Encounter with a Blue/Green Planet

by Paul Gilster on December 11, 2013

When I first read about Project Daedalus all those many years ago, I remember the image of a probe passing through a planetary system, in this case the one assumed to be around Barnard’s Star, at high velocity, taking measurements all the way through its brief encounter. And wouldn’t it be a fabulous outcome if something rare happened, like the reception of some kind of radio activity or some other sign of intelligent life on one of the planets there? That thought stayed with me when, much later, I read Greg Matloff and Eugene Mallove’s The Starflight Handbook and began thinking seriously about interstellar flight.

The chance of making such a detection would be all but non-existent if we just chose a destination at random, but by the time we get to actual interstellar spacecraft, we’ll also have an excellent idea — through space- and Earth-based instruments — about what we might find there. These days that ETI detection, while always interesting, isn’t at the top of my list of probabilities, but getting a close-up view of a world with an apparent living environment at whatever stage of evolution would be a stunning outcome. Let’s hope our descendants see such a thing.

Nearby Celestial Encounters

Triggering these musings was a space event much closer to home, the recent passage of the Juno spacecraft, which moved within 560 kilometers of the Earth’s surface on October 9 in a gravity assist maneuver designed to hasten its way to a 2016 encounter with Jupiter. Juno will orbit the giant planet 33 times, studying its northern and southern lights and passing through the vast electrical fields that generate them. I was fascinated to see that the recent close pass marked a milestone of sorts, for the spacecraft detected a shortwave message sent by amateur radio operators on Earth.

juno_hams

Image: Tony Rogers, the president of the University of Iowa ham radio club, mans the equipment used to send a message to the Juno spacecraft in October. The simple message “Hi” was sent repeatedly by ham radio operators around the world. Photos by Tim Schoon.

It’s not a starship picking up an alien civilization’s signals, but Juno did something that previous missions like Galileo and Cassini were unable to do. The latter were able to detect shortwave radio transmissions during their own Earth encounters, but it was not possible to decode intelligent information from the data they acquired. The Waves instrument on Juno, built at the University of Iowa, collected enough data that a simple Morse code message from amateur radio operators could be decoded, leading Bill Kurth, lead investigator for the Waves instrument, to say “We believe this was the first intelligent information to be transmitted to a passing interplanetary space instrument, as simple as the message may seem.”

The Juno team evaluated the Waves instrument data after the October 9 flyby and noted that the message appeared in the data when the spacecraft was still over 37,000 kilometers from Earth. The University of Iowa Amateur Radio Club contacted hundreds of ham stations in 40 states and 17 countries as part of the effort, which was managed through a website and a temporary station set up at the university. Operators from every continent coordinated transmissions carrying the same coded message, with results that can be heard in this video. As public outreach for an ongoing mission, this is prime stuff. Kurth continues:

“This was a way to involve a large number of people—those not usually associated with Juno—in a small portion of the mission. This raises awareness, and we’ve already heard from some that they’ll be motivated to follow the Juno mission through its science phase at Jupiter.”

Also qualifying as excellent public relations is the image below, which came as one of Juno’s sensors offered a low-resolution look at what a fast passage by our planet would be like.

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Image: This cosmic pirouette of Earth and our moon was captured by the Juno spacecraft as it flew by Earth on Oct. 9, 2013. Image Credit: NASA/JPL-Caltech.

Scott Bolton, Juno principal investigator, likens the view to a rather famous TV show:

“If Captain Kirk of the USS Enterprise said, ‘Take us home, Scotty,’ this is what the crew would see. In the movie, you ride aboard Juno as it approaches Earth and then soars off into the blackness of space. No previous view of our world has ever captured the heavenly waltz of Earth and moon.”

