Active/Passive Radar

[chuck_starchaser]

I described active/passive radar briefly in this other thread, and since Z30 seems to like the idea, I will expand on it here. I've no idea how easy or hard it would be to implement this, as of this writing. I'm just proposing a goal here, for now.

Active radar:
In active radar your plane or ship is beaming out electromagnetic bleeps of very high intensity, then listening for the echos. Presently, radar doesn't consume power from your generators (engines, in Privateer parlance), but this is perhaps an error that should be corrected: Active radar is a juice guzzler, because to be able to hear the faint echos returned from another craft 100 klicks away, the signals active radar must send out have to be extremely powerful. Much more powerful than standard radio and television signals. And even then, the beam must be very sharp and focused. Often people think that radar signals are like spherically expanding signals, but this is not true; they are highly focused. To get a wide picture of the theater ahead of you, the radar beam must sweep the space ahead of you vertically and horizontally. In real fighter aircraft, you have various sweep modes to choose from, such as wide sweep horizontally and narrow verticlally, or like a square sweep, or like spiral sweep drawing a circle in front of you. There's also radar modes that sweep all of the space around you, such as you would use during dogfights. You sacrifice range and angular resolution for coverage and speed of the sweep. I'm not suggesting we model all this, though it is doable, and the game TFX did.
Active radar tells the position of a craft by the angle of its dish (or virtual dish, in the case of synthetic aperture transducers) at the moment an echo is returned; and it tells the distance of the craft by the time it took the signal to get there and bounce back.

Passive radar is when you simply turn off the sending of signals. When you switch your radar to passive mode, it stops beaming out signals, and it only listens for signals, instead. The transducer continues to sweep, and it can tell the position of a craft by the angle of the dish at the moment of receiving a signal; but passive radar does not know the exact distance of the other craft, because it does not know how long the signal took to reach it. However, it will attempt to guesstimate distance from the signal's power. A very rough estimation, since it does not know how powerfully that signal is being sent.

What's the advantage of switching to passive radar?

Passive radar does NOT make you un-detectable, or un-lockable, or un-identifiable, or invisible. Passive radar is just a way of not advertising yourself too much. When your active radar is on, the signals you send out can alert enemy craft of your presence from great distances. Even from farther away than their own radar range. With passive radar, your enemies won't see you until your range is short enough that their own active radar signals bounce off you with enough power for them to hear the echos.

Let's make up an example. You're craft A flying towards enemy craft X. Assume first that both A and X are using active radar:
At a range of 200 miles, you see X on your sensor, and X sees you. But neither knows the other's range yet. By the time you're at 50 miles, your radar signals bouncing off X are strong enough you can tell X's range, and X's radar signals bouncing off you are strong enough that X knows you're 50 miles away. Ironically perhaps, between 200 miles and 50 miles range, what A and X see of each other is passive radar sensing. Passive radar is always on, implicitly; even when active radar is on. In other words, if your radar is active but you're not getting bouces yet; but you ARE getting the active signal of X, your radar will display the fact that it hears an active singnal beaming your way, but that it can't tell its range yet.

Assume now that X is in active radar mode, and you, A, are in passive radar mode:
At 200 miles, your radar senses the signal being beamed out by X. X doesn't see you at all, since X's bounce is too weak to detect, and you are not sending out a signal.
But your radadar cannot tell X's distance too precisely.
By 50 milies, X suddenly sees the bounce of "his" signals off your craft, and can tell where you are and your range. If you're still in passive mode, you're at a disadvantage now, because you're no longer hidden, and you still cannot tell X's range.

Finally, assume that both, you and X, are in passive mode. X doesn't see you, and you're blind. Got it?


