Rosetta: Solar PV fails to deliver, not enough sunshine

Posted: November 14, 2014 by tchannon in Energy, innovation, Nuclear power, Uncertainty

I hope this does not come true.

A cliff hanger descended over the Rosetta space mission as fate casts a shadow when an attempt at landing went fatally awry.

It turns out that fragile and complex technology was used instead of robust tried and tested nuclear plant. Fault intolerance.

The solar cells in Rosetta’s solar panels are based on a completely new technology, so-called Low-intensity Low Temperature Cells. Thanks to them, Rosetta is the first space mission to journey beyond the main asteroid belt relying solely on solar cells for power generation. Previous deep-space missions used nuclear RTGs (Radio isotope thermal generators). The new solar cells allow Rosetta to operate over 800 million kilometres from the Sun, where levels of sunlight are only 4% those on Earth.

But they forgot the possibility of or ignored an unknown environment might have cliffhangers waiting. It has landed in shadow.

Philae is receiving about 1.5 hours of illumination during every 12-hour rotation of the comet. [so? not designed for this then?]

This will be insufficient to top up its battery system once the primary charge it had on leaving Rosetta runs out. That was some 60-plus hours.

It means Philae is unlikely to be operating in its present state beyond Saturday. [go into low power mode, what the EU insist the prolls do]


The text above is vague, it might mean there is a primary cell system and some lesser amount of rechargeable. Why mention top-up as well?

The answer came on looking to see what battery was present

Battery assembly — The lander energy storage is based on two types of sources: primary batteries for short term activities (1000W/h), secondary batteries for long term activities (140W/h).

[should be taken loosely, batteries comprise cells but there might be multiple batteries although I doubt it]


Systems that control the temperature inside the spacecraft are another example of technological spinoffs from the Rosetta mission. When a spacecraft is near the Sun, overheating is a problem, and can be prevented by using radiators. But in the outer Solar System, the problem is keeping the spacecraft and its subsystems warm. The system devised for Rosetta employs several new techniques, including the installation of louvres over the radiators, to keep spacecraft hardware at proper operating temperatures.

Does that work if the power goes phut? 🙂
Since the above is the team text I point out spinoffs happen unintentionally, in unintended fields and after use. Guessing, all it means is some funds were spent on development.

One of the reasons for using thermonuclear is available waste heat, used to maintain a sane minimum temperature in the electronics. [1]

There is claim the craft is capable of recovering from deep chill, however, Darwin awards are littered with why testing supposed-to on your own neck is a bad idea.

Time will tell. Snatching victory from the jaws of defeat is not clever. Obviously I hope at least some useful results come from the mission.

1. It is difficult to know what won’t work at low temperature but general stuff might be okay if degraded at -40C, military and aeronautics has to endure worse than that. Radiation hard and low power in involved here as well.

Post by Tim

  1. Konrad. says:

    This is an unfortunate outcome for an otherwise successful mission. The main failure was the anchor system that failed to hold the lander down. It hit the targeted spot, which would have had enough sun, but then bounced 1.5 Km away and ended up in shadow. Initial approach images just before the bounce show a well lit area.

    It is now questionable whether the lander will even be able to use its drill as its current position appears unstable. Worse, as the lander was simply “dropped” and fell slowly in the low gravity, it does not have thrusters to reposition itself.

    While a Seebeck atomic generator may have been a better idea than solar panels, especially for the main orbiter, what they really needed was a better harpoon system. This would ideally have consisted of multiple rocket powered penetrators with cables fired slack and then reeled in. Any penetrator that fails to anchor could then just have its cable cut and you try again.

  2. wayne says:

    The current lack of Pu238 for such missions does suck forcing such compromises but I read the US is now firing up one of its old breeders for just that very reason — for space exploration RTGs. If only we had at least one LFTR running they give off Pu238 as a byproduct.

  3. tallbloke says:

    Harpoons were always a bad idea. I would have injected liquid water through the feet and frozen Philae to the surface with ice. But warming water takes more energy from those batteries which solar pv can’t replace fast enough. Good post Tim.

