Skynet-IADS

An IADS (Integrated Air Defence System) script for DCS (Digital Combat Simulator).

Abstract

This script simulates an IADS within the scripting possibilities of DCS. Early Warning Radar Stations (EW Radar) scan the sky for contacts. These contacts are correlated with SAM (Surface to Air Missile) sites. If a contact is within firing range of the SAM site it will become active.

A modern IADS also depends on command centers and datalinks to the SAM sites. The IADS can be set up with this infrastructure. Destroying it will degrade the capability of the IADS.

This all sounds gibberish to you? Watch this video by Covert Cabal on modern IADS.

Visit this DCS forum thread for development updates.

Join the Skynet discord group and get support setting up your mission.

Skynet supports the HighDigitSAMs Mod.

You can also connect Skynet with the AI_A2A_DISPATCHER by MOOSE to add interceptors to the IADS.

So far over 200 hours of work went in to the development of Skynet.
If you like using it, please consider a donation:

Table of Contents

Quick start

Tired of reading already? Download the demo mission in the persian gulf map and see Skynet in action. More complex demo missions will follow soon.

Skynet IADS Elements

IADS

A Skynet IADS is a complete operational network. You can have multiple Skynet IADS instances per coalition in a DCS mission. A simple setup would be one IADS for the blue side and one IADS for the red side.

Track files

Skynet keeps a global track file of all detected targets. It queries all its units with radars and deduplicates contacts. By default lost contacts are stored up to 32 seconds in memory.

Comand Centers

You can add multiple command centers to a Skynet IADS. Once all command centers are destroyed the IADS will go in to autonomous mode.

SAM Sites

Skynet can handle multiple SAM sites, it will try and keep emissions to a minimum, therefore by default SAM sites will be turned on only if a target is in range. Every single launcher and radar unit's distance of a SAM site is analysed individually. If at least one launcher and radar is within range, the SAM Site will become active. This allows for a scattered placement of radar and launcher units as in real life.

If SAM sites or radar guided AAA run out of ammo they will go dark. In the case of a SAM site it will wait with going dark as long as the last fired missile is still in the air.

If an EW radar or a SAM site acting as EW radar is destoyed surrounding SAM sites can be left withouth EW radar coverage. This can also happen if a SAM site is outside of AWACS coverage. SAM sites will go autonomous in such a case meaning they will use their organic radars or just stay dark depending on setup. Once a SAM site is within EW radar coverage again it will be updated by the IADS.

Early Warning Radars

Skynet can handle 0-n EW radars. For detection of a target the DCS radar detection logic is used. You can use any type of radar listed in skynet-iads-supported-types.lua in an EW role in Skynet. Some modern SAM radars have a greater detection range than older EW radars, e.g. the S-300PS 64H6E (160 km) vs EWR 55G6 (120 km).

You can also designate SAM sites to act as EW radars, in this case a SAM site will constantly have their radar on. Long range systems like the S-300 are used as EW radars in real life. SAM sites that are out of ammo will stay live if they are set to act as EW radars.

Nice to know: Terrain elevation around an EW radar will create blinds spots, allowing low and fast movers to penetrate radar networks through valleys.

Power Sources

By default Skynet IADS will run without having to add power sources. You can add multiple power sources to SAM sites, EW radars and command centers. Once a power source is fully damaged the Skynet IADS unit will stop working.

Nice to know: Taking out the power source of a command center is a real life tactic used in SEAD (Suppression of Enemy Air Defence).

Connection Nodes

By default Skynet IADS will run without having to add connection nodes. You can add multiple connection nodes to SAM sites, EW radars and command centers.

When all the unit's connection nodes are fully damaged an EW radar or SAM site will go in to autonomous mode. For a SAM site this means it will behave in its autonomous mode setting. If an EW Radar looses its node it will no longer contribute information to the IADS but otherwise the IADS will still work. Command centers do not have an autonomous mode.

Nice to know: A single node can be used to connect an arbitrary number of Skynet IADS units. This way you can add a single point of failure in to an IADS.

AWACS (Airborne Early Warning and Control System)

Any aircraft with an air to air radar can be added as AWACS. Contacts detected will be added to the IADS. The AWACS will also detect ground units like ships. These will however not be passed to the SAM sites.