Getting these images wasn’t easy. The sensors involved, cameras designed to track faint stars, are part of Juno’s Magnetic Field Investigation (MAG) and are normally used to adjust the orientation of the spacecraft’s magnetic sensors. The spacecraft was spinning at 2 rpm during the encounter, so a frame was captured each time the cameras were facing the Earth, with the results processed into video format. Juno now moves on to a Jupiter arrival on July 4 of 2016. If you want to see the Earth flyby with musical accompaniment, see this video and ponder what John Jørgensen (Danish Technical University), who designed the star tracker, says about the event: “Everything we humans are and everything we do is represented in that view.”

Rings a bell, doesn’t it? And why not. This is indeed another of those ‘pale blue dot’ moments.

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{ 15 comments… read them below or add one }

David Cummings December 11, 2013 at 12:29

“The latter were able to detect shortwave radio transmissions during their own Earth encounters, but it was not possible to decode intelligent information from the data they acquired. The Waves instrument on Juno, built at the University of Iowa, collected enough data that a simple Morse code message from amateur radio operators could be decoded…”

I’m not getting this part. Communications satellites are a dime-a-dozen. This is 2014. I’m having a hard time wrapping my head around the existence of any kind of signal receiver whatsoever that is limited to Morse code.

Paul Gilster December 11, 2013 at 13:37

This University of Iowa news release gives a bit more:

http://now.uiowa.edu/2013/10/nasas-juno-spacecraft-hears-amateur-radio-operators-say-hi

and includes this statement:

“Kirchner says that the project originated when public outreach staff at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., wanted to know if the UI receiver was able to pick up a voice message. Although that isn’t possible, Kurth and Kirchner came up with the idea that a slow Morse code message should work.”

I’m going to ask Dr. Kirchner about this and get back to you with clarification.

ljk December 11, 2013 at 15:27

Quoting from the article:

Scott Bolton, Juno principal investigator, likens the view to a rather famous TV show:

“If Captain Kirk of the USS Enterprise said, ‘Take us home, Scotty,’ this is what the crew would see. In the movie, you ride aboard Juno as it approaches Earth and then soars off into the blackness of space. No previous view of our world has ever captured the heavenly waltz of Earth and moon.”

On that last sentence I must disagree. See here:

http://www.centauri-dreams.org/?p=2023

And in another quote from the same article:

John Jørgensen (Danish Technical University), who designed the star tracker, says about the event: “Everything we humans are and everything we do is represented in that view.”

I wonder where I have heard that sentiment about our planet before….

http://www.skyimagelab.com/pale-blue-dot.html

ljk December 11, 2013 at 15:56

The Trekker in me insists on this correction:

Kirk would have likely told Sulu, not Scotty, to take them home, as Sulu was the navigator aboard the Enterprise (in most of the Original Series). While Scotty probably could have navigated the starship as well, he was best at being the ship’s Chief Engineer.

I don’t know: Can we trust someone who doesn’t know these basic Star Trek facts to fly a real spaceship all the way to Jupiter? :^)

Charley December 11, 2013 at 20:01

“Getting these images wasn’t easy. The sensors involved, cameras designed to track faint stars, are part of Juno’s Magnetic Field Investigation (MAG) and are normally used to adjust the orientation of the spacecraft’s magnetic sensors. The spacecraft was spinning at 2 rpm during the encounter, so a frame was captured each time the cameras were facing the Earth, with the results processed into video format. ”

this video points out a major shortcoming I wish jpl would
address – why not adjust camera speeds to take better videos ?

Paul Gilster December 12, 2013 at 12:55

Re David Cummings question above:

Communications satellites are a dime-a-dozen. This is 2014. I’m having a hard time wrapping my head around the existence of any kind of signal receiver whatsoever that is limited to Morse code.

This just in from Donald Kirchner:

“Paul, I just got back in the country after vacation, so I will be composing a detailed answer, but the short answer is that our Juno instrument is designed to make scientific measurements, not communications. It is a direct descendant of our instrument on the Voyager spacecraft that just detected the edge of the heliopause.”

ljk December 12, 2013 at 13:21

As I recall, the only reason Juno will be taking images at all even though that is not the main focus of the probe’s mission is that the public expects neato photographs of the planet Jupiter.

