NEMETODE: The Network for Meteor Triangulation and Orbit
Contents
1. 884 142 4478 14 3 0 958 0 933 Mean 17 2 0 950 0 932 Std dev 10 2 0 008 0 030 IAU MDC 71 4 0 953 P yer vO 00 C 70 383 150 7 137 50 114 16 61 581 148 3 137 57 114 10 37 170 148 2 137 63 107 48 224 789 152 8 137 64 112 15 23 522 150 0 137 73 115 86 53 829 152 7 142 45 114 38 78 545 150 5 138 42 113 02 73 610 2 0 1 98 2 96 151 3 140 19 113 22 WGN THE JOURNAL OF THE IMO 41 3 2013 authors equipment is limited to detecting bright multi station meteors brighter than magnitude 2 0 so we are only monitoring and analysing a restricted sample of the meteor shower SonotaCo pers comm 2012 has confirmed that orbital analysis of meteors with high geocentric velocities is at the limits of the current equip ment and it is anticipated that better results will be obtained from showers with relatively slower meteors References Armagh Observatory 2009 Automatic meteor detection system http star arm ac uk meteor cam Cobain R 2005 Setting up a meteor observing station by Robert Cobain http www eaas co uk cms index php option com_content amp view articlekid 69 setting up a meteor observing station by robert cobain amp catid 10 equipment reviews amp Itemid 16 AN a i p i 91 Cook A F 1973 A working list of meteor streams In Evolutionary and Physical Properties of Mete oroids pages 183 191 NASA SP 319 Jenniskens P Gural P Dynneson L Grigsby B Newman K Bor2. based on the PC s internal clock This can drift by varying amounts each day and as a consequence each PC is set to auto synchronise with an internet time server every 15 minutes using DIMENSION 4 software Typical corrections are of the order of 10 20 ms Without this application running the PC s in ternal clock would lose approximately 10 s every week The aforementioned software is able to gen erate a text file that provides details of the timing corrections that have been applied to the PC s in ternal clock This data is reviewed prior to each analysis to ascertain if large gt 0 5 s changes oc curred during observing runs and could there fore potentially affect the timing data A re view also helps highlight if there are avoidable scheduling issues for example regular data up loads downloads that could negatively impact bandwidth availability When running more than one system from the i 0 bmi same internet connection it is worth monitoring when the synchronisations occur Sometimes they can end up simultaneously requesting a timing correction for example if the internet connection goes down and then becomes available again per haps due to a power outage or maintenance work For autonomous operation one can reduce the im pact of this issue by having each PC synchronise after a different number of set minutes Auto synching the PC clock does require a perma nent internet connection Th
3. same meteor event from different geographical lo cations offers a number of advantages Specifically the meteoroid s trajectory through the Earth s atmosphere can be triangulated thus allowing characteristics such as the radiant and the beginning end heights to be determined Combining this information with timing data when the event occurred angular speed across the Field of View FOV permits an estimate to be made of the meteoroid s original orbit around the Sun From this an association may be made with a parent body This is discussed elsewhere in greater detail Jenniskens et al 2011 and does not warrant further discussion here 2 Network Overview NEMETODE consists of three stations or nodes The first is operated by William Stewart WS and is located in Ravensmoor near Nantwich Cheshire The second is operated by Alex R Pratt ARP and is located in Leeds West Yorkshire while the third is operated by Leonard Entwisle LE from Elland West Yorkshire 2 1 Ravensmoor Node The Ravensmoor Node operates two similar camera sys tems The cameras are Watec 902H units 1 2 sensor coupled with Computar 8 mm f 0 8 lenses The North facing camera has a Computar HGO808AFCS HSP lens while the East facing camera has a HGO808FCS HSP lens Each yields a resolution of 3 63 arcmin per pixel The instructions for this lens call for the supplied B W Aberration Compensation Filter to be fitted between the lens and