You can add a connection node for the AWACS like an antenna, if it is destroyed, the AWACS will no longer be able to contribute contacts to the IADS. Technically you can also add a power source. In this context it would represent the power source for the connection node, since an aircraft provides its own power.

Ships

Ships will contribute to the IADS the same way AWACS units do. Add them as a regular EW radar.

Tactics

HARM defence

SAM sites and EW radars will shut down their radars if they believe a HARM (High speed anti radiation missile) is heading for them. For this to happen, the IADS will evaluate contacts and determine if they are likely to be HARMs. Each SAM site or EW radar has HARM detection chance set. If a HARM is detected by more than one radar, the chance of it being identified as a HARM is increased.
See skynet-iads-supported-types.lua field ['harm_detection_chance'] for the probability per radar system.

HARM detection

let's say SAM site A has a 60% HARM detection chance and SAM site B has a 50% HARM detection cance. If a HARM is picked up by both radars the chance the IADS will identify the HARM will be 80%.

With the radar cross section updates of HARMs in DCS 2.7 older radars like the ones used in the SA-2 and SA-6 can only identifiy a HARM at very close range usualy less than 10 seconds before impact. These systems will not have a very good HARM defence with Skynet.

HARM flight path analysis

The contact needs to be traveling faster than 800 kt and it may not have changed its flight path more than 2 times (eg climb-descend, climb or descend).This is to minimise false positives, for example a fighter flying very fast.

This implementation is closer to real life. SAM sites like the patriot and most likely modern Russian systems calculate the flight path and analyse the radar cross section to determine if a contact heading inbound is a HARM.

If identified as a HARM the IADS will shut down radars 15 degrees left and right of the HARM's fight path up to a distance of 20 nautical miles in front of the HARM. The IADS will calculate time to impact and shut down radar emitters up to a maximum of 180 seconds after time to impact.

HARM radar shutdown

Once a HARM has been identified by Skynet, radars up to 20 nm ahead and 15 degrees left or right of the HARM will be notified. Depending on their settins radar emitters will shut down or start defending against the HARM.

Point defence

When a radar emitter (EW radar or SAM site) is attacked by a HARM there is a chance it may detect the HARM and go dark. If this radar emitter is acting as the sole EW radar in the area, surrounding SAM sites will not be able to go live since they rely on the EW radar for target information. This is an issue if you have SA-15 Tors next to the EW radar for point defence protection. They will stay dark and not engange the HARM.

Use this feature if you don't want the IADS to loose situational awareness just because a HARM is inbound. The radar emitter will shut down, if it believes its point defences won't be able to handle the number of HARMs inbound. As long as there is one point defence launcher and missile per HARM inbound the radar emitter will keep emitting. If the HARMs exeed the number of point defence launchers and missiles the protected asset will shut down. Tests in DCS have shown that this is roughly the saturation point. If the SAM site reling on point defence can engagen HARMs its launchers an missiles will also count to the saturation point.

See FAQ Which SAM systems can engage HARMS?

Point defence setup example

Electronic Warfare

A simple form of jamming is part of the Skynet IADS package. It's off by default. The jamming works by setting the ROE state of a SAM Site. The closer the jamming emitter gets to a SAM site the less effective jamming will become (burn through). For the jammer to work it will need LOS (line of sight) to a radar unit. Older SAM sites are more susceptible to jamming. EW radars are currently not jammable.

I recommend you add an AI unit that follows the strike package you're flying in to act as a jammer aircraft. This will give you the most realistic experience. The jammer emitter will toggle the ROE state of a SAM site which affects how the SAM site reacts to all threats near or far.

I presume an aircraft very close to a SAM site beeing jammed by a emitter very far away would most likely be detected. So the farther away you are from the jammer source the more unrealistic your experience will be.

Here is a list of SAM sites currently supported by the jammer and the jammer's effectiveness on them. When setting up a jammer you can decide which SAM sites it is able to jam. For example you could design a mission in which the jammer is not able to jam a SA-6 but is able to jam a SA-2. The jammer effectiveness is not based on any real world data I just read about the different types and made my own conclusions.

Here is an old school documentary showing the Prowler in action. They brief to turn on their jamming equipement at 60 nm from the target. I suppose that must have been the effective range of 70's jamming tech.

