Moon landing tracked with the radio telescope

The Dwingeloo radio telescope had a prime seat during the lunar landing attempt of the Israeli Moonlander “Beresheet”. Cees Bassa and Paul Boven used the new 13 cm horn antenna to listen to the carrier signal of Beresheet at 2280 MHz.

The Beresheet lander was launched on Februari 22, 2019, and made several orbits around Earth before maneuvering into an orbit around the Moon on April 4. The landing in Mare Serenitatis was planned for Thursday April 11, 21:25 CEST (Central European Summer Time).

From the radio telescope the lander signal appeared from behind the Moon on that Thursday, as expected, at 20:55 CEST. The Israeli webstream reported that the lander turned around to prepare itself for landing. Exactly as planned, the radio signal showed a kink due to the Doppler effect, indicating that the rocket enginges had started. The next 8 minutes all went according to plan; the Israeli webstream showed decreasing speed and height of the lander, while the radio signal decreased in frequency. The full landing would last for 20 minutes.

Unfortunately, after those 8 minutes, something went wrong. First, the radio signal disappeared temporarily; the webstream reported that one of the orientation sensors was reset. When the radio transmitter on Beresheet became active again, it was clear from the radio signal that the rocket engine was not working, because the Doppler curve showed an acceleration.

During the next 3 minutes there was still contact with the lander, but the engine could not be restarted. This is clearly visible in the recording from the Dwingeloo radio telescope: the Doppler curve does not change. At 21:23:01 CEST, the signal suddenly disappeared: the moment Beresheet crashed into the Lunar surface.

Despite the failed landing, Israel has showed a great achievement. Hopefully future missions from Israel and other countries have more luck, and hopefully the Dwingeloo radio telescope can tune in again.

Doppler curve of the Beresheet signal, as measured with the Dwingeloo Radio Telescope. Times are in UTC (two hours earlier than Central European Summer Time).

New photo of Lunar farside and Earth

On Monday 4th February 2019, the Dwingeloo telescope downloaded a new photo of Earth and the lunar farside. This photo, taken Sunday 3rd February 2019 at 15:20 UTC, shows the lunar farside and Earth (with South America in view). The lunar farside has more visible craters than the side of the Moon which faces Earth.

This photo was taken by the Chinese satellite LongJiang 2 in a lunar orbit. One of the devices on this satellite was made by students from the Chinese Harbin Institute of Technology. They put a (relatively) simple webcam on it that can take pictures on command. These photos are then sent to Earth with a little antenna. Because the satellite is so far away, receiving the signal requires a large radio antenna. The Chinese have asked the CAMRAS volunteers at the Dwingeloo Radio Telescope to help with this. Downloading this photo from the satellite to the Dwingeloo Telescope (16 KB in size) took 20 minutes.

The little Chinese satellite that took this photo has been in lunar orbit since the beginning of 2018. It ‘took a ride’ on the rocket that launched the bigger QueQiao satellite. That satellite also hosts antennas from ASTRON, the original owner and professional neighbour of the Dwingeloo Radio Telescope. ASTRON hopes to use the antennas on the big satellite to receive signals from just after the Big Bang as part of the Netherlands-China Low-frequency Explorer (NCLE) project.

The amateur radio payload that took this picture was developed at the Harbin Institute of Technology by Mingchuan Wei (BG2BHC), Hu Chaoran (BG2CRY), Tai Mier (KG5TEP), Zhao Yuhao (BG2DGR). Taking this photo was coordinated by Wei. While downloading this picture, the CAMRAS Dwingeloo Radio Telescope was operated by Cees Bassa, Tammo Jan Dijkema and Vanessa Moss. The commands were uplinked to the satellite by German radio amateur Reinhard Kuehn (DK5LA) with his home-built yagi array. See more details in blog post Our precious Earth and the lunar far side.

The photo has been color-corrected. Since the satellite camera lacks an infrared filter, colors come out too red. The original is below; we edited it to balance the colors, and make the Moon greyscale.

