ESA Science & Technology - Leonids 2000 Observing Campaigns

Video Observation campaign

This year, there are three different observational campaigns involving scientists from the European Space Research and Technology Centre (ESTEC) in The Netherlands: the video observation campaign by Detlef Koschny; the radio observation campaign by Jean-Pierre Lebreton and Trevor Sanderson; and the Moon flashes campaign by Håkan Svedhem and a colleague from ESTEC's Space Science Department.

Detlef Koschny - scientist from the European Space Research and Technology Centre (ESTEC) in The Netherlands - is hoping to obtain three sets of simultaneous video observations on the nights of 16-17 and 17-18 November. While Koschny's cameras will be located in the Harz Mountains of Germany, his colleague Joe Zender will be duplicating the observations in the north of the Netherlands. A group of Dutch amateur meteor observers will also be assisting by making their own observations from a third site.

By using automated video cameras to continuously watch the same region of sky from three different viewpoints, the scientists hope to be able to calculate the altitudes and orbits of the dust grains entering the upper atmosphere.

In addition, meteor detection software will be able to scan the stored video images, eventually enabling the scientists to determine the numbers of meteors down to magnitude 8 or 9 (about 10 times fainter than the human eye can see).

"The video cameras have very sensitive, wide angle lenses. They will be generally pointing away from the Moon, since its glare tends to hide the fainter meteors," explained Dr. Koschny. "By using different sites, we will obtain stereo observations of the same meteors.

"We are not expecting to see as many meteors as last year, when there were several meteors a second at the peak period, but we may see a few hundred meteors an hour," he added.

Video Observation report

18 November 2000 19.50 UT, from Joe Zender

Here is a short report of our campaign from the 'Werkgroep Meteoren' and ESA/SSD.

On the night of 16 to 17 November, only two stations succeeded in observing simultaneously: Henry Henriks (Werkgroep Meteoren) located at the Heest Observatory and Joost Haartman, Michiel Brentjens and Roy Keeris (Werkgroep Meteoren) located near Almere at the Groene Kathedraal, were able to observe with the image intensified video camera systems for about 4 hours. The camera systems are identical and later analysis will provide information on meteor rates and orbit parameters. The activity for this night was moderate and no dedicated peaks or events can be reported.

Andre Knoefel (IMO) located near Essen as well as myself, Mark Neyts and Anne van Weerden (both of Werkgroep Meteoren) had a cloudy night and the minutes of open skies just allowed us to calibrate and test the camera system for a few minutes.

On the night of 17 to 18 November, the situation for the teams changed and Andre Knoefel was clouded out for the whole night whilst the team around Joost Haartman in Almere had rain until 01.00 UT. They then decided to go east near the German border, but reported rain and clouds at 06.00 UT this morning.

The team in Hoogersmilde did observe under good conditions until 00.15 UT when clouds came in and it started raining. We dismantled the equipment and waited for a sign from Jacob Kuiper (KNMI) who reported at 03.00 UT that we could have a chance of a cloudless area near Groningen. We sped up to Groningen, found a viewing location and installed the camera equipment at 03.20 UT, about 20 minutes before the predicted peak. We did indeed observed increasing activity, but due to the weather conditions (clouds and moon) it would not be sensible to give meteor rates here. Just to give you an idea, I observed about 30 meteors in this first hour. He all had the impression that the amount of bright meteors against the weak ones was high. The activity decreased and a rain shower forced us to pack all the equipment back into the car. At about 04:45 UT we noticed increased activity and decided to install the equipment again and went on with visual and camera observations until 06.30UT. Dawn forced us to shutdown the intensified camera system but we believed to have seen an increasing activity before dawn (from 05.30 UT to 06.15 UT).

Simultaneous observations were not possible on the second night (17-18) due to the continually changing location of the teams. We hope that the analysis of the videotapes will give us a better idea of the ZHR values.

Many thanks to the teams from the Werkgroep Meteoren and Andre Knoefel for their efforts.

18 November 2000 09.50 UT, from Detlef Koschny

I left Lindau yesterday evening at around 18h in search of clear skies. Going west, I passed a few areas with clear skies. But the clouds always moved in quickly. I decided to head for the coast in the Netherlands, often the weather is different close to the sea. And indeed it was - thunderstorms and rainshowers! At around 3h in the morning the rain had stopped but it was still cloudy, so went to sleep... Just hope that my colleagues were luckier.

17 November 2000 12.40 UT, from Detlef Koschny

Bad luck so far. I am still at the Max-Planck-Institute in Lindau/Harz. I went outside last night at around 02:00 in the morning. The moon illuminated nicely some high thin clouds. Some stars were visible, but it was not very nice... Spent 30 minutes under the sky and saw two sporadic meteors, but nothing spectacular.