Game-play benefits of Active/Passive mode Radar:

The benefit is that having the choice is terrifying in and of itself. It's the kind of choice that makes you chew your fingers to the bone: The moment you turn your active radar on, even for a split second, you are advertising your position to the whole world, even very far away. You might have avoided those bogies in the asteroid field altogether, but if you succumbed to the temptation to turn active mode on, now they know where you are and can start flying in your general direction. So even if you switch back to passive mode, chances are they will now be able to come close enough to you to see you with their active radar even if you are back in passive mode.
Flying all the time in passive mode is very risky too. In a way, you have an advantage if the bogies are in active mode, as there's good chances they are not seeing you, but you are seeing them. However, it is impossible, in passive radar mode, to know for sure whether they see you or not, because it depends on range, but you don't know their range in passive mode. And there's an even greater danger in flying in passive mode: If they did see you and are coming for you, they could also switch to passive mode, and now mutual detection is totally reliant on visual spotting. And the ultimate danger in passive mode: A bogie could just be flying in passive mode also, and neither one sees the other until you have visual contact.
So the descision whether to use passive mode, and when to switch to active mode, is a gut wrenching dilemma that's always there. Without making the game easier or more difficult, this choice makes it 10 times as immersive.


About implementation:

I would suggest the simplest possible implementation. A fixed range at which signals beamed out in active mode can be detected by the other party; and a much shorter range at which bounced signals can be detected, and therefore range. In passive mode, signals are not sent out, and so you're only visible to an enemy active radar at the bouncing range. Whether you're in active or passive mode, crafts beyond bouncing range are not ranged. That is, you don't see the range numbers --only see a blip on the sensor screen.
Within bouncing distance, you can tell range if you're in active mode, but you still can't tell range if you're in passive mode.


OT:
ECM/Jamming. This subject always comes up when discussing radar.
Radar jamming is based on sending out signals that an active radar confuses with the echos it expects to hear. The simplest jammers used to produce multiple echo-like bleeps so that the active radar spotting you sees a whole row of bleeps and doesn't know which bleep is the real craft.
Modern jammers model the sweep mode of the oponent's radar to make it look like the signal comes from a different direction. In any case, jammers send very powerful and focused signals. Jammers are not wide area things that jam all readars in an area. Jammers can only work on one particular bogie radar at a time, at the expense of lighting up your craft like a chrystmas tree to all other bogies around you. Finally, you cannot be in passive radar and jamming mode at the same time. Jamming mode is like a submode of active radar.


OT2:
Radar lock is when you stop your radar from sweeping, and instead you have the dish "lock" onto the direction of the craft you tell it to lock. When you have lock, you stop seeing other bogies around you on the sensor screen, since the dish is not sweeping. (Well, I'm sure modern synthetic aperture radar gets around this problem.)

[Sunfire]

Active radar is a juice guzzler, because to be able to hear the fain echos returned from another craft 100 klicks away, the signals active radar must send out have to be extremely powerful.

not really... it more depends on the gain of your antenna, the frequency you use, and the attenuation factor of your environment.
the feds used the arecibo antennato look for soviet radar installation signals that bounced off the moon purely by passive means... scientists have used the dish in active mode to do radar maps of saturns moons
in space, you could use your usb wi-fi modem and a really good antenna for radar.... (you wouldnt tho... the wavelengh is way too long... your antenna would be HUGE if you wanted to go more than a couple hundred miles or so... )

Often people think that radar signals are like spherically expanding signals, but this is not true; they are highly focused.

the signals themselves can be... if you could use an isometric radiator, the field would be a perfect sphere (those are only theoretical, but a standard dipole would do) but then, you wont be able to tell its position, only that its there or moving
a directional antenna will make your RF signal focused and increase its range (gain), but then you have the problem of only being able to see one spot... hence, most radars 'sweep' in patterns. thus, you aquire the ability to learn position.
another soloution than having directional antennas that sweep, would be to have 3 dipole antennas, (one broadcast, 3 receive)that way you can use triangulation to determine position

To get a wide picture of the theater ahead of you, the radar beam must sweep the space ahead of you vertically and horizontally. In real fighter aircraft, you have various sweep modes to choose from, such as wide sweep horizontally and narrow verticlally, or like a square sweep, or like spiral sweep drawing a circle in front of you. There's also radar modes that sweep all of the space around you, such as you would use during dogfights. You sacrifice range and angular resolution for coverage and speed of the sweep.

yes... very true, but again, the only difference between modes is that you change the gain and sweep pattern.

