[Ground-station] Satellite program
Douglas Quagliana
dquagliana at gmail.com
Thu May 17 08:05:58 PDT 2018
I don't know what drove the design decisions. The 2-of-3 voting has the advantage for simplicity and it's easy to implement. In fact, they tested it initially by just not soldering in one of the three banks of memory!
It also has the advantage that for any 32 bit chunk of memory it can correct up to 32 bit errors (that is, ALL of them could have bit errors in one of the banks and it will be corrected), which is better than many other parity schemes which limit the number of detectable/correctable errors per chunk of memory.
Regards,
Douglas
> On May 17, 2018, at 6:29 AM, Bruce Perens <bruce at perens.com> wrote:
>
> Thanks Doug. Wow. Was an ECC chip and extra bits considered less reliable?
>
>> On Thu, May 17, 2018 at 12:02 AM, Douglas Quagliana <dquagliana at gmail.com> wrote:
>> All,
>>
>> Here's more way more information than you wanted to know on a couple of the points that Bruce mentioned.
>>
>> Bruce writes:
>> >They didn't always use rad-hard memory, just because they could not afford it,
>> >but used error-correcting memory architectures and scrubbed the memory constantly
>> >so that single-bit errors were corrected before they became large enough to be
>> >uncorrectible.
>>
>> If I recall correctly, the memory scrubbing technique was used on the LEO Microsats and a three bank memory voting scheme was used on the IHU-2 on AO-40. See
>>
>> http://www.amsat.org/amsat/articles/g3ruh/124.html
>>
>> >EDAC memory: 20 percent. The EDAC (Error Detecting And Correcting) memory scheme used requires the actual memory to be three times as large as the processor sees. This is necessary to allow a two-of-three vote for each bit.
>> >This scheme results in a much faster memory system than the Hamming 12 to 8 EDAC system used on previous designs, in order to support the much faster processor.
>>
>>
>> Bruce writes:
>> >They have their own FORTH-like language, first written in the '70's, which
>> >does concurrent but not parallel threads. Most housekeeping is written
>> >in this language.
>>
>> The language is IPS. First described in 1979! The original reference is
>>
>> Meinzer K.; IPS, An Unorthodox High Level Language, BYTE, January 1979, pps 146-159.
>>
>> which, before you groan about ancient references to out-of-print paper magazines, is actually available online at
>>
>> https://archive.org/stream/byte-magazine-1979-01/1979_01_BYTE_04-01_Life_Algorithms#page/n147/mode/2up
>>
>> But...if you want to learn IPS then you probably want the IPS book that James Miller, G3RUH, first published in 1997. Before you groan, again, about ancient references to out-of-print paper books, that book (actually the third edition of that book from 2016) is available online at
>>
>> http://www.jrmiller.demon.co.uk/IPS/IPS.pdf
>>
>> However, as you will quickly find out reading Miller's IPS book, the AO-13 IPS flight code is written in a German variant of IPS, so a lot of that IPS code looks like this:
>>
>> : TRQ-ST Z-MARKE @
>> JA? E-FLAGS @ #14 UND >0 Z @
>> MZEITGRENZE @ = ODER
>> JA? 0 M-EIN !
>> DANN Z @B 32 + #FF UND 64 < M-EIN @
>> UND 1 UND MAGNET !B
>> DANN ;
>>
>> which to some people looks a lot like line noise but here "JA" is "YES" and "DANN" is "THEN" and so on in German (hint: There is an "English/German cheat sheet" in the IPS book on page 82). If you wrote your own IPS code today you could use the English ones, but to read the old housekeeping code you need to be able to look up the equivalents in English AND understand the low level machine operations (such as byte addressing, a stack, bitwise operations... remember this language was designed and meant to be run (originally) on an 1802 or an 8080 or a 6502 with maybe thirty-two KILObytes of memory. Yes, KILO-bytes of memory. Really. I'm not making this up. Go read the IPS book.)