4. the camera but in the case of the Watec 902H this is not possible as the filter touches the inside Kmail ws nemetode org 2Email arp nemetode org 3Email le nemetode org IMO bibcode WGN 413 stewart nemetode NASA ADS bibcode 2013JIMO 41 845 of the camera body before the threads on the rear of the lens are able to engage with those on the camera Attempting to use a C CS Mount adapter ring which increases the distance between the lens and camera by 5 mm allows the filter to be fitted However when this is done it is no longer possible to focus the lens at in finity as a result the filter is not fitted The lens has an auto iris that by default is closed The Watec 902H does not support auto iris lenses so the Ravensmoor cameras operate with the iris opened fully by applying a voltage of 12 V DC across the red ve and black ve leads The white lead is not required Focus is achieved by rotating the barrel of the lens There is a screw that can be tightened to lock the focus position but repeated heating cooling hot days and cold nights can result in the screw becoming loose and the focus drifting A length of adhesive tape has there fore been affixed around the lens barrel to hold each focus ring in position Each camera is located in its own Closed Circuit Television CCTV Housing affixed to the gable end of a brick building see Figure 1 The housings are weath erproof have heated glass front windows
5. tions on the nights of maximum Rates declined rapidly after 2012 August 15 16 The activity profile is generally symmetrical with a suggestion that it is skewed to the left Note that when grouping captures Q1 includes level Q2 and Q3 data Q2 includes level Q3 data Between 2012 July 30 and September 03 a total of 40 Q1 multi station Perseids were captured by ARP and WS ARP post processed LE s tapes from the nights of 2012 August 08 09 and 09 10 via UFOCAPTURE and UFOANALYSER but could not obtain an average star alignment error lt 1 0 pixel the UFOANALYSER Manual recommends a figure of lt 0 3 pixel Almost all of the data were rejected at the Q1 level except for a Perseid on 2012 August 08 at 23 07 43 UT which is a tri station capture The ground tracks of the 40 Q1 multi station Perseids derived by UFOORBIT are shown in Figure 4 3 2 3 Radiant Drift UFOORBIT was used to derive the radiant point for each multi station Perseid corrected for Zenith Attrac tion The positions of the radiant points from 40 multi station Perseid meteors between 2012 July 30 and September 03 were used to estimate the daily drift of the radiant in Right Ascension and Declination and the results are plotted in Figure 5 3 2 4 Radiant drift in Right Ascension The method of least squares gives a good linear fit 0 1 2 3 4 Mean AT 63 3l 1 0 0 0 3 25 38 20 0 0 O 0 4 38 56 23 0 0 O 0 4 32 amp l 63 4 0 O0 0 1 9
6. 21 43 78 16 1 1 3 13 21 71 96 18 1 3 2012 07 30 2012 09 03 Figure 4 Ground tracks of 40 Q1 Perseid meteors 1 285 x o 131 56 r 0 987 1 The daily motion in RA during the observed period is estimated as 1 29 which is close to the value of 1 35 by Cook 1973 quoted in the 2012 British Astronom ical Association BAA Handbook If the Perseid maximum occurred at solar longitude 140 0 the estimated RA at maximum is a 48 3 3513 as presented in Table 2 3 2 5 Radiant drift in Declination The method of least squares gives the linear fit 0 209 x Ao 28 67 r 0 576 2 There is a lot of scatter in the data showing weak correlation but the daily motion in Declination during the observed period is estimated as 0 21 which is not too dissimilar from the value of 0 12 by Cook 1973 quoted in the 2012 BAA Handbook If the Perseid maximum occurred at solar longitude 140 0 the estimated Declination at maximum is 57 9 as presented in Table 2 Table 2 The Right Ascension and Declination of the Per seid radiant at maximum and their geocentric velocities AO RA Dec va km s ARP WS LE 140 0 483 579 591 BAA 139 9 46 58 IAU MDC 140 19 48 33 57 96 59 38 IMO 140 0 140 1 48 58 59 90 WGN THE JOURNAL OF THE IMO 41 3 2013 2012 Perseids radiant drift in Right Ascension 85 47 Right Ascension 2000 uw ul 25 4 7 j T j 1
7. 84 WGN THE JOURNAL OF THE IMO 41 3 2013 NEMETODE The Network for Meteor Triangulation and Orbit Determination System Overview and Initial Results from a UK Video Meteor Network William Stewart Alex R Pratt and Leonard Entwisle An overview is provided and first results presented from NEMETODE The Network for Meteor Triangulation and Orbit Determination This is a network of four low light video cameras based in the North of England in the United Kingdom that use UFOCapture UFOAnalyser and UFOOrbit to capture and analyse meteor data NEMETODE is intended to supplement the increasing number of comparable teams around the world who are using similar networks Many of these networks have been established to ascertain if the suspected meteor showers listed on the International Astronomical Union s Meteor Data Center actually exist and if so determine if they can be associated with known parent bodies This paper provides a detailed description of the equipment used and the techniques employed to collect and analyse the data The results from the first full collaborative month of operation 2012 August are presented with specific focus given to the 007 PER Perseids meteor shower The Perseids are a well characterised shower and were selected to verify if the results from NEMETODE were consistent with currently accepted parameters Received 2013 January 29 1 Introduction Using a network of cameras to simultaneously record the
