LRV camera remote control

[Allan F]

Hi, I'm interested in the workings of the remote control system for the TV-camera on the LRV.

I'm up on the radio side of it, but what kind of mechanism did the actual pan, tilt, zoom, focus?

Was it step motors (one beep on the channel and the camera moved a certain number of degrees)?

What was the mechanical connections?

TIA

[Kiwi]

Stand by until Dwight turns up -- he's the resident expert.  I had a quick look at his book "Live TV from the Moon" and there's heaps about the cameras, but couldn't see anything enlightening about the control mechanism.  Doesn't mean it isn't there though.

On page 202 Ed Fendell explains that his first job at each site was to do a pan in 3 degree increments with a pause at each so the backroom folk could take Polaroids and link them together to get a good view of the site, so that perhaps indicates the use of step motors.  Plus there's the fact that he made the movements with pushbuttons which must have locked down, because in the few movies I've seen, he doesn't hold them.  I've occasionally seen hoax-believers claim he must have used a joystick, which shows how much they know about Apollo.

Fendell's oral history interview might help:
http://www.hq.nasa.gov/pao/History/alsj/Fendell-OralHist.pdf

Have you Googled the subject?  There must be something out there in Cyberworld.

[Allan F]

Yes, I tried google. And NASA's technical site. But the relevant document is not available online.

[Tanalia]

Ground-Controlled Television Assembly: Final Report ( 8.6 Mb PDF )

Doesn't have details on everything, but does have a bit about the elevation drive (Section III, Page 39).

[Allan F]

Thank you - I'll read it later today.

[raven]

This should hopefully provide some insight.
It's the manual after all.

[Donnie B.]

It's stepper motors all the way down

[dwight]

Hi everyone and sorry about the delay. The result of the Leverkusen Beer Festival - and I'm not a spring chicken anymore. A Friday drinkfest means I'm out of commission for 2 days. On Apollo 15 the clutch system on the camera motion controls had seized, rendering the tilt up/down feature useless. This system was completely redesigned for Apollo 16 and 17. On both those missions, with the exception of several brief times when the camera got stuck (to be freed again with help from the astronauts) the system work as promised. Another thing: the control panel in MOCR also had incremental controls allowing easier control of the camera for more complex operations. I'll have a look through all the documentation I have when I get home to see if there is more in depth discussion somewhere on the control mechanism.

[Allan F]

@raven - thank you for the manual. Quite nerdy stuff, but I've managed to chew through the relevant part. Amazing how complicated something as "simple" as a left-right / up-down mechanism was made.

[smartcooky]

@raven - thank you for the manual. Quite nerdy stuff, but I've managed to chew through the relevant part. Amazing how complicated something as "simple" as a left-right / up-down mechanism was made.

Given that one of the camera's tasks was to survey the moonscape in 3° increments, I don't consider the complication unnecessary.

The main difficulty would surely be feedback for any remote control system that wasn't in some way analogous to a stepper motor. For a system using something like a Control Synchro, a 5 second long feedback loop (Moon - Earth - Moon) is unworkable. With a stepper motor you know that N steps = 1 degree, so you send 3N steps to the motor and the camera turns through 3° - no feedback required.

[raven]

@raven - thank you for the manual. Quite nerdy stuff, but I've managed to chew through the relevant part. Amazing how complicated something as "simple" as a left-right / up-down mechanism was made.

You are welcome.   I admit it's mostly over my head, but it seemed the logical place to find what you were looking for, at least one would hope.

[ka9q]

I agree, a stepper motor is the way to go for a system like that. Today of course it would be more automated; you'd enter a specific position and the electronics in the camera would slew to that position (by emitting the appropriate number of pulses to the stepper motors) after compensating for the orientation and tilt of the vehicle. It would be easy to build up panoramas automatically.

[dwight]

I located a cool report by Ed Fendell in which he discusses the aspects of panning, tilting, and zooming. I have uploaded it to dropbox:

https://dl.dropboxusercontent.com/u/4960558/j_mission_tv_req.pdf

Then there is a concise SMPTE article which goes more into the design characteristics of the GCTA:

https://dl.dropboxusercontent.com/u/4960558/dec72smpte.pdf

This report by Sam Russell also explains the GCTA, go to PDF page 265 (page 278 of the orginal report):

https://dl.dropboxusercontent.com/u/4960558/19730005102_1973005102.pdf

[Allan F]

I've saved the two first - the third displays an error message.

[dwight]

Yeah. Sorry its a big file and still uploading.