INDIGO : BETTER GEOMAGNETIC OBSERVATORIES WHERE WE NEED THEM

Pavel Borodin, Jorge Brenes, Elias Daudi, Noor Efendi, Simon Flower, Muhammad Hidayat, Muhammad Husni, Manuel Kampine, Oleg Kusonski, Artur Langa, Iván Monge, Antonio Mucussete, Armindo Nhatsave, I Kadek Oca Santika, Jean Rasson, John Riddick, Didik Suharyadi, Christopher Turbitt, and Mahmud Yusuf  Arti observatory, Institute of Geophysics, Urals Branch of Russian Academy of Sciences Instituto Costarricense de Electricidad, ICE, Costa Rica Direcção Nacional de Geologia, Moçambique Meteorological and Geophysical Agency, BMD, Indonesia British Geological Survey, Seismology and Geomagnetism Institut Royal Météorologique, Centre de Physique du Globe, Belgium Email : jr@oma.be Retired from British Geological Survey, Seismology and Geomagnetism Direcção Provincial de Recursos Minerais, Nampula, Moçambique  ABSTRACT  Good magnetic observatories are needed more than ever for global modeling and navigation. Magnetic satellite missions, once said to be the death of ground based observations, are now demanding quality data from fixed observations points on the Earth.


INTRODUCTION
A good magnetic observatory is a place where precise, continuous long-term measurements of the geomagnetic field are made and from where definitive data are regularly published to the wider scientific community.The INDIGO project (Riddick et al., 2009) aims to provide the means for achieving this goal in a selected set of places on the Earth.Equipment, software, training, and data processing, when missing on site, are given to colleagues worldwide so that they might improve or start their own geomagnetic observations.Usually existing premises are used and/or reconfigured to provide an adequate hosting of the INDIGO equipment (Figure 1).If necessary, local staff are trained in observatory operations and observing skills.We find that the installation of a successful observatory also depends on the motivation of the local observatory staff; with the help of the INDIGO project, most common problems can be overcome.

WHERE DO WE NEED THEM?
A state-of-the-art magnetic observatory is an expensive piece of infrastructure in equipment and in manpower since automatic observations are not possible at the moment.Therefore the good ones tend to be clustered in richer countries (Rasson et al., 2011).INDIGO tries to provide help where there are gaps in the observatories world map.
The INDIGO effort has therefore been directed towards Asia, Africa, and Latin-America; see

METHODS AND INSTRUMENTS
The original objective of the INDIGO project was to make use of fifteen EDA fluxgate variometers donated to the British Geological Survey (BGS), coupled with a low power digitiser to make filtered one-minute digital daily recordings.Use of the more precise and stable DMI variometer was later adopted for some installations.Absolute instruments like ZEISS, Ruska, and Tavistock Difluxes as well as Geometrics and GEM proton magnetometers are used.
The digitizer is based on a 16 bits ADAM ADC module and a GPS receiver with all sampling controlled by a PIC16F877 microcontroller programmed in BASIC or C. It also controls the optional proton magnetometer.
The data logger is based on a JAVA platform.Usually a PC is used with two programs running in parallel: EDA2GDAS and GDASVIEW.The former communicates with the latter and with the digitizer so that filtering and formatting to various file formats (including INTERMAGNETs imfv1.22) is performed along with graphical display (Figure 3).
The connection between the logger and the PC can be by copper cable, optical fibre or HF radio.
More recently it was realized that it would be possible to do away with the PC altogether, by connecting a USB memory stick directly to the digitizer through a custom stick writer.This allows us to log the data in the required format without use of a PC.This results in huge savings in terms of power and cost and would allow a modest battery to power the system for days.Monitoring of the data log can be done on an optional PC running a new piece of java soft: INDIGOwatch.

Figure 2 :Figure 1 .
Figure 1.Pictures of INDIGO installations.Top left: Variometer house at Maputo, Mozambique; top right: the newly erected variometer house in Pelabuhan Ratu, Indonesia.Middle left: Arti observatory in Russia; middle right: the absolute house at Tondano, Indonesia.Bottom left: the new Kupang observatory in Timor-West, Indonesia; bottom right: the observatory of Chiripa, Costa Rica.

Figure 2 .
Figure 2. Location of the INDIGO observatories: Blue dots: existing observatories; red triangles: INDIGO installations; White triangles: projected installations

Figure 3 .
Figure 3.Typical INDIGO hardware.Clockwise from top left: The EDA triaxial fluxgate sensor in Nampula, Mozambique; Absolutes in Nampula with a Ruska DIflux and a Geometrics proton; DMI and GEM recording magnetometers in Kupang, Timor-W; EDA console and INDIGO logger in Maputo, Mozambique.