Now it is raining and the weather forecast is bad. Will try to find a better place for tonight!

16 November 2000 Further details

This year's campaign is to be carried out together with the 'Werkgroep Meteoren', a Dutch meteor working group. We intend to observe during the nights of 16 to 17 November and from 17 to 18 November. We will observe from four different locations, separated by 70 km to 100 km which will allow parallel observations with our camera equipment. The set-up for the four locations is as follows:

• Hoogersmilde
  Team: Mark Neyts, Anne van Weerden, Joe Zender
  Location: lat: + 52° 55' 31.9" ± 0.7" ; lon: - 6° 23' 48.2" ± 1.1" (N52.9253, E6.396)
   
• Groene Cathedraal, Almere
  Team: M.A.Brentjens, Roy Keeris, Joost Haartman
  Location: lat: + 52° 19 29.8 ± 0.6" ; lon: - 5° 19' 7.3" ± 1.1" (N52.324944, E5.31869)
   
• Sterrewacht Heest
  Team: Henry Hendriks
  Location: lat: + 51° 42' 15.5" ± 0.6" ; lon: - 5° 29' 16.7" ± 1" (N51.704305, E 5.48797)
   
• Essen, Germany
  Team: Andre Knoefel
  Location: lat: 51° 23' 41" ; lon -6° 58' 46" (N51.39472, E 6.9794)

A second observation station in Germany will be manned by Detlef Koschny and Udo Telljohann, the precise location is as yet unknown.  Each of the observation stations will be equiped with an image-intensified video camera.

Radio Observation campaign

Jean-Pierre Lebreton and Trevor Sanderson from ESA's Space Science Department at ESTEC will be using radio signals rather than telescopes or cameras to observe the elusive meteors. Their technique uses the ability of plasma (ionised gas) clouds around glowing meteor trails to reflect radio waves.

"Signals from HF transmitters above about 10-15 MHz are not reflected back to Earth until they have travelled a few hundred kilometres or more. This creates a `Skip Zone' close to the transmitter where listeners cannot receive the signal, whereas listeners further away can. It's when we listen in the skip zone that we can best receive HF signals reflected on meteor trails," explained Dr. Sanderson.

"The night time is much less effective in reflecting HF signals in the range above 10-15 MHz. The signals at those frequencies escape into space, so the HF radio stations are usually shut down after dark. However, meteor trails can also reflect HF radio signals for brief periods at night," explained Dr. Lebreton.

This means that, at night, instead of no radio reception at all, the team can pick up brief transmissions every time they bounce off a meteor trail.

"For our experiment during night time, we have come to an arrangement with Merlin Communication, the service provider for the BBC, to continue their transmissions at 17.64 MHz," said Lebreton. "They will switch on one of their transmitters every night between 13 and 20 November. We will then use the short-lived meteor ionisation trails as mirrors to reflect the radio signals. In this way, we hope to be able to count the meteor echoes."

Not only will this technique enable the scientists to make an accurate count of meteors, but it will provide information on the winds in the upper atmosphere.

"Because upper atmospheric winds move the `mirror' a little bit, it induces a very small Doppler shift in the signal we receive," explained Lebreton. "These minute changes in the signal frequency allow us to separate the reflection from the meteor and the main signal. The fixed frequency of the HF carrier wave and the small changes caused by the reflection will be automatically recorded as dynamic spectrograms.

"We will be using advanced signal processing software provided by Dr. Bev. Ewen-Smith from the COAA observatory in southern Portugal to record and display the data on our computer screens. He is offering the licences for this software at reduced price until 15 November to anyone who is interested in using this technique."

A similar experiment will be conducted by the Radio Society of Great Britain.

Preliminary trials conducted over three nights in early November picked up echoes from numerous sporadic meteors and demonstrated that the Doppler technique does work.

"Anyone tuning in their radio to the BBC frequency can try this experiment for themselves," said Lebreton. "It should be possible to pick up the echoes - each lasting a few seconds - from the UK and all over Europe. It will be an interesting challenge for the readers of our Web site!

"This is the best way to learn about meteor showers - it works day and night, and in all weathers. It should be possible to listen to the radio broadcast and hear echoes that will last for more than a few seconds. During the peak activity at around 4:00 GMT (5:00 CET) on 18 November, we may even be able to listen continuously to the radio programme!"

Radio Observation report

23 November 2000, Report from Jean-Pierre Lebreton

We have started to summarize the HF radio observations. Below are plots for two selected time slots: 04:39 to 04:46 (Local time) and 08:55 to 09:10 (Local time) for 7 days (nights) around the Leonid shower (from 14 to 20 November). During the night timeslice, it is clear that the (non-sporadic) activity has increased significantly on 18 November, but it seems there was some activity 1-2 days before (16 and 17 November), and perhaps 1 day after (19 November).