>>
>> Emulators/simulators for running IPS code (German and English) are on the AMSAT website if you want to start coding. See
>>
>> http://www.amsat.org/amsat-new/tools/softwareArchive.php#pc-ips
>>
>> Lastly, if you feel you must have a real 1802 CPU, well, there actually are 1802 CPU chips still around (well, regular ones not the SoS rad-hard ones), and there is even an entire 1802 computer that you can buy as a kit complete with toggle switches, LEDs, and up to 64K of RAM. And it fits inside an Altoids tin! No, I'm not making this up either. See
>>
>> http://www.sunrise-ev.com/membershipcard.htm
>>
>> Note that the membership card 1802 CPUs are not rad-hard and they can run TinyBasic not IPS. But, I'm sure AMSAT still has at least one rad-hard 1802 CPU... somewhere. And, getting IPS to run on the 1802 membership card is left as an exercise to the reader. If you're successful, I'd love to hear about it.
>>
>> 73,
>> Douglas KA2UPW/5
>>
>>
>>> On Wed, May 16, 2018 at 9:08 PM, Bruce Perens via Ground-Station <ground-station at lists.openresearch.institute> wrote:
>>> OK, I'm sure I'm going to get something wrong, so please, list folks, feel free to jump in and correct me when I do. I still don't know much about satellites.
>>>
>>> Keith,
>>>
>>> While silicon-on-insulator parts are a great way to go, there is at least a $1000 cost differential for CPUs and then you get to memory... So, cubesat folks have been creative in finding radiation-tolerant parts in consumer or industrial grades. The main problem we're trying to avoid is latch-up that actually damages the part. The second problem is bit errors. I have heard that some FLASH gate-array-based CPUs do not suffer damage from radiation induced latch-up and there are viable recovery mechanisms, and their FLASH-based gate-array does not require configuration memory and is resistant to single-element errors. I googled this: https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3399&context=smallsat which discusses the Microsemi SmartFusion2 (which we used for our abortive Whitebox SDR, so Chris Testa knows it well). No doubt you can find more.
>>>
>>> Others in the group have experience with other radiation-tolerant consumer or industrial grade parts.
>>>
>>> The Cortex M0 is more than enough for housekeeping and might be enough for some signal and image processing tasks. But the housekeeping CPU need not be the signal-processing CPU as well.
>>>
>>> AMSAT has had some interesting strategies. First, they had a cache of SoS 1802s which they used for 30 years or so. They used a lot of components that were given to them from cancelled space projects. They didn't always use rad-hard memory, just because they could not afford it, but used error-correcting memory architectures and scrubbed the memory constantly so that single-bit errors were corrected before they became large enough to be uncorrectible. There was no ROM onboard, a hardware modem loaded memory from the radio and then reset the CPU and set it running. Nobody's told me, but if there was any cryptography on that it wasn't much more than exclusive-OR of a secret word. They have their own FORTH-like language, first written in the '70's, which does concurrent but not parallel threads. Most housekeeping is written in this language.
>>>
>>> So, you can expect that some of an IHU project might be prospecting for radiation-tolerant parts that don't cost so much. Others have left breadcrumbs to follow.
>>>
>>> Even when you do have rad-hard parts, generally they have a consumer or industrial grade pin-equivalent so that non-flight and LEO units don't have to be made with the most expensive parts.
>>>
>>> Thanks
>>>
>>> Bruce
>>>
>>>
>>>
>>>> On Wed, May 16, 2018 at 1:37 PM, Keith Wheeler <keith.m.wheeler at gmail.com> wrote:
>>>> Bruce,
>>>>
>>>> I'm not familiar with the requirements for an IHU, but I've done a lot of embedded firmware/hardware design. With the desire for DX (above LEO), I'm assuming rad-hard will be a requirement. I was looking at a rad-hard ARM Cortex M0. What kind of horsepower would the IHU require?
