Gan Magnetic Observatory Annual Report

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1 Gan Magnetic Observatory Maldive Islands South Indian Ocean 2013 Annual Report Aerial view of the island of Gan, the observatory is located below the runway approximately at its midpoint 1

2 List of Contents 1 Introduction Description of the observatory... 1 Gan Observatory (IAGA code: GAN) Instrumentation... 3 Block diagram of system Data Processing... 5 Checks on calculation of Annual Mean Values Annual Means Operational Diary Statistics on Gan Observatory Data Recorded Baselines Plots of daily magnetograms Gan Magnetograms January February March April May June July August September October November December Participants in Gan Observatory operation Acknowledgements Publications References i

1 Introduction This bulletin is a report of the measurements and operations carried out between 1 January and 31 December 2013 at the geomagnetic observatory on the island of Gan in the south Indian

3 1 Introduction This bulletin is a report of the measurements and operations carried out between 1 January and 31 December 2013 at the geomagnetic observatory on the island of Gan in the south Indian Ocean. Gan Observatory was installed by the Institut für Geophysik, ETH Zürich, Switzerland in April Day to day operation of the observatory is the responsibility of the local Meteorological Office staff who also carry out a regular program of absolute observations. The recorded data are automatically transmitted to a database in Zurich and also to the INTERMAGNET Geomagnetic Information Node (GIN) operated by the British Geological Survey (BGS) in Edinburgh, Scotland. All data processing and quality control procedures are carried out by suitably qualified personnel based at various locations in Europe. During 2013 Gan Observatory became a full member of INTERMAGNET. An on-line display of the Gan data can be found at 2 Description of the observatory The island of Gan is the most southerly island of the Maldive Islands and lies in the Indian Ocean almost 1 degree south of the equator. It is a coral atoll and part of the Addu Atol group of islands. The island is the second largest island of the atoll, after Hithadoo and measures square kilometres (0.87 sq mi) in area. During WWII, Gan Island was developed as an airbase for the Royal Air Force who used it as a refuelling point for flights between the UK and the Far East. The observatory in located on the west side of the main runway and comprises 3 weatherproof shelters for the instruments and a hut used for absolute observations. Equipment Housing. Magnetometers and Control Electronics in waterproof boxes, Left to right, Control Electronics, Proton magnetometer, Fluxgate magnetometer

4 Gan Observatory (IAGA code: GAN) Location: Latitude : Gan International Airport, Addu Atoll, Maldives 00 41'40.55" S Longitude : 73 09'13.47" E, Altitude: 3 m Local contact: Muslim Ahmed Regional Meteorological Office, Maldives Meteorological Service Gan Addu City Maldives Telephone: E_mail: ahmedmuslim@hotmail.com Zurich, Switzerland contact: Prof. Andrew Jackson Institut fur Geophysik, Sonneggstrasse 5 CH-8092, Zurich Switzerland Telephone: E_Mail: ajackson@ethz.ch

3 Instrumentation The instruments include a DMI Suspended FGE, 3 component fluxgate magnetometer measuring variations in the horizontal (H) and vertical (Z) intensities and the changes in the

5 3 Instrumentation The instruments include a DMI Suspended FGE, 3 component fluxgate magnetometer measuring variations in the horizontal (H) and vertical (Z) intensities and the changes in the declination (D) along with temperatures in the sensor head and fluxgate electronics. Total Field (F) is measured by a GEM Systems GSM 90F1 proton magnetometer which also supports a GPS receiver used to provide accurate timing control for the data sampling and logging. All magnetic components are sampled once a second with magnetometer sampling, data storage and systems housekeeping controlled by a low powered UNIX based PC which operates from a battery backed 12 Volt DC supply deriving its power from a bank of solar cells. As well as storing the data locally a transmission link provides communication between the observatory and the local Meteorological Office in Gan Airport. At this office Internet facilities are available to transmit all recorded data to Zurich where an on-line display and database has been set up ( The observatory is completely self-contained with all power provided by the battery backed solar panels which will support operations for over a week in the event of no solar charge. Gan Observatory Equipment Solar panels used to charge the two 225 AH sealed lead acid batteries.