Trace for 14 to 20 November, 04:39 to 04:46 local time	Trace for 14 to 19 November, 08:55 to 09:10 local time

The day timeslice is quite interesting as well. First note that the change of transmitter from Cyprus to Woofferton is very clear. Not many echoes were obtained when listening to the Cyprus transmitter. On 18 November the activity at around 09:00 was much higher than the days before or after. Some activity was also "audible" on 17 November. Note the timeslice for 20 November is not yet available.

Video of meteor with the Moon in the background.

We also managed to make a video, using a standard CCD digital camera, showing a meteor with the Moon in the background. It's not a spectacular one compared to good video movies that I have seen, but the Moon in the background doesn't help. This was a pretty bright meteor. You may also see clouds moving over the Moon. We did not have a perfectly clear sky, but it was sufficient to enjoy the show.

20 November 2000, Report from Jean-Pierre Lebreton

Pretty good show during the night of Friday to Saturday. On Friday Udo, Olivier, Hakan and myself gathered at ESTEC for a good part of the night.

We had good sky from about 02:00 onwards, while it was pouring rain until 01:30! We saw a good number of meteors from ESTEC's parking lot. We especially enjoyed lasting trails for a few seconds despite the bright moon... and patchy clouds. This was quite impressive. The radio recordings are excellent. There are plenty of very unusual echoes which can be attributed to the Leonids. The BBC transmitted from Woofferton for us until 05:00 UTC. They then switched to their nominal transmission schedule afterwards (from Cyprus between 05:00 UTC and 07:00 UTC and then from Woofferton and Skelton from 07:00 UTC onwards). We saw an increased activity between 03:00 and 05:00 UTC, and also from 07:00 UTC onwards. We could not detect echoes during the transmission from Cyprus as the geometry was not adequate.

We even managed to make a video (with a pretty standard CCD camera) and grabbed a few meteors on a bright Moon background. Mpeg files are being prepared.

Two samples of our radio recordings are shown below. They represent spectograms in a 25 Hz band around 1 kHz. Low frequency are on top and higher frequencies are on the bottom of each plot.

04:57 to 05:22 local time, 18 November

07:56 to 08:19 local time, 18 November

17 November 2000

During the night of 13 November, sound recordings were made of the Leonids. A .wav sound file of the recording can be downloaded here.

Output from the .wav sound file was analysed using advanced signal processing software provided by the COAA observatory in southern Portugal, and gave the trace seen here on the right.

16 November 2000

ESA Scientists have started listening to the Leonids. By tuning into the radio signals some recordings have already been made prior to the anticipated peaks in activity later in the week.

The image below shows the spectogram obtained during the night of 15 to 16 November for the time period 04:00 to 04:25 LT (-1 for UTC) which is near the time of the expected peak on the 18 Nov. (03:44 UTC).

On occasion the spectogram shows a spectacular echo, the trace below was obtained during the night of 14 to 15 November between 04:52 and 05:04 LT (-1 for UTC)

Note the spectrograms represent the time variation of the audio output of the receiver. The vertical scale shows frequency. It covers ± 12.5 Hz around the 1kHz central frequency. Higher frequencies are at the bottom of the figure, lower frequencies at the top.

Moon Flashes campaign

Håkan Svedhem and a colleague from ESTEC's Space Science Department will be using a 25 cm telescope to observe the dark hemisphere of the Moon on the nights of 16-17 and 17-18 November, during next week's Leonid shower.

Attached to the telescope will be a video camera and a recorder, which Svedhem hopes will capture images of the tell-tale flashes that indicate Leonid meteors are striking the lunar surface.

"These flashes are very brief - they will only last one or two frames of the video," he explained. "We will be using special software to compare each frame with the previous one."

A similar Leonids observational programme from Tenerife in November 1999 was washed out by bad weather, but Svedhem is hoping for better luck this time.

"The meteor count is not expected to be as high this year and the phase of the Moon is not very favourable, so we are not too optimistic about seeing any flashes. However, next year the lunar phase is much better and the meteor predictions are higher, so this will be a useful trial for the 2001 Leonids shower."

Moon Flashes report

17 November 2000, Håkan Svedhem reports from ESTEC in Noordwijk

I had put up the 25 cm with a video camera between the stores building and the transport office barrack to capture eventual impacts on the dark part of the moon. The moon is now fairly close to the radiant and therefore most impacts will occur on the far side. Only a very small part at the northern cusp was exposed to the stream.

The weather was quite good, considering all the rain in the evening. I did however get problems with condensation on the lens around 06:00 and onwards since the humidity increased strongly at that time. I stopped at about 6:40. That was unfortunate since the moon passed the 1932 stream only four earth radii from its maximum just at that time.