>>>>
>>>> -Keith Wheeler
>>>>
>>>>> On Wed, May 16, 2018 at 11:54 AM, Bruce Perens via Ground-Station <ground-station at lists.openresearch.institute> wrote:
>>>>>
>>>>> Legal stuff first: Image credit: XKCD #1992: "SafetySat" at http://xkcd.com/1992/ Creative Commons Attr-NC 2.5 license.
>>>>>
>>>>> Yes, we should have a satellite program and do what AMSAT is not. Everyone I have heard from so far is asking for a "DX Satellite", "like AO-13" and not LEO.
>>>>>
>>>>> Mission should include digital communications using Michelle's design. I also have some blue-sky ideas that we can discuss at Hamvention, some of them might be good grant candidates. Think grant. Money is out there, we will start soliciting as soon as we have a mission plan.
>>>>>
>>>>> Build the satellite (and maybe P-pods) first, approach launch providers with flight hardware in hand and ready to go. Satellites are cheap, launches are not. Be prepared to take advantage of opportunities on very short schedules.
>>>>>
>>>>> I think we should fabricate extras of parts we design, and sell them as TAPR does to supplement their budget, but right off of Amazon Prime. Make them really easy and fast to buy, and someone else does the shipping. Aim at flight-quality but mostly going to classroom use rather than flight, to start. Nicer for the class than the PLA 3-D printer stuff that is so obviously non-flight that they are using now.
>>>>>
>>>>> Aim for 100% to 200% markup over cost, Amazon gets around 18% of the order and a warehouse fee and fulfills from their warehouse. Most of the commercial cubesat companies, like Pumpkin, are running 500% to 1000% markup in order to amortize R&D and operational costs and still make a profit, but most of them have flight heritage that we would not start out with. We use slave labor :-) and can mostly base our final cost on fabrication and sales costs.
>>>>>
>>>>> I have been looking at cubesat structures (because I feel competent enough to make one, at least with your help) and I really like Pumpkin's design. Almost all laser-cut 5000-class sheet aluminum, bent on a brake, anodized corners on the sheet, only the 8 corner pieces are machined, and that only simple shaping and drilling of bar stock into a simple rectilinear shape with specified-radius corners and edges and a place to put the springs and cutoff switch pins. Most other designers seemed to be more interested in showing their skill in CNC machining than making a practical structure. If you look at Pumpkin's stuff, it is clear that they put a lot of thought into mechanical engineering. And they actually engineered for cost and mass-production, while few others bothered. We will not ever directly copy anything (I am an intellectual property specialist, and will keep us legal), but we can and should learn from their work.
>>>>>
>>>>> Besides the structure, other non-mission-specific stuff we should be building would include an IHU (computer) and the other general bus components: lithium battery pack with heaters and per-cell management, magnetorquer, solar panels (what cells, from where?), maybe some heat distribution components like adiabatic heat pipes?
>>>>>
>>>>> Can we hear from volunteers for any of this?
>>>>>
>>>>> LIME mini might be a good flight candidate, besides Ettus and Rincon. Their CEO and Open Source guy are very friendly and their PCB design may already be licensed appropriately. No idea how the chip would take radiation.
>>>>>
>>>>> We should look into the Open Source finite element analysis and CFD programs. We should simulate as much as possible before going to thermal vacuum, vibration and shock, etc. And publish all input data so that it can be reused along with our part designs.
>>>>>
>>>>> I saw a really nice indium electronic thruster at Cal Poly. All proprietary, of course. Goes up with the fuel solid, gets heated in flight. No moving parts, works by wicking through a sintered tip. Probably very patented. But a source of ideas.
>>>>>
>>>>> Thanks
>>>>>
>>>>> Bruce
>>>>>
>>>>>
>>>>>> On Wed, May 16, 2018, 09:23 Michelle Thompson <mountain.michelle at gmail.com> wrote:
>>>>>> Heh! The SDR really ties it all together in your sketch there.
>>>>>>
>>>>>> Yes, there's interest in building an open source satellite. The time is right and we have the best chance of making it happen that I've seen in a long time. There's a variety of forces at work in the industry, in academia, and in open source culture and achievement that help make a modern, innovative, amateur, open source payload possible.