Passive radar is when you simply turn off the sending of signals.

think radar detector in your car

What's the advantage of switching to passive radar?

its a completely awesome idea for gameplay... matter of fact, theres a bar rumor that says this happens in OP:

A pilot laid this on me last week. She was three weeks out of New Detroit, off-lane, running silent... ...when she came in visual range of this incredible ship! It was massive, not Kilrathi, not Confed...and every instrument said it wasn't there! She said she could see it, but it didn't register on her scans. You believe her? I sure don't.

Finally, assume that both, you and X, are in passive mode. X doesn't see you, and you're blind. Got it?

lol

About implementation:

the only problem i see with this, is the IFF beacon... when your beacon is on, youre telling the universe where you are, and who you are. so silent mode running craft does not do that.... you must rely on visual markings only, and you dont know their alleigence till they fire on you.... or dont.. and the minute you send out a comms in hostile territory? instant toast... unless you use lasers for comms...

EDIT: this of course assumes engines do not have an EM signature... otherwise, no passivity in AFs... and also... no EM signature of a jump in system... otherwise... everybody knows youre here...

[chuck_starchaser]

Alright, something I should have said, I'm an EE (Electrical Engineer), and RF is not my specialty, more in the HVAC, switching power supplies, motor controls and microcontroller apps, but I know enough to tell you're an EE too; and I agree with all your points; I was, on the one hand, trying to simplify the subject; and on the other hand, to destill current usage and applications of radar, rather than cover the whole field of possibilities, such as using low power signals with large receivers, triangulation methods and whatnot. And I'm not even sure I managed to simplify it enough.

Great find, that bar rumor! I did not remember it at all.

WRT IFF:
We did a huge brainstorm about this at the WCU forum. It all started when Hellcat decided to remove IFF from WCU. Don't ask me why; he's the Vegastrike top developer, not sure why he was doing stuff with WCU. But whatever the reason, his reasoning as I heard it, was that IFF did not make sense, since anyone could just hack the transponder and make "him"self look like a militia while being a pirate, or whatever.
At the same time he gave Talons jump drives.

The result was disastrous: Suppose you were running the missions for Tayla and wanted to repair your relations with the militias by sweet talking to them. You'd come out of a jump poing into a cloud of Talons, and some were pirates, some where retros, some were militias, and you couldn't tell who was who, to speak to them, so the only choice was to run away, and then they'd follow you through jump points.

So that got me thinking. How does IFF work, and is it really hackable.
Premise 1: If it were hackable it wouldn't be there at all. So it isn't.
Premise 2: Ships don't have a faction; pilots do.
Premise 3: Premises 1 and 2 make sense.
Conclusion 1: You can't hack the faction of your transponder because it doesn't have a faction code; all it identifies is the damned ship; nothing less, nothing more.
Premise 4: Hard drives are pretty good in the 27th century.
Conclusion 2: Your nav computer has a database of all ships and it stores the last known faction for whoever owns or pilots that ship.
Premise 5: One lands often
Conclusion 3: Your database is updated every time you land at a station automatically. If you got attacked by a ship, the data from your ship's log is uploaded to the distributed database, so that other ships will benefit of your experience. That is, if a ship was considered merchant, but it gets stolen by a pirate, after a couple of attacks on merchant ships, the distributed database will have caught on with the fact.

The advantage with this model of how IFF works in Privateer is that it explains away what we experience in-game without necessitating any changes. But it does raise a couple of questions:

1) Wouldn't pirates hack the transponders to change the ship ID?

