OT Rosetta arrives at comet - Page 1
Forum section: electronics / general

author: Homer J Simpson
author_rank: Super Contributor
timestamp: August 06, 2014, 03:18:20 pm
content: Imagine all of the math involved in calculating the trajectory to make this happen.10 years and 6.4 billion kilometers of travel. Two earth flybys and one mars flyby. traveling at 55,000 km/hr.Enter orbit around a comet 4 km wide.Probe also caries a surface lander.http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_arrives_at_comet_destination

author: SeanB
author_rank: Super Contributor
timestamp: August 06, 2014, 03:56:27 pm
content: Yes, they got it right, and everything is still working as designed. Shows what you can do with a good design team and good cooperation with the people who put it together and operate it.

author: ncoonrod14
author_rank: Contributor
timestamp: August 06, 2014, 05:30:23 pm
content: Not to mention 1 billion euros to date. That helps

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 06, 2014, 05:56:44 pm
content: This is a great visualisation of what they did:http://sci.esa.int/where_is_rosetta/

author: corrado33
author_rank: Frequent Contributor
timestamp: August 06, 2014, 08:05:29 pm
content: That's super cool. They really used a ton of gravity assists to get it out there! I love the simulation posted above.I can barely hit any other planet in Kerbal Space program, let alone a comet in real life.

author: TerraHertz
author_rank: Super Contributor
timestamp: August 07, 2014, 05:35:38 am
content: A nice hi-re pic of the comet:http://apod.nasa.gov/apod/image/1408/comet_on_3_august_2014.pngPresumably more and better to follow.I hope the lander ends up somewhere with a good view of that cleft. Difficult landing problem though.

author: EEVblog
author_rank: Unknown
timestamp: August 07, 2014, 05:40:49 am
content: Quote from: TerraHertz on August 07, 2014, 05:35:38 amWow

author: pickle9000
author_rank: Super Contributor
timestamp: August 07, 2014, 05:45:59 am
content: Amazing!

author: miguelvp
author_rank: Super Contributor
timestamp: August 07, 2014, 05:50:13 am
content: Quote from: PA0PBZ on August 06, 2014, 05:56:44 pmThey even have the ecliptic at the right angle with the milky way equator, at least as viewed from the northern hemisphere.

author: Kjelt
author_rank: Super Contributor
timestamp: August 07, 2014, 07:26:32 am
content: Wonderful to see that the theoretically simulation/calculation worked out.You never know what is floating out there for debris and space rock that could have crashed into the device before reaching it's target. No time or fuel for real time trajectory changes. Even some of the vapour and rocks from the comet itself could destroy the device.And then after launch you have to wait for 10 years before you know if everything you did back then was correct (software/hardware/calculations). Unbelievable.I do wonder what hardware/microcontroller(s) were used and how they are protected from the cosmic radiation.

author: KedasProbe
author_rank: Frequent Contributor
timestamp: August 07, 2014, 08:57:09 am
content: The cool stuff still has to happen: getting very close and land a probe on it.

author: KJDS
author_rank: Super Contributor
timestamp: August 07, 2014, 09:27:17 am
content: Quote from: Kjelt on August 07, 2014, 07:26:32 amWhilst I can't answer your specific questions on processors, anything used on a project like that will be old tech. The technology will already have been used on a previous satellite and established a heritage. Without that heritage then it won't get used. Radiation shielding is done using a combination of robust silicon and packages with gold lids. The closer to the device the gold shield is, the smaller it can be so the less it weighs. Weight and proof of reliability are the two most important things on a spacecraft.Given that this craft was launched 10 years ago, so first testing would have been three years before that, on a device that had already established heritage, then the processor is likely to be either a programmable device using 20 year old technology or a 20 year old processor.It may have been easier to have piled the documentation for Rosetta into a staircase and catch the comet as it went past.

author: corrado33
author_rank: Frequent Contributor
timestamp: August 07, 2014, 12:55:55 pm
content: Quote from: Kjelt on August 07, 2014, 07:26:32 amAs it turns out, space is REALLY empty. Even the infamous asteroid belt you could easily fly straight through. The spacecraft ARE getting hit by micrometeors all of the time, just look at some of the satellites sent up by the Soviets and the US. Many of them had sensors to detect small impacts.As for the electronics, as posted above, it'll be very old tech. The tech for satellites spends years getting radiation hardened, so even if they started the project with new hardware, it'd still be old by the time they launched it.

author: Wytnucls
author_rank: Super Contributor
timestamp: August 07, 2014, 02:09:43 pm
content: Professor Copeland (Sixty Symbols) comments about Rosetta:

author: SeanB
author_rank: Super Contributor
timestamp: August 07, 2014, 05:02:42 pm
content: Processor is probably a space rated 80386, as that is the processor that was rated for deep space and hard radiation 15 years ago, replacing the 80286 processor. Yes, old but very reliable.

