J. Vierinen, J. Markkanen and H. Krag

High power large aperture radar

measurements of the Iridium-Cosmos collision

Image: ESA

European Incoherent SCATter radar(EISCAT)

European Incoherent SCATter radar(EISCAT)

•UHF: Tri-static, 32 m, 930 MHz, 2 MW,12.5% duty-cycle

•ESR: Bi-static, 32 & 42 m, 500 MHz, 1 MW 25% duty

•VHF: mono-static, 120x40 m, 224 MHz, 3 MW, 12.5 % About 10 years of space debris involvement.

UHF & VHF

ESR

Iridium - Cosmos collision

Video courtesy of Analytical Graphics, Inc. (www.agi.com).

On 10.2. 2009, 16:56 UT, Iridium 33 and Cosmos 2251 satellites collided over Siberia at 789 km with a relative speed of approximately 11.7 km/s.

Analysis procedure

1.Fourier series match function model

2.Combining raw detections to form line-of-sight trajectories and radar cross-section estimates

3.Maximum a posteriori estimate using full statistical model

1. Fourier series match function

•Target rotation and numerical approximations cause spreading of target backscatter spectrum

•Target backscatter very narrow band

•Maximum likelihood estimate for Doppler, and and backscatter power.

•Corresponds to coherent integration

2. Combining detections

•Use a restricted grid search to find target trajectories amongst the sufficiently strong and separated detections within the coherent integration blocks

3. Full statistical model• Model radial trajectory using e.g., a spline

• Estimate parameters using e.g., Markov Chain Monte-Carlo

• Use parameters obtained from the detection step as prior information

Moving point model

Collision related measurements:

•Campaign measurements, December 2008

•UHF 14.2. 2009 (spade)

•ESR 19.2. 2009 (steffe)

•UHF 12-15.5. 2009 (beata, spade)

•UHF 24.6. 2009 (manda)

Spade experiment

• D-, E- and F-region ionospheric measurement

• 16000 km gapless Space Debris, meteor head echos

Tromsø 14.2.2009Magnetic field aligned

Tromsø 14.2.2009

IridiumKosmos

Svalbard 19.2. 2009Magnetic field aligned

Steffe

Tromsø 12.5.2009Magnetic field alignedBeata

Tromsø 13.5.2009Magnetic field alignedBeata

Iridium Kosmos

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Tri-static debris measurement

Tromsø 14.5.2009Tri-static (eastward)Spade

Tromsø 14.5.2009Tri-static (eastward)Spade

Iridium

Kosmos

?

?

Kiruna 14.5.2009Tri-static (eastward)Spade

Sodankylä 14.5.2009Tri-static (eastward)Spade

Debris model•ESA MASTER model (Klinkrad 1997)

•Can be used to simulate debris detected using radars and telescopes (Krag 2000)

•Not exact trajectories, stochastic model

•Used e.g., to estimate collision probability with a spacecraft

•EISCAT measurements can be used to validate the model

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Model predictsless spread

Model predicts less debris than we observe

Orbital element measurement

QuickTime™ and aPhoto - JPEG decompressor

are needed to see this picture.

• Bi-static and tri-static measurement allows full orbital element determination

• Currently smooth tracking impossible

• Stepped approach works with the current system

Trial run

RMS error 75 m

Conclusions•Due to location and sensitivity, EISCAT

offers a unique set of radars for small space object studies (2 cm at 1000 km)

•We have observed the Iridium-Kosmos debris with EISCAT radars

•New multi-purpose experiments (plasma parameters, space debris, meteors)

•Higher estimation accuracy possible with higher computational cost

•We’re moving towards tri-static measurements

Thank you...Thank you...

EISCAT 3DEISCAT 3D