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1. power supply 28V 2X12V Exide Safeguard Batteries 30Amphr Fig 6 Back up power for the MCC 1 and MNS2 24 09 275 PEM Y PEM Z J1 54 J1 T 4 cH Shields are connected P to circuit board earth and chassis of PEMs pepe The chassis of the MCC 1 is mains earth lt remote SV trigger X Y Z output shield not connected at termination box Doric Earth from main circuit board shields not connected Doric Termination Box MNS2 no shield Shield connected to earth Magnetic Variometer Hut Wombat Shield not connected Termination Box Shields not connected channels 1 2 3 channels 4 5 6 twisted pairs shielded 2 core Time mark 12V All shields not connected iis i i a 0 Attenuation Box Chassis of time mark relay driver is mains earth through the CRO Shielded 2 core Shielded 2 core EDAS Mains Mains Battery back up Fig 7 Cabling of photo electronic magnetograph system 24 09 276 gem 22 ROCK Floor steps up by Concrete floor N ORTH SOUTH REFERENCE 0 100mm Fig 8 Mawson seismic vault 247 09 277 5 04 1 0 10 100 Frequency Hz 15K I5K Vin across 560 0 Vout resistor Fig 9 Frequency response of filter from SPZ AR320 input Mawson 1985 24 09 278 MAINS MAINS CHARGER 24V CHARGER 24V 240V 240V 2x12V 2x12V BATTERIES
2. phi 7 derived residual torsion nT difference alpha correction QHM 300 until Mar 19 58 44 6 6 3 7 0 0 Mar 19 onward 58 36 22 5 12 4 0 4 QHM 301 63 53 42 4 17 0 1 1 significant QHM 302 56 69 12 4 7 5 0 1 QHM 172 59 62 14 1 7 2 0 2 HTM 704 40 92 0 1 0 1 0 0 4 INSTRUMENT DIFFERENCES 1 QHM instrument differences assuming no change in QHM 300 instrument correction Date QHM 300 301 300 QHM 302 No of observations nT nT QHM 300 301 302 1985 Feb 01 Feb 10 0 1 5 1 6 1 Feb 10 Mar 18 1 0 3 4 5 1 19 12 0 4 4 8 12 1 May 13 Nov 29 5 8 1 2 42 8 WEIGHTED MEAN 4 4 0 3 RANGE 5 7 6 3 2 QHM instrument differences assuming 300 instrument correction change of 4 3 nT on 19 March 1985 Date QHM 300 QHM 301 300 QHM 302 No of observations nT nT QHM 300 301 302 1985 Feb 01 Feb 10 0 1 5 1 6 1 Feb 10 May 12 1 4 6 3 17 2 May 13 Nov 29 1 5 3 1 42 8 WEIGHTED MEAN 0 8 3 9 RANGE 2 9 3 2 3 QHM differences from 1984 1983 and 1982 Year QHM 300 QHM 301 QHM 300 QHM 302 Comments nT n 1984 1 7 0 6 5 4 0 5 From La Cour data 1 7 1 6 4 7 1 8 From PEM data 1983 1 6 5 4 1982 2 5 2 7 io 5 SUMMARY COMPARISONS FOR 1983 1986 Date Observer HTM 704 300 172 300 nT nT Feb Mar 1983 Silberstein 5 43 Feb 1984 Crosthwaite 6 2 Feb 1985 Crosthwaite 3 9 40 9 Feb 1986 Kel
3. 41 1000 85 244 Magnifications are given at 5 set to 96dB gain 12dB attenuation 0 1 10Hz passband AR320 24dB Seismometer free period 0 98 sec Damping resistor 387 ohm Sine wave tests Weight lift tests currents used 4 7 5 0 mA approx p p value 0 031 mm mg masses used 100mg 200mg 500mg Current pulse tests 4 40 mm mA currents used 5 3 mA 5 6 mA Motor constant G 1 38 N A Magnification Conversion Tables 5 Attenuation 0 dB 6 dB 12 dB 18 dB AR320 Attenuation 6 dB 12 dB 18 dB 24 dB 30 dB 36 dB e e BS Re Oo 6 dB CO gt ro Pre Por Wr 6 08 1248 18 dB 0 508 0 254 0 125 1 0 500 0 247 2 00 1 0 494 4 04 2 02 1 12 dB 18 dB 24 dB 30 dB 36 dB 0 474 0 237 0 119 0 058 0 028 1 0 500 0 250 0 123 0 059 2 00 1 0 501 0 245 0 118 3 99 2 00 1 0 490 0 236 8 16 4 08 2 04 1 0 481 17 0 8 49 4 25 2 08 1 E 21 DAVIS INSTRUMENT COMPARISONS FEBRUARY 1985 H COMPARISONS QHM 492 Circle 73 compared with QHM 172 Circle 508813 Set Absolute hut pier BMZ Tripod Instrument H Instrument H Hl QHM 172 16645 8nT QHM 492 16650 8nT QHM 492 16642 1nT QHM 172 16694 5nT Station difference Pier Tripod 29nT 0 00174H Instrument difference 172 492 23nT 0 00138H D COMPARISONS QHM 492 Circle 73 compared with Dec 640505 Circle 508813 Set Absolute hut pier BMZ Tripod Inst
4. The coil values are nominal only less than the nominal values Bracketted values are taken from previous reports The actual values are slightly 2 19 LPZ SEISMOGRAPH CALIBRATION NOVEMBER 1985 Period secs Magnification 1 00 1630 2 00 1030 3 00 1040 4 00 776 5 00 622 5 78 469 6 00 454 7 00 420 8 00 406 9 00 387 10 0 396 11 0 322 12 0 248 13 0 190 14 0 145 15 0 119 16 0 93 6 17 0 76 4 18 0 65 9 19 0 53 8 20 0 42 9 25 0 20 8 30 0 10 1 40 0 4 77 50 0 2 21 Magnifications are given at TAM5 set to 72dB gain 24dB attenuation 0 01 20Hz passband AR320 30dB attenuation Seismometer free period 12 8 secs Damping resistor 5120 ohm Sine wave tests currents used 3 7 3 9 mA approx p p value Weight lift tests 0 532 mm mg masses used 3lmg 62mg Current pulse tests 8 11 mm mA currents used 4 3 4 5 mA Motor constant G 0 17 N A The seismometer mass used in the calculations was 6 9 Kg The distance of the center of gravity of the mass boom system from the pivot was taken to be 308 mm Silberstein 1984 The distance of the weight lift point to the pivot was measured to and was 357 mm See Cechet 1984 for Magnification Conversion Tables for TAM5 and AR320 HS 20 5 7 SEISMOGRAPH CALIBRATIOH JANUARY 1986 Period sec Magnification 157 209 260 308 407 526 613 722 824 947 0143 CO n9 m m m T C1 XO i PO CO wo gt
5. GED CLOCK 5 106 END BNC CRO TRIGGER PULSE MONITOR O AbJUS SIDE VIEW 86K 25K BROWN Pin 18 ORANGE I7 Ground aud YELLOW 14 12V BLUE 9 5 Hz GREEN 6 6 Hour PURPLE 5 IHour BLUE 4 10 GREY 3 WHITE 2 Id Sec WHITE ISec BANANA SOCKETS TO RELAYS SIDE VIEW Fig 13 Time mark relay driver box circuit 24 09 282
6. and BMR 1985 2 was 242 28 8 As these three marks are all so close to Pier it is recommended that a mark be established on one of the islands in East Bay for future use Mawson Geomagnetic Observatory 2 11 15 CHAPTER 3 SEISMOLOGICAL OBSERVATORY The Mawson seismic observatory consists of a four component seismograph system see Table 1 for details of seismograph locations Vertical seismometers a Press Ewing long period seismometer a Benioff short period seismometer Horizontal seismometers two Benioff short period seismometers During the February 1985 changeover the two horizontal seismometers were installed in the Cosray vault where the two vertical seismometers were already operating The data were collected on Geotech hot pen helicorders located in the Science Building Wombat See Table 18 for the seismograph parameters 3 1 Operation In June 1984 the Benioff short period horizontal seismometers SPE and SPN were removed from the Old Seismic Vault where they had been operating and recording on a Benioff three drum photographic recorder to the Cosray vault The Press Ewing long period vertical LPZ and the Benioff short period vertical SPZ seismometers were already operating in the Cosray vault vertical seismometer outputs were being recorded on Geotech hot pen helicorders located in Wombat During the February 1985 changeover the outgoing geophysicist Peter Crosthwaite and the author instal
7. circuit board earth common the AR320 chassis 6 0 1 microF capacitor was put across the output from the power changeover relay box which supplies 240Vac from the inverter or the mains to the helicorder The outputs from the AR320s to the helicorders are shielded two core cable the shields were not connected at the AR320s or the helicorders The modifications to the system were completed early July removed almost all the interference from the seismographs 3 3 Calibrations The LPZ seismometer was calibrated in November 1985 see Table 19 and Figure 11 The seismometer mass used in the calibrations was 6 9 Kg Press Ewing manual Since the weight lift point for the test masses does not correspond to the center of gravity of the mass boom system of the seismometer the distance of the center of gravity of the mass boom system to the pivot and the distance of the weight lift point to the pivot must be known for accurate determination of the calibration coil motor constant 6 It is possible to make rough measurement of the distance from the weight lift point to the pivot but the distance of the center of gravity of the mass boom system to the pivot is not accurately known value of 308 mm was used Silberstein 1984 Crosthwaite 1986 This value is not mentioned in the Press Ewing manual and is the value used for the long period vertical seismometers the Worldwide Standard Seismograph Networ
8. introduction of the second clock to the system should the clock in use malfunction Both clocks ran satisfactorily all year The clock used to supply the time marks was kept to within the required accuracy of 50 ms Time comparison between the clock and radio pips was done by displaying both signals on a dual channel CRO Crosthwaite 1986 The Time Mark Relay Driver Figure 13 supplied a further amplifier stage to the GED clock time mark output and supplied time signals from the clock to the seismic system the W W chart recorder and the La Cour variometer 4 3 Cables With the advent of the new magnetic variometer system the cabling has become much simpler The cables currently in use are 1 A 10 twisted pair shielded cable from the new Magnetic Variometer Building to Wombat carrying magnetic information and control signals The cable route is discussed in Section 2 3 This cable was laid in 1985 and has one join near the old Variometer Hut as it was laid in two pieces 2 A 10 twisted pair shielded cable from the Cosray vault to Wombat carrying seismic information and control signals This cable was laid in 1984 and has joins near the Pump House as it was damaged in 1984 and 1985 3 The cable carrying 12V from the Cosrologist s office to the Cosray vault All the cable joins done in 1985 were soldered This is much neater and more reliable than Scotchlock crimping connectors Aluminium foil bound with wire was used to reconnect t
9. 1985 SPZ SEISMOGRAPH CALIBRATION JANUARY 1986 DAVIS INSTRUMENT COMPARISONS FEBRUARY 1985 QHM 492 RESIDUAL TORSION CORRECTIONS DAVIS FEBRUARY 1985 FIGURES o CO OY c1 4 UMN Mawson New magnetic variometer building Instrument room layout for the photo electronic magnetograph system Orientation marks in the northern instrument room Cabling of PEMs MNS2 and Doric temperature monitors Back up power for the MCC 1 and MNS2 Cabling of photo electronic magnetograph system Mawson seismic vault Frequency response of filter from SPZ AR320 input Mawson 1985 Mawson seismic system LPZ Calibration Curve Mawson November 1985 SPZ Calibration Curve Mawson January 1986 Time mark relay driver box circuit SUMMARY The work described this report was part of the Bureau of Mineral Resources contribution to the 1985 Australian National Antarctic Research Expeditions This contribution consisted of continuous recording of global seismic activity and the geomagnetic field at Mawson The geomagnetic field was recorded using normal La Cour magnetograph recording H D and Z components photographically until 12 December 1985 and after that by Photo Electronic Magnetometers X Y and Z components connected to an os digital recorder magnetic cassette tapes and a visual multichannel recorder Seismic activity was recorded using a Benioff short period vertical seismograph two Benioff short period horizontal seismographs and
