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RemoteTech 2 is a mod for KSP that modifies remote operations of unkerballed probes by requiring the probes to have a telecommunications link back to Mission Control. Thus, to operate drones efficiently the player needs to set up a satellite network to relay and maintain communication with their probes. As a natural corollary, transmissions of science reports will also require a comms link back to the KSC.

The communications delay ,as per the speed of light, is also simulated. This could be a mere irritating 0.5s delay near Kerbin SOI, or a perilous 10-minute delay in interplanetary missions. To combat this, RemoteTech2 also provides advanced flight computers that can execute premeditated commands on mark.

This tutorial seeks to inform the player on the details of this challenging mod, and to give pointers as to how to set up a functional relay network for the Kerbin system, and further interplanetary operations.

Specifications

• Length: 45 minutes for "First Steps"
• Difficulty: Advanced - This tutorial will assume you can already get a rocket in to orbit without Remote Tech 2 and are familiar with basic orbital mechanics.
• For version: KSP 1.02 and higher and RemoteTech v1.6.5.

Introduction: Antennae and Links

First we need to understand the changes RemoteTech made to the existing probe/antenna mechanics. Simply put, two parties, can only communicate directly and remotely, if and only if both of them can reach each other with their own antenna, and is not blocked by any celestial objects. This is known as forming a link, bidirectional and unbroken. In practice, the link does not need to be point-to-point direct, other parties can come in and help relaying the signal. Thus, a satellite relay network that could do just that is highly desirable, and the properties of the pertinent antenna/celestial object is always a primary concern.

There are two types of antennae - omnidirectional and directional (a.k.a. dish). Omnidirectional antennae can broadcast in every direction, tend to be very compact, and are typically light both in weight and power usage. They however lack the range for anything beyond low orbit communications. Dish antenna have far greater range, able to communicate within and among planetary systems. But they must be targeted to function, are power intensive and comparatively unwieldy.

At the very beginning, the only antenna we have is (somewhat) safely hidden in Mission Control, it is omnidirectional and has a range of 75 Mm. This is enough to reach the LKO, Mun, Minmus, and then some. But the problem is, KSC is on one side of Kerbin and those links will be broken once line of sight is gone, likely on a daily basis at best. As we progress in career mode, we will acquire more options to better our communications network, which, at this point, is quite literally-- nominal.

NOTE: It is strongly recommended to set up a satellite network after the Electrics topic is researched.

Types of Communication Links

• Forward Link. A link from ground control to a mobile receiver.
• Reverse Link. The reverse of a forward link.
• Kerrestrial Link. A link among parties near the surface.
• Uplink (UL). A link that is going toward a satellite network, or away from the surface of the pertinent celestial body.
• Downlink (DL). The reverse of a uplink.
• Inter-Satellite-link (ISL). A link among a satellite network, this can form the backbone of said network.
• Planetary-Link (PL). A link among sub-systems within a planetary system, such as Kerbin to Mun, or Mun to Minmus communication.
• Inter-Planetary-Link (IPL). A link among planetary systems across the solar system.

First Steps

The first build-able antenna we'll get is the Communotron 16, henceforth referred to as the C-16 for brevity, and is acquired upon researching Engineering 101 (2nd tier topic). The C-16 is omnidirectional, as we know, that means it does not need to be pointed at any direction to connect. This is useful for 2 reasons: one, this means a single C-16 can connect multiple signals with ease; and two, with less power cost per connection. On the other hand, the C-16 snaps under dynamic pressure, making it ill-suited for launching or landing purposes. The C-16 also have a limited ranged of 2,500 km, but that is more than enough to cover Kerbin.

Despite its sufficient range, prior to any additional research, the C-16's only use at this point is to transfer scientific data nearby back to KSC. Which could speed up science gain if used properly.

The next available antennae are the Reflectron DP-10, unlocked by Flight control (4th tier topic); and the Comms DTS-M1, unlocked by Basic Science (another 4th tier topic), along with Stayputnik Mk. 1, the first available probe core.

