Overview of Changes and Developments in the SuperDARN Upper Atmosphere Facility

Space @ Virginia Tech 1

Overview of Changes and Developments in the SuperDARN Upper Atmosphere Facility

Raymond A. Greenwald, J. Michael Ruohoniemi, Joseph B. H. Baker Bradley Department of Electrical and Computer Engineering

Virginia Tech

Elsayed Talaat and Robin BarnesJohns Hopkins University Applied Physics Laboratory

Presented at the 2008 NSF Upper Atmosphere Facilities Workshop

1Space @ Virginia Tech


Organizational Changes

Virginia Tech is now the Principal Investigator Institution of the U.S. SuperDARN Upper Atmosphere Facility. Transition brought about by:

Retirement of Ray Greenwald from JHU/APL. Academic appointments of Mike Ruohoniemi and Joseph Baker at

Virginia Tech.

JHU/APL remains a collaborating partner within the SuperDARN UAF. Effort carried out by Elsayed Talaat and Robin Barnes.


Motivations for Change

Virginia Tech offers significantly greater opportunities for student training and development.

Virginia Tech has provided considerable institutional support for the development of the SuperDARN research effort.


New Organizational Staffing

Virginia Tech J. Michael Ruohoniemi: Associate Professor in Department of

Electrical and Computer Engineering (ECE)

Joseph B. H. Baker: Assistant Professor in ECE Raymond A. Greenwald: Part-time Research Professor in ECE

JHU/APL Elsayed Talaat JHU/APL Science Lead Robin Barnes Software Development


Organizational Responsibilities

Virginia Tech Radar operations and maintenance Scientific research Community support Education and outreach

JHU/APL Scientific research Software development Community support Outreach Data distribution


Development of SuperDARNNorthern Hemisphere

Viewgraph from 2005 UAF Meeting Situation Today


SuperDARN – Northern HemisphereFuture Development

The right-hand map includes all of the radars shown at the left plus eight radars extending from the Azores to the Aleutians that constitute an NSF MSI proposal and a single radar in violet located in the U.K. Also, shown are additional radars identified by faint dashed lines that have been proposed by other countries to various funding agencies.


Technology InnovationGreenwald Twin-Terminated Folded Dipole Antenna

The TTFD antenna has proven to be a major improvement in SuperDARN antenna usage. Reduced cost Improved azimuthal coverage Improved front-to-back ratio More rugged due to fewer electrical connections and lower wind loading Used at Wallops Island, Blackstone, Rankin Inlet, Inuvik, and Antarctica


TTFT Antenna Performance

VSWR Values: Blackstone Main Array

1

2

3

4

7 8 9 10 11 12 13 14 15 16 17 18 19 20

Frequency (MHz)

VS

WR

Ant 1 Ant 2 Ant 3 Ant 4 Ant 5 Ant 6

Ant 7 Ant 8 Ant 9 Ant 10 Ant 11 Ant 12

Ant 13 Ant 14 Ant 15 Ant 16 Model Wallops


Technology InnovationForward and Reverse Optimal Golomb Sequences

In 1972, Farley was the first to apply the concept of Golomb rulers to radar measurements in the Earth’s ionosphere.

Within the radar community, this technique is commonly referred to as multipulse sequences. Multipulse sequences provide a means of resolving the range-time

ambiguities that are common to radar Doppler measurements when there are spread targets with significant Doppler velocities.

However, multipulse techniques are notorious for adding noise due to other transmitter pulses and their returns to the analysis process.

1 7 4 2 3

6-pulse optimal ruler

Possible distances = 5+4+3+2+1 = 15

Length = 17 Missing: 10,15



The pattern above is a 13-pulse sequence consisting of a single pulse followed by forward and reverse 6-pulse optimal Golomb sequences.

This pattern is resistant to bad lags due to transmitter pulses and strong cross range noise.

In most instances there is at least one good option for each lag.


Farley, 1972

Value=0: Data Sample Value=1: Tx Pulse Value=2: Data Sample>10dB

0

1

2

3

0 50 100 150 200 250 300 350

Sample No.

Sa

mp

le T

yp

e


Sample types occurring during a 6-pulse Golomb sequence preceded by a single pulse.