Using Skynet in the mission editor

It's quite simple to setup an IADS have a look at the demo missions in the /demo-missions/ folder.

Placing units

This tutorial assumes you are familiar on how to set up a SAM site in DCS. If not I suggest you watch this video by the Grim Reapers. Place the IADS elements you wish to add on the map.

Preparing a SAM site

There may be only be one type of SAM site per group. More than one type of SAM site per group will result in Skynet no being able to properly controll the group. Also please refrain from from adding units to the SAM group that are not required for the SAM like trucks, tanks and soldiers. The skill level you set on a SAM group is retained by Skynet. Make sure you name the SAM site group in a consistent manner with a prefix e.g. 'SAM-SA-2'.

Preparing an EW radar

You can use any type of radar as an EW radar. Make sure you name the unit in a consistent manner with a prefix, e.g. 'EW-center3'. Make sure you have only one EW radar in a group otherwise Skynet will not be able to control single EW radars.

Adding the Skynet code

Skynet requires MIST. A version is provided in this repository or you can download the most current version here. Make sure you load MIST and the compiled skynet code in to a mission. The skynet-iads-compiled.lua and mist_4_5_107.lua files are located in the /demo-missions/ folder.

I recommend you create a text file e.g. 'my-iads-setup.lua' and then add the code needed to get the IADS runing. When updating the setup remember to reload the file in the mission editor. Otherwise changes will not become effective. You can also add the code directly in the mission editor, however that input field is quite small if you write more than a few lines of code.

Adding the Skynet IADS

For the IADS to work you need four lines of code.

create an instance of the IADS, the name string is optional and will be displayed in status output:

redIADS = SkynetIADS:create('name')

Give all SAM groups you want to add a common prefix in the mission editor eg: 'SAM-SA-10 west', then add this line of code:

redIADS:addSAMSitesByPrefix('SAM')

Same for the EW radars, name all units with a common prefix in the mission editor eg: 'EW-radar-south':

redIADS:addEarlyWarningRadarsByPrefix('EW')

Activate the IADS:

redIADS:activate()

Advanced setup

This is the danger zone. Call Kenny Loggins. Some experience with scripting is recommended. You can handcraft your IADS with the following functions. If you refrence units that don't exist a message will be displayed when the mission loads. The following examples use static objects for command centers, connection nodes and power sources, you can also use units instead.

IADS configuration

Call this method to add or remove a radio menu to toggle the status output of the IADS. By default the radio menu option is not visible:

redIADS:addRadioMenu()  

redIADS:removeRadioMenu()

If you dereference the IADS remember to call deactivate() otherwise background tasks of the IADS will continue running, resulting in unexpected behaviour:

redIADS:deactivate()

Set the update interval in seconds of the IADS. This determines in what interval the IADS wil turn SAM sites of or on according to targets it has detected:

redIADS:setUpdateInterval(5)

Adding a command center

The command center represents the place where information is collected and analysed. It if is destroyed the IADS disintegrates.

Add a command center like this:

local commandCenter = StaticObject.getByName("Command Center")
redIADS:addCommandCenter(commandCenter)

Power sources and connection nodes

You can use units or static objects. Call the function multiple times to add more than one power source or connection node:

unit refers to a SAM site, or EW Radar you retrieved from the IADS, see setting an option for Radar units.

local powerSource = StaticObject.getByName("EW Power Source")  
unit:addPowerSource(powerSource)

local connectionNode = Unit.getByName("EW connection node") 
unit:addConnectionNode(connectionNode)

For command centers use:

local commandCenter = StaticObject.getByName("Command Center2")
local comPowerSource = StaticObject.getByName("Command Center2 Power Source")
redIADS:addCommandCenter(commandCenter):addPowerSource(comPowerSource)

Warm up the SAM sites of an IADS

This function is deprecated and will be removed in a future release.

redIADS:setupSAMSitesAndThenActivate()

Connecting Skynet to the MOOSE AI_A2A_DISPATCHER

You can connect Skynet with MOOSE's AI_A2A_DISPATCHER. This allows the IADS not only to direct SAM sites but also to scramble fighters. Skynet will set the radars it can use on the SET_GROUP object of a dispatcher. Meaning that if a radar is lost in Skynet it will no longer be availabe to detect and scramble interceptors.