In October 2018, the Dwingeloo Telescope also cooperated in receiving a lunar farside photo (see blog post Our precious Earth and the lunar far side) and even a time-lapse showing the Earth disappear behind the Moon (see blog post Time-laps of the Earth appearing behind the Moon). At that time, the satellite was closer to the Moon, so the entire Moon did not fit in the picture. In the next months, we expect to receive more of these photos. But in August 2019, this adventure will end: then LongJiang 2 will crash in a controlled manner onto the lunar surface in a controlled manner. QueQiao will continue operating for the foreseeable future.

Possibilities of the CAMRAS webSDR

Observing meteors

During our special openings and stargazing evenings, dozens of visitors are interested in observing meteors. This is why CAMRAS volunteers Simon Bijlsma (PA7SB) and Frans de Jong (PE1RXJ) have put more information on the astronomy page for those who want to read it again or want to know more. It concerns four articles:

Antenna building
Observing meteors with radio
Visualize radio meteors
Software Defined Radio receiver

We previously wrote those articles in Dutch for the website of the KNVWS Working Group Meteors. The articles  are about observing meteor scatter with a self-built antenna in combination with an RTL SDR dongle and suitable software and visualizing and counting meteors with the SpectrumLab program. The aforementioned articles are here on the CAMRAS website in both Dutch and English,

Who is not such a self-builder or lacks the time needed to build a meteor scatter receiving station can of course also use our online CAMRAS webSDR receiver that is specially designed to receive real time meteor scatter with your own tablet, laptop, smartphone or computer.

CAMRAS volunteer Pieter-Tjerk de Boer (PA3FWM) designed this beautiful webSDR software already ten years ago. At the Amateur Radioclub of the University of Twente, his own UT webSDR receiver runs for the entire short wave spectrum from 0.1 to 30 MHz.

The CAMRAS webSDR for receiving meteor reflections was set up after a successful experiment in 2011 in which we streamed live meteor reflections over the internet for the first time during the maximum of the Perseids meteor shower. As a result, Simon Bijlsma has built the 2-meter and 6-meter Yagi antennae that are now used for the CAMRAS webSDR. The building description can be found in article 1. These antennae are linked to two RTL SDR dongles which then provide the CAMRAS webSDR stream with the help of the SDR software.

With the webSDR tuning to the frequency of the French Space radar GRAVES gives the possibility to observe aircraft and the ISS in addition to meteor reflections. Even echoes of the GRAVES radar that are reflected by the Moon are regularly seen! The distance to the Moon back and forth is about 800,000 km and the Moon is also a very bad reflector for radio waves, so most of the signal is lost. Nevertheless, the echoes are so strong that they can be clearly seen on the webSDR receiver. See above image with meteors (hook-shaped), aircraft (lines in the middle), ISS (slanted dotted line) and the moon (vertical dotted line).

Observing satellites

Recently, the webSDR has been expanded with a receiver for a Chinese moon satellite. The Dwingeloo telescope is one of the official reception ground stations for the Chinese moon satellite DSLWP-B. From Germany the uplink command signals are sent to the satellite. This satellite floats in an elliptical orbit around the moon, through which the satellite can also take pictures of the back of the moon. This is not possible from the earth. However, the nominal transmit power of this satellite is very limited and, depending on the mode used, only 1 to 2 Watt (30 – 33 dBm).

The 25m Dwingeloo telescope is used to receive the lunar photos and telemetry signals, the frequencies used in the 70cm band are 435.4 MHz and 436.4 MHz. The beautiful photos (see above) of the back of the moon and the earth can be found elsewhere on this website. Worldwide there is great interest among radio amateurs for the photos and telemetry signals of this satellite. In collaboration with Pieter Tjerk de Boer, Simon Bijlsma therefore connected a third RTL SDR dongle and connected it to the 70cm antenna of the telescope. This allows our many (international) visitors to the webSDR to follow the satellite signals in real time and decode the GMSK and FT4G signals themselves when the telescope follows the satellite.

Radio Telescope Dwingeloo commemorates Apollo 11

In ‘Echoes of Apollo’, ( the URL refers to the web archive of the no longer existing website) – a worldwide commemoration of the Apollo 11 Moon landing forty years ago – radio amateurs in the Dwingeloo Radio Telescope sent a radio speech to the Moon on June 27, 2009.

