Rosetta’s finale set for September 30

Please consider donating to Behind the Black, by giving either a one-time contribution or a regular subscription, as outlined in the tip jar to the right. Your support will allow me to continue covering science and culture as I have for the past twenty years, independent and free from any outside influence.

The Rosetta science team has set September 30th as the date when they will complete the spacecraft’s mission with a controlled descent onto Comet 67P/C-G’s surface.

Unlike in 2011, when Rosetta was put into a 31-month hibernation for the most distant part of its journey, this time it is riding alongside the comet. Comet 67P/Churyumov-Gerasimenko’s maximum distance from the Sun (over 850 million km) is more than Rosetta has ever journeyed before. The result is that there is not enough power at its most distant point to guarantee that Rosetta’s heaters would be able to keep it warm enough to survive.

Instead of risking a much longer hibernation that is unlikely to be survivable, and after consultation with Rosetta’s science team in 2014, it was decided that Rosetta would follow its lander Philae down onto the comet. The final hours of descent will enable Rosetta to make many once-in-a-lifetime measurements, including very-high-resolution imaging, boosting Rosetta’s science return with precious close-up data achievable only through such a unique conclusion. Communications will cease, however, once the orbiter reaches the surface, and its operations will then end.

The decision to end the mission this way makes great sense. I only question their decision to purposely end all communications upon impact. Though it is likely that communications will be lost anyway, wouldn’t it be better to try to get data back, like the scientists did with the American NEAR spacecraft when it touched down on the asteroid Eros at the end of its mission?


  • Wayne

    If we are conducting a Referendum, I agree with Mr. Z, let it transmit until the absolute bitter end.

    Excuse my ignorance– Rosetta is powered exclusively by solar-panels, is that correct?
    >>Just as a civilian, I really like the whole “radioisotope thermoelectric generator” ‘thing.

    I realize there are legitimate engineering factors that go into choosing a power source, just wondering aloud why we don’t go for the RTG’s “all-the-time?” (or at least a combination of RTG’s & solar-panels, especially in this instance.)

    Total tangent— The Space Show on 6-28-16 was very interesting. Looking doubly forward to reading the CNAS Policy paper!

  • Calvin Dodge

    Off the top of my head, I think the two main issues with RTGs are the limited supply of plutonium, and the anti-nuke crowds who have fits whenever an RTG goes into space.

    The main engineering considerations that I’m aware of are power to weight ratios (solar is better than RTG at our distance from the Sun, but of course solar gets worse as it gets farther away), and solar availability (on a planet or moon solar will be available only 1/2 the time). Note that even at Jupiter’s distance from the Sun, NASA seems to think solar beats RTGs for spacebound probes (like Juno).

  • Gealon

    Yeah, I don’t get the communications shutdown either. Even if Rosetta can’t point it’s high gain antenna towards Earth to continue high rate telemetry, it will have power for a time from it’s batteries (and solar panels if they aren’t shaded). So why not make use of that surface time? Switch over to the omnidirectional antenna and keep transmitting. Wouldn’t it be a shame if there were comet dwelling organisms puttering around on the surface, and we didn’t find them because they turned the radio off early?

    As for RTG’s, I think Calvin you mean anti-nuke Cowards. I am well versed in the construction of these power supplies and I can tell you there is very little to no chance of a leak of their fuel. They are designed very heartily (Which adds to their weight) and are intended to survive the destruction of the launch vehicle and re-entry into the atmosphere as well as the “landing.” Speaking specifically for Juno, that probe is only capable of function in the Jovian system because it uses Very large panels all made of the most expensive solar cells there are (But who cares about cost when you have a “Green” spacecraft.) While they might be able to pull solar off for Jupiter, you can’t for anything further out. The solar arrays at that point become so large and unwieldy that launch costs skyrocket and even if launched, the spacecraft would be too heavy to effectively maneuver it’s self.

    Unfortunate it is true that we no longer have a stockpile of Plutonium fuel to build more RTG’s. I do remember Rob posting an article a few months back that we were finally producing fuel again, but haven’t heard anything else after that. What we really need to do though is stop playing around with these low power options. We need to develop a space based reactor that can make true interplanetary travel a possibility. We have several propulsion concepts ready to go, MPD thrusters and VASIMIR engines just to name two, but they are all held back by lack of a power supply. We had a prototype nuclear thermal propulsion system in testing once (Nerva), but once again as with everything nuclear it seems, it was abandoned.

    Anyway, not going to get into the continuingly depressing state of nuclear propulsion and power technologies, just going to get back on point, there is no reason to stop transmitting before you reach the surface… Unless the Phobosians have commanded you to.

  • Edward

    Calvin Dodge wrote: “on a planet or moon solar will be available only 1/2 the time.”

    It turns out that the poles of Earth’s moon are almost 90 degrees from the direction to the sun (about 89 degrees), unlike the Earth, where they are about 67 degrees. Thus, the Moon’s “arctic circle” is about 1 degree, and solar arrays at some places near the poles can provide power around 90% of the time. Nicely convenient.

    For other locations on the Moon, some form of power storage, RTG’s, or other power generators would be necessary for the long nights.

    Gealon wrote: “As for RTG’s, I think Calvin you mean anti-nuke Cowards.”

    Not necessarily cowards. I watched, at my university, as a bunch of the anti-nuke crowd protested — with their children in tow — as they bravely stood in a parking lot right above the school’s nuclear reactor. They were willing to risk their own and their children’s health and lives in order to protest what they believed to be an evil, dangerous, and risky reactor. These were truly brave (or stupid) people, unless they understood just how safe the reactor actually was.

  • Dick Eagleson

    Times certainly change. When I was in school in the late 60’s and early 70’s, there was a small reactor located in the basement of the Engineering building on campus. One of my roommates, a fellow undergrad, was its night-shift operator. Hard to imagine such a thing now in these relentlessly PC times.

  • wayne

    Totally on-board with anything nuclear/radioactive, on Earth & in Space.
    (We need a production-line for RTG’s, up & running.)

    On oldie but a goodie–
    Nuclear Propulsion In Space, NERVA (1968)
    –imagine how advanced this type of technology would have developed over the past 50 years. (I don’t want to pay for the research 2-3X’s over again, like we did with the “bat-wing” stealth aircraft.)

Leave a Reply

Your email address will not be published. Required fields are marked *