author: Wytnucls
author_rank: Super Contributor
timestamp: August 07, 2014, 05:28:36 pm
content: The lander (Philae) uses the radiation-hardened Harris RTX2010 microprocessor made by Intersil.http://www.researchgate.net/publication/234265387_Embedded_Computer_System_on_the_Rosetta_SpacecraftRosetta uses the MIL-STD-1750A made by Dynex (MAS281)http://en.wikipedia.org/wiki/MIL-STD-1750Ahttp://books.google.mu/books?id=JUYo2E9UB18C&pg=PA41&lpg=PA41&dq=ma31750+processor&source=bl&ots=pylO5CcMq2&sig=ujkePmXZzzJlqROkcbJ6J9Cn-rc&hl=en&sa=X&ei=_sDjU4G-CIar7AbfpoHYAg&redir_esc=y#v=onepage&q=ma31750%20processor&f=false

author: bwat
author_rank: Frequent Contributor
timestamp: August 07, 2014, 06:39:28 pm
content: Quote from: Wytnucls on August 07, 2014, 05:28:36 pmKoopman's excellentStack Computers, The New Wavecovers an earlier version, the RTX2000. The author has been kind enough to put the book online:http://users.ece.cmu.edu/~koopman/stack_computers/. Anybody interested in CPU design should read the book; it's a good read, a bit dated but still worth it IMHO. I actually looked at it earlier today to check something out and was quite amazed when I recognised the name of the chip from your post this evening. I think this is the first time I've read about this chip outside the confines of that book.

author: nctnico
author_rank: Super Contributor
timestamp: August 08, 2014, 12:23:22 am
content: Quote from: Kjelt on August 07, 2014, 07:26:32 amCalculating trajectories with gravity pull seems to be relatively easy. There is no wind or friction from an atmosphere. The existence and orbit of some of the other planets which where not visible back then have been predicted by using similar calculations.QuoteMostly old stuff with large geometries so that traces or transistors on a chip don't get damaged from the impact of a particle. A couple of decades ago I got a private tour in a clean room where they where assembling a satellite (the ERS1 IIRC) and I asked the same question

author: EEVblog
author_rank: Unknown
timestamp: August 08, 2014, 12:51:03 am
content: Quote from: Wytnucls on August 07, 2014, 05:28:36 pmCode written in FORTH!

author: Wytnucls
author_rank: Super Contributor
timestamp: August 08, 2014, 04:52:27 am
content: Uses a stack and RPN arithmetic logic like the programmable HP calculators of that period.

author: Kremmen
author_rank: Super Contributor
timestamp: August 08, 2014, 05:19:39 am
content: Herehttp://space.fmi.fi/index.php?id=27is a pic and brief description of the mass memory board of the Philae lander, made by the space division of Finnish Meteo Institute. They went for robustness instead of miniaturizing the heck out of it.Another pichttp://space.fmi.fi/index.php?id=29of the Ion Composition Analyzer controller board prototype. Looks like they went for an Actel A1280 FPGA on this one. Someone might recognize the MCU used (one of the chips is bound to be one).

author: Kjelt
author_rank: Super Contributor
timestamp: August 08, 2014, 07:43:15 am
content: Wow those boards are a beauty, looks more like military spec with all those metal can packages.That is a totally different league.

author: KJDS
author_rank: Super Contributor
timestamp: August 08, 2014, 09:25:03 am
content: I've done a few bits of design work for satellites, so I'll give a brief overview of the design process.An initial design will be done and carefully analyzed and any interesting areas will have a breadboard or prototype made.. Nothing different there from a commercial project.Then the real; fun starts with the documentation. Design description, which would include everything from a general overview to the calculations used to determine the value of every component on the board, simulations, results from the breadboards and explanations for any differences. Then there's the Compliance Matrix, worse case analysis, parts stress analysis, radiation analysis, MTBF calculations and so on. It's been a while and I'm sure I've missed out a few of the design documents. Further documents will include plans for further stages, so a test plan for an amplifier would say that it will be tested at nominal, max and min supply voltages, and at various levels and frequencies with an assortment of specified waveforms and at what temperatures.At that point, it's time for the first formal design review, with the customer, possibly the end customer and also critical suppliers.About the same time, there's a whole pile of process and parts work happening. Each process needs to be space qualified. If you don't have an up to date certificate to say you can hand solder 0402 resistors with Sn53, and another with a certificate for inspecting the same then it doesn't happen. Before the iron is even turned on the documentation will need to specify solder and flux types. If the board assembly is on a P^P and reflow then that line will need space qualifying.LAT testing, or Lot Approval Testing will be going on. For each reel or tube of components a few will be taken and subjected to an accelerated life test. If one component from that lot fails, the whole lot is binned and a new lot tested. The accelerated life tests typically take 12 weeks, so a failure means a three month delay on the project. Ideally you pick what parts you need early on and get the LAT testing done early. Sometimes you need to change a resistor value, so the wise but expensive move is to LAT test more components than you need.Before production of the flight hardware starts then the second big design review happens. All the previously mentioned documentation is updated, usually by this stage a proper prototype that is intended to meet spec has been made and electrically tested with some temperature testing added in, along with any other testing that is required by the customer to provide confidence. Additional documentation would include the Test procedure, which would take the Test plan and fill in exactly what measurements are to be made, what equipment is to be used and test limits.Only after that design review will production of the flight hardware proceed.The testing of parts that are going into space is tedious. On a commercial product, designs are tested at ambient and at temperature extremes. For a space project, they are tested over a wider temperature range every 10 or 20 degrees C and in vacuum, in a Thermal Vacuum (TVAC) chamber, Usually the equipment needs to be watched whilst it is in the chamber, so the three hour wait for the temperature to stabilize is tedious, I've read a lot of books in the wait time, and ate a lot of snacks and put on 20kgs.The vibration testing is fun. Launch vibration is so high that no-one is allowed in the same room at the vibration table when it's operating and from the next room it actually sounds like a rocket taking off.Finally all the test results, and process verification documentation is collated and a final design review is carried out. A typical module in a satellite will generate about 10m high of paperwork. There are a lot of modules in a small satellite and there's more paperwork involved as the modules are integrated and tested.What I like about doing design work for space applications is that you don't get caught out at the end of a design due to skimping on analysis early on. You never need to do a quick board respin as a resistor is dissipating more power than previously anticipated. Designed get done properly. What I don't like is the huge amount of testing required. When pen plotters where the normal way to record a result, I know of someone who had done 9000 of the required 11000 plots when he was told that the project had been cancelled. Fortunately GPIB measuring is now the norm.