During the Moon landing of the Apollo 11 forty years ago, radio telescopes played a crucial role in the communication between the astronauts and the home base. During the commemoration, communication specialists and radio amateurs exchanged messages via the Moon with large parabolic antennas.

The broadcast from Dwingeloo was provided by radio amateur Jan van Muijlwijk (PA3FXB), one of the dozens of volunteers who help restore the radio telescope in Dwingeloo. Under the call sign PI9CAM, he honored all the astronauts who have been on the Moon by reading their names.

His speech was broadcast by the radio telescope to the Moon in a radio message. The Moon reflected part of the emitted radio waves back to the Earth. In that part of the world which was turned to the Moon, one could listen to his rebound speech.

Worldwide, youth was also involved in this commemoration. From Switzerland, America, and Australia, they could let their voices travel to the Moon and hear their echoes three seconds later. This delay is caused by the large distance (385,000 km) between the Earth and the Moon. A few days earlier, the New York Times published a short article A Ham Radio Weekend for Talking to the Moon about this.

During this commemoration, it turned out for the first time that with extraordinarily small transmission capacities (of less than a hundredth Watt) worldwide reliable radio connections can be realized by using the Moon as a reflector for radio waves. Herewith, the radio telescopes of Dwingeloo and Mount Pleasant (Tasmania) were used. See the blog post Low-power EME world record.

– Radio message PI9CAM

– Text radio message PI9CAM

The text below was read by Jan van Muijlwijk to Tasmania via the Moon. Recordings were made in Dwingeloo (audio) and in Tasmania (on video).


Hello nice people at the Mount Pleasant Observatory in Tasmania! Hello boys and girls “down under”. And a special hello to Rex, who initiated this operation at Mount Pleasant. Congratulations with this fantastic operation and our best wishes to you all from the Dwingeloo dish in the Netherlands.

The signals you hear now have traveled nearly 800.000 kilometers. First nearly 400.000 kilometers from Dwingeloo to the Moon and again 400.000 kilometers from the Moon to your dish at Mount Pleasant. Isn’t it a miracle?

By doing a lot of Moon bouncing today we honor the achievement of mankind 40 years ago. Because this year it is 40 years ago the first man set foot on the Moon.

I myself was only eleven years old at that time, but I have very vivid memories of the event. Our family watched television during the night to witness the famous first steps on the Moon. It was absolutely fabulous!

Some sentences spoken by the astronauts are engraved in the collective memory of mankind. Two of those sentences I would like to bounce off the Moon now:

Tranquility base here. The eagle has landed.

And the most famous of them all:

It’s one small step for man, but a giant leap for mankind!

I was thrilled by the complete Apollo project anyway. Every launch of another huge Saturn V rocket was a big adventure. And as a little boy I dreamt about how it would be like to be in space and walking on the Moon. It was a time of great expectations. I read all about it. I watched every space item on television. And what a joy it was to see the Apollo 11 mission become such a great success. And let’s not forget the other Apollo missions. Apollo 13 was a
scary adventure with a happy end. But all the other Apollo’s until nr 17 were very successful. What a time it was!

I am convinced that the Apollo project played a big role in the choices I and many others made for education and hobbies. And that it is one of the reasons I became a Ham radio operator. And thanks to that I am now involved in the restoration of this big 53 years old Dwingeloo Radio Telescope. And here we are, talking about Apollo and the Moon, via the Moon with this historic Radio Telescope. Full circle!

To conclude, back to the Apollo project. In total 12 brave man walked on the surface of the Moon. To honor their courage and to the memory of this great achievement I now read their names to the Moon to be bounced off to Tasmania:

1. Neil Armstrong
2. Edwin Aldrin
3. Charles Conrad
4. Alan Bean
5. Alan Shepard
6. Edgar Mitchell
7. David Scott
8. James Irwin
9. John Young
10.Charles Duke
11. Eugene Cernan
12. Harrison Schmitt

I hope you had good reception of our signals via the Moon! Thank you for listening and for taking part in this nice Echoes of Apollo project. And thanks to the Moon for being such a nice reflector!