10. a Press Ewing long period vertical seismograph Preliminary magnetic data were forwarded monthly to BMR Australia Preliminary seismic data were forwarded bi weekly to the National Earthquake Information Service NEIS of the USGS at Denver Colarado via the Bureau of Meteorology s Global Telecommunication System GTS and to all other Antarctic geophysical stations CHAPTER 1 INTRODUCTION Mawson Geophysical Observatory 15 operated by the Bureau of Mineral Resources BMR Division of Geophysics as part of the Australian National Antarctic Research Expeditions ANARE at Mawson Australian Antarctic Territory Logistic support is provided by the Antarctic Division of the Department of Science Station details are listed in Table l The geomagnetic observatory commenced operation in 1955 using the absolute and magnetic variometer huts and three component La Cour magnetograph from Heard Island Oldham 1957 Since then numerous instrument changes have taken place see Appendix A During the summer of 1984 85 the Department of Housing and Construction built new magnetic variometer building for the observatory This was completed May 1985 and during the latter part of the year Photo Electronic Magnetometers were installed in the building These finally replaced the La Cour magnetograph on 12 December 1985 Seismological observatory history of instrumentation is also included Appendix A February 1985 the Benioff short p
11. a temporary pier south of the absolute hut and simultaneous observations were made with the help of Pelham Williams One set of simultaneous Il comparisons was done QHM 492 circle 73 was compared with 172 circle 508813 The observing schedule was Set Absolute hut pier BMZ tripod H1 QHM 172 QHM 492 QHM 492 QHM 172 This gave an instrument difference 172 492 of 23 nT 0 00138H The station difference Pier Tripod was 29 nT 0 00174H see Table 21 The QHM calculations were done using a HP 15C calculator and include the correction for residual torsion Residual torsion corrections for all the QHM 492 H and D observations are listed in Table 22 Two sets of simultaneous D observations were done 492 circle 73 was compared with Dec 640505 circle 508813 observing schedule was Set Absolute hut pier BMZ tripod D1 Dec 505 QHM 492 QHM 492 Dec 505 D2 QHM 492 Dec 505 Dec 505 QHM 492 The calculations of the declination observations allowed for the residual torsion of the QHM fibre and the collimation angle of the magnet mirror assembly McGregor 1967 Thus complete QHM 492 observations were made in order to measure the residual torsion Table 22 The collimation angle was taken to be 8 The two sets of D observations did not produce consistent results Since the QHM 492 exhibited a residual torsion of 1 15 9 equivalent to a correction of 5 2 nT to observed H value in the
12. by DHC and skirts the rock quarry adjacent to the 014 variometer hut At the time of inception the route was very safe from any interference likely to cause damage to the cables Apart from its electrical design the new magnetic variometer building is an excellent building and should provide more than adequate housing for any variometers BMR requires to operate at their Mawson Observatory The level of ferrous interference mentioned previously 15 quite acceptable in a variometer building However when the Mawson Absolute Hut is replaced a building of simpler design should be considered pre fabricated insulated fibreglass shell bolted to a concrete slab would be very adequate Besides greatly reducing cost this would decrease possible sources of ferrous interference Mawson Geomagnetic Observatory 2 5 O 2 4 New Magnetic Variometer System Following the completion of the new magnetic variometer building the northern instrument room was prepared for the three component X Y and Z PEM system and an MNS2 PPM The X and Y PEMs were relocated from the old variometer hut see Table 2 the Z PEM was a new instrument from BMR Canberra and the PPM was to be either the MNS2 1 or the MNS2 2 used with a new noise cancelling sensor built by BMR doric temperature monitor 346904 was installed to monitor the temperature of the instrument room Back up DC power was installed for the MNS2 and the Magnetic Controller MCC 1 of the PEM syst
13. for the H D and 7 variometers are listed in Table 6 During every scale value observation the calibration current was monitored using a Fluke digital multimeter The nominal calibration currents used were 60 mA for H 40 mA for D and 70 mA for Z adopted scale values are listed in Table 7 The H and D scale values compare well with those of 1984 Crosthwaite 1986 However there is a significant change in the Z scale value from 22 65 0 08 nT mm in 1984 to 23 33 0 07 nT mm 1985 January 1985 a blast in the rock quarry adjacent to the old variometer hut dislodged the Z magnet from its agate The magnet and agate were thoroughly cleaned before the magnet was replaced The Z scale value change is attributed to this event Note that the Z temperature coefficient also changed Table 7 Absolute observations were performed about seven times per month As the geomagnetic field at Mawson is very active absolute observations were done during periods of little magnetic activity and reasonable weather conditions This meant that observations were not spread evenly throughout the month Mawson Geomagnetic Observatory 2 3 2 observing schedule was PPM 6816 1024 DEC 630332 QHM 300 DEC 630332 PPM 6816 1024 La Cour baseline values are given in Table 8 QHM calculations do not take into account residual torsion see Appendix B QHM observations were corrected for declination variation using data from the X and Y compon
14. include residual torsion corrections and the QHM 300 baseline value is not corrected by 4 3 nT see Section 2 1 As a quality check on observer performance variometer sensitivity and absolute instrument reliability one may note the following observation scatters Instr ment Difference between observations in the SAME set Average Maximum HTM 570704 2 5 nT 4 1 nT QHM 172 1 0 nT 3 2 nT QHM 300 0 5 nT 1 5 nT Dec 640505 0 3 0 7 630332 0 2 0 2 ul 18 SEISMOGRAPH PARAMETERS 1985 Component SP Z SP NS SP EW LP Z Seismometer Type Benioff Benioff Benioff Press Ewing SN 55 SN 58 SN 61 Model SV 282 SN 11 Free Period s 1 0 1 0 1 0 12 8 Mass Kg 107 5 107 5 107 5 6 9 Coil Resistance 1000 ohms 1000 ohms 1000 ohms 500 ohms Damping Resistance 387 ohms 820 ohms 820 ohms 5120 ohms Power Supply PP2 PP2 PP2 ad hoc Preamplifier Type 5 5 5 5 Gain Attenuator settings gain attenuation recorded on seismogram Bandpass filter 1 10 Hz 1 10 Hz 1 10 Hz 01 20 Hz Recorder Amplifier Type Geotech Geotech Geotech Geotech Model AR320 AR320 AR320 AR320 Attenuator setting recorded on seismograms Recorder Type Geotech Geotech Geotech Geotech Model RV 301 RV 301 RV 301 RV 301 Chart rate 60 mm min 30 mm min 60 mm min 30 mm min Calibrator Motor constant 1 38 N A not measured not measured 0 17 N A Coil resistance 247 ohm 249 ohm 258 ohm 3 3 ohm System Polarity Up Up North Up East Up Up Up
15. or non viable As the probability of this happening was negligible and an external power supply close to the building would cause magnetic interference it was recommended that this socket not be installed The magnetic variometer building is nominally non magnetic However ferrous materials are included in many components of the electrical circuit board eg the transformer iron core circuit breakers bi metallic including ferrous strips and springs and the main switch steel structure and also in the door latches parts of the internal mechanism In addition some magnet interference originates from the transformer and relays in the electrical circuit board The purpose of these was for load shedding from the main power house should station power consumption become critical As the power consumption of the new magnetic variometer building is quite small these relays and the transformer were bypassed but not removed Thus the transformer merely supplies additional ferrous interference instead of a fluctuating magnetic interference Station power to the new magnetic variometer building arrives via Ring Main Unit No 4 RMU 4 The data cable from Wombat follows the existing cable tray to a point near RMU 4 separate fire alarm cable was installed All three cables leave the cable tray near RMU 4 and are laid along the ground to the new magnetic variometer building see Figure 1 This route requires road crossing which was installed
16. to peak Z PEM also exhibited 0 4 V peak to peak spikes at the chopper frequency of the LED superimposed this The 7 PEM was using a new temperature compensating circuit board while the X and Y PEMs were using the older style circuit boards This chopper frequency interference on the output signal is characteristic of the new circuit boards The PEM signals at the Wombat termination box exhibited a similar level of high frequency noise but with a 0 3 V peak to peak 50 Hz signal superimposed upon this The MNS2 10075 and F10 s signals at the variometer building termination box displayed high frequency noise of about 0 1 V peak to peak whether the PEMs were off or on At the Wombat termination box the MNS2 signals exhibited high frequency noise of about the same magnitude when the PEMs were off but 50 Hz 0 3 V peak to peak noise was superimposed upon this when the PEMs were operating This made the MNS2 signal very similar to the PEM signals These noise levels were reported to H Q and the reply received indicated that they were quite acceptable PEMs have an output sensitivity of lOmV nT and a resolution of better than 0 04 nT under ideal conditions Seers and Black 1984 In view of this it is suggested that the noise on the data lines from the new variometer building be examined and hopefully decreased 2 4 6 MNS2 Proton Precession Magnetometers MNS2 2 was installed in the new variometer hut in