author: HP-ILnerd
author_rank: Frequent Contributor
timestamp: August 08, 2014, 11:00:22 am
content: Of course, NASA has been known to over-do it on the analysis:http://images.spaceref.com/news/2011/KSC-MSL-2011-0045.pdf

author: Kjelt
author_rank: Super Contributor
timestamp: August 08, 2014, 12:28:58 pm
content: Quote from: HP-ILnerd on August 08, 2014, 11:00:22 amWell sice they have no more spaceship accidents to investigate and clearly they still have their jobs they can better keep their skills up to date with other assignments .

author: Wh1sper
author_rank: Regular Contributor
timestamp: August 08, 2014, 12:41:24 pm
content: Quote from: Wytnucls on August 08, 2014, 04:52:27 amMy long standing favorite Language!(ago)

author: miguelvp
author_rank: Super Contributor
timestamp: August 08, 2014, 07:13:42 pm
content: I'm pretty sure compilers always generate RPN code when they encounter formulas, it wouldn't make sense to do it a different way.

author: jaxbird
author_rank: Frequent Contributor
timestamp: August 08, 2014, 07:27:49 pm
content: I find it incredibly impressive to have a space craft doing a 10 year journey to orbit and possibly land on a comet, while the comet is travelling at incredible speeds around our sun!...Truly amazing in my book, I'd rather we spent a much larger budged on science and space exploration that currently. It's the future, it's worth the money!

author: bwat
author_rank: Frequent Contributor
timestamp: August 08, 2014, 07:49:11 pm
content: Quote from: miguelvp on August 08, 2014, 07:13:42 pmThis isn't really applicable in this case. The microprocessor in question has a stack architecture - it's essentially a FORTH microprocessor - it's ALU instructions don't take specific operands as the operands are on the data stack. The machine basically has a type of FORTH as it's assembly mnemonics. This is from Koopman's book I linked to earlier and it has the instruction set:http://users.ece.cmu.edu/~koopman/stack_computers/sec4_5.html.As for compilers in general, there's no need to generate RPN code if you've got a typical accumulator architecture or a general purpose register architecture. Say you had a typical RISC machine with 31/32 registers, then you would do this:Code:adi r3, r0, 99 ; r0 contains 0, so r3 <= 99adi r4, r0, 98 ; r0 contains 0, so r4 <= 98add r5, r3, r4 ; r5 <= 99+98and not something equivalent to this which needs a data stack and potentially memory accesses if the stack is not on the chip:Code:LIT 99LIT 98PLUS[EDIT: I've realised that when you write RPN you're meaning the order of evaluation, i.e. evaluate the operands then perform the operation. When I read RPN I think stack plus zero operand instructions. Actually, it's syntax not semantics. Anyway, if I'm right in my assumption about what your interpretation is, then you're correct as the arithmetic operation will have its operands evaluated before the operation takes place - even in a non-strict functional programming language.]

author: miguelvp
author_rank: Super Contributor
timestamp: August 08, 2014, 08:25:21 pm
content: I was thinking more of floating point processors, where you do fld to load the values and then do the operation. All the ones I've seen are stack based.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: August 09, 2014, 04:55:47 am
content: I look at few pages of that book - only ones shared by Google and what surprised me, somewhat is that book describes use of components in BGA (Ball Grid Array) packages. I was under impression that BGA would be too risky and not reliable enough for space applications comparable to one of those gold lead ceramic QFP packages. Don't want to get red circle of death on your $1B space toy.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 09, 2014, 04:37:53 pm
content: It's my understanding, BGA is more reliable per-pin than QFPs. And you can get a hell of a lot more pins down...They also use leaded solder, not the stuff prone to cracking. Though the higher strength of RoHS processes tends to lead to higher reliability anyway; it seems tin whiskers were much ado about nothing after all.Tim