Add the object of type SET_GROUP to the iads like this (in this example DectionSetGroup):

redIADS:addMooseSetGroup(DetectionSetGroup)

SAM site configuration

Adding SAM sites

Add multiple SAM sites

Adds SAM sites with prefix in group name to the IADS. Previously added SAM sites are cleared:

redIADS:addSAMSitesByPrefix('SAM')

Add a SAM site manually

You can manually add a SAM site, must be a valid group name:

redIADS:addSAMSite('SA-6 Group2')

Accessing SAM sites in the IADS

The following functions exist to access SAM sites added to the IADS. They all support daisy chaining options:

Returns all SAM sites with the corresponding Nato name, see skynet-iads-supported-types.lua. For all units beginning with 'SA-': Don't add Nato code names (Guideline, Gainful), just write 'SA-2', 'SA-6':

redIADS:getSAMSitesByNatoName('SA-6')

Returns all SAM sites in the IADS:

redIADS:getSAMSites()

Returns a SAM site with the specified group name:

redIADS:getSAMSiteByGroupName('SAM-SA-6')

Returns a SAM site with the specified group name prefix. Let's say you have a bunch of SAM sites that all will share the same power source. Give these sites a special prefix in the group name, e.g.: 'SAM-SECTOR-A'. Once you have added the SAM sites you can access them via the prefix to set whatever options you want:

redIADS:getSAMSitesByPrefix('SAM-SECTOR-A')

Act as EW radar

Will set the SAM site to act as an EW radar. This will result in the SAM site always having its radar on. Contacts the SAM site sees are reported to the IADS. This option is recomended for long range systems like the S-300:

samSite:setActAsEW(true)

Engagement zone

Set the distance at which a SAM site will switch on its radar:

samSite:setEngagementZone(SkynetIADSAbstractRadarElement.GO_LIVE_WHEN_IN_SEARCH_RANGE)

Engagement zone options

SAM site will go live when target is within the red circle in the mission editor (default Skynet behaviour):

SkynetIADSAbstractRadarElement.GO_LIVE_WHEN_IN_KILL_ZONE

SAM site will go live when target is within the yelow circle in the mission editor:

SkynetIADSAbstractRadarElement.GO_LIVE_WHEN_IN_SEARCH_RANGE

This option sets the range in relation to the zone you set in setEngagementZone for a SAM site to go live. Be careful not to set the value too low. Some SAM sites need up to 30 seconds until they can fire. During this time a target might have already left the engagement zone of SAM site. This option is intended for long range systems like the S-300. You can also set the range above 100 this will have the effect that the SAM site goes live earlier:

samSite:setGoLiveRangeInPercent(90)

Engage air weapons

Will set the SAM site to engage air weapons, if it is able to do so in DCS. It is a wrapper for the ENGAGE_AIR_WEAPONS setting.

samSite:setCanEngageAirWeapons(true)

Engage HARM

Will set the SAM site to engage HARMs, if it is able to do so in DCS. If set to false the SAM site will shut down if a HARM that has been identified by the IADS is inbound. SAM sites that can engage HARMS are set to true by default.

samSite:setCanEngageHARM(true)

Add go live constraints

You can include constraints wich must be satisfied for the SAM site to go live. Please note this only controls activation of the SAM site. There is currently no way to tell a SAM site to only target a certain contact via the lua scripting engine in DCS.

The constraint must evaluate to true and the contact must be in range of the SAM site (handled by Skynet).

Use cases

Place a SAM site on an flight path that you suspect strike strike fighters will pass. Add a heading constraint to ensure that the SAM site will only go ive when fighters are on their way back from the target.

Set a SAM site to only go live if aircraft are in a certain altitude band.

SAM site shall only go live once a strike package has destroyed a certain building or unit.

You do not have to use the contact provided in the function to evaluate the constraint. You can make any assertion you want.

