# Talk:Viking program

## NSSDC

Spacecraft and mission descriptions courtesy NASA's National Space Science Data Center. http://nssdc.gsfc.nasa.gov/planetary/viking.html

## lost data

Within a magazine's context I read part of the data collected from the Viking Mars mission was lost. Is that true? --Abdull 15:43, 22 October 2005 (UTC)

## end of Viking Lander

If possible, I believe this page should include the end of the Viking probe:

Basically, I don't know if that's true or not, so I believe it should be considered until we can get an authoritive answer in one place.

"Battery failure" appears correct for Viking 2's lander. "Faulty command" is correct for Viking 1. The Slashdotter's indignation over "revisionist history" looks to me like confusion between 1 and 2. gparker 06:55, 30 September 2006 (UTC)
Agreed, Gparker. Either way, wikipedia internally should agree, so I synched up the reasons for failure with the reasons in the Viking 1 and Viking 2 articles. The former article is well sourced, the latter does not appear to be in contention. Porkrind 04:02, 17 August 2007 (UTC)

## confusion over delta-v?

The article quotes a delta-v as "1480 m/s" for the Viking Orbiter. Since delta-v is an acceleration the unit should be m/s^2, but 1480 m/s^2 is much too large (amounting to nearly 150 g!) The correct figure would appear to be an initial 0.57 m/s^2 (1323N/2328kg=0.568m/s^2 -- figures taken from the article). Alternatively the article could mean that the rocket engine could change the velocity of the spacecraft by 1480 m/s, but this would depend on how long the engine was running. A similar use of the terms above occurs in the Lander section. Could someone who knows more than me either correct the article or correct me! Thanks —The preceding unsigned comment was added by Hammerandfeather (talkcontribs) 20:10, 27 February 2007 (UTC).

Delta-v means total change in velocity. It implies an acceleration, but it doesn't give the magnitude of the acceleration. It's like stepping on the gas in your car to speed up. If you go from 40mph to 60mph, that's a delta-v of 20mph. That particular fact doesn't, however, reveal the acceleration which the car suffered during that transition. More information is needed. For example, if you know that the car goes from 40 to 60 in 10-seconds, then the acceleration is knowable, namely in this case an average of 2mph/second. — Preceding unsigned comment added by 24.223.130.32 (talk) 02:10, 1 October 2015 (UTC)
The units in the article are correct. A thrust of 1323 N acting on a spacecraft of mass 3527 kg gives an acceleration of 1323/3527 = 0.3751 m/s^2. The orbit insertion burn built up the 1480 m/s delta-v over a period of about 3946 seconds. (A more accurate calculation would account for the reduced mass due to expending propellant.) Old Viking (talk) 03:24, 4 October 2011 (UTC)

## In Popular Culture

AMCKen (talk) 05:38, 10 April 2009 (UTC)AMCKen

## computer

Despite begin "common knowledge", and stated many places on the internet, neither the orbiter nor the lander used the RCA CDP1802 "COSMAC" microprocessor, nor the earlier CDP1801 two-chip processor; neither were commercially available early enough to be designed into Viking. The actual computers used an architecture derived from the Honeywell DDP-516, with plated-wire memory. Unfortunately I can't find an authoritative reference at the moment, but there also is no authoritative reference claiming that they used the CDP1802. --Brouhaha (talk) 08:09, 31 January 2010 (UTC)