The DP-10 is also omnidirectional, but has a even more limited range of 500 km, it could form a 4-sat. network around the Mun and Eeloo, and a 3-sat. network for anything smaller, like Minmus. But it is difficult to form a network around Kerbin with the DP-10. Nonetheless, the DP-10 is built to withstand dynamic pressure, making it perfect for launching purposes. It could even work for landing operations, but the probe will need to be precision landed near KSC or any connected ground installations (or, 'in uplink range'). For convenience, the DP-10 is activated by default, and the power cost for DP-10 is negligible, so it is always preferable if range is not an issue.

The DTS-M1 is the first available dish antenna, as we know, that means to be used effectively they will need to be directed at a celestial body or craft. Although we do have the option to order dish antennae to cover currently active craft. They are also power-intensive and has greater range. Specifically, The DTS-M1 consume power at a rate 6-fold of that of C-16. But the DTS-M1 has a range of 50 Mm, capable of reaching Minmus.

With the C-16, DP-10, and DTS-M1, we can now build a fully functional, fully unkerballed satellite network whose signal could reach Minmus. However, those satellites won't last very long, as we likely have no access to any solar panels yet, meaning the satellites can only last as long as the amount of their Z-100 batteries allow.

This is why the player is advised to only consider making communication satellites once they have gotten the Electrics topic unlocked (5th tier topic)...

Maximal Altitude Table for an Initial Kerbin Satellite Network

The following table shows the maximal and minimal altitude for a given set of evenly spaced satellites each rigged with a low tech antenna for interlink purposes on a Kerbin equatorial orbit.

Kerbsl Relay Satellites

Once the Electrics topic is unlocked, the OX-STAT Photovoltaic Panels will now be available, a far superior option to stuffing our satellites with batteries, which will still run down quite quickly powering several antennae. On a positive side note, this will also unlock the Reflectron KR-7 dish as well as the Probodobodyne OKTO. The OKTO drone core can provide basic SAS and the KR-7 has even more range than the DTS-M1 and isn't as fragile, so we can switch it on on the launch pad. More importantly, once our relay network is up, the KR-7 will grant control to a probe during Kerbin landing, without the need of precision landing in uplink range, unlike the DP-10.

With 4 antennae at our disposal and the capability of power generation, we can finally start with our satellite network! Our aim here is to put at least 3 relay satellites in Kerbin orbit so that we can bounce the signal from the KSC to anywhere around Kerbin, and, if we are feeling ambitious, to the Mun and Minmus.

We'll want our satellites to have the following 5 capabilities, in addition to a rocket able to reach the designated orbit:

1. Control during launch. This can be a DP-10 (initial uplink), or alternatively a kerballed lower stage, which will also allow a pilot to grant SAS. The KR-7 is also an option, but it will require another uplink as it needs to be targeted towards mission control prior to launch, specifically the TT18-A Launch Stability Enhancer can grant kerrestrial uplink prior to detachment.
2. Connection to KSC in orbit (orbital uplink reciever). Either the KR-7, DTS-M1, or C-16 will do, depending on the orbital altitude and power generation.
3. Connection among the network (inter-satellite-link). Again, all 3 antenna could do. But a C-16 will be very economical on power consumption. This is especially true if the omnidirectional antenna also covers the previous item, as a single C-16 can deliver 3 links. If we are using dish antennae though, we will need two of them due to cone angle, three if they also act as uplink receiver.
4. Connection to desired locations (downlink). Unless we are content with mere Kerbin coverage, we will want either/both of the dish antenna for the job. DTS-M1 has a shorter reach but lighter, whereas KR-7 has almost double the range but weighs half a tonne, on top of being not very aerodynamic. Although both takes the same amount of power. So the decision here depends upon our delta-v budget and desired reach. We will want at least one downlink antenna for the "active vessel", and, if we are committed, additional ones for each of the moons.
5. Enough power generation and storage. The night time of a given orbit needs to be considered here, the higher the orbit, the longer the night. For example, an equatorial LKO has a ten minute night, the KEO has a twenty-minute night, and an equatorial SOI-edge orbit will have a hundred minute night!

