1. The TIDDBIT HF Doppler Radar G. Crowley and F. Rodrigues
Atmospheric & Space Technology Research Associates
(ASTRA)
Abstract: HF Doppler sounders represent a low-cost and low-maintenance solution for monitoring gravity wave activity in the F-region ionosphere. HF Doppler sounders together with modern data analysis techniques provide both horizontal and vertical velocities across the entire TID spectrum. ASTRA has extensive experience with HF systems, and is currently building Doppler sounders in Texas, Virginia, and Peru.
(TIDDBIT = TID Detector Built In Texas)

2. HF DOPPLER SOUNDER PRINCIPLE
F-Region Ionosphere km
Radar Principle
Df = -1/l (dP/dt)
dP can be caused by:
a) changes in reflection height
b) changes in refractive index (electron density profile)
3-10 MHz Tx Rx

3. HF DOPPLER SOUNDER ARRAY
F-Region Ionosphere km Tx
3-10 MHz Rx Tx Tx

4. TYPICAL RADAR SPECIFICATIONS
3 Transmitters, Single Receiver
Spacing: 50 – 300 km
Dual Frequency (Altitude separation)
CW system
Advantages:
Power: W
Continuous
30 sec cadence Tx X X Rx Tx X
Scale: 50 – 300 km Tx

5. Original TIDDBIT Array in Texas
The TIDDBIT array has baseline dimensions of 140 x 210 km, ideal for TID studies.

6. Typical Doppler Data
TIDs on three propagation paths for 4.5 MHz sounding frequency on January 30th, 2002

7. TIDDBIT Radar at Wallops IslandRx 1 2 3
TIDDBIT Radar at Wallops Island
Rocket

8. Wallops Island IRI Sept 1, 2006
TIDDBIT Data Depends on Propagation Conditions

9. Gravity Waves – An Introduction
Waves Everywhere!
Growth with Altitude
rV2
Sources: Aurora
Weather Fronts
Thunderstorms Topography & winds
Explosions
Restoring Force
Acoustic Waves - Pressure
Gravity Waves Gravity
Measures Acoustic waves (τ ~ 1 min) to Large Scale TIDs (τ ~ 4 hrs)

10. Classification of Gravity Waves/TIDs
Medium Scale Large Scale
Period min hr
VH (m/s)
lH (km)
Measures Acoustic waves (τ ~ 1 min) to Large Scale TIDs (τ ~ 4 hrs)

11. TID Parameters Provided by TIDDBIT radar
TID Accurately Represents Underlying Gravity Wave Properties?
Wave Period
YES
Horizontal Phase Trace Speeds (as fctn of period)
Vertical Phase Trace Speeds (as fctn of period)
Horiz. & Vertical Wavelengths (as fctn of period)
Spectrum (Wave Amplitude as function of Period)
Requires Calibration
Measures Acoustic waves (τ ~ 1 min) to Large Scale TIDs (τ ~ 4 hrs)

12. 1. Calculate mean and standard deviation for each peak range.
Raw Data
1. Calculate mean and standard deviation for each peak range.
2. Find values above threshold (set in number of standard deviations from the mean).
3. Calculate equation parameters for Gaussian curve with IDL gaussfit routine.
4. Calculate peak values with equation parameters.
5. Get Chi-squared value.
Peak Detection
1. Detrend the data
2. Calculate Variance
3. Perform FFT
4. Compute the Period
FFT Calculation
1. Take input from two stations.
2. Perform cross-spectral analysis
3. Compute relative time delays
Delays Calculation
1. Test to see if data is usable for horizontal velocity
calculation (based on coherency).
2. Determine the two largest coherencies
3. Compute 95% confidence intervals based on coherencies
4. Call separate subroutine for each pair.
5. Take relative times and compute velocity and azimuth
for station configuration.
Horizontal Velocity

13. Observed TID Spectra
Measures Acoustic waves (τ ~ 1 min) to Large Scale TIDs (τ ~ 4 hrs)

14. Horizontal Phase Trace Speed
1 hr
30 min
Horizontal Phase Trace Speed
500
Measures Acoustic waves (τ ~ 1 min) to Large Scale TIDs (τ ~ 4 hrs)
1 hr
30 min
Horizontal Azimuth

15. Quiet Day Wave Propagation (1/30/2002)
Wave periods 10 – 45 min.
Wave periods 30 min – 4 hr.

16. Quiet Day (1/30/2002) Active Day (2/6/2002)
Wave velocities for periods of 10 – 45 minutes.
Quiet Day (1/30/2002)
Active Day (2/6/2002)

17. Quiet Day (1/30/2002) Active Day (2/6/2002)
Wave velocities for periods of 30 minutes – 4 hours.
Quiet Day (1/30/2002)
Active Day (2/6/2002)

18. QUIET DAY
STORM DAY

19. Azimuth versus Local Time (Oct 11-26, 2006)
Period = 30 min 90
180
Horiz Azimuth ( ºE of N)
TIMEGCM Wind Azimuth
270
360
Local Time

20. Horiz. Phase Speed versus Local Time (Oct 11-26, 2006)
Period = 30 min
Horiz Phase Trace Speed ( m/s)
TIMEGCM Wind Speed
Local Time

21. Deriving Horizontal Thermospheric Winds from Gravity Waves
From Vadas and Fritts (2005):
Given GW wave-vector and background neutral parameters, one can try to solve for UH !
First successful attempts made with multi-beam ISR observations (Vadas and Nicolls, 2008)

22. TIDDBIT Radar Planned for Jicamarca
100 km
50 km
Tx-1
Tx-2
Tx-3 Rx

23. C/NOFS-RELATED SCIENCE STUDIES
Possible Triggers for Instability generation
TID Studies
Spectral Morphology
Underlying Wave Characteristics
Effects of Waves
Separation of triggering mechanisms
E-field measurement capability
Continuous measurement of iso-ionic contour drifts

24. TIDDBIT Radar in New Mexico
75 km
50 km
25 km

25. Value of Deploying a 2nd system around Socorro
100 km

26. Conclusions Successfully built and operated TIDDBIT radar.
Continuous operation: 2002, January - April , Jan - May
Successfully developed end-to-end data analysis.
Complete description of TID characteristics: Period, VH, VZ, λH, λZ, as a function of τ.
Acoustic waves (τ ~ 1 min) to Large Scale TIDs (τ ~ 4 hrs)
Day-to-day variability in TID characteristics.
Developed real time displays
Deployment near Wallops (July 2006)
Continuous operation: 2006, July-Sept
Continuous operation: 2007, Aug-Nov
Partial deployment in New Mexico: June 2008
Deployment at Jicamarca, Peru – Oct 2008
C/NOFS – TIDs, Triggers of ESF, E-fields
Gravity wave propagation/raytracing studies