17. 04 7 46186 4 37 Vertical Intensity from BMZ 62 Observations nT 1985 Feb 01 OOUT Nov 29 040 46161 10 22 Remarks QHM 300 QHM 301 QHM 302 new observer QHM 300 QHM 300 new observer QHM 301 QHM 302 drift QHM 300 QHM 301 QHM 302 Z magnet removed QHM 300 drift 2 magnet removed new PPM drift BY Temperature Vertical Thermograph 1985 Feb 01 OOUT Feb 25 00071 103 5 0 2 24 Feb 25 00UT Apr 30 0007 103 7 0 2 64 Apr 30 0001 Jun 07 OOUT 104 0 0 2 38 Jun 07 OOUT Nov 29 O4UT 103 6 0 2 175 Temperature Horizontal Thermograph 1985 Feb 01 OOUT Oct 28 0007 37 39 0 04 269 Oct 28 OOUT Dec 12 0607 36 91 0 06 46 drift drift drift drift The BLV determined from QHM 300 observations changed 19 March 1985 due to an instrument correction change to QHM 300 This change was estimated to be 4 3 nT from this BLV shift Even though there was a new observer doing the absolute observations from 10 February 1985 the D BLVs matched Peter Crosthwaite s corrected by 1 2 West see 1986 9 DATA LOSSES FOR PEMS DURING DECEMBER 1985 JANUARY AND PEMs commenced operating on 12 December 1985 0500UT exactly once Crosthwaite FEBRUARY 1986 Period of Data Loss Reason 1985 Dec 22 1020 UT 1444 UT Fixing MCC 1 Dec 24 0900 UT 1000 UT Working in new magnetic variometer building control room ferrous in
18. 508 6 nT 46357 4 46405 13 46273 23 46273 23 C 0 5 0 1 Number of Remarks Values 29 30 PEM disturbed PEM circuit board replaced Corrected polarity of circuit board No absolute observations were done in this period but as only the polarity of the Z PEM board was changed the baseline value should have remained the same Tables SS 14 PRELIMINARY MEAN MONTIILY AND K INDEX VALUES 1985 6 H nT 1985 Crosthwaite January 18466 February 18452 1985 Kelsey March 18456 April 18450 May 18439 June 18457 July 18457 August 18447 September 18460 October 18461 November 18466 X December 8188 1986 January 8166 February 8156 H and D values derived from PEM X H D 1985 December 18475 1986 January 18454 February 18466 Mean 1985 18457 Jan Dec Note 63 35 63 38 63 38 63 40 63 39 63 40 63 40 63 41 63 41 63 42 63 42 o OO tO O0 16562 16549 16567 63 41 6 63 44 2 63 47 3 63 40 3 46368 46372 46367 46362 46352 46339 46336 46339 46331 46319 46317 Z 46312 46268 46319 49910 49908 49905 49898 49885 49879 49877 49875 49873 49862 49863 F 49861 49812 49864 and Y values 46343 49883 K INDEX av median max 3 8 3 7 3 8 4 7 3 2 3 7 3 8 3 8 3 0 3 8 3 3 3 8 3 9 4 8 3 7 4 8 3 5 3 7 3 7 4 8 3 7 4 7 3 6 3 7 3 5 3 122 4 1 4
19. 9 3 6 1 A preliminary magnetometer correction of 5 nT has been applied to H No corrections have been applied to 7 even though this correction of 5 nT to H contributes to a correction of 2 nT to 2 No corrections have been applied to the X Y 2 data 3 F is derived from the H and Z values or the X Y and Z values 4 Rodney Hutchinson s calculations 24 15 PRELIMINARY GEOMAGNETIC ANNUAL MEAN VALUES 1975 1985 YEAR D I 1975 62 31 4 68 44 0 1976 62 37 3 68 40 0 1977 62 43 9 68 36 9 1978 62 51 9 68 35 5 1979 62 57 9 68 32 9 1980 63 05 8 68 29 8 1981 63 14 6 68 27 1 1982 63 21 2 68 25 5 1983 63 26 6 68 22 3 1984 63 33 1 68 19 2 1985 63 40 3 68 17 1 Mean annual changes 1975 1985 6 9 2 7 1975 1980 6 9 2 8 1980 1985 6 9 2 5 1985 results have Z correction of 18397 18418 18425 18421 18425 18432 18443 18433 18439 18446 18457 6 0 7 0 5 0 8488 8470 8442 8402 8375 8340 8303 8267 8245 8216 8186 30 2 29 6 30 8 16321 16354 16376 16392 16411 16436 16467 16475 16493 16515 16542 22 1 23 0 21 2 47269 47157 47051 46986 46890 46784 46705 46616 46503 46398 46345 92 4 97 0 87 8 50723 50626 50530 50468 50380 50284 50215 50128 50025 49930 49885 83 8 87 8 79 8 2 nT applied to the annual average as the preliminary means did not This correction is applied nowhere else in
20. 985 February 23 060001 25 Q600UT April 24 1900UT 25 0250 28 0550 29 06200 July 05 1420UT 08 085001 October 15 1140UT 15 1220UT This was a total of 147 5 hours or 1 9 of the total recording period The primary reasons for data loss and the degradation of data quality were 1 failure of station power supply 2 loose intermittent connections in the power supply and timing circuits PPT 1 and TMU 1 3 overfixation of photographic records The D timemark trace the D reserve trace were missing from the La Cour magnetograms all year The 2 reserve trace was apparent but very faint No attempts were made to restore or improve these traces as previous geophysicists had had no success when tackling this problem Crosthwaite 1986 Also very little data were lost during magnetic storms All other traces were considered to be acceptable so no adjustments were required Mawson Geomagnetic Observatory 2 2 Blasting at the rock quarry site adjacent to the old variometer hut ceased at the end of February 1985 The rock crusher and other plant were not removed No blasting was done in the 85 86 summer Orientation tests were not done on the La Cour as 1985 was its last year of operation The labelling of Mawson La Cour magnetograms is misleading Generally the H D Z and T stamps on a magnetogram have an arrow which indicates the direction of increasing field or temperature On Mawson La Cour magnetograms the arro
21. August and was operating while the 5 were being installed The MNS2 electronics were situated in the control room noise cancelling head was installed on the F pier in the instrument room cycling rate was altered to 15 seconds per Mawson Geomagnetic Observatory 2 9 cycle The temperature the head was monitored by attaching the spare Doric 346901 sensor to the head temperature of the head was about 20 C when the room was kept at about 10 C Although no calibrations were done the MNS2 2 appeared to be working well giving the expected output on the chart recorder until 23 November when it started giving spurious field values The PEM installations were completed and the new observatory operational before the problem with the MNS2 2 was considered The IPS electronic engineer bench tested both the MNS2 1 and the MNS2 2 MNS2 2 bench tested OK The MNS2 1 had a track open circuit on the most significant bit DVI board Once this was repaired the MNS2 1 was also OK The two PPMs were both tried with cycling rates of 15 seconds per cycle and 60 seconds per cycle but spurious field values were still apparent This problem was left with the incoming geophysicist During PEM installations the PPM MNS2 2 was operating During the set up of the X PEM some interference was seen on the X PEM voltage output at the circiut board However this was not evident when all the instruments were operating
22. BATTERIES 12V T12V 12V VOLTAGE REGULATOR 1 0 uF DC DISTRIBUTION PANEL 12V OV 24V MAINS 0 1 uF to radio 240V CLOCK SPZ calibrator SK 106 PIN 17 TIMEMARKS T12V OV HELICORDER Shield is RELAY DRIVER MAINS AMPLIFIERS not connected 240V to chassis Amplifier board pins MS qb 5 time mark pulse 1 NPL to AR320s oL mains earth via CRO to W W hour time mark relays Data input from TAM5 COSRAY to CRO for time comparison Fig 10 Mawson seismic system PRIMARY POWER SECONDARY MAINS 240V POWER AUTOTIMERS REQUIRED 24 09 279 10 Magnification 000 1000 100 10 100 Period s Fig 11 LPZ Calibration curve Mawson November 1985 5 gain 48dB AR320 attenuation 30dB 24 09 280 56 100 Magnification x 1000 0 1 1 0 10 Period s Fig 12 SPZ Calibration curve Mawson January 1986 5 gain 84dB AR320 attenuation 24dB 24 09 28 W amp W SPN COUR RECORDER Hour Hour Minute LN V SPZ t Minute t Radio pips 1 SEC GED MONITOR E CRO O l ALF TRIGGER NOISE PULSE REDUCING q CAPACITORS 4 35UW I Min CLOSURE TO 10 GROUND FROM Hour GED CLOCK CLOSURE TO Pips GROUND FROM RADIO RELAY 6Hour CLOSURE TO e OSec GROUND FROM ISec GED CLOCK 1 WF Tantalum RADIO CLOSURE RIBBON CABLE TO
23. BMR PUBLICATIONS COMPACTUS LENDING SECTION BUREAU OF MINERAL RESOURCES GEOLOGY AND GEOPHYSICS CRINES LIBRARy ao 7 RECORD Y 1997 j SA 1987 2 9 MAWSON GEOPHYSICAL OBSERVATORY ANNUAL REPORT 1985 BY P J KELSEY 148720 5 e The information contained in this report has been obtained by the Bureau of Mineral Resources Geology and Geophysics as opment of mineral resources it may not part of the policy of the Australian Governmept to assist in the exploration and devel published in any form or used in a company prospectus or statement without the permission in writing of the Director Cop ex Record 1987 2 9 MAWSON GEOPHYSICAL OBSERVATORY ANNUAL REPORT 1985 BY J KELSEY 11 Contents SUMMARY 1 INTRODUCTION 2 MAWSON GEOMAGNETIC OBSERVATORY 2 1 Absolute lt 2 2 La Cour Magnetograph a 2 3 New Magnetic Variometer 11 2 4 New Magnetic Variometer 5 i 2 5 Data from the New Magnetic Variometer System 2 6 Preliminary Data e vow 4 26058 cee a week n 2 7 l strument 1 2 8 Rounds of Angles e vv e 3 SEISMOLOGICAL OBSERVATORY Operati n A ose Se QR wa B
24. MCC 1 Magnetic Controller 2nd Edition Bureau of Mineral Resources Australia Record not published Instrument Manual for the Model SV 282 Press Ewing Vertical Seismometer United ElectroDynamics Inc QHM The Quartz Horizontal Force Magnetometer User s Manual Danish Meteorological Institute DK 2100 Copenhagen February 1978 McGregor P M 1967 Notes on the Use of the Magnetometer the Measurement of Horizontal Intensity and Declination Bureau of Mineral Resources Australia Record 1967 140 Acknowledgements References 25 APPENDIX brief Jul Jan Dec Sep Feb Dec Mar Aug Jul Jul May Mar Dec HISTORY OF INSTRUMENTATION UP TO 1985 summary of the developement of Mawson Geophysical Observatory in terms of instrumentation until 1985 is presented below 1955 1955 1957 1961 1967 1968 1975 1975 1981 1982 1983 1983 1984 1985 1985 Geomagnetic Absolute instruments used for regular observations of H D amp Z Oldham 1957 Continuous recording commenced by three component normal La Cour magnetograph Oldham 1957 Bar fluxmeter magnetograph installed Pinn 1961 Three component insensitive La Cour magnetograph installed and recording commenced Merrick 1961 Bar fluxmeter magnetograph withdrawn Dent 1971 Insensitive La Cour magnetograph converted to medium sensitivity and renamed normal magnetograph The norma
25. aite Cechet 1984 Crosthwaite 1986 that thermometer 1416 QHM 301 was inconsistent with the other thermometers the calibrations of most QHM thermometers are very dated it is expected that instrument correction discontinuities will occur should any of them be replaced All data derived from QHM 300 observations from 19 March 1985 onwards are adjusted to allow for the change in its instrument correction 301 clamping mechanism is sticky and introduces nuisance vibrations at the beginning of an observation Declinometer 630332 and BMZ 62 worked satisfactorily all year PPM G816 1024 proved not to be a reliable instrument in Antarctic conditions The connections to the sensor were replaced a couple of times and the dry cell batteries were an inadequate power source However it was used fairly successfully for total field observations until 15 November when it died completely Its repair was inhibited by lack of documentation 2 2 La Cour Magnetograph The La Cour Magnetograph was used to photographically record the H D and Z components of the geomagnetic field from 01 February to 12 December 1985 Table 2 On 29 November 1985 the Z magnet of the La Cour was removed as it was to be installed in the new Z PEM Thus for this period 29 November to 12 December only the H and D components of the field were recorded Otherwise the La Cour operated continuously except for the following periods of record loss 1