  4. tallbloke says:

    Speaking of ice; how’s that ‘dirty snowball’ theory of comet composition coming along? Looks like a chunk of rock from the photos. Perhaps Wal Thornhill was right again?

  5. Brian H says:

    The old-timey expression: “Too clever by half” springs to mind.

  6. Stephen Richards says:

    Ah Europe and solar panels. They always think they can do more other fuels.

  7. Joe Public says:

    Oh dear.

    Why does the Cadbury’s Smash advert immediately springs to mind?

    A slightly amended script:

    “The Smash Martians were the stars of a series of 1970s and early 1980s TV advertising campaigns for Smash instant mashed potato in the UK. They were a family of Martian robots who would watch humans laboriously preparing a lander for a decade-long journey into the unknown. The robots would then mock what they saw by chortling as they heard how the “Earth people designed & developed state-of-the-art solar cells, but failed to consider the lander may fail to orientate them to the light source. “

  8. donfjr09 says:

    I am struggling to understand how the ‘anchors’ were expected to work. Surely if they were ‘fired’ there would be an equal and opposite reaction and in a low gravity environment the lander would have taken off………… Am I missing something?

  9. tallbloke says:

    Donfjr:there are several waya of creating a ‘recoilless’ system. E.g. you can fire a charge or gas jet upwards at the same time as the harpoon is launched downwards.

    The problem with the harpoon system was that it assumed the surface was an aggregate of ice and gravel (comet tails are ice particles, or so the longstanding assumption goes). Harpoons don’t penetrate solid rock too well.

  10. donfjr09 says:

    So, a harpoon hitting a harder than expected surface would……………..

  11. tchannon says:

    Wondered what the take would be.

    Looking first is a good idea but then an age old tried and tested method, you poke it with a stick, maybe touch it, feel it. Those of a more measured bent would hit it with a hammer and notice what happens.

    Blashford-Snell has a different method, the Ickham case of the goldfish will do, more dynamite. Nothing like the direct approach. (hell of a character, the English eccentric who does a lot of good)

    I wonder if they talked to the Japanese Hyabusa team, who must have thought long and hard on what was feasible, although an asteroid is expected to be hard rock. Is the Rosetta mission going to return a fragment to earth?

  12. oldbrew says:

    Comets and asteroids are not the same thing, although the difference is not always clear.

    ‘Asteroids formed much closer to the sun, where it was too warm for ices to remain solid. Comets formed farther from the sun where ices would not melt.’

    But as TB points out: where’s the ice on ‘comet’ Rosetta?

    ‘We’re a bit surprised at just how unreflective the comet’s surface is and how little evidence of exposed water-ice it shows’

    ‘They [scientists] also found that the ‘coma’ – or atmosphere – around the comet contains [sic] of hydrogen and oxygen. This is surprising as comas are generally thought to be composed of water vapour and dust.’

  13. Stephen Richards says:

    A recent discovery found several Astrod-comets. They appear to be a hybrid of the two bodies.

  14. Nuclear would have provided baseload. They forgot the smart meter needed with solar.

  15. Edim says:

    More recent still, the materials retrieved demonstrate that the “comet dust resembles asteroid materials”.[143] These new results have forced scientists to rethink the nature of comets and their distinction from asteroids.[144]

  16. Edim says:

    2060 Chiron, whose unstable orbit is between Saturn and Uranus, was originally classified as an asteroid until a faint coma was noticed.[156] Similarly, Comet Shoemaker–Levy 2 was originally designated asteroid 1990 UL3.[157]

  17. Edim says:

    “Data from Giotto’s camera, which used an automated targeting system, included a spectacular image of the potato shaped nucleus that measures roughly 15 km across. What surprised everyone was that the nucleus was not a snow-white ice ball, but dark as a lump of coal. Some craggy surface features and craters could be seen, and jets of gas and dust streaming into Halley’s coma. This was the first-ever image of a “primitive body,” and a highly active one at that. The automated targeting device was even fooled, homing in on a jet coming off the dark surface as the spacecraft flew past (rather than the surface itself, which was expected to be bright). Data obtained on the composition of single comet grains discovered something new — grains of pure organic material or “CHON” — and nothing else, proving that comets are largely organic material rather than snowballs!”