8. TODE was created after an exchange of com ments on a meteor forum relating to a fireball event that occurred over northern England at 2012 July 28 00 58 47 UT While ARP and LE were aware of each other s work they were not aware of WS s setup or he of theirs Following discussion of the July fireball it was realised that fortuitously the same volume of atmosphere was being monitored by different cameras and that as a consequence triangulation could be per formed using SonotaCo s UFOORBIT program The baseline between Leeds and Elland is relatively short 21 km but between Leeds and Ravensmoor it is 107 km a distance that is much more effective for triangulation work Figure 2 shows the coverage plot for Ravensmoor and Leeds It was obvious from the outset that overall coverage could be improved through simply re aligning some of the cameras However ARP and WS decided to leave their cameras on their orig inal elevation azimuth settings for the remainder of 2012 in order to ascertain the quality of data from their existing setups As of the time of writing 2013 Jan uary this initial commissioning phase has been com pleted and the cameras have been re aligned and aug mented with an additional camera in order to max imise dual station coverage Further details of this en hanced coverage are available on the authors website http www nemetode org 88 2 5 Software The data from all NEMETODE nodes
9. al OS issues when it needs to write video data It also avoids the need for regular data transfer from one HDD to an archive A minimum of 30 GB space is kept free at all times and the disk is regularly defragmented circa once per week again video frames can be dropped if the HDD Read Write Head has to execute significant movements between sectors when writing to the disk During nights of ex ceptionally poor seeing the detection software can 86 iji iv V vi WGN THE JOURNAL OF THE IMO 41 3 2013 interpret excessive scintillation as movement that should be recorded some videos can then become a few minutes as opposed to a few seconds long thus consuming considerable HDD space UFO CAPTURE provides the user with extensive tuning capabilities to minimise such occurrences but the preference amongst the NEMETODE members is to have the detection threshold as low as possi ble in order to reduce the likelihood of a missed meteor Set the PC time to GMT and disable the Auto matically Adjust to Daylight Savings Time fea ture The timestamps for each file will then al ways be in UTC and won t suddenly jump by one hour twice per year when daylight savings starts finishes This is particularly useful when checking if the same event has been captured by another system data files can be compared automatically without the need for manual tweaking The timestamp for each file is
10. and sufficient internal space for ease of fitting of access to the cam eras Pointing and FOV details are as follows Ravensmoor North East Azimuth centre 18 5 90 8 Elevation centre 48 9 46 8 Field of View 43 5 H x 33 3 V The camera iris on the lens and the heater on the CCTV housings all operate at 12 V DC Laptop style power supplies were initially used to convert 230 V AC to 12 V DC but these were susceptible to intermittent problems with banding on the videos and images The problem was traced to the push fit electrical connec tions Slightly twisting them temporarily cured the problem but it always came back after a few days Re placements that made use of screw terminals as op posed to the problematic push fit connectors were re quired but during the specification phase it was deter WGN THE JOURNAL OF THE IMO 41 3 2013 L SD hy N SF EC 4 Figure 1 Both cameras of the Ravensmoor Node perma nently affixed to the gable end of a brick building The unit on the left faces east while that on the right faces north Note the black spacer block on the left hand unit between the camera housing and the mounting bracket This modifi cation was required in order to allow the appropriate eleva tion to be achieved without the rear of the housing fouling on the horizontal support bracket mined that a power supply that provided enough cur rent to drive additional systems for future expansion w
11. den M Koop M and Holman D 2011 CAMS Cameras for Allsky Meteor Surveillance to establish minor meteor showers Icarus 216 40 61 JPL SSD 2013 109P Swift Tuttle http ssd jpl nasa gov sbdb cgi sstr 109P McBeath A 2011 IMO 2012 Meteor Shower Calen dar IMO_INFO 2 11 Handling Editor Javor Kac Figure 7 Top view of the computed orbits of the 6 Q3 Perseid meteors