6 Block diagram of system DMI triaxial suspended fluxgate magnetometer with the protective fibreglass waterproof removed. Power box showing the solar regulator and two, 6 Volt 225 AH batteries.

7 4 Data Processing Throughout 2013 systems on Gan automatically updated the archive computer at ETH, Zurich several times a day. These data were then retrieved and checked, magnetograms plotted and baselines calculated using the GDASView software, (Turbitt, In Press). The daily processing also included a visual check for intermittent, man-made, spikes which were then edited out using the GDASView software. Once the quality control checks were completed the data were uploaded to the BGS Geomagnetic Information Node (GIN) in Edinburgh and the daily magnetograms for the monthly bulletins plotted. Shown left is a typical magnetogram of the daily variations measured at Gan. The fluxgate data, vertical (Z, blue), horizontal (H, red) and declination (D, green) along with total field (F, pink) calculated from the fluxgate H and Z variations are displayed in the upper 4 traces. The total field (F, orange) measured by the proton magnetometer and the difference between F calculated from the fluxgate and F measured by the proton (bottom plot, yellow) are displayed in the lower two traces. These plots gives an excellent indication that both the fluxgate and the proton are operating correctly. In November, following the successful application by Gan Observatory for membership to INTERMAGNET and also the requirement to provide more timely data, following the successful launch of the SWARM satellites, the data processing procedures were revised. These included, an hourly transmission of the Gan data to the Edinburgh GIN providing an on-line provisional data set and at monthly intervals, once baselines had been established, the generation and transmission to the GIN of quasi-definitive observatory data in IAGA 2002 format. Using GDASView in processing Gan data has greatly simplified the data processing and the support of BGS,Edinburgh is acknowledged in providing regular upgrades to this product.

Currently a database of all Gan data is maintained on the ETH, Zurich database Data Structure on ETH, Zurich Database The files in the directories, shown above, contain 3 component fluxgate (H D Z)

8 Currently a database of all Gan data is maintained on the ETH, Zurich database Data Structure on ETH, Zurich Database The files in the directories, shown above, contain 3 component fluxgate (H D Z) and proton variometer data in a variety of formats and sampling rates from the 1 second recorded data to the baseline corrected, definitive data of minute and annual means in IAGA 2002 format. Gan system housekeeping data, including, temperature, humidity, solar panel, battery and load voltages is also stored along with all absolute observations and baseline data. The Edinburgh GIN database contains day files of Gan minute mean data in INTERMAGNET format. Note: All access to Gan data in both the ETH and BGS databases is password protected. Checks on calculation of Annual Mean Values As a check against the GDASView software and to confirm that the baselines were correctly applied and Annual Means correctly calculated a program to calculate the daily mean from baseline corrected IAGA 2002 format data was written. Using this software the daily mean value for every day in 2013 was calculated and plotted along with selected absolute observations and the Annual Mean calculated by GDASView. Shown below are the results obtained from this comparison. The plots indicate that the absolute spot observation values agree and follow the trend of the daily means and the Annual Mean (yellow triangle) calculated by GDASView is in good agreement with the midpoint of the daily mean plots.

9 37800 H Component Daily Mean Abs Obs Annual Mean Jan Apr Jul Oct Feb-14 D Component Jan Apr Jul Oct Feb Daily Mean Abs Obs Annual Mean -280

10 40200 Total Field Daily Mean Abs Obs Annual Mean Jan Apr Jul Oct Feb Z Component Jan Apr Jul Oct Feb Daily Mean Abs Obs Annual Mean

11 Annual Mean (Degrees) Rate of Change (Minutes) 5 Annual Means Since the observatory was installed in April 2011 Annual Mean values of all components have been calculated from the baseline corrected minute mean values. In 2011, as the observatory had not been operating for a full year, the Annual Mean was estimated from the baseline corrected daily mean using a linear interpolation at For 2012 and 2013, GDASView software has been used to calculate Annual Mean values, the results are shown in the table below. GAN COLATITUDE LONGITUDE ELEVATION 2m YEAR D I H X Y Z F Deg Min Deg Min nt nt nt nt nt Gan Declination Annual Change Annual Mean Rate of Change

12 Annual Mean (Degrees) Rate of Change (nt) Annual Mean (Degrees) Rate of Chanhe (Minutes) Gan Inclination Annual Change Annual Mean Rate of Change Gan Total Field Annual Change Annual Mean Rate of Change

