicopters, unmanned aerial vehicles (UAVs), etc.]

driven by:

Convenience – mesoscale coverage in USA, over ocean with satellite communications, difficult/dangerous regions via UAVs

Sensor accuracy – dramatic turn for the better with new technology

Demand for more accurate data – socioeconomic demand is accelerating

Water vapor from mobile platforms

History: WVSS-I

Results and why RH by thin film rejected: www.joss.ucar.edu/wvss/

Why WVSS-I (RH sensor) Abandoned by FAA and NOAA/OGP

4 years of flight tests with UPS [Vaisala thin film sensor–best of radiosondes – has following known problems in measuring relative humidity (RH)] -- difficult to calibrate at very low and high RH values -- calibration changes over time -- sensor response time is very slow at cold temperatures -- sensor reads well over 100% when wet; cosmetic fix; takes time to dry

Mach effect on aircraft bad for RH measurement (not for mixing ratio or dew pt.) -- amplifies sfc random error (5%) by factor: (3) for turboprops (17) for jets

Found large changes between aircraft to aircraft over time -- limitation of thin film – each manufactured lot is different, and within each lot each radiosonde has to be calibrated individually -- results show average lifetime 6 months (based upon loss of sensitivity at upper levels)

European Project MOSAIC (Measurement of Ozone by Airbus In-service Aircraft) -- 10 year effort of recording ozone and water vapor (using Vaisala thin film sensor) produced over 2500 over-ocean flights with 140,000 hours of data -- had to recalibrate the Vaisala sensor every month (Herman Smit, Germany)

Error analysis: Mach Number Effect

z:/fleming/vgraphs/Error analysis.ppt

If Mach # = 0.8, Ts = -60C = 213.15K

then:Tprobe = Tstatic (1 + 0.2M 2) = Tstatic (1.128) = 240.43

Pprobe = Pstatic (1 + 0.2M 2) 3.5 = Ps (1.524)and:

es, s (213.15) = 1.76

es, p (240.43) = 38.41

and from RHstatic = RHprobe (es,probe / es,static ) (Pstatic / Pprobe )

RHstatic / RHprobe = (es, probe/es, static) (Pstatic/Pprobe)

= (38.41/1.76) / (1.524) = 14.32

I = intensity at detector I0 = initial intensity

σ n L = absorbance

= α

WVSS-II Sensor Technology: absorption spectroscopy – transmission of laser light through absorbing gas ( diode laser @ 1.37 micron)

I = I0 exp ( - σ n L )

I0

n = number density of gas

L = path length

σ = molecular absorbing cross section = σ ( μ P T )

I

Photo: WVSS-II Air Sampler

Figure 2. Cross section of complete sampler

Turbulence enhancer

Cylindrical sampling tube

Inertial separator (inside, see Fig. 3)

Aircraft skin

8.89 cm

24 cm

WVSS-II on UPS B-757

Installed System Photos

WVSS-II Air Sampler

Open Path Sensor

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• Air Sampler: Flush mounted / low drag / no heater required• Diode laser, 20 year life, telecommunications standard• System weight (electronics box, cables, air sampler) < 7 lbs• Overall Box Dimensions 5.0” x 9.0” x 3.1”

WVSS-II on UPS B-757

Key Events in Operational WVSS-II Product HistoryFAA Certification for B-757 cargo aircraft 12/04

UPS installation of 25 units 3/05 to 6/05

Early results (all on internet in real time) -- 3 of 4 errors proven fixed on subsequent installations -- 4th error fix proven in lab (being certified)– heated hose -- all units retrofitted after certification

WVSS-II vs radiosonde in U. of Wisconsin tests 6/05 -- conducted by W. Feltz and R. Petersen

Six units shipped to Germany for A320 certification 3/06

Airbus visit to SpectraSensors for final evaluation 5/06 -- European AMDAR requested Airbus consider the WVSS-II for all Airbus aircraft (considerable exchange) -- visit by Airbus staff for final check of manufacturing ability, quality control, and meeting schedules for deliveries

Laser

Detector

Simple Optical Layout of WVSS-II H2O Sensor

(not to scale)

Mirror

Thermal Block

12 cm each way

24 cm optical absorption pathlength for measurements

Note that there is a 0.5 cm path within optical head

1st Hardware change: Remove leak in optical head

First 11 aircraft carried surface water vapor aloft

Problem identified and solution found:

-- profile comparison with radiosondes great, but some a/c always had 100% RH in upper trop. (most distressing because every decision has been driven to obtain accuracy in this very poorly measured portion of the atmosphere).

-- connector to back of optical head was not truly hermetic allowing vapor behind a 1.0 cm path (compared to true measurement over a 24 cm path).

-- natural gas water vapor sensors of SSI have better connector and 4X more desiccant in optical head (field proven 3+ years of lifetime)

-- solution two fold: source found for true hermetic versions of same connector (tests indicate desiccant would last 200 years) and simple design changes in optical head allow 6X more desiccant.

2nd hardware change required: heated hoses

Had debate three years ago about descent into very warm and humid conditions – would condensation be an impact (system or data) ?