26. and the output voltage lines were checked at the termination box the control room of the variometer building 2 5 Data from the New Magnetic Variometer System The three component PEM system was used to monitor the X Y and Z components of the geomagnetic field from 12 December 1985 onwards PEM data up to the end of February 1986 were analysed for this report Several data losses were incurred during this period Table 9 2 5 1 X and 7 Baseline Value Control Absolute observations were carried out with the same frequency and observing schedule as was used for the La Cour baseline value control Scale value tests were made following each set of absolute observations The constants for the scale value coils of the X Y and Z variometers are listed in Table 6 The scale value calibration currents were checked once per month Table 11 Preliminary and adopted scale values for the X Y and 7 PEMs are given in Table 12 Baseline values for the X Y and Z PEMs are given in Table 13 The scatter in the Z PEM baseline values was quite low when first operating standard deviation was 3 6 nT However on 08 January 1986 the light in the room was inadverently turned on while the PEMs were operating This did not affect the X and Y PEMs but caused the Z PEM to start oscillating on its agates Z magnet vibrated itself to one side of its support It had to be re centered manually This caused Z baseline value shift as was expe
27. arty for their assistance and co operation particular special thanks are due to Danny O Reilly Tony Everett and the rest of the DHC crew for completing the new magnetic variometer building as early in the year as possible for their help in fitting out the interior and for their excellent road crossing for the data and mains power cables near RMU 4 Also special thanks are due to Mark Loveridge for his help with electronic problems and assistance in performing the daily routine during the author s absence to John McIlwham for braving the blizzard and changing the La Cour records and to Grant Morrison and Gina Price for help with the daily routine during the author s absence REFERENCES Oldham W H 1957 Magnetic Work at Mawson Antarctica 1955 56 Bureau of Mineral Resources Australia Record 1957 79 Crosthwaite Peter 1986 Mawson Geophysical Observatory Annual Report 1984 Bureau of Mineral Resources Australia Record 1986 12 Cechet R P 1984 Mawson Geophysical Observatory Annual Report 1983 Bureau of Mineral Resources Australia Record 1984 36 Silberstein R P 1984 Mawson Geophysical Observatory Annual Report 1982 Bureau of Mineral Resources Australia Record 1984 35 Wienert K A 1970 Notes on geomagnetic observatory and survey practice UNESCO 1970 Seers K J and Black G W 1984 Handbooks for MPE 1 Photo electronic Magnetometer Horizontal MPE 2 Photo electronic Magnetometer Vertical and
28. ary Scale Value Temperature Coefficient Edas W W nT count X nT mm nT C 1985 X December 0 1968 8 88 3 1 1986 January 0 1986 8 74 3 1 February 0 1986 8 65 3 1 1985 Y December 0 2065 8 88 8 0 1986 January 0 1990 8 78 8 0 February 0 1990 8 71 8 0 1985 2 December 0 2 8 92 14 05 1986 January 0 1950 8 72 14 05 February 0 1950 8 67 5 54 C count C mm 1985 December 0 0736 1986 January 0 0205 0 065 5 February 0 0205 0 3738 Component Adopted Adopted Scale value Temperature Coefficient Edas WW nT count nT mm nT C 0 198 003 8 68 2 45 0 198 002 8 74 6 35 7 0 194 003 8 70 12 94 until Jan 30 0219UT 7 17 after Jan 30 1058UT C count C mm T 0 0206 0 07 until Jan 31 0805UT 0 37 after Jan 31 0805UT New PEM Z circuit board installed on 30 January 1986 W W temperature channel setting changed from 2 VFS to 10 VFS on 31 January 1986 O805UT 57 13 OBSERVED BASELINE December 1985 January Component Date X True North 1985 Dec 12 0500UT Y True East 1985 Dec 12 0500UT Dec 12 0500UT 1986 Jan 08 1413UT Jan 30 1058UT Feb 24 0614UT 1985 Dec 12 0500UT 1986 Mar 01 1986 Mar 01 1986 Jan 06 Jan 30 Feb 24 01 1986 01 VALUES FOR PEMS AND DORIC THERMOGRAPH and February 1986 0000UT 0000UT 0427UT 0219UT 0358UT 0000UT 0000UT Baseline Value at 10 C nT 8187 3 nT 16
29. cted but also the scatter the 7 baseline values increased the standard deviation increased to 13 nT See Table 13 On 30 January 1986 one of the new temperature compensating boards was installed in the PEM Z by the incoming geophysicist Rodney Hutchinson It was installed to measure Z instead of Z This was corrected on 24 February 1986 For absolute observations done during this period the values of the Z ordinate from the Edas data were reflected about the zero values of the Edas approximately 5000 counts The Z PEM baseline values thus derived were very scattered standard deviation 23 nT Temperature coefficients for the X Y and 7 PEMs were determined by a least squares analysis of baseline value vs temperature data See Table 12 Mawson Geomagnetic Observatory 2 10 2 5 2 Temperature baseline and scale values The temperature of the PEMs was monitored using a Doric temperature monitor The sensor was mounted adjacent to the Y PEM Before and after absolute observations the temperature of the Doric display was read least squares analysis of these observed temperatures vs the corresponding Edas counts was used to determine the temperature scale and baseline values See Tables 12 and 13 2 6 Preliminary Data K indices preliminary baseline values scale values and preliminary monthly mean values were transmitted monthly to BMR geomagnetism section Canberra These data were derived from the La Cour variometer
30. data until 12 December 1985 after that from the PEM data K indices were calculated from H and D indices from the La Cour data and X and Y indices from the PEM data Adopted scale values and observed baseline values are shown in Tables 7 8 12 and 13 Preliminary monthly mean geomagnetic field values and annual mean values are listed in Tables 14 and 15 Preliminary instrument corrections applied to these data are listed in Table 16 K indices are listed in Table 14 2 7 Instrument Comparisons In January February 1986 the 300 was compared to the travelling standards QHM 172 and HIM 570704 the Dec 630332 was compared to the travelling standard Dec 640505 Askania circle 611665 was used with all instruments During the comparisons the Edas sampled at 10 second intervals usually a minute sampling interval Six sets of each of the H and D comparisons were done These results are tabulated in Table 17 2 8 Rounds of Angles Rounds of angles from Pier in the Absolute Hut were carried out on 15 and 18 January and 08 March 1986 Askania circle 611665 was used to observe the relative azimuths of the three marks BMR 1985 2 SOH and Short Peg ref Crosthwaite 1986 The average angle between BMR 1985 2 and SOH was 33 11 1 which agrees with Peter Crosthwaite s azimuths average angle between SOH and Short Peg was 84 20 1 and the average angle between Short Peg
31. e 3 2 Radio Frequency Interference Calibrations e qo A uen eh tee e ae 4 CONTROL EQUIPMENT Scb Power Supplies fe tn one E ao EI woe C ng 4 2 Timing ow e s xS D a e 24 26 5 BUILDINGS AND BUILDING MAINTENANCE 6 OTHER DUTIES ACKNOWLEDGEMENTS REFERENCES APPENDIX A HISTORY OF INSTRUMENTATION UP TO 1985 APPENDIX B CALCULATIONS APPENDIX C DAVIS ABSOLUTE INSTRUMENT COMPARISONS TABLES O O N CO Contents STATION DATA FOR MAWSON 1985 MAGNETIC VARIOMETERS USED AT MAWSON DURING 1985 QHM RESIDUAL TORSION CORRECTIONS AT MAWSON 1985 QHM INSTRUMENT DIFFERENCES SUMMARY OF QHM COMPARISONS FOR 1983 1986 SCALE VALUE AND ORIENTATION COIL CONSTANTS 1985 LA COUR MAGNETOGRAPH PARAMETERS 1985 OBSERVED BASELINE VALUES FOR LA COUR MAGNETOGRAPH 1985 DATA LOSSES FOR PEMS DURING DECEMBER 1985 JANUARY AND FEBRUARY 1986 EDAS AND ATTENUATION BOX SETTINGS PEM CALIBRATION CURRENTS PHOTO ELECTRONIC MAGNETOGRAPH AND DORIC PARAMETERS OBSERVED BASELINE VALUES FOR PEMS AND DORIC THERMOGRAPH PRELIMINARY MEAN MONTHLY AND K INDEX VALUES 1985 6 PRELIMINARY GEOMAGNETIC ANNUAL MEAN VALUES 1975 1985 PRELIMINARY INSTRUMENT CORRECTIONS 1985 INTERCOMPARISONS OF MAGNETOMETERS MAWSON 1985 6 SEISMOGRAPH PARAMETERS 1985 LPZ SEISMOGRAPH CALIBRATION NOVEMBER
32. eers and Black 1984 was followed There were errors in the manual relating to polarities of the magnetic field components and to the directions of reflected light spot movement when scale value set gain or orientation currents are applied to the helmholtz coils This caused some confusion when the PEM set up procedure was first followed were also a few ambiguous sections in the manual and one of the crucial diagrams was missing Hardware faults in the system included some mild steel nuts and bolts being used in the Z PEM output pins of the circuit board of the 2 were connected in reverse at the plug Jl on the PEM casing three component MCC 1 supplied only 1 minute scale value pulses instead of 2 minute pulses Despite these setbacks the PEMs were finally installed satisfactorily Setting up of the PPM Noise cancelling Head The PPM was orientated on the F pier such that the axes of the detection coils are roughly perpendicular to the geomagnetic field vector Note that the axes of the detection coils are perpendicular to the long axis of the cylindrical case Temperature Control It was decided to use 10 as the standard temperature of the new variometer system building is heated in both instrument rooms by non magnetic heaters mounted on the walls about 200 mm from the floor The heaters both have thermostats However a temperature controller built by BMR was used to control the heater
33. em The data were logged in the Science Building Wombat by a digital recorder Edas unit utilizing magnetic cassette drive and visual multichannel chart recorder W W 2 4 1 Preparation of Instrument Room Layout of the Instrument Piers Tests were undertaken to determine the minimum permissible separation between the PPM noise cancelling sensor and the PEMs These tests were carried out on the X and Y PEMs while they were operating in the old variometer hut The PPM noise cancelling sensor affected the X PEM when the distance between the PPM sensor and the helmholtz coils of the PEM was less than 790mm The PPM affected the Y PEM when this distance was less than 960mm The closest spacing allowable between adjacent PEM helmholtz coils is deemed to be 1000mm The PEMs should be arranged in a manner such that there is no light interference between them PPMs have stronger signal strengths if the sensor head is of the order of 2000mm above the ground Wienert 1970 All the above points were considered in the internal design of the northern instrument room of the new magnetic variometer building which was to house the X Y and Z PEMs and the noise cancelling sensor of the MNS2 PPM No heights or sizes were specified for the PEM piers so these were made to accomodate the slate pier tops available at Mawson to be reasonably stable and to be of a reasonable height to work at during the PEM installations The final layout of the i