Just keep in mind that sourcing for these sorts of things is absolutely vital. As WP:V states, "The threshold for inclusion in Wikipedia is verifiability, not truth". The point being, if there are a multitude of sources which state that "the lander used the RCA CDP1802 "COSMAC" microprocessor" then that's what we should say until there is a reliable source available which states otherwise.
— V = I * R (Talk • Contribs) 15:09, 31 January 2010 (UTC)
OK, I see what the issue is. It seems that the Honeywell DDP-516 (← which needs an article, incidentally) was actually used in Sweden's Viking, but the source for that is behind a paywall so it'll take me a few days to verify that. I've sourced the use of an SOS version of the CDP-1802 in NASA's Viking probes, though. Keep in mind that NASA used a special custom part, not the commercially available components (COTS as a concept didn't really come about until about 20 years later.)
— V = I * R (Talk • Contribs) 15:54, 31 January 2010 (UTC)
I realize that verifiability is required, and that's why I didn't change it. However, I know from personal discussions with the people that wrote the software that NASA's Viking did NOT use the CDP1802, which wasn't even commercially available at the time (not even sampled until 1975), so it couldn't have been used during the development of the orbiter and lander, which started several years before that. Unfortunately this spread as a rumor/urban legend, so there are now MANY sources that claim it. I'm trying to track down an authoritative source to cite. --Brouhaha (talk) 18:57, 5 February 2010 (UTC)
OK, gotcha. If it's actually an urban legend then we definitely should correct it if there is a source that makes a clear case on the subject. If you track something down, even if it's offline, and you need any help adding it, then feel free to ping me either here or on my talk page and I'll lend you a hand. Note however that the CDP1802 will require some mention here regardless, if even to point out that most people claim that it is what was used. Incidentally, from what I read about this last week, my understanding was that the commercial product is not what is claimed to have been used. The way that I understand the claim, what eventually was developed into the commercial CDP1802 was originally developed for use on the Viking, primarily because RCA had some engineering knowledge in the use of Silicon on sapphire epitaxial manufacturing processes.
— V = I * R (Talk • Contribs) 19:15, 5 February 2010 (UTC)
Found a pretty good reference, the book "Encyclopedia of Computer Science And Technology, by Allen Kent and James G. Williams. They describe the development of the Viking Lander computer starting on page 164, and at the top of page 169 they state that the lander used two Honeywell HDC 402 processors each with 18K of 2-mil plated-wire memory. It's a 24-bit processor with no significant similarity to the 1802. They describe the design of the custom processor for the Viking Orbiter starting on page 156.
This is only a single reference, but it is clearly more authoritative than just any random web page. However, I'm continuing to seek additional authoritative references before I actually make changes to the article. I think I've found some of the original technical reports in the Dr. James E. Tomayko Collection at the Wichita State University library, but I'm not going to be able to visit that library for a while.
Agree that the CDP1802 has to be mentioned in a negative sense. As far as I can tell, though, Viking had no influence on the CDP1802 design or vice versa; the 1802 architecture had been in development at RCA since 1961 (based on U.S. patent filings).
A SOS version of the CDP1802 couldn't have been used in Viking because it came *later* than the ordinary CMOS version. RCA was only just barely able to produce a small quantity of engineering samples of the two-chip CDP1801 in ordinary CMOS in 1975. --Brouhaha (talk) 19:28, 5 February 2010 (UTC)
Oh good, I have access to the Encyclopedia of Computer Science And Technology myself, during the week. I'll check it out for myself on Monday, and then I/we can do something about straightening this out. Anything about where the CDP1802 idea came from would be extremely helpful as well. I'm betting that some media outlet (newspaper or magazine) started it, and I have access to a decent collection of publications, so maybe I can track that down. I'll have to find/request some more books about the Viking program as well; I know that some relatively contemporary books, and many contemporary magazine articles, were written, so this could turn into a decent research project. My main concern originally was just that there was a mixup with the Swedish satellite though, as I mentioned about, because that uses a Honeywell processor as well.
— V = I * R (Talk • Contribs) 22:52, 5 February 2010 (UTC)
People also seem to think that the Voyager spacecraft used the CDP1802, and I'm pretty sure that's false also, but I haven't yet tried to verify. My friend that actually worked on software for the Viking GCSC (lander computer) at Martin-Marietta pointed out another NASA reference describing the GCSC: "Computers in Spaceflight: The NASA Experience", Chapter Five <http://history.nasa.gov/computers/Ch5-6.html>, and also the book "Viking Lander 'As Built' Performance Capabilities" published by Martin-Marietta in June 1976. --Brouhaha (talk) 10:23, 6 February 2010 (UTC)
And somehow I'd managed to overlook the NASA technical reports cited in the "further reading" section of the article. Volume 1 p. 98 describes the lander's GCSC, and volume 2 pp. 155ff describe the orbiter's CCS, both of which are described in enough detail that it is clear that they are not CDP1802 based. Seems like we've got plenty of authoritative references now. --Brouhaha (talk) 10:37, 6 February 2010 (UTC)

## Power

The following comment was posted in the main article space by User:76.169.229.208

The above seems in error. The JPL website says Thermoelectric generators provided the power for the Viking landers.

"For example, the Viking landers, each with a radioisotope thermoelectric generator, landed on Mars in 1976 and operated on Mars for four and six years respectively." (direct quote from the jpl website http://mars.jpl.nasa.gov/msl/mission/technology/technologiesofbroadbenefit/power/) Someone who knows wikipedia better can please reformat this and the citation?

Re-posted by  Velella  Velella Talk   22:11, 1 December 2011 (UTC)