12. e Ravensmoor sys tems use AVG FREE as a firewall and MALWARE BYTES for additional protection Ensure that security updates and scans using these or other programs together with any Windows Updates are scheduled for daylight hours when the PC will not be busy detecting meteors It is also important to set the Windows security set tings to not automatically install updates as these can at times trigger an auto restart of the PC It http www thinkman com dimension4 has also been found to be beneficial to restart the PC every so often again during daylight hours just to ensure that any cumulative memory is sues don t lead to problems during the observing runs For the Ravensmoor systems this is per formed once per week Overall PC maintenance is essential and so it is important to monitor air inlets for the computer and vacuum them clean when they become dusty if the PC runs 24 hours per day 7 days per week then it may overheat and crash lockup dur ing warm weather Keeping the cables at the rear of the PC neatly bundled away from the exhaust vents also helps with the airflow viii The initial selection of video cards to accept the sig nal from the cameras resulted in less than ideal perfor mance While they worked most of the time a signifi cant number of frames were being dropped WS is in debted to Robert Cobain Cobain 2005 who operates a dual station meteor detection system in conjunction with A
13. e investment in and the installation of the UPS the local power lines have been replaced and the frequency of power outages has decreased from once per week to less than once per year The systems are very sensitive on a clear moonless night they are each capable of detecting in real time stars down to better than magnitude 5 5 though in practice the system struggles to detect meteors fainter than magnitude 4 While UFOCAPTURE does have excellent config urable settings to reduce the likelihood of non meteor events resulting in a clip some do on occasion slip WGN THE JOURNAL OF THE IMO 41 3 2013 through Depending on the time of year and local light ing conditions these can include birds bats insects firework flashes snowflakes falling leaves and of course aeroplanes and satellites On a regular basis typically daily the video clips from the previous night are re viewed and unwanted clips deleted The data is copied to separate hard drives for analysis and backup 2 2 Leeds Node The Leeds node operates a South facing Watec 902H2 Ultimate camera 1 2 sensor with a Computar HG3808 FCS HSP 3 8 mm f 0 8 lens and B W Aberration Com pensation Filter giving a resolution of 6 63 arcmin per pixel The auto iris is driven by the camera The camera and lens and a large bag of silica des iccant gel reside in the same model of CCTV housing as used by the Ravensmoor node It is mounted on the southwest co
14. eath 2011 data see Table 2 3 2 8 Orbits of Perseid meteors UFOORBIT computed the orbital elements of 6 Q3 Per seids For each pair of observations it calculated 2 orbits and a Unified orbit Key Characteristics of the Unified orbits are given in Table 3 while Figure 7 displays the Top view of the orbits 3 2 9 Conclusions The results derived from the video observations of the Perseids meteors by NEMETODE are consistent with the shower data catalogued by the BAA IAU MDC and IMO By applying Quality Assurance checks the authors now have confidence that NEMETODE equip ment and methods should give reliable results for other meteor showers There is some variability in the Perseid orbital ele ments especially the estimates of the semi major axis a and period P presented in Table 3 The authors value of a is significantly different from that quoted by the IAU MDC and is nearer to the value of the Perseids parent comet 109P Swift Tuttle JPL SSD 2013 A small error in the measured position and estimated geo centric velocity can give larger errors in the values of the orbital parameters a and P As shown in Table 1 the http www astro amu edu pl jopek MDC2007 Table 3 Orbital parameters of 6 Perseid meteors with IAU MDC shower data shown for comparison o a AU q AU e 137 5025 17 0 0 951 0 944 137 5710 15 6 0 941 0 940 137 6279 11 1 0 941 0 916 137 6401 37 0 0 958 0 974 137 7316 8 2 0 950 0
15. est compromise between not too bright to risk damage to the system and dark enough that there was the possibility of detecting a meteor However two problems became apparent i The settings on the rotary time switch had to be regularly altered particularly at times close to the equinox when the start end of nautical twilight changed rapidly from one day to the next http aa usno navy mil data 89 ii As the power for the heater on the CCTV housing was activating at the same time as the camera and iris on the lens initial video images were not good on occasions when there was condensation on the glass window at the front of the CCTV Housing it took a few minutes for the heater to clear the condensation Images taken at sunset sunrise were not saturating the sensor the shutter switch on the rear of the Wa tec 902H camera is set to the on position and so WS decided to have the switch activation coincide with sun rise and sunset Although the sky would be too bright to detect meteors it would give time for the heater to do its job and clear any condensation before the sky became dark enough for meteors to become visible The best solution found was to make use of a Theben SEL170 time switch This self contained device is able to switch 240 V AC takes account of the observer s location and date and automatically adjusts the on off times based on local sunset sunrise times that it itself calculate
