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Jairo
2012-Mar-21, 02:06 PM
What was the precision of navigation, and specially landing, of unmanned spacecrafts near the Apollo era? They couldn't make visual navigation like astronauts. Could a Surveyor intentionally land inside a crater like Tycho or Copernicus, or was it chance?

antoniseb
2012-Mar-21, 03:19 PM
People with more details than I have will give specifics, but your general question is broad, and I feel safe in saying that the later surveyors would have had no trouble landing thing a 100 mile circle like Tycho or Copernicus. A few years earlier, the Ranger series had a much wider uncertainty of destination. Our Mars probes still have uncertainty because of the vagaries of the atmosphere.

ngc3314
2012-Mar-21, 04:37 PM
Interesting - some links on this say that Rangers 7-9 impacted within ~10 km of their aim points, and Surveyor 7 was within 3 km next door to Tycho. I'm retrospectively impressed, considering that for mission success the accuracy required for the first of each would have been one lunar radius from the center (although in fact the celestial mechanics probably wouldn't have allowed a landing very far from the aim point and still come to landing velocity with fuel left).

antoniseb
2012-Mar-21, 05:09 PM
Interesting - some links on this say that Rangers 7-9 impacted within ~10 km of their aim points, ...
I probably should have said "early Rangers"... IIRC Ranger 2 missed the Moon completely.

Hornblower
2012-Mar-21, 05:30 PM
The first few Rangers missed because of major breakdowns that left them unable to do midcourse corrections.

astromark
2012-Mar-22, 06:25 AM
Please correct me if any of this is found wrong.. but as I recall It was not until Apollo 8. that men went to the moon..

and they did not have the lander to even try a landing.. round it and back... Docking and turning it all around..

and then 9 had the hardware but did not leave Earth orbit.. un docking.. re docking and testing it all..

and then 10 did the whole thing but did not have a completed lander so did not, could not land..

and of coarse it was 11. That did have, and did.. but there was a little 'but' to be mentioned...

It required a trained pilot to land the LEM...( Lunar Excursion Module...)

That is how and why they could select the actual landing spot..' Having a pilot to make that choice.'

All lander missions before the piloted craft.. were automated..

Very little ( none.) flying about looking for a place to put down.. They did not have a remote control lander option..

Does this address your question...

astromark
2012-Mar-22, 06:37 AM
Under your heading.. Unmanned-landing-precision.. I wish to ask...

Today with modern electronics and the advances since those early 1970's..

Would we insert three lunar saterlites so as to GPS the moon..( LPS ).?

I am thinking that it would ensure great pin point landings....

Jeff Root
2012-Mar-22, 08:42 AM
As Mark indicated, none of the impactors or landers had any
guidence for the last few minutes or hours. The Rangers just
fell freely from the last time their courses were adjusted from
Earth. I believe the Surveyors had radar to determine height
above the surface and rate of descent to automatically start
and shut off the landing rockets in order to slow to a soft
landing. They had no sideways maneuvering capability.

Course corrections were calculated from radar and radio
ranging from Earth. The Deep Space Network (DSN) was
built for that purpose, as well as for retrieving the data.

-- Jeff, in Minneapolis

JustAFriend
2012-Mar-22, 02:06 PM
Back then people did MATH... in their heads and with slide rules. And learned to do things like windage and guesstimating.

:D

publiusr
2012-Mar-24, 07:31 PM
Landing can be a problem. But here is something to interest you in going the other way--a sample return mission...
http://www.airspacemag.com/space-exploration/The-One-Pound-Problem.html

"A terrestrial rocket has to push through a plug of air equivalent to a 30-foot column of water, and physics dictates that the smallest vehicle capable of moving all that atmospheric mass without paying a penalty in momentum is about 30 feet long...What was the smallest rocket that could possibly leave the surface of Mars and make it into space? "And I knew that answer because I'd discussed it with my father many times. The answer is: about the size of a pencil."

cjameshuff
2012-Mar-24, 08:55 PM
What was the precision of navigation, and specially landing, of unmanned spacecrafts near the Apollo era? They couldn't make visual navigation like astronauts. Could a Surveyor intentionally land inside a crater like Tycho or Copernicus, or was it chance?

The actual vehicles sent (the ones that functioned properly, anyway) got within tens or hundreds of km of their targets. If you're asking what could have been achieved with the available technology, the optical guidance systems of the time might have been able to target a specific crater with distinct enough markings (with some kind of high-contrast feature to lock onto), and navigation beacons at known locations on the surface would allow very precise landings. As others mentioned, you'd need to add a whole terminal guidance system to do this, though.