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What mission was this?
ddeerrff
post Oct 24 2018, 06:59 PM
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When I was a teenager (45 - 50 years ago), there was a mission launched where the main parabolic high gain antenna did not open fully. What was this mission and how did they solve the antenna problem?
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mcaplinger
post Oct 24 2018, 07:09 PM
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QUOTE (ddeerrff @ Oct 24 2018, 10:59 AM) *
When I was a teenager (45 - 50 years ago), there was a mission launched where the main parabolic high gain antenna did not open fully. What was this mission and how did they solve the antenna problem?

Galileo. They didn't solve the problem and the mission only returned a tiny fraction of the planned data. They compressed the data heavily to try to get back as much as possible. [Mods, obviously this thread is misplaced.]

ADMIN: Not anymore. smile.gif


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ddeerrff
post Oct 25 2018, 03:02 AM
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Thanks. Been bugging me for quite some time now that I couldn't remember the mission. Seems my sense of time is way off though. I remembered this as something that happened in my late teens, maybe early 20's. That would have been late 60's early 70's. But Galileo was launched in 1989......


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[Mods, obviously this thread is misplaced.]

rolleyes.gif
I almost posted in "Chit Chat", but the description of Chit Chat is "Outside the realms of Spaceflight all together." I didn't think my question was Outside the realms of Spaceflight all together.

The description of "Past and Future" is "...missions from the past and the future". I thought that best fit my question. tongue.gif
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ngunn
post Oct 25 2018, 08:36 AM
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QUOTE (ddeerrff @ Oct 25 2018, 04:02 AM) *
The description of "Past and Future" is "...missions from the past and the future". I thought that best fit my question.


You're right, there wasn't an obvious place to put a general spaceflight enquiry if the mission destination was part of the question. One suggestion would be to preface the subtitle of Chit Chat so it reads "Including outside the realms of - " etc.
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nprev
post Oct 25 2018, 03:15 PM
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Yeah, that's all true. We'll take a look at modifying the thread description.


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Steve G
post Oct 27 2018, 02:32 AM
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[attachment=43606:Honeymoo...37_small.jpg]
QUOTE (mcaplinger @ Oct 24 2018, 12:09 PM) *
Galileo. They didn't solve the problem and the mission only returned a tiny fraction of the planned data. They compressed the data heavily to try to get back as much as possible. [Mods, obviously this thread is misplaced.]

ADMIN: Not anymore. smile.gif


Ironically, on my honeymoon in 1980, I somehow convinced JPL to let me have a private tour even though it was closed to the public. I met a scientist working on Galileo whose job it was to make sure the probe could survive the vibrations of launch. I said it was a good thing it was going to be launched by the shuttle, just in case the main antenna fails to unfurl and the crew could EVA to fix it. (Notwithstanding I didn't know the launch and deploy sequence, and the Challenger tragedy changed the entire launch profile which ultimately impacted the deployment of the antenna.)

Sorry about posting the pic twice, i couldn't figure a way of removing it. [ADMIN: Fixed. smile.gif ]
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RoverDriver
post Oct 27 2018, 03:21 PM
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I think that this picture is of the Voyager mode in the VK exhibit at JPL? If I remember correctly, the trick that was used on Galileo was to record the data to the on-board tape recorder (yes!), rewind the tape and play it back at a slower speed to send the data at a slower data rate through the LGA.

Paolo


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mcaplinger
post Oct 27 2018, 04:12 PM
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A lot more to it than that -- see https://www.nasa.gov/audience/formedia/fact..._factsheet.html and (for more technical details) https://descanso.jpl.nasa.gov/monograph/ser...er4--141029.pdf .

Compressed data was stored on the tape recorder; some particles and fields data was stored in memory buffers. There was a tape recorder anomaly early in the mission that would have further degraded data return, but they managed to work around it.


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stevesliva
post Oct 27 2018, 07:52 PM
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That tape recorder was a nightmare, too. The whole "stuck head" thing was just miserable to read about in the status reports. But at least they had lots of power to "condition" things.

I work in solid state memory development, and from afar, the reverse engineering they have to do on the Flash memories these days seems just about as painful. I'd love to hear what actually makes these things debuggable. From what I can tell, all the hopes about being "rad hard" devolve into "what now?" after a few years, so perhaps simple architectures are what's really needed.
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mcaplinger
post Oct 27 2018, 11:26 PM
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QUOTE (stevesliva @ Oct 27 2018, 11:52 AM) *
I'd love to hear what actually makes [space flash memory] debuggable.

Paywalled, but this is the most technical description I could find.
https://ieeexplore.ieee.org/document/7119257

Near as I can tell, most of these flash issues have been more about software and less about hardware. For the internal flash in our instruments on MSL, I intentionally used the simplest possible flash management code, all written in-house, instead of a more featureful but more complex file system. So far, so good. Our application, by design, is not very stressing. For example, erasing is pretty rare.


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