16. is captured and analysed using SonotaCo s UFO Suite In addition a number of custom spreadsheets are used to analyse tim ing corrections to the PC s internal clock to provide an independent check of concurrence of event start times and to perform orbital parameter analysis 3 Data Analysis Members of NEMETODE adopt the same consistent approach when analysing their data and complete a shared checklist to minimise variation Although UFO ANALYSER has automated functionality for data reduc tion the NEMETODE team has found that in a few cases lt 10 the assigned meteor trajectory is slightly misaligned but can be corrected by adjusting a num ber of software parameters as described in the UFO ANALYSER manual As a result the NEMETODE team perform a series of manual checks for each event 3 1 Analysis Methodology For each event the following checks are applied i Timing corrections that have been applied to the PC s internal clock are reviewed to ascertain if there is an error of gt 1 0 s in any of the time stamps associated with each video clip ii The SonotaCo BBS Forum is checked to verify if there are any software updates that need to be ap plied e g updated software versions leap second corrections iii The assigned stellar background for a given profile is checked to ensure it is a good match for the stars visible in the composite image If not a new profile is generated iv Each clip is revie
17. jj j 125 130 135 140 145 150 1553 160 165 Solar longitude 2000 2012 Perseids radiant drift in Declination 66 ui fe Oy co oO N Declination 2000 UI eD 54 52 l 4 j 125 130 135 140 145 150 155 160 165 Solar longitude 2000 Figure 5 Radiant drift in Right Ascension top and in Declination bottom 3 2 6 Meteor detection and extinction altitudes UFOORBIT computed the start and end heights of 15 Q2 Perseid meteors captured between 2012 July 30 and August 15 see Figure 6 The method of least squares gives the linear fits Ay 1 29 x M 113 0 r 0 447 3 he 4 24 x M 99 3 r 0 785 4 where h is detection altitude he is extinction altitude and M is absolute magnitude This suggests that Perseids burn up about 4 km lower in altitude for every 1 magnitude increase in brightness Perseids 2012 detection and extinction heights 425 ee a_n r e z a T 405 e s v eo 3 Detection 95 lt ee Extinction 4 3 2 1 0 1 Absolute magnitude Figure 6 Detection and extinction heights of 15 Q2 Perseid meteors 3 2 7 Geocentric velocities UFOORBIT computed the geocentric velocities vg of the 15 Q2 Perseid meteors which gave the following Vg 59 1 0 96 km s This compares well with the International Astronomical Union s Meteor Data Center hereafter referred to as IAU MDC and IMO McB
18. ould be desirable A Sunpower 60 W 12 V DC 5 A Sin gle Output AC DC Enclosed Power Supply was selected and installed This power supply is passively cooled and so no cooling fans are required All of the power is linked together i e the power for the camera iris on the lens and the heater on the CCTV housing all come from the same source the power sup ply described above and switch on off together Some meteor detection networks recommend having separate power supplies for the camera and the heater in order to avoid the potential of introducing noise to the system when the heater switches on and off The Ravensmoor system has as noted above a common power supply and has not experienced any such switching issues In order to protect the camera and lens from dam age it is essential that the iris on the lens is closed and the camera powered off during daylight hours particu larly as one of the cameras is east facing Direct sun light falling on the fully operational system will quickly damage the sensor Initially a simple rotary time switch with the settings corresponding to the hours of nauti cal twilight was used The times of nautical twilight can be easily determined for the observer s particular location by using the website of the US Naval Observa tory This website allows the user to choose between civil nautical and astronomical twilight Settings for nautical twilight were initially chosen as this seemed to be the b
