Probe Control on Far Side of Mun

[Redster]

During my recent attempt at rendezvousing two craft in orbit around the Mun (which was my first successful attempt! ) I ran into an issue with my probe.

I was attempting to rendezvous a piloted craft with a probe-driven fuel depot in orbit around the Mun. As I was approaching the probe with my piloted craft, I switched to the probe to try and orient it normal/anti-normal in order to make the approach easier. However when I switched to the probe I was not able to control its orientation. I checked and made sure that there was indeed electrical charge but was still not able to control anything.

After a lot of RCS maneuvering I was able to make the rendezvous anyways and after successfully returning Jeb to the KSP went back to my orbiting probe and found that I could only control it on the near-side of the Mun. 

What does it take in order to control a probe when there is no line-of-site to Kerbin? Do I need some kind of satellite network? Is it necessary to have a satellite network around every celestial body you intend to visit?

Thanks in advance!

 

[Snark]

Hello, and welcome to the forums! 

2 hours ago, Redster said:

I was attempting to rendezvous a piloted craft with a probe-driven fuel depot in orbit around the Mun. As I was approaching the probe with my piloted craft, I switched to the probe to try and orient it normal/anti-normal in order to make the approach easier. However when I switched to the probe I was not able to control its orientation. I checked and made sure that there was indeed electrical charge but was still not able to control anything.

Most likely a communications issue.  Easy way to tell is to look at the comms indicator at top left (the thing that looks like a cell phone's signal-strength indicator).  It'll tell you whether you have comms back to KSC or not.

If you lose comms, you may lose some degree of control (how much it hurts depends on how you've set the difficulty for your game-- could be anywhere from "no effect" to "partial control" to "total loss of control, it's a doorstop until you have comms again").

2 hours ago, Redster said:

What does it take in order to control a probe when there is no line-of-site to Kerbin? Do I need some kind of satellite network? Is it necessary to have a satellite network around every celestial body you intend to visit?

Well, it depends on whether you like that it's kind of a challenge.    Some people do, some people don't.

If you find it to be an annoying hassle rather than an interesting challenge, then you can simply turn off CommNet (it's in the game difficulty settings) so that you can do whatever you want wherever you want and never have to worry about LOS to Kerbin, or the range of your antennas, or anything like that.

If you do like the challenge and just want to know how to design around it, here's the deal:

You need to have a communications route back to Kerbin.  The simplest such route is a direct link, i.e. when your probe has a direct LOS to Kerbin so it's a chain with just one link in it.

However, for cases where you don't have LOS, then what you need is a relay.  Certain antennas in the game are designated as "relay-capable".  These include the HG-5, RA-2, RA-15, and RA-100.  So you can still control your probe on the far side of the Mun (or wherever) if it has LOS to a a craft that has a relay antenna on it, and that craft either has LOS to Kerbin or has LOS to another relay-equipped craft that has a comms route back to Kerbin.  (Note that your probe doesn't need a relay antenna, it can have any antenna you want.  It's just the craft in the middle of the chain that need to be relay-equipped.)

So, for example, you could loft a relay-equipped satellite into a high Kerbin orbit, positioned such that it can "see" the back side of the Mun, so your craft can relay through that.  Or you could put a relay in some high orbit over the Mun, to serve a similar purpose.  There are a variety of ways you can set up the comms geometry, it's one of the fun creative challenges in the game.  (Well, at least for people who like that sort of thing, which admittedly isn't everyone.) 

There are other options, too.  For example, in the case of the Mun, its rotation is locked to Kerbin so you pretty much have to use a relay if you want something to explore the back side.  But for other places, you can get away without it if you're okay with temporary control interruptions.  For example, Minmus does rotate relative to Kerbin.  So if you wanted to explore all over Minmus but a place you want to land is currently facing away from Kerbin, then you could simply wait a few hours for that spot to rotate until it's facing Kerbin, and then do all your landing.

[Pecan]

On 9/10/2019 at 4:35 PM, Snark said:

Well, it depends on whether you like that it's kind of a challenge.    Some people do, some people don't.

Snark, your answers are brilliantly comprehensive and well written.  :-)