Category Archives: Space Exploration

Cassini End of Mission

After twenty years in space (launched 10 years Bi, Before iPhone), traveling over a billion KM, and returning data for 13 years from more than a light-hour from Earth, the Cassini Spacecraft ended its mission this week.

The project has accomplished lots of amazing science, represented by 3,948 papers so far. There will surely be a few more—lets go for 5K papers!

The end was a planned dive into the atmosphere of Saturn, collecting a few more bits of data on the way down, and assuring the complete destruction of the spacecraft.

As has been explained before, the spacecraft needed to be vaporized to prevent even the slighted chance that it might contaminate the area with Earth microbes. Aside from not wanting to harm any life that might exist on the moons or dust, we also don’t want to accidentally leave something that a later spacecraft might find and not realize was inadvertently sent from Earth.

(Which, if you think about it is way, way cool. How many human endeavors have to worry about the possibility of contaminating alien ecosystems, even in principle?)

Hence, the final dive.

This montage of images, made from data obtained by Cassini’s visual and infrared mapping spectrometer, shows the location on Saturn where the NASA spacecraft entered Saturn’s atmosphere on Sept. 15, 2017. Credit NASA/JPL-Caltech/Space Science Institute

Cassini signed off permanently on September 15. Loss of Signal. End of Mission. Lots of accomplishments.


Space Saturday

Interplanetary Networking

Space travel faces inevitable communication challenges. Even within the solar system, distances are light minutes to hours, which means round trip latencies that preclude easy conversation. In addition, signals decay quadradically, so there is a brutal power-to-distance relationship—and power is precious in space.

Can we do better than radio signals?

Gregory Mone reports in CACM that the answer is, lasers, man! [2]

Lasers are higher frequency and narrower beams, so they can transmit more data for the same power. This can’t eliminate the latency, but can push more data in a given time. As much as 10-100 times the data, which is worth a lot of effort to make happen.

A laser is much more directional than radio, and the receiver is a telescope. The narrow beam is a challenge, because the signal has to be aimed precisely. Given than everything is moving rapidly relative to everything else, it isn’t trivial to keep a signaling laser pointed at a very distant target.

If you were to aim a beam of radio waves back at Earth from Mars, the beam would spread out so much that the footprint would be much larger than the size of our planet. “If you did the same thing with a laser,” Biswas  [of NASA JPL] says, “the beam footprint would be about the size of California.”” ([2], p. 18)

Experiments have demonstrated space laser communication, utilizing error correcting codes (to mitigate lost signals) and advanced nanoactuators to precisely aim the laser. At very large distances, power will be at a premium, so there will be no bits to spare for error correction.

The receivers are essentially telescopes, which are a very well known technology. Receiving weaker signals from farther away means bigger telescopes. Mone says that signals from the solar system need a 10-15 meter scope.

These links will still have extremely long latencies compared to terrestrial networks. This means that our Earth bound protocols need to be redesigned for the Interplanetary Internet. (Hint: timeouts don’t work well if the round trip time for an ACK is variable and measured in hours.) This work is well underway [1].


  1. InterPlanetary Networking Special Interest Group (IPNSIG). InterPlanetary Networking Special Interest Group (IPNSIG). 2017,
  2. Gregory Mone, Broadband to Mars. Commun. ACM, 60 (9):16-17, 2017.


Remote Fun Park On The Moon?

As we approach the fiftieth anniversary of the first moon landing, it is clear that humans have pulled back from space exploration and from science in general. NASA’s budget has steadily declined, dedicated scientists politically suppressed and much of the space program has calcified into a jobs program.

What can be done?

Toys! Theme parks!

There is a lot of interest these days in sending swarms of small robots to the moon. Perhaps inspired by ubiquitous remote piloted drones, why not remote operate a moon rover?  And why can’t anybody drive one, with a game controller?

The Lunatix company is proposing to sell moon-rover-driving as a game. Earth bound computer games would be linked to the lander, and could purchase driving time. Kind of like consumer drones, except on the moon [3].

The lander might have a small science payload, but mainly it is dedicated to the commercial use. (There would be merchandise and other associated sales, as well.)

This seems relatively straightforward technically. There are some tricky bits, such as linking a consumer via the Internet to an uplink to the moon. Safely linking. Securely linking. (Hint: space communications are expensive and rare, and generally not connected to the public.)

I have no idea about the commercial case. Space projects are obscenely expensive, but getting cheaper. At something like 25 Euros per minute, it seems to me that driving time would be pretty damn expensive, at least for peasants like me. But who knows? My intuitions about business plans are often wrong.