  18. Joe Public says:

    Torygraph: #Rosetta scientist breaks down in tears as he apologises for ‘sexist’ shirt

    Subsequent Twitter comment: “Well that’s just wonderful. Space scientist’s “sexist and inappropriate” shirt was designed & made by a woman.

  19. tallbloke says:

    From Joe’s link :



    Dr Stephan Ulamec, Philae Lander Manager, was just asked what he would have changed on the lander. His answer?

    Quote A larger battery. And I would have taken ten years ago if it had been available then.

    The stupid; it hurts…

  20. gregole says:

    Reblogged this on Alan Olee Book Report and commented:
    Excellent discussion of Rosetta mission problems…

  21. oldbrew says:

    ‘Torygraph: #Rosetta scientist breaks down in tears as he apologises for ‘sexist’ shirt’

    Last heard muttering ‘I’m too sexist for my shirt’

  22. Kon Dealer says:

    Who would have thought that solar power could be unreliable?
    Green technology has screwed what was basically a very successful mission.

  23. tchannon says:

    Limited radio comms windows and worries over sufficient power for comms.

    Heroics time.

    Compounding problems caused by the lack of light reaching its solar panels, an ESA command for Philae to enter low power mode to maximize battery life did not get through.

  24. Konrad. says:

    There may still be hope, they have been successful with a drilling attempt and also a slight rotation of the lander body to catch more light, but the battery is still fading fast…

  25. DirkH says:

    2 dayys after ESA’s Rosetta sent its Philae lander to the comet, the batteries of the lander are empty.


    Let me say this again.


    Because, you obviously can’t have a 1 kg Plutonium battery in a 100 kg lander giving you 1 kW for, well at least several millenia.

    Not if you’re a stupid, <snip> [little green men]. (giggle, not on this thread please, puts off certain serious readers who then won’t mention us)

    Well I predicted an electric discharge on contact of the Philae lander with the comet.
    (a few days ago at suyts)
    ESA was smart enough to NOT show video of the landing.
    Instead they showed the most boring video of their people staring at monitors.
    So I’m not refuted. ESA has now joined the ranks of NASA, never show the public unredacted stuff.

    Or did anyone find pictures?

  26. DirkH says:

    wayne says:
    November 14, 2014 at 5:08 am
    “The current lack of Pu238 for such missions does suck forcing such compromises”

    Lack? NASA’s rover thing had a 5 kg Plutonium load. Funnily the Green NGO’s and rags didn’t predict end of the world while the thing was rocket launched. According to their belief system that was enough Plutonium to kill everyone if finely distributed in the atmosphere. Somebody must have told them to zip it, or maybe they just didn’t pay attention.

    Also, I think 10 years ago you could have easily asked the Russians for a kilo of Plutonium.

  27. michael hart says:

    Good catch, Tim.

    Slightly related, would they expect the ‘comet’ to have significant magnetic properties?

  28. wayne says:

    Dirk, sounds like you are speaking of Pu239… no shortage there, that’s for sure.

  29. DirkH says:

    Wayne, what’s the difference re use in batteries?

  30. wayne says:

    Best just to look that up. I really don’t know why Pu239 cannot substitute… 1/2 life I would think. Seems 238’s is like 80 years and isn’t 239’s much longer, like 10,000 years. If so, that is the answer. Need something a bit hotter.

  31. DirkH says:

    Ah. You’re right.

  32. tchannon says:

    It’s gone.

    The lander has produced some data from drilling and local analysis. And expired after the effort.

    With luck it will wake up occasionally and who knows, the body might change orientation.

  33. kuhnkat says:

    The harpoon momentum was supposed to be offset by a thruster operating to force the lander down. Observations of note from the team were that there was a sensor error on the thruster, but, they went ahead with the landing. I agree that their consensus science view of comets being dirty snowballs or rocky slushballs led them to believe they could get away with a failed thruster. In the event, the surface was harder than their prediction and gave the lander extra energy to bounce when the thruster failed to counteract, Another indicator was that the initial impact was much gentler than they expected. (thruster not firing)

    They seemed to be hung up on finding volatiles. They did not in the amounts their evolutionary expectations led them to expect.