Best regards to Mount Pleasant Tasmania from Dwingeloo The Netherlands. Good luck to you all.
PI9CAM end of transmission. Bye bye.

– Video impression of RTVDrenthe

Together with RTVDrenthe, Jan van Muijlwijk made a video impression of this broadcast combined with images of the moon landing on July 20, 2019.

Since January 2007, the CAMRAS foundation (with its volunteers and donors) has been working on renovating the Dwingeloo Radio Telescope and making it usable again in order to stimulate the interest in science and technology among young people.

Low-power EME world record

World Moon Bounce Day June 27, 2009

This year marks the 40th anniversary of the first human being walking on the Moon. To commemorate that in an appropriate way, Pat Barthelow (AA6EG, USA) and Robert Brand (Australia) devised a special day with many EME activities. A call was made to activate worldwide especially large dishes for EME at 23 cm so that it would be possible to make good SSB connections via the Moon. The project was named Echoes of Apollo and Saturday June 27, 2019, was named World Moon Bounce Day. Of course, the Dwingeloo radio telescope had to be there too!

The low-power EME experiment between Dwingeloo and Mount Pleasant

In the week prior to World Moon Bounce Day, Jan van Muijlwijk (PA3FXB) received an e-mail from Tasmania from Rex Moncur (VK7MO). He was busy preparing the 26-meter Mount Pleasant dish for 23 cm reception. At first, transmitting seemed not allowed because of the sensitive radio astronomical frontends which remained present. But transmission power of about 10 milliwatts could be admitted. And after some calculations, he came to the conclusion that an EME connection with this super low power might still be possible! Of course, if a counter station with a large antenna would be available. And the CAMRAS radio amateurs have such an antenna in Dwingeloo.

Jan, PA3FXB, and Rex, VK7MO, agreed to immediately try it on June 27 when the rising Moon reached an elevation of 10 degrees in Dwingeloo. In Tasmania, the setting Moon would then be around 15 degrees in elevation. That gave a lot of joint “lunar time”. Jan was joined in the radio telescope by Ard Hartsuijker, René Hasper (PE1L), John Lambo (PA7JB) and Fred Tak (PA0WTA).

The construction of the 23 cm station went very well with the help of the clear instructions from Eene de Weerd (PA3CEG). At the agreed time, Dwingeloo (PI9CAM) was ready to receive the signals from Tasmania. We used the JT65c technology for this, which makes it possible to receive approximately 10 dB better than the weakest Morse signal. Great was our enthusiasm when the first connection with a 10-mW signal from Tasmania was successful! Even with a 3-mW signal, the connection was established without any problems. As far as we know this is a world record. A signal of 1 mW was also tried, but it turned out to be too weak.

10 milliwatt QRP EME Mount PLeasant to Dwingeloo Radio Telescope

3 milliwatt QRP EME Mount PLeasant to Dwingeloo Radio Telescope

After the low-power EME connection, Jan van Muijlwijk gave a speech This is PI9CAM for the ECHOES OF APOLLO PROJECT JUNE 27, 2009 to the visitors of the dish in Tasmania. See blog post Radio Telescope Dwingeloo commemorates Apollo 11.

About this low-power experiment and World Moon Bounce Day Rex Moncur (VK7MO) and Justin Giles-Clark (VK7TW) offered the following text Echoes of Apollo – EME on three milliwatts! to the Amateur Radio magazine of the Wireless Institute of Australia.

Echoes of Apollo – EME on three milliwatts!

Authors: Rex Moncur (VK7MO) and Justin Giles-Clark (VK7TW) 

27 June 2009 was designated World Moon Bounce Day as an amateur radio contribution to the celebrations of the 40th anniversary of man’s first landing on the moon. The event was organized by a US group of amateurs who had access to the Stanford University 45 meter dish and they sought the involvement of some of the larger radio astronomy dishes around the world. A key objective was to involve and interest school children in science and amateur radio by allowing children to hear voices from the moon. The event was supplemented by amateur Earth Moon Earth (EME) stations all around the world and particularly those with SSB capability on 23 cm.