13 Annual Mean (nt) Rate of Change (nt) Annual Mean (nt) Rate of Change (nt) Gan Horizontal Component Annual Change Annual Mean Rate of Change Gan Vertical Component Annual Change Annual Mean Rate of Change

14 6 Operational Diary The following details are taken from the Gan Observatory Monthly Bulletins. This summary gives details of any site changes and operational problems experienced during January 2013 Throughout the month problems continued with the WiFi link between the observatory and the Meteorological Office. On 16 January 2013 the fluxgate magnetometer was replaced. Original fluxgate in operation from May 2011 to 16 January 2013 Fluxgate S0331, Electronics E0398 Scale values X nt/v Y nt/v Z nt/v Replacement fluxgate in operation from 17 January 2013 Fluxgate S0375, Electronics E0475 Scale values X nt/v Y nt/v Z nt/v The replacement of the fluxgate was necessary as over the preceeding 6 months comparisons between the fluxgate and the proton indicated that the fluxgate was becoming increasingly unstable, possibly due to a build up of moisture in the triaxial head. February 2013 During this month problems were experienced with both the WiFi link and the data logging PC, these resulted in considerable data losses. On 25 February the site was visited by members of ETH, Zurich staff and the communications and interfacing problems resolved. A new WiFi antenna was installed under the roof of the electronics hut. The proton interface, USB-RS232 converter was replaced and the USB hub (which was used to connect all instruments (except the Overhauser proton magnetometer) to the USB port on the master motherboard was replaced, unfortunately this did not solve the proton interface problems so finally the data logging the master motherboard was also replaced.

15 March 2013 all systems operated well and no problems were noted, absolute observations made during the month indicate that the replacement fluxgate is producing stable results. April 2013 all systems operated well and no problems were noted.. May all systems operated well and no problems were noted..intermittent communication problems between Gan ant ETHz were experienced June all systems operated well and no problems were noted. July 2013 Disk capacity problems resulted in the loss of 3 days data, 19, 20 and 21 July. August 2013 Throughout the month no problems were experienced with the observatory hardware and no data lost. On several days communication problems were experienced between Gan and ETHz. September Throughout the month no problems were experienced with the observatory hardware and no data were lost. Ibrahim Ziyad began training in making absolute observations and to date has made excellent progress. October Throughout the month no problems were experienced with the observatory hardware and no data were lost. Routine operations and the absolute observation program are now the responsibility of Ibrahim Ziyad. The application to join INTERMAGNET was successful and Gan is now a full member of INTERMAGNET. November 2013 Disk capacity problems resulted in the loss of 21 hours of data between the 23 rd and 24 th of November. This was traced to a faulty script and hopefully this problem has been resolved. During November the Edinburgh GIN database was automatically updated with Gan preliminary data every hour. Procedures have also been set in place to generate quasi-absolute minute values which will be sent to the GIN at monthly intervals.from November 2013 the magnetograms presented in the bulletin will be generated using these quasi-absolute minute values. December Throughout the month no problems were experienced with the observatory hardware and no data were lost.

16 Statistics on Gan Observatory Data Recorded Apart from a period in February when the data logging PC gave problems and on two ocasions in July and November when the disk filled up, throught 2013 all the equipment on Gan operated very reliably. In normal operation 1440 minute samples of all components are generated every day. Shown below is a plot of the data recorded throughout the year Gan 2013 data received by GIN /01/ /04/ /07/ /10/2013 In 2013 Gan obseravtory was operational for 91.3% of the time Baselines Throughout the year a regular program of absolute measurements of declination (D) and inclination (I) have been carried out by the Meteorological Office staff on Gan and the observers are to be congratulated on their excellent work. Depending on the weather and available staff time observations are made twice a week. The results from these observations have indicated that after replacing the fluxgate magnetometer in January this instrument has produced very stable results. Using the measured absolute value of D and I and a site corrected value of total field (F), measured by the recording proton, the absolute value of the horizontal (H) and vertical (Z)

intensities at the D/I pillar are calculated. From these results the fluxgate H,D and Z baselines are derived. It should be noted that the current site correction for the proton magnetometer of 24.