Impact issue was more about the system rather than the data

-- heated hose was considered rather more complicated and system would flush any water on next ascent taxi

-- now appears that the condensation does pull sufficient water vapor from the air sample to lower the mixing ratio (despite the fact that 2500 Joules per gram of water are released as heat to help reduce the condensation).

Solution is same easy solution used by Randy May for NASA: same company makes heated hoses with a controller.Circuit keeps measurement cell at 35 C.

The German Weather Service working with Lufthansa and Airbus will fund the certification of the A320 family of a/c (A319, A320, A321)

The first 10 WVSS-II units will go on new A320 aircraft to be delivered to Lufthansa (5), Air New Zealand (1) Jet Star –Australia (2), and South African Airlines (2)

Herman Smit (scientist with MOSAIC project has been testing the WVSS-II Electronics box in his lab – if they like, they will certify for A340 and put on 6-8 MOSAIC aircraft

The European AMDAR group has asked Airbus to consider the WVSS-II as an optional product for all of their aircraft (they have come to SpectraSensors with detailed questions and are still evaluating)

Summary of European Activity Concerning WVSS-II

Temperature from mobile platforms

Commercial Aircraft measurements of atmospheric temperature

8 years ago I first heard about problem – Qantas B-747 (3 sensors)

4 years ago I began thinking about the problem – subliminally

2 years ago I solved problem ,conceptually, and verified via complex simulations that it would work

6 months ago Randy May and I proved the concept at the U. of Washington wind tunnel

While I believe the solution is proven by wind tunnel results and simulations, you and others will believe it only after actual flight tests in the next 6-8 months – of course!

Today, you will hear some detail, not all; fully patent protected

Commercial Aircraft measurements of atmospheric temperature

TT = TS ( 1 + 0.2 M 2 ) Measurements are:

Indirect: avionics measure TT not TS (which we want)

Affected by heated probe: outside a/c skin boundary layer, therefore FAA requires the Total Air Temperature (TAT) probe be heated

Intrusive: measurement affected by environment over time--------------------------------------------------------------------------------------------

Solution: Measure TS directly

Measure TS within boundary layer (no heater); isolate effect of friction and model that effect via singular value decomposition (SVD)

Imbed sensors (2) within walls (5/1000 of inch) protected from environment

Four Requirements for a Successful Flush Mounted Temperature Sensor

Location on fuselage with reasonably laminar flow

Sensor housing thermally shielded with insulating gaskets (from external heat source (sun) and internal heat sources)

Friction effects (thus isolated with above shielding) produce temperature increase modeled with a polynomial in Mach Number:

ΔTF = A1 + A2 M + A3 M2 + A4 M3

Model parameters (AK) determined from powerful Singular Value Decomposition and additional optimizing proprietary software

• Sensor Systems TAT sensors are the industry standard – all Boeing aircraft – all Airbus aircraft – all Canadair jets – all Gulfstream jets – all Embraer regional jets – all US Military aircraft

Problems with TAT probes (Our fixes)1) Accuracy (0.3 is expected error: 2 to 3 times better)

at best, 0.6 to 0.8º accurate large variability seen (random errors and biases) changing calibration (birds, other factors)

2) Probe heater (no heater required) largest failure mode = delay time, repair costs limits temperature accuracy

3) Probe drag (far less drag) additional fuel costs = approximately $3M per year

for 8000 aircraft in USA

4) Probe’s radar cross section (far less cross section)Military already seeking flush mounted versions of TAT and pitot tube

TT = TAT TS = SAT TM = measured total temperature TR = recovery temp

TT = TS ( 1 + 0.2 M 2 )

Extreme: long term effects of rain, snow, hail, icing can damage sensor

Figure from Rosemount (BF Goodrich) Technical Report 5755, Rev B, 1990

Possible errors:

Probe heater

Correction factor

Slow time response

Self heating (I2 R )

Extreme environment

WVSSII Installation at United Parcel Service Maintenance Facility

Photo Credit: UPS Dispatch Contact for Usage: Randy Baker/UPS; Email: air1rtb@ups.com

13.8 cm

air flow

double/filler plate

aircraft skin original flow obstacle

Thermal shielding (insolating gaskets) above and below T sensor area

UCAR Patented Mobile Temperature Sensor (MTS)

Run 04 data (trend removed)

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1 31 61 91 121 151 181 211 241 271 301 331 361

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Ztest Mach data # of data points Average difference STD of difference 1.00 all 386 0.27 x 10 -7 0.0278 0.96 all 384 -0.11 x 10 -6 0.0272 0.92 all 382 -0.63 x 10 -6 0.0266 0.88 all 381 -0.15 x 10 -7 0.0263 0.84 all 379 0.40 x 10 -7 0.0256 0.84 M > 0.20 110 0.79 x 10 -3 0.0296 0.84 M > 0.21 90 0.20 x 10 -2 0.0281 Table 6. Mach correction: TS data from Run 04 compared to actual data from 04.

