Indian Moon landing followed by radio telescope

This year 2019 is a busy year for lunar exploration. On January 3, China successfully landed a probe and rover on the backside of the Moon, and on April 11, Israel attempted to land Beresheet, a small lander. Unfortunately that landing failed, as we observed with the Dwingeloo radio telescope.

On September 6, India was the third country to attempt a lunar landing this year. The Chandrayaan-2 mission included the Vikram lander, which was aimed to land near the lunar South Pole. Fortunately, the Moon was above the horizon, and the Dwingeloo radio telescope was ready to track the landing attempt. Simon Bijlsma, Michel Arts, Tammo Jan Dijkema and Cees Bassa used the 13 cm horn antenna to listen to radio transmissions from the Vikram lander at 2284 MHz.

The Dwingeloo signal chain was tested around 18:20 UTC (20:20 CEST), just before the Vikram lander disappeared behind the Moon for its final orbit. At 19:18 UTC, as predicted, the lander reappeared from behind the Moon and quickly got in contact with the Madrid Deep Space Network station; the radio signals received by the Dwingeloo telescope showed that Vikram locked to Madrid and began downlinking telemetry.

The landing burn started at 20:08 UTC when Vikram was at 30 kilometers altitude. The effect of the burn was immediately visible as a sharp kink in the Doppler curve, shortly followed by the announcements from the Indian livestream, which had a delay of about half a minute. The landing burn consisted of two phases: a ten minutes long rough braking phase to reduce the velocity as quickly as possible, followed by a two minutes fine braking phase to reduce errors in the trajectory. With the start of this fine braking phase at 20:18 UTC, when Vikram was at 7 kilometers altitude, the Doppler curve as received by the Dwingeloo telescope started to show unexpected small oscillations, which grew during the next two minutes, with the signal disappearing at 20:20UTC, three minutes before Vikram was planned to land on the Moon.

The oscillations in the Doppler curve, and the loss of signal three minutes before the expected landing time, suggests that Vikram had a problem during the final phases of the descent, and probably crashed onto the lunar surface. It is not clear how hard Vikram crashed and if the lander survived. About a day later the Indian Space Research Organization (ISRO) managed to image the lander on the lunar surface using the orbiter of the Chandrayaan-2 mission. So far ISRO has not managed to communicate with the lander.

Dwingeloo sends heart beat Neil Armstrong back to the Moon

When on 20 and 21 July everyone is looking back on the 50 year Moon landing anniversary, CAMRAS volunteers (in particular Harry Keizer and Jan van Muijlwijk) are working hard in the Dwingeloo Radio Telescope.

In the night of 20 to 21 July 2019, exactly 50 years after the Moon landing, they will bounce radio waves off the surface of the Moon, and catch their reflection (moon bounce). The radio telescope will be used for this from about Saturday 20 23:00 UTC to Sunday 21 06:30 UTC.

Other dishes, even small ones, can also receive the moon echos. A bigger dish that will listen in part of the time is the Mark II telescope of Jodrell Bank Observatory near Manchester. This weekend it hosts the Blue Dot festival; the Moon echos will be played live on the festival.

Early in the morning, at 02:56 UTC, it is exactly 50 years ago that Neil Armstrong set foot on the Moon. While he did this, his heart beat was recorded. Now 50 years later, the Dwingeloo telescope will send this heartbeat back to the Moon, as part of the art project “Giant step” of artist Richard Clar. He translated the heart beat to audio, adding in the famous words “That’s one small step for [a] man, one giant leap for mankind”.

Other sounds that Dwingeloo will moon bounce are the things that kids (and grown-ups) would say when they would set foot on the Moon. These sentences were recorded by artist Martine-Nicole Rojina in her ‘First Steps’-project.

Even more, the CAMRAS radio amateurs will send pictures to the moon using ‘visual moonbounce’, a technique similar to fax.

At the end of the morning, from 05:30 – 07:30 UTC, the telescope will download images off the Chinese satellite in Lunar orbit.

All these activities will take place between Sat 23:00 UTC and Sun 7:30 UTC. During these hours the telescope is not open to the public. Sending the sounds can be followed via webradio

The telescope is open to the public on Sunday 21 July 2019 from 11:30 tot 14:00 UTC (13:30 – 16:00 local Dwingeloo time). See Zomerse zondagmiddagopening 2019 (in Dutch) for details. The Moon will not be above the horizon then, but we will of course pay special attention to it.

Planned times (in Dwingeloo local time, CEST)

  • Blue Dot: 02:15 – 03:00
  • 04:56 sonified heart beat Neil Armstrong
  • Blue Dot: 05:00 – 07:30
  • Chinese Lunar satellite DSLWP-B: 7:30 – 9:30 uur

Photos: Boot and bootprint in lunar soil (NASA; Apollo Archive Project),  Dwingeloo Radio Telescope (Harry Keizer; CAMRAS), Mark II telescope (Mike Peel; Jodrell Bank Centre for Astrophysics, University of Manchester)

Photo solar eclipse from Chinese lunar satellite

Last Wednesday morning, July 3, the Dwingeloo Radio Telescope downloaded this eclipse photo from the Chinese lunar satellite DSLWP-B. The photo was taken on Tuesday evening, July 2, 2019, when a full solar eclipse was seen in South America. That is where the shadow of the Moon fell on Earth. That shadow is clearly visible in the photo.

The ISS and weather satellites have previously taken pictures of the shadow of the Moon on Earth, but this picture is – as far as we can ascertain – the first ever photograph of a solar eclipse taken from an orbit around the Moon. And the Dwingeloo Radio Telescope cooperated!

This year and last year many CAMRAS volunteers contributed to the collaboration in this special satellite webcam project from MingChuan Wei (BG2BHC/BY2HIT) of the Harbin Institute of Technology. A project that will end in the course of this month as the DSLWP-B satellite will crash onto the Moon in a controlled manner.

The CAMRAS-DSLWP-B team consisted of Cees Bassa, Paul Boven (PE1NUT), Tammo Jan Dijkema, Harry Keizer (PE1CHQ), Jan van Muijlwijk (PA3FXB) and André Offringa. Pieter-Tjerk de Boer (PA3FWM) and Simon Bijlsma (PA7SB) enabled streaming over WebSDR; Michel Roelofs (PA1MEF) made it possible to share raw data. In a broader scope, the team consists of the team at Harbin, specifically MingChuan Wei, and Reinhard Kühn (DK5LA) for uplink and Daniel Estévez (EA4GPZ/M0HXM) for analyses of the satellite orbit.

More info about this project in our blog posts Our precious Earth and the lunar far side, Time-laps of the Earth appearing behind the Moon and New photo of Lunar farside and Earth. Also, see our guest blog on The Planetary Society.

Israeli 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 eight 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 eight 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 three 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.