19. rmagh Observatory in Northern Ireland Armagh Observatory 2009 for his recommendation to use an Osprey 210 Video Card While these are slightly more expensive than other cards they do have excellent per formance characteristics and since switching to this card the system has worked perfectly The cable run from each camera to each PC is of the order of 10 m Initially a combined video power cable solution was implemented but this proved short lived as part of the cable run is outside and is therefore exposed to the elements The cable failed after a few months as repeated exposure to frost snapped the very fine in ner cores of the power lead The combined lead was replaced with separate dedicated lines for power and video A double shielded RCA video lead one with a central core copper braid and a foil sheath was selected both for its robustness thicker wires and in order to reduce the amount of noise on the video signal The two core power lead has an exterior grade sleeve to protect it from the elements The whole system PC camera iris on the lens heater on the CCTV housing all operate off an Un interruptable Power Supply UPS so that in the event the mains power is interrupted the system will con tinue to operate for up to 30 minutes The system is located in an area that was prone to intermittent power outages lasting a second or two just long enough to crash the PC It should however be noted that since th
20. rner of the house Pointing and FOV details are as follows Leeds 184 3 49 8 89 2 H x68 6 V Azimuth centre Elevation centre Field of View The camera and heater are powered by separate 12 V DC mains adapters They are not triggered by a self timer so ARP manually switches them on off at dusk dawn The Leeds system has not yet had prob lems with condensation so the heater is rarely switched on The Leeds node uses a dedicated tower PC a Dell Dimension DXPO0O61 running under Windows Vista Home Premium with dual Intel 2 13 GHz CPUs 4 GB RAM and a 300 GB HDD The disk is defragmented every week and a separate HDD has not been neces sary Anti Virus and Firewall protection are provided by Norton s software Automatic Windows Updates are disabled then checked manually and applied during the day As with the Ravensmoor node the Windows set ting for HDD Power Saving was disabled The PC was synchronised once per evening with an Internet time service Some of the Perseids captures had to be time corrected using the method described in Sec tion 3 1 Commencing 2012 October the PC is just like at Ravensmoor synchronised every 15 minutes with an NTP time server using DIMENSION 4 software Video capture is performed by a USB 2 0 device from ClimaxDigital and in normal operation resolution 720 x 576 25 fps the CPU load is about 20 The ca ble run is also 10 m with a combined power video cable for
21. s This solution has now been implemented at the Ravensmoor node and controls the power to all cameras lenses and heaters Each camera is connected to its own dedicated desk top PC A desktop was chosen as they are relatively inexpensive powerful for the price easy to repair and upgrade have enough slots for extra RAM and space for additional Hard Disk Drives HDDs IBM M51 3 2 GHz P4 HT models were selected and upgraded from the standard specification to ones with 2 GB RAM and an additional 250 GB HDD Under normal opera tion resolution 762 x 576 25 frames per second fps the CPU load is in the region of 17 18 The Operat ing System is Windows XP The following lessons were learnt during the commissioning phase i Disable HDD Power Saving This can be done through the BIOS and or via the Power Options menu in Windows When a meteor is detected the PC will need to transfer significant amounts of data from the memory buffer to the HDD in a very short period of time while at the same time read and monitor the ongoing live video stream into the memory buffer Prior to disabling the HDD Power Saving feature it was found that after a period of inactivity frames were being lost from video clips while the HDD spun up from the auto powered down state ii A reasonable size HDD gt 100 GB dedicated to the data i e separate from the main HDD for the Operating System OS avoids issues with the PC being occupied with norm
22. te was recorded at Leeds on 2012 July 12 01524 56 UT and the last on 2012 September 11 23 06 20 UT again at Leeds The magnitude distribution from 2012 July 11 to September 12 measured by UFOANALYSER is given in Table 1 meteors from minor showers are not included The activity profile of the Perseids is presented in the graph in Figure 3 All dates are 00 00 00 UT 3 2 2 Multi station Perseid Meteors UFOORBIT provides three built in Quality Assurance criteria Q1 minimum criteria for radiant computation Q2 standard criteria for radiant and velocity computation Q3 criteria for high precision computation WGN THE JOURNAL OF THE IMO 41 3 2013 89 Table 1 Magnitude distribution of Perseid and sporadic meteors 4 3 2 Leeds Perseids 0 3 14 Sporadics 1 3 H Ravensmoor East Perseids 2 3 13 Sporadics 0 2 T Ravensmoor North Perseids 0 3 3 Sporadics 0 1 2 2012 Perseids daily captures 90 og 80 70 60 E Ravensmoor North a a Ravensmbor East E Leeds A 30 20 4 10 T oho Li all a a Jul 12 Jul 19 Jul 26 Aug 02 Aug 09 Aug 16 Aug 23 Aug 30 Sep 06 Figure 3 Daily Perseid Video Captures The histogram indicates that Perseid rates were low until there was a small increase around 2012 July 20 21 Activity picked up after 2012 August 04 05 with peak activity between 2012 August 08 09 to 13 14 although bad weather hampered observa