The possibilities here are endless, we could build a very economical 3 satellite network that uses C-16 for KSC and network connection, plus one or more dish antenna(e) each for further relays, at an altitude between 600 km and 843 km. Alternatively, we could--if power demand is not an issue-- use the dish antennae instead and build a network at keostationary orbit.

Here's an example of the latter if you get stuck:

Spoiler:

Needs more solar panels?

An upper stage of two FL-T400 Fuel Tanks attached to an LV-909 Liquid Fuel Engine. A middle stage of two FL-T400s attached to an LV-T30 Liquid Fuel Engine and the first stage consisting of 6 FL-T400/LV-T30s attached with TT-38K Radial Decouplers. There are of course many other ways of designing this rocket, this is just an example if you get stuck. Note the single DP-10, 3 DTS-M1s and at least one KR-7. This rocket will just about reach KEO with a well executed ascent through the atmosphere, though a lower orbit will do.

Operational Details

We start by launching the first satellite over KSC for a LKO, ideally during the day. If we are using a KR-7 as our uplink. we should target it towards KSC prior to launch. Once launched, Unless the vessel is kerballed, we will need to orbit before it goes over the horizon. Failing to do so will doom the vessel to catastrophic failure!

Once the LKO is reached, we can now transfer the craft to the intended orbit, if we were using DP-10 as our uplink this is a good time to activate a more powerful antenna(remember to target KSC if it's a direcitonal!), after that and only after that we can deactivate the DP-10 to save power.

If we have reached LKO and our uplink receiver is nominal, we need not worry if uplink is broken prior to reaching the intended orbit, we can always continue the job when the craft is above KSC once again.

After the first satellite is in position, we can launch the remaining satellites into LKO, as we did with the first satellite. If we are using dish antenna for inter-satellite-links, it would behoove us to target the satellites towards each other as soon as possible. As, by doing so we will extend the time window in which the satellites are controllable.

Here's the tricky part, we want to put all of our satellites at a similar altitude as the first one but evenly spaced.

The easy way to do this, is to simply put the satellite in the same altitude, and then raise or lower the orbit a bit to let the satellites "chase" or "wait for" each other, once in position, we can put the "chasing" or "waiting" satellite back into the previous orbit. This just like orbital rendezvous except we intend to miss the target for up to 120 degrees!

Once the satellites are roughly evenly spaced, we can finalize the operation by reducing inclination and eccentricity by burning normal/anti-normal and radial/anti-radial, and finally synchronizing the satellites.

To synchronize. the orbital period difference should be under a second, the higher the orbit, the longer the orbital period. Lowering the thrust limits we help with further precision. (We can calculate orbital period by doubling the difference of our time-to-apoapsis and time-to-periapsis, alternatively we can use mods that give us this information, such as MechJeb or Kerbal Engineer Redux)

And that's it! Hopefully your satellites now look something like this in the Tracking Station:

If so, congratulations, you've made your first set of relay satellites!

Finally, activate all of the downlink antennae, which ideally should be directional. If they are direction, pick "Active Vessel" under target selection, and the network will automatically cover the spacecraft currently under your control. For those more ambitious players who packed extra downlink antenna for Mun and/or Minmus communication, don't forget to target Mun and/or Minmus with your extra antennae!

Next Steps

Now that you've got your first set of satellites equipped with KR-7s, you can control a probe almost anywhere in the Kerbin sphere of influence. Equip any probe with 3 KR-7s and point them at your relay satellites and activate. Your relay satellites will already target one of their KR-7s at your probe because you set it up to target your active vessel. Despite their appearance, KR-7s don't need to be physically faced towards the target. You should now be well set to send a probe to the Mun. There are still two places your communications network can't reach, and that's directly behind the Mun and Minmus, so make sure you plan your route so you don't need to make a burn when behind them.