17 intensities at the D/I pillar are calculated. From these results the fluxgate H,D and Z baselines are derived. It should be noted that the current site correction for the proton magnetometer of 24.2 nt ( F D/I pillar F Measured) was measured in 2011 when the observatory was set up. In 2013 a new GSM-90T proton was purchased and this instrument will be used to check this site difference in Using the GDASView software, baselines along with observation and instrument quality control measures are derived from the absolute observations. Below the baselines for 2013 are plotted. Note the large step in January is due to the fluxgate replacement. Gan 2013 Baseline plot

18 8 Plots of daily magnetograms The plots show the baseline corrected magnetograms of the horizontal (H), declination (D), vertical (Z) fluxgate variations along with the total field (F). The data are plotted for each month in 7 day sections, dates 1-7 th, 8-14 th, st, th followed by the remaining days of each month in a 2 or 3 day plot. Gan Magnetograms January 2013

22 Gan Magnetograms February 2013 Note During February 2013 problems with the data logging PC resulted in significant losses of data.

25 Gan Magnetograms March 2013

29 Gan Magnetograms April 2013

33 Gan Magnetograms May 2013

37 Gan Magnetograms June 2013

41 Gan Magnetograms July 2013

45 Gan Magnetograms August 2013

49 Gan Magnetograms September 2013

53 Gan Magnetograms October 2013

57 Gan Magnetograms November 2013

61 Gan Magnetograms December 2013

65 9 Participants in Gan Observatory operation Gan Operations and Observers Mr Ahmed Muslim, Climatologist, Maldive Meteorological Office. Mr Ibrahim Ziyad, Assistant Meteorological Technician, Maldive Meteorological Office. European Operations. Professor A Jackson, Project Leader, Institute of Geophysics, ETH Zürich, Switzerland. Dr Jakub Velimsky, Dept. of Geophysics, Charles University in Prague, Czech Republic. Dr Alexei Kuvshinov, Institute of Geophysics, ETH Zürich, Switzerland. Mr Friedman Samrock, Institute of Geophysics, ETH Zürich, Switzerland. Mr John C. Riddick, Scotland. 10 Acknowledgements We would like to acknowledge and thank the following people for their help in setting up Gan Observatory. Dr Lars W. Pedersen, National Space Institute, Technical University of Denmark, for visiting Gan, in January and replacing the triaxial fluxgate his assistance was greatly appreciated. Mr. Abdulla Wahid, Executive Director of Maldives Meteorological Service. Mr. Ali Wafir, Head of Gan Meteorological Office - for logistical and management support; Dr. Juergen Matzka and Dr. Chris Finlay, National Space Institute, Technical University of Denmark - for assistance at initial stages of the project; Mr. K.C.S. Rao and Dr. Kusumita Arora, National Geophysical Research Institute, Hyderabad - for assistance in installation of instruments, and training observers. Mr C. Turbitt and Mr T. Shanahan, British Geological Survey for their assistance in the development and use of GDASView software. Mr T Harris, British Geological Survey for post production & PDF development

66 11 Publications Gan Observatory Monthly Bulletins, J. Velímský, A. Muslim, A. Jackson, A. Kuvshinov, F. Samrock, K. Arora, K.C.S. Rao, L. Pedersen, C. Finlay, J. Riddick, Geomagnetic observatory Gan, XVth IAGA Workshop on Geomagnetic Observatory Instruments, Data Acquisition and Processing, Cadiz, J. Velímský, A. Muslim, A. Jackson, A. Kuvshinov, F. Samrock, K. Arora, K.C.S. Rao, L. Pedersen, C. Finlay, J. Riddick, Geomagnetic Observatory Gan, IAGA XIIth Scientific Assembly, Merida, References Turbitt, C.W., GDASView Users' Guide, Seismology & Geomagnetism Programme Internal Report (In press).

Gan Magnetic Observatory. Maldive Islands South Indian Ocean Annual Report

Gan Magnetic Observatory. Maldive Islands South Indian Ocean Annual Report Gan Magnetic Observatory Maldive Islands South Indian Ocean 2016 Annual Report 1 Institut für Geophysik, Zürich Gan Magnetic Observatory Maldive Islands South Indian Ocean 2016 Annual Report Report Editor