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: August 09, 2014, 06:08:20 pm
content: Well it is strange. Why spend ll effort to make components in "military packages". I mean those pinkish ceramic QFPs with gold leads, extended temperature ranges etc. and then use BGAs. I am not an expert in designing hardware for space applications but there is definitely huge temp variations, absence of air/gas that allow for heat transfer, vibration during launch that can knock your teeth out and then on top of that radiation. And yet we have BGA-related problems in room environments.I have heard (or watched in some video) that sometimes BGA component sort of under-filled with epoxy. It have to be very thin runny epoxy to be able to squeeze it in between soldered balls. I have seen it done on one board from cable modem. Is this something I can buy from DigiKey? Just curious.

author: KJDS
author_rank: Super Contributor
timestamp: August 09, 2014, 07:02:16 pm
content: Every BGA will have been xrayed from a few different angles. It becomes very obvious if a joint isn't good.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 09, 2014, 07:46:42 pm
content: Quote from: Alexei.Polkhanov on August 09, 2014, 06:08:20 pmA shittily engineered product is a shittily engineered product... what do you expect?Examples of consumer use:Plop down a footprint either from the manufacturer's suggestion, or IPC guidelines.Solder in standard reflow.Ship product.Whereas aerospace may go back all the way to the footprint to optimize geometry for their process; the board material TCE can be matched to that of the device (I've seen it in IPC books but never IRL: there are PCB materials with rigid metal supporting cores to control CTE and such -- this isn't your average aluminum PCB), and the solder alloy, flux and reflow profile can all be optimized for best reliability. Test data is generated from accelerated life and vibration testing, presumably with a margin beyond the (already severe) stresses of launch or whatever.Tim

author: TerraHertz
author_rank: Super Contributor
timestamp: August 11, 2014, 02:31:52 am
content: Meanwhile, more pics:http://www.esa.int/Our_Activities/Space_Science/Rosettahttp://www.esa.int/Our_Activities/Space_Science/Rosetta/Highlights/Postcards_from_RosettaLatest imagesMy favorite so far:Considering the comet is about 4Km in some dimension, and that view is kind of looking 'down' towards the center of gravity, it gives me that aching-fingertips climbing risk-exposure feeling. At least if you fell there, you'd have a long time to wonder how much your impact was going to hurt. Also, you'd get a number of preview impacts on the way down.Thanks for the link to the Forth-CPU book.

author: firewalker
author_rank: Super Contributor
timestamp: November 10, 2014, 08:14:15 pm
content: One day to go.QuoteAlexander.

author: German_EE
author_rank: Super Contributor
timestamp: November 10, 2014, 08:39:32 pm
content: 16:00 UTC or 17:00 CET for those of us in Europe (Mission Control at ESOC are about thirty minutes walk away from me).

author: JoeN
author_rank: Frequent Contributor
timestamp: November 10, 2014, 08:59:06 pm
content: Quote from: Wytnucls on August 07, 2014, 05:28:36 pmNRND!http://www.intersil.com/en/products/space-and-harsh-environment/rad-hard-digital/rh-microprocessors-and-peripherals/HS-RTX2010RH.html

author: Kjelt
author_rank: Super Contributor
timestamp: November 10, 2014, 10:08:06 pm
content: Quote from: TerraHertz on August 11, 2014, 02:31:52 amSo what is the gravity on that thing? Will it attract enough to keep on standing on it or if you jump you will float into space?

author: Frost
author_rank: Regular Contributor
timestamp: November 10, 2014, 11:42:20 pm
content: Quote from: Kjelt on November 10, 2014, 10:08:06 pmThe gavity 1:100.000 compared with the earth.The weight of the lander Philae is 100kg here on earthbut it only 1g when Philae lands on the comet.Quote from: Kjelt on November 10, 2014, 10:08:06 pmNo, it depends on the unknown underground if its to densethe lander might jump back into space.But they use a gas jet to force Philae to stay on the groundas long as they need to apply the harpoons and the self-drillinganchors.

author: EEVblog
author_rank: Unknown
timestamp: November 11, 2014, 12:27:25 am
content: Aussie systems engineer gives it a 50% chance of touchdown successhttp://www.abc.net.au/science/articles/2014/11/10/4123194.htm

author: DJohn
author_rank: Regular Contributor
timestamp: November 11, 2014, 11:41:04 am
content: Quote from: miguelvp on August 08, 2014, 08:25:21 pmSorry, this is an old post, but I've only just seen it. The only stack-based floating point I know is the old x87. It still survives in modern x86/x64 processors, but compilers will try to use the register-based SSE instructions instead (for single precision at least, which is all I usually care about).Floating point in everything else I've used (MIPS, PPC, ARM, 68K, vector processors from various Playstations, GPUs) has been register based.