Can’t say I blame them and I am sure some closeup images of the gas giant will be beneficial to science. Not aware of any other Jovian missions headed that way for at least a decade or more as it is.

The early Mariners to Venus, numbers 2 and 5, did not have imaging systems because it was thought there would be nothing of value or interest to see above the thick clouds of that planet. Mariner 10 proved those naysayers wrong.

David Cummings December 12, 2013 at 15:51

Thank you, Paul, and thanks to Donald Kirchner for his quick reply. That was very nice of him, and yes, that does clear things up. I was actually going to suggest that as a possibility after I thought about it some more (I was walking home last night thinking about this) but I thought since I put the question out there I’d wait for the answer.

Thanks again, to both of you. If the detailed answer gets posted I will read it with great interest.

Donald Kirchner December 14, 2013 at 0:16

There is a little more information available at the AGU press conference: http://www.ustream.tv/recorded/41576257 (Warning, over 40 minutes long.)

Our instrument is basically a spectrum analyzer, it is not designed for communications. Building spacecraft instruments is always a matter of compromise between power, mass, volume, data volume, and the scientific measurement requirements. In this case, we wanted to be able to sample the electric field spectrum that the instrument sees from 50Hz to 40MHz as high as once per second. This rate was determined by how fast the spacecraft will be flying through the Jovian auroral zone. After the sun, Jupiter is the most powerful radio source in the sky. From previous measurements, we know these emission come from the auroral region, just as lower frequency radio waves are generated at the Earth. There are estimates of the size of these structures and given the velocity Juno will be traveling , we set the spectrum cadence to be able to resolve them. Stepping at a higher rate, or using a narrower detection bandwidth would increase the data volume required.

Remember that Juno is solar powered, there is not a lot of power available for the downlink, the spacecraft spends much of the 11 day orbit around Jupiter transmitting back the data collected in the 6 hours around the closest approach, so we have to carefully balance the desire to have higher resolution measurements with the impact of increasing the amount of data produced.

The HI Juno project was dreamed up after the command sequences had been argued over, approved, and uplinked to the spacecraft, so I was stuck with coming up with a way to get a message to Juno using the instrument in the modes we had already designed for Earth observations. Luckily, based on flybys by our Galileo and Cassini instruments, we had already planned to observe broadcast shortwave stations. See the paper by Carl Sagan et al: http://www-pw.physics.uiowa.edu/~dag/publications/1993_ASearchForLifeOnEarthFromTheGalileoSpacecraft_NATURE.pdf

The Waves instrument was set to give us a full spectrum sweep once per second, from 50Hz to 40MHz, so the high frequency spectrum analyzer (covering 3MHz to 40MHz) would be sitting on the 28.5MHz+/-0.5MHz step for 25msec every second. We estimate 5V/m electric fields in the source region, so the instrument is designed to handle high intensity signals. If you spend any time listening to a shortwave radio, some of the static crashes you hear will be Jupiter noise, not lightning. Juno is also spinning once per 30 seconds, so making the dits 30 second long gives us 30 samples along one spin of the spacecraft. A quick calculation of our sensitivity indicated a pretty reasonable 100kW EIRP(Effective Isotropic Radiated Power) would be detectable. This calculation however completely ignored ionospheric effects, in reality, only radio waves with a high angle of radiation will escape, the rest of the power gets trapped inside the ionosphere and ends up somewhere else on earth. That’s why I was hoping for poor radio conditions, or in amateur radio jargon that the band was “closed” that day.