Within Australia the University of Tasmania agreed to take part using their 26 meter dish which was originally used by NASA in the Orroral Valley near Canberra between 1964-1985 after which it was gifted to the University and transported to Mt Pleasant near Richmond in Southern Tasmania. Our involvement was to provide amateur EME equipment, help set up and test the system and operate the station on the day. As it eventuated the availability of large dishes provided the opportunity to explore QRP EME at as low a level as possible and we are pleased to report completion of a JT65 EME contact between the University of Tasmania’s 26 meter dish and a Dutch 25 meter dish, PI9CAM, with the Tasmanian end running only 3 milliwatts.

Mt Pleasant Radio Telescope

Mt Pleasant Liquid helium cooled receivers

– Setting up the University of Tasmania dish

While Dr Jim Lovell of the University of Tasmania willingly offered their dish and the support of the site technician Eric Baynes (VK7BB) it was first necessary to consider what was practical. At our first meeting it became clear that transmitting any sort of high power as required for SSB would be out of the question as the dish is fitted with five extremely sensitive liquid helium cooled receivers working from 4 to 22 GHz. There is no protection for RF and we could not risk damage to these receivers which are involved in ongoing international research programs. Accordingly, the Echoes of Apollo team where advised that we would contribute to the event but as a receive station only.

The feeds and receivers for the 26 meter dish are mounted in a small feed cabin (approx 2 meter cube) behind a Teflon window approx 1 meter in diameter. Within the cabin there is a remotely controlled 3 axis focus frame that allows the feeds and receivers to be moved into the correct focal position depending on which feed is in use. There is space for a 2 GHz noncooled feed and receiver which fortunately was not required around the time of the Echoes of Apollo event and the University agreed that this could be removed and replaced with a 23 cm antenna. Because of space limitations it was decided to use a small 3 turn helical. There is over 100 meters of LDF-4-50 coax between the dish and the control building where we could operate and for this reason we decided to down-convert at the feed and receive on 144 MHz. Eric, VK7BB, constructed a down-converter and the VK7MO EME station provided pre-amplifiers, 144 MHz receiver, GPS frequency reference, computer running WSJT and bandpass filters at 1296 MHz and 144 MHz to limit interference from microwave systems at the nearby Hobart airport.

A few weeks prior to the event tests were conducted with Dave Scott (VK2JDS) with JT65c signal levels much worse than expected at -9 dB and no prospect of copying SSB. A sun noise test gave around 18 dB compared to 27 to 28 dB determined with the VK3UM EME Calculator. The time for testing was limited as this is an operational radio astronomy research facility but the system was gradually refined with additional pre-amps and filters and through adjusting levels at all stages – as well as resolving the occasional ‘Murphy’ problem. Finally, we decided that the helical feed must be the remaining limitation and did some estimates to see if a Septum feed and choke ring could be physically mounted. Initially it fouled other equipment but after a redesign of the mount it was successfully installed. In the end we achieved a sun noise of 25 dB which was within a few dB of what could be expected. Every time the system needed adjustment Eric, VK7BB, had to do a safety harness and go up in a cherry picker.

Tests were now conducted with Doug McArthur (VK3UM) who runs 400 watts and an 8.6 meter dish. Doug’s SSB came through at 5/6 sufficient to be heard in a room filled with children – so with just four days to go we reported to the Echoes of Apollo team we were ready to go.

Mt Pleasant Access to feed cabin via cherry picker

Mt Pleasant Control room view

– Could we transmit QRP?

With the RX side resolved our minds turned to the possibility of transmitting QRP at a few tens of milliwatts to avoid any possibility of damaging the radio astronomy receivers. A quick calculation suggested that we should be able to work the 25 meter Dutch station PI9CAM at less than 10 milliwatts using JT65 and after an email Jan van Muijlwijk (PA3FXB) told us they would be delighted to try JT65 at 10 milliwatts. While we did not have time to test the system until the day of the event WSJT echo testing on the day gave a signal level of -31 dB at 10 milliwatts and this was improved to -27.8 dB by careful adjustment of the focus of the feed.