Create a function that will evaluate if the constraint is satisfied. The function will have access to the contact the SAM site is evaluating:

--SAM site will only go live if the contact is below 1000 feet.
local function goLiveConstraint(contact)
	return ( contact:getHeightInFeetMSL() < 1000 )
end

Add the function to the SAM site and give it a name. You can add as many constraints as you wish:

self.samSite:addGoLiveConstraint('ignore-low-flying-contacts', goLiveConstraint)

Remove constraint you no longer wish to use:

self.samSite:removeGoLiveConstraint('ignore-low-flying-contacts')

Get a table of all constraints:

self.samSite:getGoLiveConstraints()

Contact

You can use the following methods to get information about a contact.

Will return true if contact has been identified as a HARM by Skynet:

contact:isIdentifiedAsHARM()

Will return the height of a contact:

contact:getHeightInFeetMSL()

Will return the current magnetic heading of a contact. Note the heading is availble only after a contact has been tracked in more than one cycle by the IADS. Until that has happened heading will be 0:

contact:getMagneticHeading()

Will return the current ground speed of a contact. Note the speed is availble only after a contact has been tracked in more than one cycle by the IADS. Until that has happend speed will be 0:

contact:getMagneticHeading()

Will return the time in seconds a contact has been known to the IADS:

contact:getAge()

Will return the type as a Object.Category:

contact:getTypeName()

Will return the unit name:

contact:getName()

EW radar configuration

Adding EW radars

Add multiple EW radars

Adds EW radars with prefix in unit name to the IADS. Previously added EW sites are cleared:

redIADS:addEarlyWarningRadarsByPrefix('EW')

Add an EW radar manually

You can add EW radars manually, must be a valid unit name:

redIADS:addEarlyWarningRadar('EWR West')

Accessing EW radars in the IADS

The following functions exist to access EW radars added to the IADS. They all support daisy chaining options.

Returns all EW radars in the IADS:

redIADS:getEarlyWarningRadars()

Returns the EW radar with the specified unit name:

redIADS:getEarlyWarningRadarByUnitName('EW-west')

Options for SAM sites and EW radars

Setting an option

In the following examples ewRadarOrSamSite refers to an single EW radar or SAM site or a table of EW radars and SAM sites you got from the Skynet IADS, by calling one of the functions named in accessing EW radars or accessing SAM sites.

Daisy chaining options

You can daisy chain options on a single SAM site / EW Radar or a table of SAM sites / EW radars like this:

redIADS:getSAMSites():setActAsEW(true):addPowerSource(powerSource):addConnectionNode(connectionNode):setEngagementZone(SkynetIADSAbstractRadarElement.GO_LIVE_WHEN_IN_SEARCH_RANGE):setGoLiveRangeInPercent(90):setAutonomousBehaviour(SkynetIADSAbstractRadarElement.AUTONOMOUS_STATE_DARK)

HARM Defence

You can set the reaction probability (between 0 and 100 percent). See skynet-iads-supported-types.lua field ['harm_detection_chance'] for default detection probabilities:

ewRadarOrSamSite:setHARMDetectionChance(50)

Point defence

You must use a point defence SAM that can engage HARM missiles. Can be used to protect SAM sites or EW radars. See point defence for information what this does:

If you want the point defences to coordinate their HARM defence then you can add multiple point defence SAM sites in to one group. This is the only place where you should add multiple SAM sites in to one group in Skynet. Let's assume you have two SA-15 units defending a radar. If the SA-15 units are in separate groups they will both fire at the same HARM inbound. However if they are in the same group and multiple HARMS are inbound they will each pick a separate HARM to engage.

--first get the SAM site you want to use as point defence from the IADS:
local sa15 = redIADS:getSAMSiteByGroupName('SAM-SA-15')
--then add it to the SAM site it should protect:
redIADS:getSAMSiteByGroupName('SAM-SA-10'):addPointDefence(sa15)

This function is deprecated and will be removed in a future release.

ewRadarOrSamSite:setIgnoreHARMSWhilePointDefencesHaveAmmo(true)

Autonomous mode behaviour

Set how the SAM site or EW radar will behave if it looses connection to the IADS:

ewRadarOrSamSite:setAutonomousBehaviour(SkynetIADSAbstractRadarElement.AUTONOMOUS_STATE_DARK)

Autonomous mode options

SAM site or EW radar will behave in the default DCS AI. Alarm State will be red and ROE weapons free (default Skynet behaviour for SAM sites):

SkynetIADSAbstractRadarElement.AUTONOMOUS_STATE_DCS_AI

SAM Site or EW radar will go dark if it looses connection to IADS (default behaviour for EW radars):

SkynetIADSAbstractRadarElement.AUTONOMOUS_STATE_DARK

Adding a jammer

The jammer is quite easy to set up. You need a unit that acts as a jammer source, preferably it will be an aircraft in the strike package. Once the jammer detects an emitter it starts jamming the radar. Set the coresponding debug variable jammerProbability to see what the jammer is doing. Check skynet-iads-jammer.lua to see which SAM sites are supported.