Range Gates 10-14 have >10 db signal



Farley 1972

0

5

10

15

0 20 40 60 80 100

Range Gate

Bad

Lag

s

7-Pulse Sequence: 15,1,7,4,2,3Cross-range noise: Range Gates 10-14

Bad Lags due to Transmitter Pulses and Cross-Range Noise on First 100 Ranges Gates Using Farley Sequence.



Bi-Directional - 13-Pulse Sequence

Value=0: Data Sample Value=1: Tx Pulse

0

1

2

3

0 100 200 300 400 500 600

Sample No.

Sam

ple

Typ

e

Farley Sequence Farley Sequence Reversed

What happens if we have a choice between two potential solutions for each tau?



0

5

10

15

0 20 40 60 80 100

Range Gate

Bad

Lag

s

Bad lags due to transmitter pulses for 13-pulse forward and reverse sequence.



Tauscan

0

5

10

15

0 20 40 60 80 100

Range Gate

Ba

d L

ag

s

Tauscan

0

5

10

15

0 20 40 60 80 100

Range Gate

Ba

d L

ag

s

(>10 dB Signals at range gates 10-14)

(>10 dB Signals at range gates 15-19)

Bad lags due to Tx pulse and cross-range noise is highly variable and depends on interplay between two independent processes.


Improved Phase Vs. Lag Measurements Allow Doppler Velocities to be Determined from Individual Pulse Sequences


Doppler Velocity Vs. Time200 ms Temporal Resolution


14-sec Doppler Velocity Pulsation Observed With Wallops Island Radar (Greenwald et al., 2008)

Note Similar period on Ottawa magnetometer


Science: Extended Observations of Sub-Auroral Plasma Streams (Oksavik et al., 2006)


Science: Identification of Temperature Gradient Instability Onset (Greenwald et al., 2006)

Sequence of Events

22-00 UT: Poleward motion of ocean scatter footprint following sunset.

00-0120 UT: Irregularities form in post-sunset ionosphere. Possibly associated with F-region gradient-drift instability as reported previously.

0120 UT onwards: Temperature gradient reverses and steepens. Backscatter intensifies. Onset of TGI.

22 23 00 01 02 03 04 UT

THEMIS-SuperDARN Substorm Studies


During THEMIS tail conjunctions SuperDARN radars run a special THEMIS mode that increase temporal sensitivity to substorm dynamics:

Dwell time reduced from 7 to 4 seconds.

SD radars returns to a designated camping-beam between each successive scan beam.

THEMIS Mode camping beams (Blue)

THEMIS-SuperDARN Substorm StudiesFebruary 22, 2008


Substorm expansion phase onset at approximately 0437 UT:

THEMIS spacecraft measure two bursts of Earthward convection in the tail.

Ground-based magnetometers measure the onset of Pi2 oscillations.

Blackstone Radar Measurements:

Pi2 oscillations measured on camping beam at approximately location of plasmapause (Alfven Waves?).

Science: Upper Atmosphere Variability at Mid-Latitudes



Education and TrainingAdvanced Degree Students @ Virginia Tech

Student Advanced Degree

Nathaniel Frissell PhD

Yin Yan PhD

Kevin Sterne MS

Frederick Wilder (Bob Clauer) PhD

Lyndell Hockersmith (Bob Clauer) MS

SuperDARN: Issues and Concerns

The reconstitution of the JHU/APL SuperDARN activity at Virginia Tech and JHU/APL will still require some time to bring to completion. At Virginia Tech, We have a good group of involved students. We hope to add an engineer with SuperDARN experience.

Goose Bay and Kapuskasing have upgrade/ maintenance needs: Kapuskasing: digital receiver Kapuskasing and Goose Bay: new low-loss cables Kapuskasing and Goose Bay: potential antenna deterioration

Serious issues in obtaining maintenance support at Wallops


SuperDARN: Issues and Concerns

Air Force infrastructure support for Goose Bay disappearing Ionosonde no longer in operation No Air Force funds for heat, electricity, or snow plowing

Death of Dr. Jean-Paul Villain raises concerns about future support for Stokkseryi radar We are working with University of Leicester to identify magnitude of

problem and possible solutions.

Full SuperDARN network can produce 4+TB of data samples per year. How do we gather and disseminate data?


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Overview of Changes and Developments in the SuperDARN Upper Atmosphere Facility

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