– The day of the Event

Because of uncertainty about working the Stanford group with SSB at an adequate level for a room full of children the university decided not to actively advertise the event to the public but agreed that we could advertise on the VK7WI broadcast for hams to come along with children and friends. Our first reception was from Doug, VK3UM, at 5/7 who we worded up by telephone to talk to the children. It was a joy to see the smiles when they heard their names off the moon. While as hams we could copy Dave, VK2JDS, on SSB at 5/2 it was not quite strong enough for the children to resolve the voice, but using JT65 messages such as the following, Dave produced a great reaction from the children who then got out their cameras to photograph their names coming back from the moon.

082700  7 -10  0.2  38  10  *    HI    JESSICA  1  0
082800  8  -8  0.1  30  11  *    HI    NICOLE   1  0
082900  9  -9  0.2  19  11  *    MOON  ECHOS    1  0
083000  6  -9  0.3   8  10  *    MOON  ECHOS    1  0
083100  9  -7 -0.3  -5  10  *    HAVE  FUN      1  0

The Stanford group was received at around 5/7 for a short period but then had to remove their feed to repair a pre-amp. Later we had various children and the media visit and arranged for Doug, VK3UM, to be the voice from the moon with great effect.

As the European window opened, we could copy Dan, HB9Q, on his 15 meter dish calling CQ on JT65c at -1 dB. The university technician agreed we could up to power to 30 milliwatts and Dan responded to our call giving us a -23 dB report. Power was then reduced to 10 milliwatts and with some effort we again completed with Dan at -29 dB. It is noted that given the 18 dB isolation of the Septum feed we did not need to use a TX relay as 18 dB down on even 30 milliwatts is quite safe for a low noise pre-amp.

The PI9CAM team using a 25 meter dish completed quickly with us at 10milliwatts giving us -22 dB and again at 3 milliwatts with signal levels of -26 dB. An attempt at 1 milli-watt was not successful. Never-the-less with a 3 milli-watt completion we were “over the moon!”.

Other Stations copied on SSB were VE3KEP, 4/1; W5J, 5/8; N6JMC, 5/8; VK5MC, 5/6; KF6JBP, 5/7; SP6JLW; 5/6; N6BDE, 5/8 and RD3DA at -5 on JT65.

We also took many hours of video that will be cut into a TV-presentation in the near future.

– Acknowledgement

We acknowledge the support of the University of Tasmania and Dr Jim Lovell in providing access to the dish and especially the efforts of the site technician, Eric Baynes (VK7BB) in making this a very successful exercise which allowed us to explore the limits of QRP EME.

Video low-power EME

Some more World Moon Bounce Day in Dwingeloo

This success was followed by an EME connection with a group in Switzerland. HB9MOON is a club station that has a beautiful 10 meter dish. A number of enthusiastic volunteers from this club had decided to use World Moon Bounce Day to promote amateur radio and EME in particular. During the day there were about forty children who spoke greetings in many languages towards the Moon so that this could be received by other groups around the world. It was very nice to make a connection through the Moon with these Swiss children. Some of them had such a microphone fear that only a timid “hello” was heard, while others read their text clearly and loudly so that it was perfectly understandable in Dwingeloo. (Added later Since February 2011, the club station is no longer operational because the owner sold the dish.)

In addition to these prearranged EME contacts, we also made thirty other connections in Dwingeloo. Many in SSB with the somewhat larger stations, and with the help of JT65 also with a number of small stations. The smallest was probably RA0ACM this time with a single yagi of 45 elements and only 70 watts.

During the day, several visitors came by, most of them radio amateurs who wanted to see the Dwingeloo Radio Telescope live. After explaining how you can sing “Father Jacob” with the Moon, a few children were able to imitate it flawlessly.

The webSDR receiver developed by Pieter Tjerk de Boer (PA3FWM) is really a great success. It has functioned throughout the event and again there were dozens of listeners.

Photos: CAMRAS (Tom Fossen and Ard Hartsuijker) and Mount Pleasant