Remember to set the AI aircraft acting as jammer in the Mission editor to Reaction to Threat = EVADE FIRE otherwise the AI will try and actively attack the SAM site. This way it will stick to the preset flight plan.

Create a jammer and assign it to an unit. Also make sure you add the IADS you wan't the jammer to work for:

local jammerSource = Unit.getByName("F-4 AI")
jammer = SkynetIADSJammer:create(jammerSource, iads)

The jammer will start listening for emitters and if it finds one of the emitters it is able to jam it will start jamming it:

jammer:masterArmOn()

Will disable jamming for the specified SAM type, pass the Nato name:

jammer:disableFor('SA-2')

Will turn off the jammer. Make sure you call this function before you dereference a jammer in the code, otherwise a background task will keep on jamming:

jammer:masterArmSafe()

Will add jammer on / off to the radio menu:

jammer:addRadioMenu()

Will remove jammer on / off from the radio menu:

jammer:removeRadioMenu()

Advanced functions

Add a second IADS the jammer should be able to jam, for example if you have two separate IADS running:

jammer:addIADS(iads2)

Add a new jammer function:

-- write a lambda function that expects one parameter:
-- given public available data on jammers their effeciveness drastically decreases the closer you get, so a non-linear function would make sense:
local function f(distanceNM)
	return ( 1.4 ^ distanceNM ) + 80
end

-- add the function: specify which SAM type it should apply for:
self.jammer:addFunction('SA-10', f)

Set the maximum range the jammer will work, the default value is set to 200 nautical miles:

jammer:setMaximumEffectiveDistance(100)

Setting debug information

When developing a mission I suggest you add debug output to check how the IADS reacts to threats. Debug output may slow down DCS, so it's recommended to turn it off in a live environment:

Access the debug settings:

local iadsDebug = redIADS:getDebugSettings()  

Output in game:

iadsDebug.IADSStatus = true
iadsDebug.contacts = true
iadsDebug.jammerProbability = true

Output to dcs.log:

iadsDebug.addedEWRadar = true
iadsDebug.addedSAMSite = true
iadsDebug.warnings = true
iadsDebug.radarWentLive = true
iadsDebug.radarWentDark = true
iadsDebug.harmDefence = true

These three options will output detailed information on every radar in the IADS to the dcs.log file. Enabling these may have an impact on performance:

iadsDebug.samSiteStatusEnvOutput = true
iadsDebug.earlyWarningRadarStatusEnvOutput = true
iadsDebug.commandCenterStatusEnvOutput = true

Example Setup

This is an example of how you can set up your IADS used in the demo mission:

do

--create an instance of the IADS
redIADS = SkynetIADS:create('RED IADS')

---debug settings remove from here on if you do not wan't any output on what the IADS is doing by default
local iadsDebug = redIADS:getDebugSettings()
iadsDebug.IADSStatus = true
iadsDebug.radarWentDark = true
iadsDebug.contacts = true
iadsDebug.radarWentLive = true
iadsDebug.noWorkingCommmandCenter = true
iadsDebug.samNoConnection = true
iadsDebug.jammerProbability = true
iadsDebug.addedEWRadar = true
iadsDebug.harmDefence = true
---end remove debug ---

--add all units with unit name beginning with 'EW' to the IADS:
redIADS:addEarlyWarningRadarsByPrefix('EW')

--add all groups begining with group name 'SAM' to the IADS:
redIADS:addSAMSitesByPrefix('SAM')

--add a command center:
commandCenter = StaticObject.getByName('Command-Center')
redIADS:addCommandCenter(commandCenter)

---we add a K-50 AWACs, manually. This could just as well be automated by adding an 'EW' prefix to the unit name:
redIADS:addEarlyWarningRadar('AWACS-K-50')