    I was also disappointed by the lack of fireworks, I then went to find what I missed. This “comet” does not leave the orbits of the planets so would not be out past the suns electromagnetic influence long enough to gain charge. It may be that this object would be better classified an asteroid as it would appear to be debris from the system and not the mythical OORT Cloud.

  34. oldbrew says:

    Its orbit period is only 6.44 years so definitely not from ‘way out there’. With aphelion at 5.6829 AU it doesn’t get much further than Jupiter.

    It had ‘a close encounter with Jupiter’ in 1959 which pushed its perihelion much nearer to Earth than it was before.

    Using the Wikipedia data I find it rotates four times per five Jupiter rotations.

    comet 67P orbit
    [credit: / Randy Russell]

  35. Konrad says:

    Yes, the lander has run out of juice, but may have transmitted drill data before it died. Last power was used for telemetry. It is still possible that it can do more as it gets more sun on closer approach.

    Still, a spectacular achievement by ESA. Intercept and landing on an object travelling at 55,000 Kph!! How’s AGW “post normal science” compare to that?

  36. Hans Jelbring says:

    The project is a fantsytic success. Information from the lander is just plus information. I waded throuth +100 images yesterday.We now can see what a commet look like. Congratulations to the engineering feat.

  37. KuhnKat says:

    I saw an article this morning that says the drill data was returned.

    “It retrieved a number of temperature profiles but broke as it tried to burrow its way into the comet’s subsurface.

    Scientists say this shows the icy material underlying 67P’s dust covering to be far harder than anyone anticipated – having the tensile strength of some rocks.”

    Even with the obvious staring them in the face they hypothesize that the frozen material has the tensile strength of some rocks!!


    Another good chuckle occurred to me. They COULD HAVE made the solar panels work even with this result. Think back to OLD tech from Tesla. Rosetta could be beaming power to the lander to charge its batteries and the lander would not have needed panels at all!! Wonder if anyone else has considered combining broadcast power with renewables?!?!


  38. West Clintwood says:

    We will do better next time – cough up 4bn please…

  39. w.w.wygart says:

    Well, congratulations to the Rosetta/Philae team are in order for what has been accomplished, but I’m still completely amazed at the number of superlatives and uncontained gushing coming from the ESA. What adjectives would be left for them to use if the mission genuinely exceeded expectations? Ok, the mission wasn’t a total failure, it looks like the mission planners have done a very good job of managing the situation so that as much good science could be extracted in the available time as possible, maybe they’ll get some more things working again in the future – we’ll see. No doubt a lot will be learned, even if in the negative sense, undoubtedly money well spent – even if everyone learned nine years into the ten year flight that the nitrocellulose propellent for the harpoon doesn’t store well in a vacuum. This was a genuinely difficult first time mission everyone understood this going in; it’s ok to call a spade a spade, and a spade it is, just not the Ace. We’ll do better at it next time – or maybe it will be the Chinese.


  40. kuhnkat says:

    wygart, the really amazing part of those superlatives were how many were delivered while the lander was on its first “bounce”!!

  41. kuhnkat says:


    Click to access 1128.pdf

    If the solar wind can “implant” carbon on the moon finding carbon containing molecules in the comet’s “atmosphere” after 3 impacts by the lander isn’t a stretch. Still, the details are something to look forward to.

  42. tchannon says:

    The EU is planning to tax comets, all that carbon tax is too tempting.

    At least when they can figure who owns the things.

  43. oldbrew says:

    Lander is back.

  44. tchannon says:

    Thanks oldbrew, saved me forgetting the item.

  45. oldbrew says:

    TB’s link above (Nov.21) says: ‘closest approach to the sun in August 2015’.

  46. oldbrew says:

    ‘Exposed water ice detected on comet’s surface’

    ‘But some of the comet’s dust also remains on the surface as the ice below sublimates, or falls back on to the nucleus elsewhere, coating it with a thin layer of dusty material and leaving very little ice directly exposed on the surface. These processes help to explain why Comet 67P/Churyumov-Gerasimenko and other comets seen in previous flyby missions are so dark.’