Evan Ackerman points out that this purely commercial project raises legal questions. The moon is more or less under the jurisdiction of the United Nations, as defined by treaties among nations. There seems to be no specific framework for commercial exploitation of the moon, though there will surely need to be one soon.

Aside from the equity issues about sucking money out of the lunar commons (the moon is the common heritage of all human kind), there may be environmental and other regulatory issues.

I note that a company slogan is “Leave Your Mark on the Moon!”  The users will leave behind tracks, indelible tracks, visible from Earth.  This will surely have consequences.

How happy are we going to be when the moon is covered with tread marks? Do you want to see rude graffiti defacing the surface? How will we feel about a giant cola ad written in the dust? How will Earthly strongmen react to uncensored political messages, indelibly written on the moon?

The company proposal seems to wave its hands at the legal problems and doesn’t even list any legal issues under “Risks”. That may be optimistic.

In the end, it is quite possible that money will talk. As Ackerman puts it, despite his own misgivings, “If this is the best way to get robots to the moon, then so be it”.

While there’s a small section in the Lunatix executive summary on “Legal Framework,” there are few specifics about whether or not the United Nations would approve something like this. Lunatix seems to suggest that its use case is covered under “the common interest of all mankind in the progress of the exploration and use of outer space for peaceful purposes,” but I’m not so sure. It may be that no framework exists yet (either for or against), and my gut reaction that commercializing the moon in this way somehow cheapens it is probably just me being old and grumpy. If this is the best way to get robots to the moon, then so be it.” (From Ackerman [1])

I have my doubts about this concept. We’ll see.

But the general idea that some kind of entertainment business might be one of the earliest commercial successes for space seems to be plausible. Many important technologies started out as entertainment, or were driven by markets for entertainment [2].

For example, the Internet was designed for military and scientific applications, but the earliest commercial successes were music theft, games, and pornography, which drove markets for servers, GPUs and broadband, among other things. Today’s cord cutters are simply taking advantage of the second and third generation of these technologies. And, just as the Internet has never been comfortable with the fact that it is a great mechanism for delivering pornography, space entertainment may not turn out quite as imagined.


  1. Evan Ackerman, How Much Would You Pay to Drive a Jumping Robot on the Moon?, in IEEE Spectrum – Automation. 2017.
  2. Steven Johnson, Wonderland: How Play Made the Modern World, New York, Riverhead Books, 2016.
  3. Space Tech, Luniatix. Graz University of Technology Institute of Communication Networks and Satellite Communications, 2017.



Space Saturday

Happy Anniversary Voyager I and II

Forty years in space and billions of kms out, and still going!  Over half a light-day out, and heading for the stars.

As they say, “The Interstellar Mission”.

A few years ago, I asked a friend of mine, who was and is ON ONE OF THE VOYAGER SCIENCE TEAMS (we are not worthy! we are not worthy!), what’s up with the Voyagers?

He told me that the signal is getting weaker, but antennas are getting a lot better—so they still get a trickle of data back.

The don’t make ‘em like they used to!

Well done all.


Space Saturday

Grand Finale And A New Target

In the next weeks Cassini enters its final 5 orbits, swooping lower and lower, flying inside the rings of Saturn, until the final plunge on September 15, the “Grand Finale”.

At the same time, the New Horizons probe screamed past Pluto two years ago, but it has no brakes so it is still going out into the Kuiper Belt, which is cold, far away, and gigantic. The probe is still alive, though slumbering.   But with luck, it will wake up in 2019 and take some pix of Kuiper Belt object (KBO) 2014 MU69. This will be up close images 6 billion KM from home.

You can tell this is a long way out, because New Horizons is now half way between Pluto and the second stop on the itinerary.  This second leg is four years to complete.

This cunning plan got even more interesting this week, with reports from an occultation study in July that suggests that 2014 MU68 is not a ball. It may be an odd shaped blob or even two objects close together.

Whatever MUey-69 looks like, New Horizons may be able to get a good look.   Cool.

  1. Cassini Science Communications Team. The Grand Finale Toolkit 2017,
  2. Bill Keeter. New Horizons’ Next Target Just Got a Lot More Interesting. 2017,



Space Saturday

PS.  Yet more names for bands:

Final Five Orbits
Kuiper Belt & Braces
A Belt of Kuiper
The Grand Finale Toolkit

NASA Investigating Clockwork Rover Technology

NASA has the coolest projects!

With a long-term mission to visit and measure everywhere in the Solar System, NASA has not ticked off the easy stuff—Earth orbit, Moon, Mars, orbiting all the Planets.

There are plenty of places we really want to visit, but haven’t been able to. Cold places like the ice moons. And really hot places like the Sun  and the surface of Venus.