I do not yet know if I got any impacts since a flash is only one or two frames typically, and they will have to be searched for by computer which compares consecutive frames. Surprisingly I saw only a few meteors during the whole night, perhaps because the moon was too bright and there were other ESTEC lights on around me (the major street lights and parking lot lights had been switched off).

I will try once more coming night, from about midnight.

Results

Dual Camera Observations

During the nights of 16-17 and 17-18 November, Joe Zender and Detlef Koschny of ESA's Space Science Department at ESTEC attempted to obtain 'stereo' observations of the Leonid meteors with image intensified video cameras. These cameras are equipped with wide-angle lenses and can record meteors that are too faint to be seen with the naked eye.

It was hoped that the various observing teams would be able to obtain parallel observations from four different locations 70 km to 100 km apart. Zender was observing with a team from the Dutch Werkgroep Meteoren at Hogersmilde in the Netherlands. Unfortunately, poor weather only allowed his team to record about 1.5 hours of video data outside the time of the maximum activity.

Other teams had a little more success. On the night of 16 - 17 November, two stations succeeded in observing simultaneously: Henry Henriks (Werkgroep Meteoren) located at the Heest Observatory and Joost Haartman, Michiel Brentjens and Roy Keeris (Werkgroep Meteoren) located near Almere at the Groene Kathedraal, were able to observe with the video cameras for about 4 hours. However, activity was moderate and no dedicated peaks or events could be reported.

On the next night, the team in Hoogersmilde was able to observe under good conditions until 00:15 UT. When the clouds and rain closed in, they were able to dismantle their equipment and rapidly move to a relatively cloud-free area near Groningen. The camera equipment was set up again by 03:20 UT, about 20 minutes before the predicted peak. Despite problems with the clouds and Moon, they were able to observe increasing activity, with about 30 meteors in the first hour. Overcoming more disruption from the weather, the team was able to recognise another spell of increased activity at about 04:45 UT. Visual and camera observations continued until 06:30 UT, with another suggestion of increasing activity before dawn (from 05:30 UT to 06:15 UT).

Koschny's attempted observations in the Harz mountains of Germany were also plagued by bad weather. Apart from two sporadic meteors seen from the Max-Planck-Institute in Lindau-Harz on 17 November, there was nothing to report.

Simultaneous observations from different sites were not possible on the second night due to the continually changing location of the teams, but it is hoped that analysis of the videotapes will give a better idea of the ZHR (zenithal hourly rate) values. Everyone is hoping for better luck with the video observations next year!

Echoes of the Leonids

Olivier Moullard, Jean-Pierre Lebreton and Udo Telljohann

The BBC helped the experiment by transmitting from Woofferton until 06:00 UT (7 Local time), and then switched to its normal transmission schedule (from Cyprus between 06:00 UT and 08:00 UT, and then from both Woofferton and Skelton from 08:00 UT onwards).

The radio recordings were excellent, with numerous very unusual echoes which can be attributed to the Leonids. Preliminary analysis of the High Frequency night-time radio observations indicates that the (non-sporadic) activity increased significantly on 18 November, but it seems there was some activity 1-2 days before (16 and 17 November), and perhaps 1 day after (19 November).

A rise in activity was noticeable on 18 November between 03:00 and 05:00 UT, and also from 07:00 UT onwards. Few daytime echoes could be detected during the transmission from Cyprus as the geometry was unfavourable. However, the activity at around 09:00 on 18 November was much higher than on the days before or after.

Despite pouring rain until 01:30, the team also managed to capture a few meteors against the bright Moonlit background on a video taken with a standard CCD camera. Some of the Leonids displayed impressive trails that lingered for a few seconds.

Reference plot for 12-11-2000	24-hr plot, 17-11-2005
24-hr plot, 18-11-2005	24-hr plot, 19-11-2005

24 hour plots have been produced for the following 3 days: 17 November, 18 November, and 19 November. A reference plot, (when the BBC transmission was OFF over night) was also produced for 12 November.

Tell-tale Flashes on the Moon?

Håkan Svedhem at his telescope

The search for impacts is a difficult, time-consuming business, since a flash typically lasts for only one or two video frames. Expectations were also limited since most impacts were predicted to occur on the lunar far side, and only a very small visible area at the Moon's northern cusp was exposed to the meteor stream.

Problems with condensation on the lens forced Svedhem to stop at about 05:40 UT on 17 November - unfortunate timing, since predictions indicated that the Moon would pass close to the 1932 dust stream at that time.

The next day proved more rewarding, and he was able to observe the Moon from 02:19 UT onwards. Unfortunately, after careful analysis of the videotape, Svedhem failed to find any flashes of light that could definitely be attributed to a Leonid impact (although there was one flash image that could have been caused by a sporadic meteor).