author: Kjelt
author_rank: Super Contributor
timestamp: November 12, 2014, 08:30:25 am
content: Quote from: EEVblog on November 11, 2014, 12:27:25 amIn the newspaper today it said 25% chance on failure esp. possible tumbling of the Philae lander, that would be 75% chance on success.Well in 8 hours we will know, keep our fingers crossed.Impression of how it should look best case

author: Homer J Simpson
author_rank: Super Contributor
timestamp: November 12, 2014, 02:57:38 pm
content: Live landing coverage.http://www.space.com/17933-nasa-television-webcasts-live-space-tv.htmlAmazing stuff.

author: Kjelt
author_rank: Super Contributor
timestamp: November 12, 2014, 03:44:05 pm
content: or here:http://rosetta.esa.int/still 15 minutes to wait till we know if it succeeded or not

author: KJDS
author_rank: Super Contributor
timestamp: November 12, 2014, 04:04:55 pm
content: cheers in the control room

author: Kjelt
author_rank: Super Contributor
timestamp: November 12, 2014, 04:06:48 pm
content: Yeah they look happy still waiting official words

author: Kjelt
author_rank: Super Contributor
timestamp: November 12, 2014, 04:08:06 pm
content: they are receiving telemetry data, if it would have bounced off this would not be the case (what I can understand from the discussion).

author: bookaboo
author_rank: Frequent Contributor
timestamp: November 12, 2014, 04:09:54 pm
content: Thanks for link, all looking good."Sitting on surface, talking to us"

author: Homer J Simpson
author_rank: Super Contributor
timestamp: November 12, 2014, 04:28:15 pm
content: Congratulations to all of those involved. Outstanding achievement.These are the types of things that inspire a new generation of kids to be scientists and engineers.The pride in the faces and words of those evolved is well deserved.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: November 12, 2014, 06:28:31 pm
content: First broken thruster, then harpoons that did not workDoes not sound very "inspirational" to me. I hope they can trace the problem back to its origin whoever or whatever it is.

author: bitwelder
author_rank: Super Contributor
timestamp: November 12, 2014, 06:30:01 pm
content: For those who missed the event, the landing sequence in 136+ steps by Randall Munroe:http://xkcd1446.org/

author: miguelvp
author_rank: Super Contributor
timestamp: November 12, 2014, 06:48:49 pm
content: Quote from: Alexei.Polkhanov on November 12, 2014, 06:28:31 pmAfter a 10 year trip in space and actually doing a successful landing I don't see why it wouldn't be inspirational.

author: KJDS
author_rank: Super Contributor
timestamp: November 12, 2014, 07:26:53 pm
content: Quote from: Alexei.Polkhanov on November 12, 2014, 06:28:31 pmIt was designed in the 90's, using 80's technology. Whoever chaired the design reviews will now be retired. Procedures for running the reviews will have changed significantly and the probability of working out exactly why things didn't work perfectly is remote.No-one will get blamed for it, for the moment you start blaming people for mistakes is when they stop taking risks, and it would be a very dull world without risk.

author: Monkeh
author_rank: Super Contributor
timestamp: November 12, 2014, 07:30:30 pm
content: Quote from: Alexei.Polkhanov on November 12, 2014, 06:28:31 pmIt's the first time we've ever sent a lander to a comet. You expected it to go perfectly?

author: Royce
author_rank: Contributor
timestamp: November 12, 2014, 07:36:47 pm
content: On the DLR stream (but not the ESA stream) they indicated that they suspect the lander bounced off and then landed again. They got some indications that the lander began rotating after landing but after while the rotation just stopped.Hopefully the radio link comes back as expected when Rosetta comes back up over the horizon for the lander. I want to see some super close in pics!

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: November 12, 2014, 08:08:51 pm
content: Quote from: Monkeh on November 12, 2014, 07:30:30 pmThat is absolutely not true - Japanese Space Agency tried it first 11 years ago:http://en.wikipedia.org/wiki/Hayabusa.

author: PA0PBZ
author_rank: Super Contributor
timestamp: November 12, 2014, 08:26:57 pm
content: Quote from: Alexei.Polkhanov on November 12, 2014, 08:08:51 pmhttp://www.diffen.com/difference/Asteroid_vs_Comet

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: November 12, 2014, 08:48:45 pm
content: Well if you take the orbital period then 67P falls under meteorite, (Orbital period (years) 1-100 for meteorites vs 75 to 100,000++ for comets) plus its orbit is not as eccentric as most of comets. I am not sure if dusty/soft surface of a comet vs meteorite makes it more or less challenging to land on. Obviously we can argue forever here - comet or meteorite or something in between like planet or dwarf planet - and what would be the point?

author: i4004
author_rank: Regular Contributor
timestamp: November 12, 2014, 09:05:26 pm
content: what (radio) modulation scheme do they use on these things(?), that data is not that easy to come by on the web, it seems...i see thishttp://www.brighthub.com/science/space/articles/116036.aspxbut that's kinda inconclusive and vague (pcm in itself has nothing to do with radio)..and thishttp://deepblue.lib.umich.edu/bitstream/2027.42/6820/5/bac9829.0001.001.pdfis rather old...1956pcm-am is mentioned in that old paper....