34. ent PEMs until 24 June 1985 After that the declination corrections were measured from La Cour magnetograms The baseline value change 19 March 1985 for baseline values derived from QHM 300 data is result of instrument correction change to 300 Some drift was seen in all of the H D and Z La Cour baseline values derived during 1985 This is depicted as discrete baseline value changes on 13 May for H and D and on 01 July for Z 301 and 302 observations were included once per month Even though the La Cour H baseline values Table 8 derived for each of the QHMs were fairly consistent it is recommended that in the future QHM 301 302 observations are done as frequently as QHM 300 observations as has been the practice in the past The BMZ 62 was the back up absolute instrument for the PPM 6816 1024 and was used only once per month As there is large scatter Z baseline values Table 8 derived from BMZ observations a range of 30 nT in 1985 it may be advisable that BMZ observations are done more often than once per month in the future When the 7 magnet was removed from the La Cour variometer on 29 November 1985 for installation in the new PEM system the H and D baseline values changed These baseline value changes were observed on the 29 November magnetogram However during the period 29 November to 12 December no absolute observations were made as all effort was being used to complete the PEM installations as
35. eriod horizontal seismometers were installed in the Cosray vault where the Benioff short period vertical and the Press Ewing long period vertical seismometers were already operating Figure 8 This completed the conversion from photographic to visual recording of the seismic system The author arrived at Mawson on 06 February 1985 on the Icebird to replace Peter Crosthwaite who departed after an extended changeover on 05 March 1985 on the Icebird The replacement geophysicist Rodney Hutchinson arrived on the Nella Dan on 29 January 1986 and after another extended changeover the author departed Mawson on 14 March 1986 on the Nella Dan Absolute instrument comparisons were done at Davis in February 1985 during a stop over visit on the way to Mawson Introduction 1 1 s CHAPTER 2 MAWSON GEOMAGNETIC OBSERVATORY During 1985 a new magnetic variometer system was installed at Mawson It consisted of X Y and Z component Photo electronic Magnetometers PEMs anda Proton Precession Magnetometer PPM with noise cancelling sensor These instruments were installed in the new magnetic variometer building The X and Y PEMs used were those previously installed in the old variometer hut 7 PEM and the noise cancelling sensor to be used with an MNS2 PPM were brought from BMR Canberra The magnetic field data were recorded digitally on magnetic cassettes by an Edas data logger as well as visually on W W chart recorder The new variometer sys
36. first set of D comparisons the instrument and pier differences were calculated from the second set only instrument difference Dec 505 QHM 492 was 1 1 East and the station difference Pier Tripod was 13 0 East Table 21 The QHM observations took approximately 20 minutes as it was difficult to get sufficient light into the QHMs when operating them on the BMZ tripod outside Comparisons of the Davis BMZ 115 with QHM 172 and Geometrics 1024 PPM were also made However the PPM gave incorrect F readings probably tuned to the wrong setting so these observations were unusable Appendices C 1 1 STATION DATA FOR MAWSON 1985 Magnetic Absolute Hut Pier A instrument level Geographic co ordinates 67 36 14 2 S 62 52 45 4 E Geomagnetic co ordinates 73 34 5 105 89 from DGRF 1980 0 Elevation m 12 Foundation Precambrian Granite Magnetic Variometer Building NEW Mark 1 Geographic co ordinates 67 36 11 4 5 62 52 38 5 E Elevation m 09 Foundation Precambrian Granite Magnetic Variometer Building OLD Geographic co ordinates 67 36 13 0 5 62 52 38 5 E Foundation Precambrian Granite Cosray Building Seismometer platform Geographic co ordinates 67 36 16 6 S 62 52716 6 Elevation m 17 Foundation Precambrian Granite The co ordinates of Pier A Mark N1 and the Cosray building seismometer platform were measured by Crosthwaite in 1984 using 1515 51 as reference location This reference i
37. he cable shield The completed joins were encased in two layers of heavy duty heat shrink tubing Because of the low temperatures it was necessary that all joins be done in a parially enclosed space cold porch of Variometer Hut ute cab or tent Control Equipment 4 2 CHAPTER 5 BUILDINGS AND BUILDING MAINTENANCE The buildings used in the operation of the BMR observatories are 1 Magnetic Absolute Hut 2 Old Magnetic Variometer Hut 3 New Magnetic Variometer Building 4 Micropulsations Building or Variometer Power Supply Building 5 014 Seismic Vault 6 Cosray Building 7 Wombat Science Building Only minimal maintenance was done to the buildings in 1985 The Old Variometer Hut is in poor condition and should be removed Absolute Hut is in fair condition considering its age ex Heard Island and given the correct maintenance would last for several more years new Magnetic Variometer Building is excellent 1985 short circuit the station mains power cable between the Variometer Power Supply Building and the Old Variometer Hut became apparent When the station electrician repaired the cable he bypassed the Variometer Power Supply Building so this building is of no further importance to BMR The Old Seismic Hut continued in its role as general store room and is very useful providing a place for the storage of RTA crates and other bulky items which would be a nuisance in Wombat It will require pain
38. in operation this would cause one of the 12V lead acid batteries to be shorted out The seismometers in the cosray vault use station mains and a 12V dc power system W W chart recorder uses station mains Edas uses station mains as its primary power source and an internal battery mains failure However when this battery back up system was checked in January 1986 it was found to be faulty so was repaired and new batteries were installed The new variometer system PEMs and MNS2 utilizes station mains power and a 24V dc back up power system see Section 2 4 3 located in the new magnetic variometer building Control Equipment 4 1 2 4 2 Timing Control 4 2 1 Time Signals A new Labtronics radio was installed at the beginning of 1985 The Ionospheric Prediction Service IPS supplied BMR with an antenna initially from an aerial just north of Wombat and later from a V antenna located on IPS aerials to the east of the station Generally VNG Lyndhurst Victoria was used to provide accurate time signals for comparison with the GED crystal oven clock See Crosthwaite 1986 Table 21 for available stations frequency and propagation delays to Mawson 4 2 2 GED Digital Crystal Oven Clock A GED clock was used to provide time marks to the seismic and magnetic systems Two new GED clocks were brought from Canberra at the beginning of 1985 Both of these were installed and kept operating This was to facilitate the
39. in the PEM instrument room and maintain the room at 10 C 2 4 3 DC Back Up Power Supply A 24 Volt DC power supply utilizing two lead acid batteries was installed in the magnetic variometer building to supply back up power to the MCC 1 the MNS2 see Figure 6 MNS2 Hewlett Packard HP power supply was used to charge the batteries When the back up power system was installed it caused a lot of noise on the MNS2 outputs Diodes were included the circuit to isolate the HP power supply MNS2 and the batteries This solved the problem As the ventilation in the new magnetic variometer building is extremely poor two completely sealed Exide Safeguard 30 Amphour 12V batteries were used preference to normal lead acid batteries 2 4 4 Data Acquisition System The data acquisition system was located in Wombat and consisted Edas digital recorder utilizing magnetic cassette drive and also a WW visual multichannel chart recorder The data were transmitted to the Edas and the via an attenuation box which allowed attenuation settings of 1 or 10 and attenuation box settings and the Edas settings and input module types and ranges are included in Mawson Geomagnetic Observatory 2 8 v3 Table 10 2 4 5 Noise on the Data Signal Lines from the Variometer Building Once the new variometer system was installed and operating the noise on the data lines was examined an optimal earthing arrange
40. k To obtain accurate LPZ calibrations an accurate determination of G needs to be made either by determining accurately the two distances mentioned above or by some other method The SPZ seismometer was calibrated in January 1986 see Table 20 and Figure 12 The short period horizontal seismometers were not calibrated during 1985 Seismological Observatory s 9 3 4 Data Seismological Information Service Meteorology s Global data were reported bi weekly to the National Earthquake NEIS of the USGS at Denver Colarado via the Bureau of Telecommunication System GTS and to all other Antarctic geophysical stations Seismological Observatory 3 4 20 CHAPTER 4 CONTROL EQUIPMENT In 1985 the Time Mark Unit TMU the Power and Timing Unit PPT 1 and the Timing Board were removed from operation Time Mark Relay Driver was installed Invertech Serial No 1781 inverter and a new voltage stalilizer were installed to supply frequency and voltage stabilized power to the helicorders changeover relay allows switching to mains power if the inverter fails dc power system was re organised and dc distribution board installed Back up dc power was supplied to the AR320 amplifiers 4 1 Power Supplies Station mains 240V ac and two lead acid battery systems supply power to the seismic system AR320 amplifiers are powered by station mains with 12V 0 121 dc back up power helicorders r
41. l La Cour magnetograph was renamed sensitive magnetograph Smith 1971 15 mm hr normal recorder replaced by 20 mm hr recorder Hill 1978 15 mm hr sensitive recorder replaced by 20 mm hr recorder MNS2 proton precession magnetometer installed for absolute measurements La Cour sensitive magnetograph removed Silberstein 1984 Photo electronic magnetometer PEM X and Y components installed Cechet 1984 MNS2 1 proton precession magnetometer ceased operation Cechet 1984 Digital recording of PEM X and Y component data began Crosthwaite 1986 QHM 300 thermometer 2143 replaced by thermometer 1650 Residual torsion of QHM 300 also changed Total instrument correction change to QHM 300 was 4 3 nT Kelsey in prep La Cour normal magnetograph ceased operation X Y and 7 PEMs commenced operation Kelsey in prep Appendices 1 Leo Jul Feb Sep Dec Apr Jul Aug May Feb 1956 1960 1963 1970 1973 1977 1978 1981 1983 1984 1985 Seismological Three component Leet Blumberg seismograph recorder installed Three component seismograph installed consisting of Benioff seismometers free period 1 0 s and three channel single drum recorder Z galvanometer 0 2 free period horizontal galvanometers free period 70 s Merrick 1961 recorder replaced by Benioff 60 mm min three channel recorder 14 5 free period horizon
