Geomagnetic observatory GAN [width=0.95]foto/P1110555.jpg *-0.5cm

Geomagnetic observatory GAN

Jakub Velımsky K. Chandra Shakar Rao Lars W. Pedersen Ahmed MuslimETH Zurich

Charles University in Prague NGRI Hyderabad DTU Space Copenhagen Gan Met. Office

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 1 / 16

Participating institutionsI ETH Zurich

I Andy JacksonI Alexei KuvshinovI Chris FinlayI Hanspeter Hachler

I NGRI HyderabadI Kusumita AroraI K. Chandra Shakar Rao

I Gan Meteorological Office, Dept. of MeteorologyI Muslim Ahmed

I With support and help from:I Jakub Velımsky (Charles University in Prague)I Lars W. Pedersen (DTU Space)I Jurgen Matzka (DTU Space)I Lukas Zimmermann (ITECO Ingenieurunternehmung AG)I Rudolf Widmer-Schnidrig (BFO Observatory, Univ. Stuttgart)I John Riddick (BGS, retired)

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 2 / 16

Geomagnetic observatories

I The objective of geomagnetic observatories is to recordcontinuously, and over the long term, the time variations of themagnetic field vector and to maintain the accurate absolutestandard of the measurements. (IAGA Guide for MagneticMeasurements and Observatory Practice, 1996)

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 3 / 16

Intermagnet

I 116 operating observatoriesI strict quality standards

I Definitive Data Accuracy: ±5 nTI Vector Magnetometer

I Resolution: 0.1 nTI Dynamic Range: 8000 nT High Latitude,

6000 nT Mid/Equatorial LatitudeI Sampling rate: 1 HzI Thermal stability: 0.25 nT/◦C

I Long term stability: 5 nT/year

I Scalar MagnetometerI Resolution: 0.1 nTI Accuracy: 1 nTI Sampling rate: 0.033 Hz (30 sec)

I data available on CDs and online

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 4 / 16

Site selection

I initial visit January 2009 (Alexei & Chris)

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 5 / 16

InstrumentsAbsolute measurements

I fluxgate Declinometer/Inclinometer Instrument MINGEO 020(Zeiss THEO 020 + DMI Model G FGM)

I measurement accuracy < 3”

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 6 / 16

InstrumentsAbsolute measurements

I Overhauser precession magnetometer (Gemsys GSM-90F1)

I accuracy 0.2 nT

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 7 / 16

InstrumentsRelative measurements

I fluxgate magnetometer (suspended FGM-FGE variometer)

I Resolution: 0.1 nTLong time drift: < 3 nT/year

Temp. coeff. of sensor: < 0.3 nT/◦C Temp. coeff. of electronics:< 0.1 nT/◦C

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 8 / 16

Observatory sketch

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 9 / 16

Hut designs

I concrete pillarsI concrete block wallsI wooden/glassfiber roofsI brass fitting

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 10 / 16

Hut designsABS

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 10 / 16

Hut designsABS

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 10 / 16

Hut designsElectronics

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 10 / 16

Hut designsOverhauser

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 10 / 16

Hut designsVariometer

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 10 / 16

Hut designs

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 10 / 16

Connection scheme

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SolarBox 12V DC

GPS antenna

WiFi antenna

Solar Panel

Electronics hut

Datalogger

OVM electronics

FGM electronics

OVM sensor

FGM sensor

OVM hut

FGM hut

WiFi access point

PC

routerETH

Met Office

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 11 / 16

DataloggerI Alix3d2 board

I AMD Geode 500 MHz, 256 MB Dram, 4 GB CF cardI fanless, 5 W peak, 12 V DCI 1 Ethernet, 2 USB, 1 RS-232I Wistron DCMA81 miniPCI card (WiFi, 2.4 GHz,

WPA2)I Voyage linux 0.6.1I Data recorded via simple program in Python

I 1 s data sampling with GPS trigger and stamp fromOVM

I conversion of FGM voltages to nTI computation of 1 min averages using Gaussian filter

I Data stored locally (capacity at least 2 year)I Regular synchronization of data to computers in the

MetOffice and ETH (rsync)I Display of data via cgi script and www browser

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 12 / 16

Current problems

I interference in OVM during charging of batteries from the solarpanel (approx. 9:00–16:00 GMT)

I probable cause: PWM used in charging processI suggested remedies: DC-DC converter, secondary battery

charged overnight from the main batteryI to be tested with another GEM-90 in Zurich this summer

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 13 / 16

Current problems

I temperature variations of FGM sensors (up to 5 ◦C dailyvariations)

I styrofoam: installed yesterdayI more water?I tri-iso external insulation?I white paint on huts

Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 14 / 16

To do list

I absolutes training program in Hyderabad (planned in June 2011)I implementation of baselines in the processing chainI output format according to Intermagnet standardI long-term control of qualityI application to IntermagnetI for induction studies: measurement of horizontal electrical field

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Velımsky et al. (ETH,UK,DTU,NGRI,GMO) Geomagnetic observatory GAN 27.4.2011/KG MFF UK 16 / 16