--add a power source and a connection node for this EW radar:
local powerSource = StaticObject.getByName('Power-Source-EW-Center3')
local connectionNodeEW = StaticObject.getByName('Connection-Node-EW-Center3')
redIADS:getEarlyWarningRadarByUnitName('EW-Center3'):addPowerSource(powerSource):addConnectionNode(connectionNodeEW)

--add a connection node to this SA-2 site, and set the option for it to go dark, if it looses connection to the IADS:
local connectionNode = Unit.getByName('Mobile-Command-Post-SAM-SA-2')
redIADS:getSAMSiteByGroupName('SAM-SA-2'):addConnectionNode(connectionNode):setAutonomousBehaviour(SkynetIADSAbstractRadarElement.AUTONOMOUS_STATE_DARK)

--this SA-2 site will go live at 70% of its max search range:
redIADS:getSAMSiteByGroupName('SAM-SA-2'):setEngagementZone(SkynetIADSAbstractRadarElement.GO_LIVE_WHEN_IN_SEARCH_RANGE):setGoLiveRangeInPercent(70)

--all SA-10 sites shall act as EW sites, meaning their radars will be on all the time:
redIADS:getSAMSitesByNatoName('SA-10'):setActAsEW(true)

--set the SA-15's as point defence for the SA-10 site. We set the SA-10 to always identify HARMs so we can demonstrate the point defence mechanism in Skynet.
--the SA-10 will stay online when shot at by HARMS as long as the point defences and SAM site have ammo and the saturation point is not reached.
local sa15 = redIADS:getSAMSiteByGroupName('SAM-SA-15-point-defence-SA-10')
redIADS:getSAMSiteByGroupName('SAM-SA-10'):addPointDefence(sa15):setHARMDetectionChance(100)

--set this SA-11 site to go live 70% of max range of its missiles (default value: 100%), its HARM detection probability is set to 50% (default value: 70%)
redIADS:getSAMSiteByGroupName('SAM-SA-11'):setGoLiveRangeInPercent(70):setHARMDetectionChance(50)

--this SA-6 site will always react to a HARM being fired at it:
redIADS:getSAMSiteByGroupName('SAM-SA-6'):setHARMDetectionChance(100)

--set this SA-11 site to go live at maximunm search range (default is at maximung firing range):
redIADS:getSAMSiteByGroupName('SAM-SA-11-2'):setEngagementZone(SkynetIADSAbstractRadarElement.GO_LIVE_WHEN_IN_SEARCH_RANGE)

--activate the radio menu to toggle IADS Status output
redIADS:addRadioMenu()

--activate the IADS
redIADS:activate()	

--add the jammer
local jammer = SkynetIADSJammer:create(Unit.getByName('jammer-emitter'), redIADS)
jammer:masterArmOn()

--setup blue IADS:
blueIADS = SkynetIADS:create('BLUE IADS')
blueIADS:addSAMSitesByPrefix('BLUE-SAM')
blueIADS:addEarlyWarningRadarsByPrefix('BLUE-EW')
blueIADS:activate()
blueIADS:addRadioMenu()

local iadsDebug = blueIADS:getDebugSettings()
iadsDebug.IADSStatus = true
iadsDebug.contacts = true

end

FAQ

Does Skynet IADS have an impact on game performance?

Skynet may actually improve game performance when using a lot of SAM AI units. This is because Skynet will turn off radar emissions of all SAM groups currently not in range of a target. By default these SAM groups would otherwise have their radars on. Skynet caches target information for a few seconds to reduce expensive calls on DCS radar detection.

What air defence units shall I add to the Skynet IADS?

In theory you can add all the types that are listed in the skynet-iads-supported-types.lua file. Very short range units (like the Shilka AAA, Rapier) won't really benefit from the IADS apart from reacting to HARMs. These are better just placed in a mission and handeled by the default AI of DCS. This is due to the short range of their radars. By the time the IADS wakes them up, the contact has likely passed their engagement range. The strength of the Skynet IADS lies with handling long range systems that operate by radar.

Which SAM systems can engage HARMS?

As of July 2022 I have only been able to get the SA-15, SA-10, NASAMS and Patriot to engage HARMS. The best option for a solid HARM defence is to add SA-15's around EW radars or high value SAM sites.