42. led the horizontal seismometers in the Cosray vault see Crosthwaite 1986 To do this the SPZ seismometer was moved and the two horizontal seismometers were installed adjacent to the LPZ seismometer on the seismic platform see Figure 8 Due to an oversight the spacings between the seismometers are somewhat less than the stated acceptable requirements Press Ewing manual No interference was evident during 1985 but it is recommended that tests be done on the system to verify this The existing two Geotech helicorders in Wombat were converted to dual operation The SPZ and SPE were recorded on one helicorder with a recording speed of 60 mm min while the SPN and LPZ were recorded on the other helicorder with a recording speed of 30 mm min The nominal record duration was 12 hours However one of the helicorders lasted less than 12 hours initially and just over 12 hours after its microswitch had been shifted lack of grace these record changes caused some small record losses during 1985 Thus on 02 September the helicorders were converted back to single operation 24 hour record duration and only the SPZ and the LPZ data recorded This situation persisted until February 1986 when the incoming geophysicist Rodney Hutchinson installed third helicorder and all four components were again recorded Besides the shifting of the SPZ seismometer few changes were made to the vertical seismograph system The LPZ TAM 5 am
43. m Y 845mm Z 848mm 1397mm 24 09 272 Fig 3 Instrument room layout for the photo electronic magnetograph system True North 649 55 Instrument piers N Fig 4 Orientation marks the northern instrument room 24 09 273 to R1 Brass nails used as orientation marks Wooden railings AM Magnetic Variometer Building MCC 1 6 core table Termination J6 remote recorder grey Box Output Pin X A blue blue COM B white white SHIELD K shield shield Y C green green COM D white white SHEILD L 2 G orange orange COM H white white SHEILD J 2 core cable black SCALE VALUE E red grey COM F black red SHIELD M shield shield earth terminal of termination MNS2 box is earthed to the switchboard PIN A green COM B white white E brown Doric 346904 monitoring blue PEMY temp red Doric 346901 orange spare red Termination Box blue white shield green white orange white grey red shield green white white brown blue red Wombat 2 core cable shields are not earthed in Wombat Fig 5 Cabling of PEMs MNS2 and Doric temperature monitors Atte mma uation Box Chan Setting 10 10 10 10 Edas Type to switch Input Module Setting 10V 10V 10V 0 20 0 20 10V 24 09 274 MCC 1 2A fuse MNS2 2 BYX21L 200R Z 25A max ByYx211 200 25A max
44. m was tidied up New cable teminations were installed and the equipment in the rack was re shuffled However the remote end of the seismic system Cosray vault is very messy The rack containing the SPZ TAM 5 amplifier is inadequately documented non rackmounted LPZ TAM 5 amplifier has no back up power in case of mains power failure The SP horizontals and the LPZ do not have calibration pulses cabling around the room is extremely messy short period horizontal TAM 5 amplifiers are in temporary rack built by Peter Crosthwaite Crosthwaite 1986 Thus it is recommended that the remote end of the seismic system be completely upgraded the layout of the seismometers should be assessed the pre amplifiers should be adequately rackmounted back up power should be made reliable calibration pulses should be available on all seismometers and the cabling should be tidied up and adequately shielded to inhibit any interference 3 2 Radio Frequency Interference Radio frequency interference was evident on the Mawson seismic records during 1985 Many simple modifications were done to the seismic system to overcome this problem Interference from routine radio transmissions from VLV Mawson Radio was apparent but the problem was greatly accentuated by the ham operators The following modifications were made to the seismic system in Wombat refer to Figure 10 1 Data inputs to AR320s These were twisted pairs from the terminatio
45. ment Two lengths of timber 70 mm x 30 mm were installed along each of the long walls of the northern PEM instrument room to accomodate orientation marks for the PEM alignment The lengths of timber were mounted 52 mm to 58 mm off the walls Three pairs of orientation marks were installed see Figure 4 Brass nails were used as the marks The marks were derived from marks and R1 which define an azimuth of 131 49 2 Crosthwaite 1986 and are embedded into the concrete floor of the building see Figure 2 The line defined by the marks labelled 1 see Figure 4 is due north south and has an error estimated to be 0 05 The line defined by the marks labelled 2 is also due north south and has an error estimated to be 0 06 The line defined by the marks labelled 3 is 64 West However since this is a new building and some shrinkage was already evident between 04 May 1985 when it was completed and January 1986 these marks will not retain this accuracy as the building moves These marks should be checked from marks 1 and R1 before they are used to check the PEM orientations 2 4 2 Installation of PEMs PPM and the Doric Temperature Monitor The X Y and Z PEMs and the noise cancelling sensor of the PPM were installed on their respective piers in the northern most instrument room of the magnetic variometer building The Doric temperature sensor was installed adjacent to the Y PEM sensor and at about the same height as the mag
46. ment considered Due to the lack of moisture the soil good earths a rarity at Mawson main switch board the new variometer building is earthed back to the main power house the Blue Box An earth was taken from the main switch board in the variometer building to the crushing terminal box which terminates the data cable from Wombat This was used to earth the shields of the data cable from Wombat and the cables from the MCC 1 Figure 7 depicts the layout of the variometer system and the earthing of the various data cables The shield of the data cable between Wombat and the variometer building is not earthed at Wombat Taking an earth from the main switch board in the variometer building was actually unnecessary MCC 1 circuit board earth is connected to its chassis and mains earth via its mains power cable The shields of all MCC 1 cables are connected to circuit board earth Thus an earth could have been obtained at the crushing terminal box via the shield of the output data cable from the MCC 1 However the earth from the main switch board was used because it was considered to be better than an earth via the MCC 1 The noise on the Doric signal was unaffected by either the MNS2 or the PEMs and was seen to be about 0 2 V peak to peak The PEM signals were unaffected by the operation of the MNS2 At the termination box the magnetic variometer hut the PEM signals displayed high frequency noise of about 0 08 V peak
47. n box of the data cable from Cosray to the inputs of the AR320s pins 1 and 2 These were replaced by shielded two core cable The shields of these cables were connected to the shield of the data cable from Cosray the pin 975 commons of the AR320 amplifier boards via a 0 01 microF capacitor and to the chassis of the AR320s 2 Time mark inputs to AR320s from the relay driver The twisted pairs were replaced by shielded two core cables The shields were connected to the pin 9 s commons of the AR320 amplifier boards via a 0 01 microF capacitor and Seismological Observatory 12 to the chassis 0 1 microF capacitor was put across all time mark outputs in the Relay Driver box Cable shields were not connected at the Relay Driver box However the circuit board earth of the Relay Driver circuit is connected to the chassis of the Relay Driver box This is connected to mains earth via the CRO 3 A 0 1 microF capacitor was put across the OV 12V supply in the time mark Relay Driver 4 A 1 0 microF capacitor was put between the OV and the chassis of the clock currently in use ref no N 1 There is a 0 1 microF capacitor between the OV and 24V input to the clock in the original clock wiring 5 0 1 microF capacitors were put across the OV 12V and the OV 12V back up power inputs to the AR320s ie across pins 4 and 5 and pins 3 and 4 of the power supply board of the AR320s Internally there isa 4 7 microF capacitor between the 0
48. net of the QHM 291 in the Y PEM The MCC 1 MNS2 and the Doric temperature monitor were installed in the control room see Figure 2 The outputs of the MCC 1 MNS2 and Doric are fed into a crushing terminal box which terminates the data cable from Wombat A similar crushing terminal box is used in Wombat to terminate the other end of the cable Figure 5 shows the cabling from the MCC 1 MNS2 and Doric in the variometer building to the Edas data logger and the W W chart recorder in Wombat Setting up of PEMs The physical alignment of the PEMs was carried out using the orientation marks previously described The total error in the alignment of the helmholtz coils of the X and Y PEMs is estimated to be 0 18 This is well within the acceptable 0 25 The line defined by the orientation marks labelled 3 64 West was used to align the Z PEM The total alignment error of the Z PEM Helmholtz coils to this line was not estimated The Z PEM is required to be aligned to within 10 of magnetic North As the annual mean declination for Mawson for 1985 was 63 40 3 west and has been changing at a rate of about 7 west per year for the past 10 years this Z PEM alignment is quite adequate critical aspect of the 7 alignment is that the feedback coils be horizontal Mawson Geomagnetic Observatory V Once the physical alignment of the PEMs was completed the setting up procedure in the Photo electronic Magnetometer manual S