>>>>>>
>>>>>> I don't know enough about MEO but I'm game for supporting any payload that enables an enduring amateur community through reliable communications in space. I'm very happy we get the chance to dig into this and I want to enable and support it as much as possible.
>>>>>>
>>>>>> The Careful COTS of an Ettus USRP effort is one way to get a capable SDR for space. This is a joint project between Phase 4 Space and GOLF to get the E310 in play soon/now for GOLF and the E320 later for Phase 4 Space. Business unit at Ettus is reviewing it. Systems engineering lead for GOLF endorsed it as an open source effort. Meeting minutes were posted to the list. Next steps depend on what IP from Ettus. We'll proceed with the E320 as far as it takes us regardless. I expect to make a lot more progress here in late summer/early fall, especially at GNU Radio Conference 2018.
>>>>>>
>>>>>> The Rincon AstroSDR is another option, and Rincon has reached out with questions and clarifications in response to the Kittens Weekly Report. There will be more talks after Hamvention. Rincon will be a significant presence at GNU Radio Conference 2018.
>>>>>>
>>>>>> Propulsion, attitude control, solar power, and a variety of antennas all have open source flight-tested options at LEO. I don't know much about navigation.
>>>>>>
>>>>>> I do know that we have a lot of support out there from like-minded organizations and projects.
>>>>>>
>>>>>> I do know that a payload design is within the capabilities of people on this list and within our extended Slack/GitHub/phone/email/club/conference network. That does not mean it's easy by any stretch, and it means that our economic development team will be tested. I think we are up to the challenge.
>>>>>>
>>>>>> What's the first thing that you think we need to do?
>>>>>>
>>>>>> -Michelle W5NYV
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ---------- Forwarded message ----------
>>>>>>> From: Howie DeFelice <howied231 at hotmail.com>
>>>>>>> To: "ground-station at lists.openresearch.institute" <ground-station at lists.openresearch.institute>
>>>>>>> Cc:
>>>>>>> Bcc:
>>>>>>> Date: Wed, 16 May 2018 04:16:15 +0000
>>>>>>> Subject: Satellite Building
>>>>>>> Just wondering if there is interest in putting together a project to build a satellite. There is no particular launch in mind and no particular mission at this pint other than the generic Amateur Radio goal of furthering the art of communication. I think most will agree that the LAST thing we need another LEO. To simply exploit the microwave bands I think we want to consider orbits that allow hours of coverage at a time. A GEO would be great, a HEO would be really good. An overlooked orbit, at least in ham radio, is MEO. An orbit between 8000 and 10,000 Km would provide about 2 hours of coverage and orbit the earth about twice a day. The problem is that not too many people fly there so we need another strategy. If we aren't in a big hurry, maybe we can get there from LEO. This means we need propulsion, attitude control, navigation, lots of solar power and a really cool radio. Does this sound reasonable? How long would this actually take with a milli-Newton thruster ? I have attached a sketch of my first ideas.
>>>>>>>
>>>>>>> - Howie AB2S
>>>>>>>
>>>>>>>
>>>>>>> ---------- Forwarded message ----------
>>>>>>> From: ground-station-request at lists.openresearch.institute
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>>>>>>> Cc:
>>>>>>> Bcc:
>>>>>>> Date: Wed, 16 May 2018 00:16:18 -0400
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>>>>>
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>>>
>>>
>>> --
>>> Bruce Perens K6BP - CEO, Legal Engineering
>>> Standards committee chair, license review committee member, co-founder, Open Source Initiative
>>> President, Open Research Institute; Board Member, Fashion Freedom Initiative.
>>>
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>
>
>
> --
> Bruce Perens K6BP - CEO, Legal Engineering
> Standards committee chair, license review committee member, co-founder, Open Source Initiative
> President, Open Research Institute; Board Member, Fashion Freedom Initiative.
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