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: November 12, 2014, 09:30:21 pm
content: There is whole book on subject:http://www.amazon.com/dp/0471445363/ref=rdr_ext_tmbBooks are publicly available from NASA website here:http://descanso.jpl.nasa.gov/monograph/mono.html

author: Howardlong
author_rank: Super Contributor
timestamp: November 13, 2014, 07:42:14 am
content: Quote from: i4004 on November 12, 2014, 09:05:26 pmAlmost certainly it will be a PSK based scheme, this has been the standard for decades for space telemetry due to link budget efficiency, together with a FEC coding scheme, and almost certainly it'll be using CCSDS standards.http://public.ccsds.org/publications/BlueBooks.aspx

author: Howardlong
author_rank: Super Contributor
timestamp: November 13, 2014, 09:11:19 am
content: Here you go:http://www.esa.int/esapub/bulletin/bullet95/CALZOLARI.pdfPopping "CCSDS" and "Rosetta" into Google generated a number of other good results too.

author: rs20
author_rank: Super Contributor
timestamp: November 15, 2014, 06:31:26 am
content: Quote from: Monkeh on November 12, 2014, 07:30:30 pmThe trouble is, the failures weren't really comet-specific -- explosive in the harpoons going lame in the vacuum of space? Nothing to do with comets. The thruster completely failing? Nothing to do with comets. I'd completely agree with your comment if it landed and, I dunno, it cracked the surface and got launched up by a jet of gas or something; or if the harpoons failed to grip the unknown material of the comet. These are "first time we tried it"-relevant excuses. It appears the reality isn't quite as easy to dismiss.On the other hand, they seem to be saying that the mission will be 90%+ successful from a scientific standpoint, so it's all good.

author: Kjelt
author_rank: Super Contributor
timestamp: November 15, 2014, 08:49:24 am
content: I bet you guys build way better and sturdier space exploration ships all the time. We have a saying in our country: the best helmsmen are standing on the shore, meaning the people always commenting on others without having any or little experience themselves always seem to know better or claim to do it better.

author: rs20
author_rank: Super Contributor
timestamp: November 15, 2014, 01:23:24 pm
content: Quote from: Kjelt on November 15, 2014, 08:49:24 amYes, a nice, albeit vague saying. But what I ask you is: if an organisation that makes thrusters is asked to make a thruster, is it not reasonable to expect that thruster to work, or be at least vaguely critical if it doesn't, jeopardizing a billion dollar project? Same for explosives that just have to go "pop" after being in space for a while. This should be a solved problem, there are many many pyrotechnics that have worked fine after years in space.

author: KJDS
author_rank: Super Contributor
timestamp: November 15, 2014, 03:21:28 pm
content: Quote from: rs20 on November 15, 2014, 01:23:24 pmHaving done a fair bit of designing for satellites, it's very likely that they were using technology that had been used on previous missions. Heritage is everything and nothing new is included without very good reason.

author: zapta
author_rank: Super Contributor
timestamp: November 15, 2014, 03:48:08 pm
content: Quote from: Kjelt on November 15, 2014, 08:49:24 amHere it's called 'monday morning quarterback' (or to paraphrase your saying: the best quarterbacks are on the couch).Overall the goal and the technical achievements look very impressive to me.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: November 15, 2014, 08:16:22 pm
content: What will be more interesting is to see whether the team are able determine what caused the failure. Trite statement or not such information will be useful for the future. Wonder whether there is anything in the data so far to aid diagnosis.

author: Howardlong
author_rank: Super Contributor
timestamp: November 15, 2014, 09:00:11 pm
content: Quote from: Kjelt on November 15, 2014, 08:49:24 amSpeaking for myself, I have half a dozen spacecraft orbiting the planet right now that I had a direct hand in, and three more in development. Does that count? ;-)I've had my fair share of problems in the projects I've worked on, plenty of battle scars believe me, some that would make your retrospective toes curl. But we learn from those mistakes. It goes with the turf.

author: lapm
author_rank: Frequent Contributor
timestamp: November 15, 2014, 10:44:37 pm
content: I think its just huge thing that they can take old proven technology and turn it into spacecraft. kick it out of atmosphere, let it pretty much freeze up for few years and its still mostly works after that time.About that thruster that did-int work, all it takes is small micro meteorite hit to damage cable or something in right spot to prevent it firing.. If that's the only problem that machine after being 10 years in space, that's good...

author: Kjelt
author_rank: Super Contributor
timestamp: November 15, 2014, 11:32:11 pm
content: Well just look at the blunders made with the european gps satelites this year, two came in the wrong orbit due to a probably russian software failure. Look how many times this had already been done succesfully , tested and still some error occurs, now if you make a comment about that I would partially agree, this should not happen unless an accident occurred.But still it did and often does which tells me this is science at the cutting edge, they don,t call it rocket science for nothing.But this mission was even more unique, a one of a kind, the thing has been out there for ten years and travelled 6.4 billion kilometres , the rendez vous was a succes and they even landed the lander on the comet with some glitches yes. Two things did not work, out of, what? two thousand things that could have gone wrong? They gave it a 50% chance from the get go.No I can only be very silent on this achievement in awe what they did achieve and so are other space organisations that congratulated ESA on this achievement.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: November 16, 2014, 02:30:41 pm
content: Given just the known scrap orbiting the planet it's becoming a bit of a lottery just getting to outer earth orbit.http://www.space.com/16518-space-junk.htmlJust perhaps funding could be found to try out one of the many proposed 'vacuum' sweepersto deal with the problem. I'm sure that would lead to many new discoveries.Perhaps Dyson could be consulted!