49. nstrument piers allows the maximum possible spacing between the instruments see Figure 3 The closest distance between any of the sensors is about 1340 mm between the X and Z PEMs The separation of the PPM sensor from the sensors of the X Y and 7 PEMs is approximately 1800mm 3900mm and 1680mm respectively The X and Y piers are both 300mm x 600mm Their pier tops are 915mm x 380mm x 49mm and 1115mm x 459mm x 49mm respectively heights of the X and Y piers with their tops in place are both 845mm The Z pier is 300mm x 450mm and its pier top is 610mm x 458mm x 55mm The height of the 7 pier with its pier top in place is 848mm three pier tops are pieces of slate previously used in the old variometer hut or the old seismic hut F pier for the PPM sensor is 300mm x 300mm pier top is made from compressed cement AC sheet is 347mm x 350mm x 17mm The height of the F pier with the pier top in place is 1397mm Mawson Geomagnetic Observatory 2 6 The piers are made of poured concrete with non magnetic grade stainless steel 316 re inforcing In January 1986 whilst working on the PEM Z during a blizzard noise coinciding with wind gusts was observed on the output of the PEM This noise did not appear to be of sufficient magnitude to affect the Edas recording Nevertheless future installations of this nature should consider using piers of more solid and stable construction Orientation Marks for PEM align
50. on angle cl temperature coefficient t mean value of temperature in the two deflected positions c2 induction coefficient Preliminary calculations of the routine QHM observations done in conjunction with the PEMs and the H instrument comparisons done in January February 1986 were calculated on HP15C desk calculator using the following formula which includes the residual torsion correction log H C log n log sin phi cl t c2 H cos phi log cos b where b phi phi 2 a deviation due to residual torsion phi deflection angle when n positive phi deflection angle when n negative All these routine calculations 12 December onwards were later recalculated BMR s HP1000 computer using the formula which includes the residual torsion correction K n 1 k1 t 1 k2 H cos phi sin phi cos b where K main QHM constant kl temperature coefficient k2 induction coefficient The QHM coefficients are given below 1 10 5 2 10 10 300 4 19467 17 1 30 301 4 21644 17 4 40 302 4 18696 18 4 40 172 4 20077 17 0 20 HTM 704 4 081045 11 3 1 10 4 2 10 9 300 15655 61 3 94 6 91 Appendices a 22 APPENDIX C DAVIS ABSOLUTE INSTRUMENT COMPARISONS During a stop over visit at Davis February 1985 instrument comparisons were done between the QHM 492 used to measure H and D and the travelling standards BMZ tripod was used as
51. ory 2 4 2 room and two instrument rooms Figure 2 construction of the building is quite elaborate The building consists of two independent non connecting shells The outer shell is built from panels which are a sandwich of polystyrene between two layers of marine plywood and oregon studs The panels of the inner shell are similar except that the polystryrene is omitted The panels are nailed together using bronze nails In the construction of both shells the panels were connected using non magnetic grade stainless steel 316 bolts and each shell was anchored to the concrete slab using similar grade hold down bolts The concrete slab has non magnetic grade stainless steel reinforcing The slab is insulated from the ground except where it is keyed into the rock via 4 keyways each 200mm square by 600mm deep The building is finished with fibreglass capping and all external bolt heads are insulated A few points should be noted 1 The escape hatch over the door is useless and unnecessary 2 The electrical circuit board is grossly over designed and complicated and contributes to magnetic interference 3 The electrical cabling goes underneath the floor of the southern most instrument room from where it enters the building to the electrical circuit board Figure 2 4 external socket was in the original plans to accomodate an external generator to supply 240VAC to the building if mains power to the building became unreliable
52. plifier was left non rackmounted as previous attemps to rackmount it adjacent to the SPZ TAM 5 amplifier had caused cross talk between the SPZ and LPZ signals see Crosthwaite 1986 The active Seismological Observatory 3 1 17 50 Hz filter which was on the SPZ 5 output was removed at the beginning of the year No evidence of 50 Hz was seen on the SPZ signal during the year There was also a filter on the SPZ input signal to the AR320 This was removed on 23 April as it initially was not connected correctly and when connected correctly it did not improve the problems of radio frequency interference that occuring The frequency response of the filter was determined see Figure 9 in case it should be required in the future During the worst blizzard of the year 21 June the LPZ seismometer exhibited an extremely unstable output The LPZ signal was disconnected from the AR320 input to stop the helicorder pen from self destructing After the blizzard had abated the signal was reconnected and the LPZ system behaved as normal This was the only time such an event occured during the year The reason for this is unknown but bad connection or some other electrical problem seems the most probable cause Many modifications were made to the Wombat end of the seismic system to help reduce radio frequency interference These will be described later Also with the advent of the 1986 geophysicist the Wombat end of the seismic syste
53. quickly as possible Before the La Cour was dismantled and RTA d February 1986 several sets of absolute observations were done in order to calculate the H and D baseline values for this period The temperatures of the H and Z variometers were read every chart change and before and after each set of absolute observations These measurements were related to scalings on the magnetograms and least squares analyses were used to determine the temperature scale values The adopted H and 2 temperature scale values were then used to determine the baseline values See Tables 7 and 8 2 3 New Magnetic Variometer Building During the 1984 85 summer the Department of Housing and Contruction DHC commenced building the new magnetic variometer building in East Bay see Figure 1 The building was satisfactorily completed by 04 May 1985 allowing the installation of the PEM system to commence However the official handover of the building from DHC to the Antarctic Division did not occur until 30 January 1986 This caused some data losses in December 1985 and January 1986 see Table 9 as the PEMs were operational by this time The data losses occurred when DHC built the external stairs concrete pouring can only be done during summer and undertook remedial work inside the building and during the inspections required by DHC and the Antarctic Division The new magnetic variometer building consists of cold porch control Mawson Geomagnetic Observat
54. rument D Mest Instrument D West Di Dec 505 76 45 5 QHM 492 75 48 2 492 76 40 9 505 77 02 0 02 492 76 52 1 505 77 03 9 Dec 505 76 49 9 QHM 492 77 04 0 Station difference Pier Tripod 13 0 East Instrument difference Dec 505 QHM 492 1 1 East 22 492 RESIDUAL TORSION CORRECTIONS DAVIS FEBRUARY 1985 Set Date phi phi derived 7 residual torsion Time difference alpha correction nT 02 Feb 1985 09 56 4 27 44 4 4 17 3 0 9 i 10 35 5 27 50 9 0 35 3 1 1 03 Feb 1985 Di 02 18 5 27 52 19 4 75 9 5 2 03 01 7 27 50 2 0 7 8 0 1 02 03 25 5 27 51 0 1 0 5 0 0 03 52 0 27 38 0 6 2 5 0 0 ur HORSESHOE HARBOUR Power House Vehicle Workshop Building DHC Offices Old Station Buildings Living 2 Quarters Variometer e Power ea ae ea AM RACE lt Building Site Radio ANARESAT Rock Quarry 5 N Office RADOME EN Magnetic Variometer 2 Absolute Hut Aeronomy Temporary Temporary 2 Storage Storage 7 Water Supply Old Water Supply Building K BELL MELT LAKE 24 09 283 Fig 1 Mawson J NORTHERN INSTRUMENT ROOM 1000mm MAIN SWITCH BOARD COLD PORCH Fig 2 New magnetic variometer building SOUTHERN INSTRUMENT ROOM 24 09 2714 concrete pier 1 True North Height of piers X 845m
55. s a satellite trig station positioned by the road near the Old Seismic Vault and the Bureau of Meteorology buildings Its location is 67 36 04 95 S 62 52 23 66 E its height above mean sea level is 9 79 and its spheroidal height is 39 37m The co ordinates of all buildings were measured by Australian Survey Office surveyors and the WGS 72 co ordinates provided by ASO agree within 0 2 of latitude and longitude with the instrument pier co ordinates measured by Crosthwaite Elevations quoted are Height Above Mean Sea Level elevations of Pier A Mark and the top of the Cosray shaft were measured relative to ISTS 51 quoted elevation of the seismometer platform assumes the shaft to be 13m deep 2 MAGNETIC VARIOMETERS USED AT MAWSON DURING 1985 Magnetometer Location Dates Operated Comments Component La Cour H old hut Feb 01 0000UT Dec 12 0600UT De commissioned and 4 old hut Feb 01 0000UT Dec 12 060001 De commissioned and RTA d Z old hut Feb 01 0000UT Nov 29 0400UT 7 magnet removed for installation in the 3 component PEM system PEM 2 Component X old hut Feb 01 0000UT Jun 24 1417UT Removed for re installation in the new hut Y old hut Feb 01 O000UT Jun 24 1417UT Removed for re installation in the new hut PEM 3 Component X new hut Dec 12 0500UT onwards Y new hut Dec 12 0500UT onwards Z new hut Dec 12 0500UT onwards 3 QHM RESIDUAL TORSION CORRECTIONS AT MAWSON 1985 Instrument phi
56. sey 9 4 41 0 6 SCALE VALUE AND ORTENTATION COIL CONSTANTS 1985 Component Scale Value Constant Orientation Constant nT mA nT mA La Cour Magnetometers H 8 07 8 07 D 8 07 8 07 Z 7 49 Photo Electronic Magnetometers X 8 03 8 03 8 03 1 8 03 8 03 7 LA COUR MAGNETOGRAPH PARAMETERS 1985 Component Preliminary Preliminary Adopted Adopted Scale Value Temperature Scale Value Temperature Coefficient Coefficient H 21 3 nT mm 40 8 nT C 21 03 0 26 nT mm 40 6 nT C D 2 44 mm 2 42 4 0 02 mm 7 22 8 nT mm 1 0 1 23 33 4 0 07 nT mm 0 0 nT C Tz 1 73 C mm 1 76 C mm Th 2 48 C mm 2 46 C mm 8 OBSERVED BASELINE VALUES FOR LA COUR MAGNETOGRAPH 1985 No of absolute Date Baseline Values observations BLV used to determine BLV Horizontal Intensity nT 1985 Feb 01 0001 Feb 10 OS3UT 17406 2 6 17406 1 17411 1 Feb 10 O3UT Mar 19 000 17417 4 5 Mar 19 0001 May 13 00 1 17421 3 12 Feb 10 03UT May 13 000 17418 4 2 17423 4 2 13 0007 Nov 29 0407 17426 2 42 17420 3 8 17424 4 5 8 Nov 29 O4UT Dec 12 O6UT 17406 2 22 Declination 1985 Feb 01 0001 13 OOUT 61 40 4 4 0 6 48 13 0001 Nov 29 04 7 61 39 9 4 0 6 102 Nov 29 O4UT Dec 12 06 7 61 40 7 4 0 4 19 Vertical Intensity from PPM 6816 1024 Observations nT 1985 Feb 01 OOUT Jul 01 OOUT 46182 4 5 55 Jul 01 OOUT Nov 29
