Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: timey on 04/09/2015 16:50:40
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I have this memory of a program that I watched concerning the history of the Voyager missions. They said that one of the Voyager's became 12 years ahead of schedule. That there was a scramble to set up the earth bound equipment because they were not even yet set up to receive pictures from the craft, whereas they had anticipated the journey would take much longer than it did and they would have had plenty more time in which to prepare.
However... I cannot find any info regarding this 'early arrival' on the net - does anyone have any recollection?
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Ok, so no one has any details on this question...
Can anyone tell me if it is actually true? Or did I dream up this 'ahead of schedule' business?
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The only link I can find to 12 years is that Voyager was planned to use gravity assist, without it the flight to Neptune would have taken 30 yrs instead of 12. Perhaps a reporter got the wrong idea, not the first time!
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Ah...top of the morning to you Colin, yes, well, I'm not dismissing the fact that it may well have been 'my' error of understanding. :)
My memory of the program I watched is that yes, the plan was to use gravity assist, as you put it, this being something to do with a rare planetary alignment. That this gravity assist far outstretched all expectations and the craft arrived significantly ahead of schedule. That the headquarters for receiving pictures from the voyager had not been completed because the craft was not due to arrive at destination so soon.
I think it may have been 'Wonders of the Solar System' that I got this from. Hmmm...
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Although the technique had been tested by the Mariner series this was the first time it had been tried over such a large distance. Given the large number of variables it is conceivable that an error of at least 2% would be possible, added to original estimate being conservative, could easily result in a few months ahead of schedule.
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one of the Voyager's became 12 years ahead of schedule
I don't believe this. I even think Colin2B's 2% error margin is far too pessimistic.
In the Solar System, outside Earth's orbit, Newton's law of universal gravitation is extremely accurate. If you are going near the orbit of Mercury, it would be advisable to use Einstein's tiny tweak due to time dilation deep in the Sun's gravitational well (but this is so easy to apply that I am sure NASA used it even on the Voyager journey).
The mass of Jupiter and Saturn (in fact any astronomical body with a natural satellite) was known quite accurately well before Voyager arrived there, so the slingshot maneuver could be planned quite precisely.
The incredible precision of NASA's orbit calculations can be seen by the "Pioneer Anomaly (https://en.wikipedia.org/wiki/Pioneer_anomaly)", which became too big to ignore by 1994. This was an unexpected velocity deviation of just 1km/h from the actual ≈15,000km/h, accumulated over a period of 10 years. It was eventually traced to the infinitessimal recoil from infra-red photons bouncing off the spacecraft's body!
Wikipedia says that the Planetary segment of the Voyager 2 mission (https://en.wikipedia.org/wiki/Voyager_2) was 12 years & 1 month long. However, it's Interstellar mission has continued beyond that, for another 25 years (so far).
So I suspect that the 12 years Timey recalls has to do with the planned=actual duration of the initial planetary survey mission, ie the initial part of the schedule.
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one of the Voyager's became 12 years ahead of schedule
I don't believe this. I even think Colin2B's 2% error margin is far too pessimistic.
I agree. I was trying to be pessimistic, but could only make a few months even then. NASA say the journey would take 30 yrs without gravity assist, 12 with, so I think the misunderstanding is in the reporting.
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Ok, thanks for the answers Colin and Evan.
I daresay I probably 'have' got myself muddled, however I can see that this bothersome memory of mine concerning ground based operations not been completed in time, or having to be hurriedly commenced ahead of schedule due to early arrival of craft, is now going to 'force' me to watch 'Wonders of the Solar System' again.
I had hoped to avoid this, we did it to death back in the day. It was my son that pointed out that the musical montages were a bit on the 'much' side. (Sorry Brian, no offence). But there is something nagging me.