If you're doing your first Mun probe without the Electrics topic unlocked then you'll be using DTS-M1 or Communotron-16s for your long range communications. This has the unfortunate problem that these antennae will burn up on reentry, causing you to lose control of your probe and be unable to open parachutes or fine tune your landing. You can solve this problem two ways:

• Perform any actions required for landing, such as opening chutes and deploying landing legs in the upper atmosphere. KSP doesn't simulate reentry heating, so your parachutes won't be destroyed.
• Re-enter within 500 km of the KSC. This will allow your DP-10 antenna to link with the KSC and keep control of the probe.

While your probe to the Mun will likely only have 0.1s or so signal delay, a probe around Minmus can easily end up with around 0.5s signal delay, which is enough to become noticeable. Be careful when landing or docking when that far out, because fine control movements can be difficult.

If you want perfect coverage around Kerbin, including behind the Mun and Minmus, you can launch a further set of satellites out beyond their orbit, which will allow you to bounce a signal out and back behind them, or deploy a set of satellites around the Mun and Minmus like you did around Kerbin.

Going Interplanetary

Your KR-7s can talk to any satellite in Kerbin's sphere of influence, but they won't reach much beyond that. For that you'll need to unlock the Reflectron KR-14, with its 60 Gm range. The KR-14 can reliably reach Moho, Eve and Duna and just about reach Dres, but it can't reliably reach Jool. To reach Jool and Eeloo you'll need to unlock the Reflectron GX-128 or CommTech-1 with massive 350 Gm+ ranges. Remember links need to be bidirectional, so you'll need the strong antenna on the probe you send AND launch some satellites in to Kerbin orbit with the strong antenna on them to relay between the probe and the KSC.

Other than needing the more powerful antennae, once you send probes to interplanetary distances the signal delay will reach several minutes, making interactive control of your probe unfeasible. To make burns you'll need to use the Flight Computer, which comes with every probe core and can be accessed with the calculator icon next to the signal delay display. The simplest way to execute a burn with the flight computer is to create a maneuver node with the maneuver you want, instruct the computer to NODE, which will pre-orient the spacecraft in the burn direction of the next maneuver node, then EXEC to schedule a burn of the correct length at the correct time. By clicking the >> icon you can see the commands being sent to the probe and the time it'll take for them to get there. Signal delay affects most operations on your probe, such as using science instruments, ejecting a stage, extending solar panels, etc. If something doesn't seem to have worked, check the flight computer to see if your command has been delayed.

Remember that you'll lose contact with your probe while on the far side of the planet from Kerbin. You can solve this problem by stationing a satellite in high orbit over your destination planet (either send it as a second craft or decouple it from your main craft) to bounce a signal off.

Landing probes on a planet with minutes of signal delay can be extremely difficult. Planets and moons with atmospheres are easier because you can use parachutes for the final descent, making control inputs unnecessary, or at least less important. Remember to take in to account the time delay of the command to open your chutes. Landing on planets and moons without atmospheres is likely to be an exercise in frustration, but killing your surface horizontal velocity and instructing your flight computer to hold the spacecraft directly up while applying a constant burn to slow your descent may work.

Antennae Specification Table

Remote Mission Control

Once you unlock the Large Probes topic you'll get access to the RC-L01 Remote Guidance Unit. This probe core is special because it contains a Command signal processor, which allows a ship equipped with it to act as remote Mission Control to any probes connected to it, however to do this the ship must also be crewed by 6 or more Kerbals. The main advantage of this is that a command ship can control probes near it with very little signal delay, even if far from Kerbin. Note that transmitting science results back to Kerbin still requires a link to the KSC.

Related Links

• Tutorial: Basic Probe And Satellite Building