57. tal galvanometers installed Black 1965 14 8 free period horizontal galvanomters replaced short period 0 2 s galvanometers Robertson 1972 2 seismometer transferred to vault beneath Cosray building Almond 1975 Transfer of Geophysics office including power and timing to Wombat Science Building Recording of SP N Benioff seismometer discontinued Petkovic not published Helicorder hot pen recorder installed for SP Z and LP Z and SP N Benioff restored Four Teledyne Geotech seismic amplifiers AR320 installed for connection to twin hot pen recorders Cechet 1984 Horizontal seismometers and the Benioff photographic recorder disconnected Crosthwaite 1986 Horizontal seismometers installed in Cosray vault output to visual hot pen recorders in Wombat Crosthwaite 1986 Kelsey in prep Appendices A 2 I APPENDIX B QHM CALCULATIONS All QHM observations preliminary and final done with the La Cour variometer operational 01 February 12 December 1985 were calculated using the following formula QHM User s Manual Residual torsion corrections were not included McGregor 1967 Crosthwaite 1986 Appendix D Residual torsion corrections for QHMs used at Mawson in 1985 are listed in Table 3 log log n log sin phi cl t c2 H cos phi where H horizontal field strength C main QHM constant n number of whole turns of the QHM from the zero position phi mean deflecti
58. tem commenced recording on 12 December 1985 Previous to this a La Cour magnetograph was used to record photographically the H D and Z components of the geomagnetic field It operated in the old variometer hut Table 2 outlines the operating periods and locations of the different variometers used at Mawson during 1985 All published magnetic data from Mawson were derived from the La Cour variometer until 12 December 1985 Subsequently they were derived from the system 2 1 Absolute Instruments The instruments used were QHM 300 with thermometers 2143 and 1650 QHM 301 thermometer 1416 QHM 302 thermometer 1401 Askania Declinometer 630332 Askania circle 611665 BMZ 62 thermometer 2501 and Geometrics PPM 6816 1024 The QHMs were all used with the Askania circle 611665 The QHMs gave few problems However the QHM 300 thermometer 2143 was difficult to read so it was replaced by thermometer 1650 on 19 March Coincident to this the residual torsion of QHM 300 also changed Table 3 For 300 observations up until 19 March the mean residual torsion was 3 7 minutes of arc from 19 March onwards the mean residual torsion was 12 4 minutes of arc Since residual torsion was not allowed for in the QHM calculations see Appendix this increase in residual torsion should have caused an instrument correction change of 40 4 nT to QHM 300 This was not the case an instrument correction change of 4 3 nT was actually observed If
59. terference 1985 1986 Dec 28 0200 UT Jan 03 1200 UT DHC installing steps outside magnetic variometer building ferrous interference 1985 Dec 30 0330 UT Dec 31 0500 UT DHC inspecting interior of building 1986 1986 Jan 06 0427 UT Jan 08 1413 UT DHC doing remedial work to the magnetic variometer building Jan 30 0219 UT 1058 UT Installation of new PEM Z circuit board and official handover of magnetic variometer building Feb 04 2019 UT Feb 05 1129 UT Drive spring in Edas broken Feb 11 0332 UT 1703 UT Rod re arranging instrument racks in Wombat Feb 24 0358 UT Feb 24 0614 UT Corrected polarity of PEM Z 10 EDAS W W AND ATTENUATION BOX SETTINGS December 1985 January and February 1986 Edas and W W Component Sensor Attenuation W W Edas Input Module Channel Box Setting Settings Type Range 1 10 2 VFS 2 10V 2 Y PEM 10 2 VFS 2 10V 3 7 10 2 VFS 2 10V 4 F 0 990 MNS2 10 2 VFS 1 0 20V 5 F 0 99 MNS2 10 2 VFS 1 0 20V 6 T Doric 1 2 10 VFS 2 10V This was 1 on some records W W setting was changed from 2 VFS to 10 VFS on 31 January 1986 0805UT 11 CALIBRATION CURRENTS MCC 1 Setting Positive Current Negative Current 4 mA 4 1 mA 4 1 mA 8 mA 8 0 mA 8 0 mA 20 mA 19 8 mA 19 7 mA 40 mA 39 8 mA 39 6 mA 80 mA 79 6 mA 77 8 mA 12 PHOTO ELECTRONIC MAGNETOGRAPH AND DORIC PARAMETERS December 1985 January and February 1986 Component Preliminary Prelimin
60. this change in instrument correction of 4 3 nT for 300 15 in fact real it should be apparent in the QHM instument differences calculated through baseline value determinations during the year also in the yearly instrument comparisons done between QHM 300 and the travelling standards The instrument differences between QHMs 300 and 301 and QHMs 300 and 302 are given in Table 4 for 1985 with and without the inclusion of the instrument correction change for QHM 300 Also the QHM instrument differences for the previous three years are included Crosthwaite 1986 Cechet 1984 Silberstein 1984 The 1985 values that allow for the QHM 300 instrument correction change are more consistent and compare better to the values from previous years than the values that do not include this change Table 5 summarizes the yearly QHM instrument comparisions done over the past 3 years In 1983 1985 and 1986 the travelling standards for QHM comparison were HTM 570704 and QHM 172 while in 1984 they were HTM 570704 and QHM 174 The HTM Mawson Geomagnetic Observatory 2 1 2 570704 QHM 300 comparisons confirm a possible instrument correction change to QHM 300 of 4 3 nT while the data from QHM 172 QHM 300 comparisons do not The change in 300 instrument correction is primarily due to the change of thermometer It would seem that either or both of the thermometers 2143 and 1650 do not have accurate calibrations It was noted by Cechet and Crosthw
61. this record 16 PRELIMINARY INSTRUMENT CORRECTIONS 1985 Instrument Correction at H 18457 nT QHM 300 5 nT Askania Dec 630332 0 min BMZ 62 PPM 6816 1024 0 apply a correction Correction 0 000271 H to 1 17 INTERCOMPARISONS OF MAGNETOMETERS MAWSON 1985 6 31 January 01 04 and 05 February 1986 Instrument A Instrument B Difference A B at H 18500 nT HTM 570704 QHM 300 9 2 nT 0 00051H QHM 172 QHM 300 41 2 nT 0 00222H Dec 640506 Dec 630332 0 3 0 27 East Cir 611665 Cir 611665 Circle 611665 was used with all the instruments QHM calculations include the residual torsion correction values of the residual torsion alpha for these observations were HTM 570704 0 1 1 2 QHM 172 7 2 4 3 X QHM 300 12 47 0 5 These values decreased in linear manner from 12 97 to 2 6 during the comparisons Values are given with no instrument corrections applied data were used to calculate delta H and delta D to reduce all H and D comparisons to a common time for each set Six sets of H comparisons HTM704 QHM172 QHM300 QHM300 QHM172 704 and six sets of D comparisons 640505 630332 630332 640505 were made Through routine baseline value determinations from March 19 1985 to November 29 1985 using reductions from La Cour magnetograms 300 QHM 301 4 6 QHM 300 QHM 301 0 1 nT The above calculations do not
62. ting in the near furture The Cosray building houses all of the seismometers and preamplifier calibration rack deep in its mine shaft and a 12V power supply in the office Despite requests to the Antarctic Division carpentar ceiling was not installed in the seismic vault in 1985 but would still be a good idea in the furture pump is also required to empty the sump in the shaft during the melt The Science Building or Wombat is externally good condition However the interior could be re painted and some of the furniture upgraded to make it a more comfortable working enviroment Wombat was still not connected to site services at the end of 1985 Buildings and Building Maintenance 29 CHAPTER 6 OTHER DUTIES The author was sea ice observer for 1985 This involved taking measurements of the depth of the sea ice either weekly monthly at various sample points in the Mawson area and noting the formation and decay pattern of the ice It also involved at times reconnaissance of the sea ice to judge its safety regarding travel and recreation The usual station duties were performed This included one night per month nightwatch a couple of weeks of full time kitchen duties and Saturday afternoon council duties garbage disposal etc Volunteer cooking was also done to enable the full time cook to go on field trips Other Duties 6 1 ACKNOWLEDGEMENTS The author wishes to express her thanks to the Mawson 1985 wintering p
63. un off an Invertech inverter 240V ac with switching to station mains if the inverter fails inverter 15 powered by the 12V 0 12V battery system radio SPZ calibrator are also powered by this 12V 0 12 battery system primary power to the GED clock is from station mains with the 0 24V battery system supplying dc back up power Time Mark Relay Driver which supplies time marks from the clock to the AR320 amplifiers and the W W chart recorder is powered from the clock 0 412V This was initially designed with a 0 12V external power supply but was modfied to be powered from the clock Figure 13 Figure 10 illustrates the seismic system and the power supplies If all the instruments were floating circuit board earth not connected to mains earth only one dc battery system would be required to supply the 0 24V 12V 0 412V power to the system The inverter AR320 amplifiers clock and radio are all floating However in order to do time comparison between the clock and radio pips the respective time signals are displayed on the CRO via the Time Mark Relay Driver This connects the OV circuit board earth of the Time Mark Relay Driver to mains earth via the CRO hence the OV of the 0 24V battery system to mains earth demonstrated by the incoming 1986 geophysicist it is easy to inadvertently earth the AR320 amplifiers or any other component of the system If only one dc battery system was
64. ws indicate directions of increasing magnitude of geomagnetic field components However the stamps do not indicate that magnitudes are being considered Thus the D and Z labelling is incorrect as D and Z are both negative at Mawson 2 2 1 Parallax Tests Parallax tests were performed shortly before or after each set of absolute observations for baseline value determination This was done to allow the event marks for the observations to be accurately transferred to the data traces using a parallel rule There is very small parallax between both the 7 traces and their respective timemark traces In both cases the data trace is 0 1 mm or 0 3 minutes of time to the left of the corresponding timemark i e the parallax corrections are 0 3 minutes As previously mentioned there is no D timemark trace Any other set of timemarks on the magnetogram could be used The D trace is not more than 1 mm or 3 0 minutes to the right of the corresponding H timemark and not more than 1 7 mm or 5 0 minutes to the right of the corresponding Z timemark i e the parallax corrections for the D trace are 3 0 minutes using H timemarks and 5 0 minutes using Z timemarks These measurements are difficult to do accurately as the H and Z timemark traces are a long way from the D data trace on the magnetogram 2 2 2 Baseline Value Control La Cour scale value observations were done approximately four times per month constants for the scale value coils

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