Two-Body Calculation?

[CincySpaceGeek]

I recently saw the excellent Aussie film "The Dish" which tells the (humorous) story of the Parkes radiotelescope's role in the Apollo 11 landing and TV broadcast. Now, granted...I'm sure some artistic license was taken to make the film flow but I was curious about one thing. At one point in the story Parkes loses contact with the "Tin Can" during TLI and a NASA guy suggests using a "Two-Body Calculation" to try and get a ballpark fix for reaquisition. Anybody know and can explain a Two-Body Calculation? :-s

Thanks!!!!

[Glom]

At that stage of the TLC, we could probably still consider Apollo 11 to be in a highly eccentric elliptical orbit.

If Parkes knew the position, r at time to TLI, the velocity v after TLI and the time t since TLI, then they could use the method I described here. There are other methods using different inputs but I can't remember them right now.

[kucharek]

Some clarification about "The Dish" can be found here:
http://www.tip.net.au/~mdinn/TheDish/

I'll ask Mike Dinn for any comments on your question.

[mike_d]

Parkes' role in Apollo 11 was lunar surface EVA operations only. It was not needed for earth orbit, TLI or TLC. It could not track fast enough near earth anyway, even if in view. TLI was generally planned to be in view of Carnavon, at least for the final "go for TLI". ARIAs were positioned over Australia to track during the actual burn and sometimes the tracking ships were used. See my
http://www.pcug.org.au/~mdinn/apollo...ps/ap13tli.jpg
for the Apollo 13 TLI coverage which was fairly typical

So the movie's depiction of TLC dramas at Parkes is pure fiction, as is the direct communications with Houston from Parkes, and the "go for command". All this was done by us from Honeysuckle after reports from Parkes. And Parkes could not "command" - it had no transmitter.

I think there was some TLC tracking by Parkes for training purposes but I'm not sure. When it came to pointing at the right place on the moon we had complete faith in John Bolton knowing how to do that (being one of the world's leading radio astonomers) or that he would ask if he needed any additional pointing info.

Mike Dinn - Canberra

[CincySpaceGeek]

...the movie's depiction of TLC dramas at Parkes is pure fiction, as is the direct communications with Houston from Parkes, and the "go for command". All this was done by us from Honeysuckle after reports from Parkes. And Parkes could not "command" - it had no transmitter.

I think there was some TLC tracking by Parkes for training purposes but I'm not sure. When it came to pointing at the right place on the moon we had complete faith in John Bolton knowing how to do that (being one of the world's leading radio astonomers) or that he would ask if he needed any additional pointing info.

Mike Dinn - Canberra

Mike: Thanks so much for your input. As you already know movie makers in general tend to take broad liberties to tell a story at the expense of historical fact and true human accomplishment. I'm sure that was also the case with "Dish". Just look at "Braveheart" for another example.

After seeing the movie I spent quite a lot of time researching actual Parkes and Honeysuckle activites during Apollo and found the info even more informative (and historically accurate) than the film. A lot of what I found was "WOW! I had NO idea!" type stuff. What was accomplished by the Austrailian personnel at all the sites was and still is, IMHO, nothing short of astounding!

Nicely done!!! =D>

[tracer]

It was not needed for earth orbit, TLI or TLC.

I know TLI stands for Trans-Lunar Injection, the rocket burn that put the low-earth-orbiting Apollo spacecraft onto a free-return trajectory to the moon.

But what's TLC? (Other than Tender Loving Care and The Learning Channel, I mean. :P )

[Glom]

TLC - Trans Lunar Coast

[tracer]

Ah -- so, then, the TLC would be everything between the end of the TLI burn and the start of the LOI burn?

[mike_d]

Yep. And we also had "TEC" for the return leg. And during TLC (and TEC) there were several "mid-course manoeuvres" scheduled although not usually all needed or done. I didn't see the irony (?) of the term for quite a while until someone asked how you could have more than one. I think the term originated with Ranger unmanned lunar missions, and was also applied to most of the unmanned 60s missions

Mike Dinn - Canberra

[tracer]

And during TLC (and TEC) there were several "mid-course manoeuvres" scheduled although not usually all needed or done.

But were they really spelled "manoevres"? I mean, this is the American space program we're talking about, after all.

[mike_d]

Actually "MCM"s would you believe!

[tracer]

1900s?