23. ted in step ii above iv If it already exists from a previous analysis the MA XML file is deleted v UFOANALYSER is re run for this particular video clip using the updated M XML file vi The new M CSV file is saved and verification that the correct meteor start time has been written to the MA XML and M CSV files is performed note that the filenames will remain unchanged and will still show the original start time of the video clip In a typical month each camera of the NEME TODE network will record a minimum of 100 meteors often more depending on shower season and weather and so while this level of diligence may seem onerous the au thors feel it is essential in order to maximise the data set with which further analysis can be reliably performed The resultant M CSV files are then emailed between the members of the NEMETODE team As an addi tional check however the data is also compared in a custom spreadsheet to ascertain how many events have a common start time 1 0 s and thus may be different captures of the same event The data then undergoes an initial analysis using UFOORBIT and the number of events compared against the aforementioned spreadsheet Any discrepancies are investigated and dispositioned at this stage and the spreadsheet that tracks the efficiency of NEMETODE network updated A more detailed analysis is then per formed 3 2 Perseids Analysis 3 2 1 Preamble The first likely Perseid candida
24. the camera and a separate cable for the heater The cables have not caused any problems Power cuts are very rare for the Leeds node so a UPS is not required although the equipment is connected to a mains surge protector The city sky is ight polluted with a video limiting magnitude of about 3 5 Captures often include many aeroplanes so unwanted videos are deleted each day Data backups are saved to external drives and to an other PC on which the analyses are performed S87 Figure 2 Field of View FOV coverage of the NEME TODE cameras for Leeds and Ravensmoor for the period 2012 July December The different colours represent dif ferent altitudes The red represents 80 km the light blue 100 km and the dark blue 120 km The almost transparent white is where there is single station coverage of a layer be tween 80 km and 120 km while the almost opaque white is where there is dual station coverage of a layer between 80 km and 120 km While this shows the FOV other factors such as local weather and the effects of atmospheric extinction limit the range over which meteors are detected 2 3 Elland Node The Elland node is not a UFOCAPTURE station LE occasionally runs a tripod mounted Watec 902H cam era with an aspherical Computar 3 8 mm f 0 8 lens facing South Recordings are made to VHS tapes with a manually synchronised time and date inserter The video limiting magnitude is 3 2 4 Overall Coverage NEME
25. wed to ensure the meteor com mences within 1 0 s of the time stamp assigned to the video clip v The assigned meteor trajectory is checked to en sure it is a good match for the meteor trail on the composite image If not adjustments are made to the appropriate settings within the UFOANAL YSER software as detailed in the user manual and the analysis re performed until a good match is obtained As can be seen from Section 3 1 points i and iv there are occasions when the time stamp attributed to an event may be incorrect Examples of this include the PC Clock being incorrect or a video clip is triggered by a non meteor event e g excessive stellar scintillation or an aeroplane enters the FOV but a meteor does subsequently appear and is recorded within the video clip Under these circumstances a timing correction needs to be applied and the following process is followed 3http sonotaco jp forum viewforum php f 17 WGN THE JOURNAL OF THE IMO 41 3 2013 i A copy of the original M XML file which contains details of the start time of the meteor event is saved in a secure location for archival purposes ii The frames of the video clip are stepped through one at a time until the first evidence of the meteor appears The start time of the meteor from the time code at the bottom of the frame 0 1 s is noted iii The original M XML file not the copied version is edited to give the start time of the meteor no
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