Ztest Mach data # of data points Average difference STD of difference 1.00 all 386 -0.18 x 10 -6 0.0768 0.96 all 381 -0.22 x 10 -6 0.0748 0.92 all 379 -0.73 x 10 -7 0.0740 0.88 all 375 -0.142 x 10 -7 0.0726 0.84 all 370 0.32 x 10 -6 0.0708 0.84 M > 0.20 110 0.13 x 10 -2 0.0734 0.84 M > 0.21 88 0.86 x 10 -2 0.0731 Table 8. Mach correction: TT data from Run 04 compared to actual data for 04.

Ztest Mach data # of data points Average difference STD of difference 1.00 all 386 0.013 0.2077 0.98 all 384 0.010 0.2058 0.94 all 383 0.009 0.2048 0.90 all 378 0.004 0.2005 0.86 all 370 -0.005 0.1936 0.82 all 362 -0.014 0.1864 0.78 all 356 -0.020 0.1812 0.74 all 350 -0.027 0.1760 Table 9. Mach correction: TT data from Run 07 compared to actual data for 04

Atmospheric trace gases

from mobile platforms

Diode lasers and quantum cascade (QC) lasers for various trace gases

Air quality (regional and global pollution) and climate change

QC lasers invented in 1994

these are very small lasers (smaller than diode laser)

key is operation at room temperature in continuous wave (cw) mode

prices are still coming down

Diode lasers or QC lasers for atmospheric trace gases

Same architecture as WVSS-II

-- same air sampler; 1.37 μm replaced with longer wavelength laser -- single path or multiple path (Herriott cell) depending on species -- internal Systems Electronic Box (SEB) about same size -- higher price than WVSS-II (function of laser costs)

Initial products design for CO2 and O3 [α = 1 x 10-4 accuracy = 5%]

Feature ozone (9.2 μm) Carbon dioxide (2.7 μm) minimum detectable signal 0.01 ppmv 0.1 to 0.5 ppmv

maximum detectable signal 10 ppmv 1000 ppmv

path length (in centimeters) 600 24

measured precision 2% or 0.01 ppmv 1% or 0.1 to 0.5 ppmv

What is driving the need for more accuracy?

An evolving, complex, global society –

where all inhabitants are striving to raise

their standard of living

• Weather and climate already impact about 1/7 of a 7 trillion dollar USA economy

• Consider growth in 7 major socioeconomic areas Energy: largest single issue for USA and world (see charts) Water: second largest issue for society (see chart) Food: not as serious as before (see chart) Transportation: major growth area (see chart) Weather impacts (human health, safety, etc) vs 1.1% pop. growth Climate change (global warming uncertainty vs energy conflict) Construction: population growth 1% per year for several decades

• Value of “accurate” environmental data will double approximately every 6-8 years in future.

“Accurate” Atmospheric Monitoring Data will escalate in value over time

Next Generation Air Transportation System (NGATS): Projected demand 120 million additional international passengers are expected by 2025

one billion expected in US air space by 2015

passenger demand will double or triple by 2025; cargo will triple

speed and predictability of air transportation has businesses depending upon just in time air shipments for production efficiency and for keeping inventory costs low – improving our standard of living)

doing nothing will cost consumers $30 billion annually

Importance to United States civil aviation products and services generate a significant surplus for US trade accounts

contribute to the $100 billion a year tourism from abroad

air transportation has spawned a highly technical work force

aviation technologies, products, and services underpin the advanced capabilities of our national defense and homeland security

The Next Generation Air Transportation System

The affordability of fossil fuels

The emergence of new markets in Asia that drive air transportation development

The increased importance of timeliness (speed and predictability)

The continuing or increasing level of world tension

The health and environmental concerns pervading normal every day routine and the growing issue of aviation’s role in climate change

Variations in the above scenarios will drive major changes in the way air traffic is managed, lead to more efficient and environmentally friendly vehicles, leadto more point-to-point operations, greater use of satellite and reliever airports,and new types of aircraft in the National Airspace System:

5000 microjets employed by on-demand air taxi services by 2010; 13,500 by ’22

greater use of UAVs for many applications (e.g. forest fires, surveillance, etc)

Three areas demanding more accurate dataAviation industry: (water vapor and temperature)

-- industry in trouble now (fuel costs have strong wx dependence)

-- future problems with global climate change; “Aviation and the …

Global climate change: (water vapor, temperature, and trace gases)

-- reducing uncertainties in timing and intensity

-- more accurate temperatures in upper troposphere

-- water vapor (loading and role in clouds and aerosols)

Global air quality: ( 3-D pollution near cities & trace gas information)

-- this application just beginning to resemble weather prediction in early days – need more3-D data from aircraft and satellite

Concluding remarks

You have heard some new technology coming from commercial aircraft(and eventually used on many other mobile platforms).

There are other technologies that have are also coming:

Doppler lidar winds

slant path water vapor metric from such aircraft

a turbulence metric from commercial aircraft based upon GPS which contributes to a similar metric from ground sites -- together making a national turbulence product available in real time (provisional patents for each component submitted by R. J. Fleming, Global Aerospace,LLC)

In all of these applications I would ask that you help push for the highestpossible accuracy – our scientific challenges demand no less.