Since I wanted to minimize ionospheric effects, the ten meter ham band (28MHz) was the highest frequency ham band in our detection range. Naturally, the sun didn’t cooperate too well, and the solar flux index which is a measure of how much solar energy is available to dissociate atoms in the ionosphere that day was about 120, rather than the low 90s I hoped for. I had reports from Germany early in the day that 10m was open to South America, which I didn’t see as a good sign, but nothing could be done about it at that point, Isaac Newton was in the drivers seat and Juno was coming in whether conditions were optimal or not.

To generate the audio of the CW message, I first took the time series of samples from the channel centered at 28.5MHz and did a running average on it to bring up the signal. Then I clipped the noise level off which left only the signal peaks. I took those signal peaks and formed an audio spectrogram with the signal at about the frequency you would expect to copy CW. I next processed that spectrogram image through some software I wrote which inverts the spectrogram and turns it into time series for an audio .wav file. That is also how I generated the background audio of the signals the instrument heard. For the video, JPL then took my audio of the CW and generated their own spectrum of it, so that bit is a little overprocessed.
You may have heard some of the other audio I have generated, my favorite is the “Halloween storm” at Saturn: http://www-pw.physics.uiowa.edu/space-audio/cassini/SKR1/
More recent is our detection of the heliopause by Voyager 1:https://www.youtube.com/watch?feature=player_embedded&v=LIAZWb9_si4

Hopefully, we can try this again some day. The European JUICE spacecraft with have a high frequency receiver and do a flyby sometime in the 2020s.

David Cummings December 15, 2013 at 10:04

Thanks, Donald. That’s an extremely interesting story of putting all those factors together, the limitations of the signal available and the shifting radio conditions in the Earth’s atmosphere. Thanks explaining the factors involved and why the old (and now mostly abandoned) system of Morse Code came in handy.

Paul Gilster December 15, 2013 at 15:04

I agree with David, and thank Dr. Kirchner for taking the time to clarify the issues here. Much appreciated!

ljk December 16, 2013 at 11:06

Online paper from Nature published in 1993 on Galileo’s flyby of Earth in 1990 and its detection of life intelligent and otherwise on that planet:

http://www-pw.physics.uiowa.edu/~dag/publications/1993_ASearchForLifeOnEarthFromTheGalileoSpacecraft_NATURE.pdf

ljk December 18, 2013 at 13:41

Conversations with an interplanetary spacecraft: “Hi, Juno!”

Posted by Emily Lakdawalla

2013/12/17 09:37 CST

Topics: citizen science, personal stories, Earth, Juno

There was so much news at the American Geophysical Union meeting last week that I am still drowning in material. One of the many press briefings concerned the scientific data gathered by the Juno Jupiter orbiter when it flew past Earth in October. This was so cool.

The Earth flyby represented the first opportunity for many of the science instruments to be used on a planetary target. Earth is a very different planet from Jupiter, though. Not all of Juno’s instruments could “see” the phenomena they were designed to study. Earth lacks the strong magnetic field of Jupiter, so it’s dim to fields-and-particles instruments, but visually it’s a much brighter target than the optical instruments were intended for. Still, most of the science instruments gathered data, and some of that data will be useful to calibrate and check the performance of the instruments in space.

But the science team took data on our home planet for other reasons. It’s fun to ask the question: if this flyby were of an alien planet, could we detect the presence of life down there? Photos of the whole Earth are not terribly suggestive. Life isn’t obvious in photographs of the multicolored surface of Earth unless you happen to be expecting chlorophyll’s distinctive dark appearance in visual wavelengths and bright appearance in the near-infrared:

Full article here:

http://www.planetary.org/blogs/emily-lakdawalla/2013/12170800-conversations-with-juno.html

David Hoskins January 5, 2014 at 2:58

In the animation right before the end is that the ISS that you can briefly see? It’s below the equator but not by much maybe 1/3 the distance from the equator to the south pole.

ljk February 7, 2014 at 13:21

Earth and Luna as seen from the Curiosity rover on Mars in January of 2014:

http://www.universetoday.com/109095/you-are-here-curiositys-1st-photo-of-home-planet-earth-from-mars/

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