author: miguelvp
author_rank: Super Contributor
timestamp: November 16, 2014, 06:50:58 pm
content: And suddenly the image of mega maid from spaceballs came to mind

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 16, 2014, 08:49:48 pm
content: Comets kind of are just cosmic dustballs...Tim

author: i4004
author_rank: Regular Contributor
timestamp: November 17, 2014, 04:19:28 pm
content: Quote from: Kjelt on November 15, 2014, 08:49:24 amsome folks have a saying that two man know more than one....hehe...those working should listen to those on the shores, from time to time they'll get good suggestion.and, thus far, i just love the "experience argument" which seems to be all-encompassing many times in human conversations overall...experience didn't exist prior to this, yet they did it somehow, how come?experience seems a bit outdated in these times when you can learn to solder just by watching yt...and frankly, i find that not a bad thing...it's not important how you learn it, it's important to learn it.esa learned quite a bit from this mission i would imagine.i learned it takes too much damn time to go there!also, imagine you work on something for 10 years and it flops once there....they shouldk of made 2 completely different systems, just incase one failes.and if they made 3, then they could do anything!(each system would have 2 probes!)i mean if you wanna spend money in that way, spend it!here's an interesting thought: how much better would the same thing be today, knowing how much things improve in 10yrs, esp. in electronics.perhaps it could include a cpu fast enough to deploy hooks at time?(sorry, can't resist! i mean the thing was obviously slow if it bouned few times off the comet)perhaps they could think of a way to launch hooks first, like a harpoon....and aim for the brightest spot on the comet, not the best shade!Quotehttp://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questionsdid anybody even think about possibility that sun would be shaded on some places on the comet, i wonder...perhaps the panls shoudl be om the harpoon to launch them anywhere near?gosh, how succesfull would the mission be if we had to comment it 10 years ago! wooohoooo!

author: Howardlong
author_rank: Super Contributor
timestamp: November 17, 2014, 07:00:24 pm
content: While working on a project at ESA some years ago, a few of us had an impromptu space soldering course which was an eye opener. There are guys there where that's all they do, professional space solder dudes.There were plenty of things to think about, most notably when soldering down wires to lands on boards, once the wire had been stripped (there was an expensive and underused machine to do this, you program in that you wanted, say, 50 x 23.6cm lengths of wire, and it would cut and strip them for you precisely, just moments later), after soldering the stripped end, a short loop was made a few mm long and the teflon insulation was glued down with special glue to the board. This was to mitigate against vibration during launch. All solder is full fat of course. You could then crimp the other end with a $1000 crimping tool for the D connector.We also could only cycle SMA connectors once on flight hardware, of course that was with a $500 SMA torque wrench while wearing fetching dinner lady outfits and sweaty blue plastic gloves. Connectors were replaced after that one cycle. In contrast, I have a test fixture for one of my non-space designs that uses SMA connectors. I use a half turn SMA saver test connector to avoid having to reterminate the SMA on the test fixture. Those saver test connectors last around 6000 cycles before they need replacing. When you look at the pin of a 6000 cycle SMA connector, you can see that it's gradually been worn down by the abrasive effect of plugging it in and out.Almost everything is conformally coated, but some RF stuff doesn't work too well with all that gunk on it and is left alone if you can pursuade them. Part of the reason to do this is for vibration, and part is to control outgassing.

author: i4004
author_rank: Regular Contributor
timestamp: November 17, 2014, 10:43:12 pm
content: Quote from: Howardlong on November 17, 2014, 07:00:24 pmwhat, prevent pros from adhering to their standards?come on, that can't be possible!as for "space soldering" whiskers fenomenon is interestinghttp://nepp.nasa.gov/whisker/http://en.wikipedia.org/wiki/Whisker_%28metallurgy%29#Effectsalthough it exists on earth too...

author: Howardlong
author_rank: Super Contributor
timestamp: November 18, 2014, 04:45:26 pm
content: There's a process you can do to re-tin ROHS COTS parts to mitigate against tin whiskers. It's potentially a big problem as parts get smaller. That's also the main reason that aerospace stuff doesn't use diet solder.There are a number of good reason to use COTS rather than specially designed devices in space applications, it's not just cost. One is that COTS parts, made in high volume, are well characterised, in contrast to very low volume devices.You can mitigate against things like outgassing as well as total dose and single event effects when using COTS parts to some extent, but again, the continuing miniaturisation doesn't help with transistor gate insulation gaps becoming smaller and smaller. In some scenarios, particularly orbiting within the van Allen belts, the effects of radiation are greatly reduced.

author: Howardlong
author_rank: Super Contributor
timestamp: November 18, 2014, 04:53:34 pm
content: Quote from: i4004 on November 17, 2014, 04:19:28 pmYes, they did, they chose a spot free from rocks and with maximum solar visibility, but as we now know it bounced a few times and landed in an unplanned location.