In the case of Venus,several spacecraft have orbited and are orbiting, and a handful of probes have reached the surface–just barely. The surface is hot, over 400 degrees C, and the pressure is a crushing 90 atmospheres. Most electronics simply don’t work at these temperatures. And it’s very cloudy, so solar power is minimal.  And so on.

In short, conventional engineering has little chance. To date, the record time to failure is 2 hours, set by a heroically insulated Vernera 13 probe in 1982. Building such extreme systems is hard and very expensive.

There is no way to make a rover to explore Venus. What’s to be done?

A NASA design group is exploring ways to build a rover that uses mechanical parts—clockwork—instead of electronics and computers. This is called “Automaton Rover for Extreme Environments (AREE)”.

When I saw their animation of some initial concepts, I immediately recognized that this is a Strandbeestand indeed they did invite Theo Jansen to JPL for some advice. (Evidently, Jansen’s advice was to get rid of the legs.)

Alternative locomotive ideas include wheels and tank treads.

But moving around is the least of the problems. How do you collect data?

In an interview with Evan Ackerman, they report several intriguing ideas under development.

First of all, mechanical calculation and number storage should be doable. And rough forms of obstacle avoidance are well known, too. (Toy cars navigate around furniture by bumping and backing up, no?.)

Image: Jonathan Sauder/NASA/JPL-Caltech Obstacle avoidance is another simple mechanical system that uses a bumper, reverse gearing, and a cam to back the rover up a bit after it hits something, and then reset the bumper and the gearing afterwards to continue on. During normal forward motion, power is transferred from the input shaft through the gears on the right hand side of the diagram and onto the output shaft. The remaining gears will spin but not transmit power. When the rover contacts an obstacle, the reverse gearing is engaged by the synchronizer, thus having the opposite effect. After the cam makes a full revolution it will push the bumper back to its forward position. A similar cam can be used to turn the wheels of the rover at the end of the reverse portion of the drive.

But if you had some data, how would you return data to Earth (i.e., to an orbital relay)? One possibility would be some kind of hard copy (e.g., etched into a metal disk), which is then lifted with a balloon and potentially pick up be a high altitude UAV. That sounds cool, but pretty iffy.

Another idea is to do semaphore code with radar reflectors. The orbiter beams radar and the rover reflects back on-off signals are certain wavelengths. This might have a bandwidth of a few bits per second (one way). That’s not much, but it’s a lot more than zero bps!   Pretty cool.

They are also trying to develop some kinds of sensors that will work under these conditions. This is difficult and it might be an area where small amounts of exotic high temperature electronics might be used.

This is such a cool design project!

I’m not sure how these ideas will pan out, but this work

is also important for changing the conversation on exploring Venus. Today, long duration in-situ mobile access on Venus has not been considered a realistic option. AREE demonstrates how such a system can be achieved today by cleverly utilizing current technology and enhanced by the technology of tomorrow.”

  1. Evan Ackerman, JPL’s Design for a Clockwork Rover to Explore Venus, in IEEE Spectrum – Automation. 2017.
  2. Jonathan Sauder. Automaton Rover for Extreme Environments (AREE). 2017,



Robot Wednesday

Juno Red Spot Images

If you’re going to go all the way out to Jupiter, and spend months snapping pix, you really, really ought to get some pictures of the Red Spot. The Great Red Spot has been observed since 1830, but never from this close.

This week’s close flyby picked up the best pictures ever from this giant hurricane.

The visual imagery was rapidly processed to produce a pretty picture. The entire data collection will be analyzed and described soon (presumably by the end of the year conferences).

This enhanced-color image of Jupiter’s Great Red Spot was created by citizen scientist Jason Major using data from the JunoCam imager on NASA’s Juno spacecraft. The image was taken on July 10, 2017 at 07:10 p.m. PDT (10:10 p.m. EDT), as the Juno spacecraft performed its 7th close flyby of Jupiter. At the time the image was taken, the spacecraft was about 8,648 miles (13,917 kilometers) from the tops of the clouds of the planet. JunoCam’s raw images are available for the public to peruse and process into image products at: More information about Juno is at: and Credits: NASA/JPL-Caltech/SwRI/MSSS/Jason Major

The composite image gives us the impression of this massive storm. Visually, it is clearly a really complicated “hurricane of hurricanes”.

The more detailed analysis may suggest a more refined understanding of how this storm developed and has persisted for at least 150 Earth years.


There will be another close pass on 1 September, just before Cassini’s finial dive at Saturn. The Juno mission will end in February with a deliberate dive into the atmosphere.

  1. Agle, DC, Dwayne Brown, and Laurie Cantillo, NASA’s Juno Spacecraft Spots Jupiter’s Great Red Spot, in NASA Latest, M. Perez, Editor. 2017.


Space Saturday