What exactly does Skynet do with the SAMS?

Via the scripting engine one can toggle the radar emitters on and off. Further options are the alarm state and the rules of engagement. In a nutshell that's all that Skynet does. Skynet does also read the radar and firing range properties of a SAM site. Based on that data and the setup options a mission designer provides Skynet will turn a SAM site on or off.

No god like intervention is used (like magically exploding HARMS via the scripting engine). If a SAM site or EW radar detects an inbound HARM it just turns off its radar as in real life. The HARM as it is programmed in DCS will try and glide in to the last known position mostly resulting in misses by 50-100 meters.

Are there known bugs?

Yes, when placing multi unit SAM sites (e.g. SA-3, Patriot..) make sure the first unit you place is the search radar. If you add any other element as the first unit, Skynet will not be able to read radar data. The result will be that the SAM site won't go live. This bug was observed in DCS 2.5.5. The SAM site will work fine when used as a standalone unit outside of Skynet.

How do I know if a SAM site is in range of an EW site or a SAM site in EW mode?

To get a rough idea you can look at the range circles in the mission editor. However these ranges are greater than the actual in game detection ranges of an EW radar or SAM site. The following screenshot shows the range of the 1L13 EWR. The mission editor shows a range of 64 NM (nautical miles) where as the in game range is 43 NM.

In this example the SAM site to the north east would not be in range of the EW radar, therefore it would go in to autonomous mode once the mission starts.

Set the debug options samSiteStatusEnvOutput and earlyWarningRadarStatusEnvOutput to get detailed information on every SAM site and EW radar. The text marked in the red box will show you which SAM sites are in the covered area of a SAM site or EW radar.

How do I connect Skynet with the MOOSE AI_A2A_DISPATCHER and what are the benefits of that?

IRL an IADS would most likely not only handle SAM sites but also pass information to interceptor aircraft. By connecting Skynet to the AI_A2A_DISPATCHER by MOOSE you are able to add interceptors to the IADS. See Skynet Moose AI_A2A_DISPATCHER and the moose_a2a_connector demo mission for more information.

An example setup of Skynet and the AI_A2A_DISPATCHER :

--Setup Syknet IADS:
redIADS = SkynetIADS:create('Enemy IADS')
redIADS:addSAMSitesByPrefix('SAM')
redIADS:addEarlyWarningRadarsByPrefix('EW')
redIADS:activate()

-- START MOOSE CODE:
-- Define a SET_GROUP object that builds a collection of groups that define the EWR network.
DetectionSetGroup = SET_GROUP:New()

-- Setup the detection and group targets to a 30km range!
Detection = DETECTION_AREAS:New( DetectionSetGroup, 30000 )

-- Setup the A2A dispatcher, and initialize it.
A2ADispatcher = AI_A2A_DISPATCHER:New( Detection )

-- Set 100km as the radius to engage any target by airborne friendlies.
A2ADispatcher:SetEngageRadius() -- 100000 is the default value.

-- Set 200km as the radius to ground control intercept.
A2ADispatcher:SetGciRadius() -- 200000 is the default value.

CCCPBorderZone = ZONE_POLYGON:New( "RED-BORDER", GROUP:FindByName( "RED-BORDER" ) )
A2ADispatcher:SetBorderZone( CCCPBorderZone )
A2ADispatcher:SetSquadron( "Kutaisi", AIRBASE.Caucasus.Kutaisi, { "Squadron red SU-27" }, 2 )
A2ADispatcher:SetSquadronGrouping( "Kutaisi", 2 )
A2ADispatcher:SetSquadronGci( "Kutaisi", 900, 1200 )
A2ADispatcher:SetTacticalDisplay(true)
A2ADispatcher:Start()
--END MOOSE CODE

-- add the MOOSE SET_GROUP to the IADS, from now on Skynet will update active radars that the MOOSE SET_GROUP can use for EW detection.
redIADS:addMooseSetGroup(DetectionSetGroup)

Thanks

Special thaks to Spearzone and Coranthia for researching public available information on IADS networks and getting me up to speed on how such a system works. I based the SAM site setup on Grimes SAM DB from his IADS script, however I removed range data since Skynet loads that from DCS.