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 14, 2015, 12:00:27 pm
content: It's awake!

author: EEVblog
author_rank: Unknown
timestamp: June 14, 2015, 12:30:00 pm
content: Quote from: PA0PBZ on June 14, 2015, 12:00:27 pmExciting!

author: benst
author_rank: Regular Contributor
timestamp: June 14, 2015, 12:47:47 pm
content: Quote from: EEVblog on June 14, 2015, 12:30:00 pm+1E9

author: Howardlong
author_rank: Super Contributor
timestamp: June 14, 2015, 01:23:03 pm
content: It's the lead story on the BBC website in the UK at the moment. Who says space is boring?24W of power available, I guess that's solar and not WiFi or ultrasonic powered.Somewhat reminiscent of the AO-7 satellite that remained dormant for 21 years, until a shorted battery became open circuit after years of attempted recharge cycles. It remains functional for two way voice communication, when not in eclipse, to this day.

author: rr100
author_rank: Frequent Contributor
timestamp: June 14, 2015, 01:57:45 pm
content: Outstanding!Go, Philae, go!

author: Kjelt
author_rank: Super Contributor
timestamp: June 14, 2015, 07:41:08 pm
content: What an incredible fast service repair team ESA haveNow lets wait what exciting stuff the data has in store for us

author: Fraser
author_rank: Super Contributor
timestamp: June 28, 2015, 04:05:12 pm
content: I was so pleased to just read that Philae has managed to charge her batteries and phone home.YayI only hope it doesn't get too rough up there with the suns rays melting ice. It would be a real shame if she got dislodged after surviving to data.At this point I should admit that, as a child, I was quite sad when researching the various Roving Probes that had been sent to the moon. I hated the fact that they 'died' or were shut down and abandoned up thereDaft I know but I actually cared about the probes !https://en.wikipedia.org/wiki/List_of_lunar_probesMy favourite was the Russian Lukokhod (meaning moon walker) rover and she was Nuclear heatedhttps://en.wikipedia.org/wiki/Lunokhod_programmehttps://en.wikipedia.org/wiki/Lunokhod_2Who else watched the live TV coverage of Giotto's approach to Halley's Comet in 1986? Her debris shield got pelted badly and she was 'blinded' ... I was really rooting for her and was so chuffed that she survived the encounter.Uh-Oh, the men in white coats have just turned up outside the house.......

author: TerraHertz
author_rank: Super Contributor
timestamp: June 29, 2015, 11:38:34 am
content: https://www.flickr.com/photos/europeanspaceagency/sets/72157638315605535Rosetta photo set.Note there are 6 pages of pics. Index is at the bottom of the loooong pages.

author: PA0PBZ
author_rank: Super Contributor
timestamp: September 05, 2016, 02:46:09 pm
content: They found the little bugger!https://twitter.com/ESA_Rosetta/status/772803496420704256https://twitter.com/esascience/status/772804570598760452

author: Fraser
author_rank: Super Contributor
timestamp: September 05, 2016, 03:04:53 pm
content: Great news.Some more comment on the search and Rosetta's final mission task here....http://m.esa.int/Our_Activities/Space_Science/Rosetta/Philae_foundFraser

author: Kjelt
author_rank: Super Contributor
timestamp: September 05, 2016, 03:58:32 pm
content: Just a side thought, is there no other way to get energy besides sunpower when sitting on an asteroid ?It is such a waste that a bit of shade makes an apparatus travelling such a huge distance succesfully, totally useless in the end.

author: Gyro
author_rank: Super Contributor
timestamp: September 05, 2016, 04:21:22 pm
content: Agreed, a great shame but not a total loss. It did manage three days of science before the batteries went flat and locating it has added some very useful context to the measurements it did manage.http://www.bbc.co.uk/news/science-environment-37276221It looks as if Rosetta is destined to join it in a few weeks time, though a little more violently.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 05, 2016, 05:51:28 pm
content: Quote from: Kjelt on September 05, 2016, 03:58:32 pmRTGs are expensive, and Pu238 is at a bit of a shortage right now (Juno's entirely solar powered, despite being in the outer solar system!), so they probably took that risk in relation to other options or costs.Tim

author: SeanB
author_rank: Super Contributor
timestamp: September 05, 2016, 07:07:03 pm
content: Pu238 is around in large quantities, just that there is no incentive to set up the reprocessing facilities to get it out of the spent PWR fuel rods that are sitting around in ton lots in reactor storage ponds.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 05, 2016, 07:40:03 pm
content: No, that's Pu244 (and a little Pu239). Pu238 is made from Np:https://en.wikipedia.org/wiki/Plutonium-238#ProductionWell, it's still present... but separating Pu isotopes sounds awful. Better to chemically separate, then transmute..(?!)Repro in the US is a big deal/problem, though. Well, not really a problem, in and of itself, but it probably will be in the semi-near future.Tim