I think that ship ID's could be like 700 digit prime numbers, or something very unique you can't just randomly produce. Primality is one simple property but one could use more sophisticated numeric properties.
The number could be etched into the transponder chip, rather than stored in some kind of EEPROM or FLASH. I.e.: Expensive and non-hackable. And when a ship is manufactured, the engines, nav computer and other vital parts could all have minitransponders with the same number, which periodically check on each other; so you couldn't just change the main transponder and expect the ship to work. Even the ship manufacturers could not mess with the numbers, since there would be an enumberation and escrow government agency that issues preprogrammed transponder sets.

2) Wouldn't computers be programmed to show authorities always as friendly so that you cannot target them?
Pointless, because the nav computer software could easily be hacked, and to have such a feature might create a false sense of security among its beneficiaries which migh result in worse outcomes that the simpler approach of letting the nav computers serve their owners best interests.

[micheal_andreas_stahl]

1) Wouldn't pirates hack the transponders to change the ship ID?

I think that ship ID's could be like 700 digit prime numbers, or something very unique you can't just randomly produce. Primality is one simple property but one could use more sophisticated numeric properties.
The number could be etched into the transponder chip, rather than stored in some kind of EEPROM or FLASH. I.e.: Expensive and non-hackable. And when a ship is manufactured, the engines, nav computer and other vital parts could all have minitransponders with the same number, which periodically check on each other; so you couldn't just change the main transponder and expect the ship to work. Even the ship manufacturers could not mess with the numbers, since there would be an enumberation and escrow government agency that issues preprogrammed transponder sets.

There would have to be experts who can do this and computers. I know for a fact that pirates are not that stupid and backward.

So that got me thinking. How does IFF work, and is it really hackable.
Premise 1: If it were hackable it wouldn't be there at all. So it isn't.
Premise 2: Ships don't have a faction; pilots do.
Premise 3: Premises 1 and 2 make sense.
Conclusion 1: You can't hack the faction of your transponder because it doesn't have a faction code; all it identifies is the damned ship; nothing less, nothing more.
Premise 4: Hard drives are pretty good in the 27th century.
Conclusion 2: Your nav computer has a database of all ships and it stores the last known faction for whoever owns or pilots that ship.
Premise 5: One lands often
Conclusion 3: Your database is updated every time you land at a station automatically. If you got attacked by a ship, the data from your ship's log is uploaded to the distributed database, so that other ships will benefit of your experience. That is, if a ship was considered merchant, but it gets stolen by a pirate, after a couple of attacks on merchant ships, the distributed database will have caught on with the fact.

Makes sense. It would be interesting if someone borrowed your ship, comitted a crime then returnec it. Dispite it being so far in the future it would still be the same as today. Someone nicks of with your ship, commits a crime and you get the blame because it is your ship. But, I like it.

I also like the idea of having active and passive modes of radar with different radar sweeps.

[chuck_starchaser]

The transponder could only be hackable if there was a way to reprogram it. That's why I suggested its program is etched into the silicon, rather than stored in any kind of non-volatile memory. There'd be absolutely no physical way to hack it. This is doable today; just too expensive with current technology, since etching masks cost tens of millions of dollars, and you'd have to change the mask for each chip you produce.

Different radar sweeps would be quite a challenge to model. We can postpone that to "some day", but active/passive modes should be quite doable. Currently I'm looking at armor code, but later I'll take a look at radar code, see if I can figure it out.

[Sunfire]

I'm an EE (Electrical Engineer), and RF is not my specialty. I was, on the one hand, trying to simplify the subject; and on the other hand, to destill current usage and applications of radar, And I'm not even sure I managed to simplify it enough.

i feel as tho i should apologize... i certanly didnt mean to step on your toes, and i was just thinking about what would be possible in space... when you dont have to worry about atmosphere and the dang planet getting in the way... furthermore, my comments may or may not have helped anyone understand it better... if the latter is the case, then i aplogize again...

lol... and you could say i know a bit about RF...

The result was disastrous:

yick....

So that got me thinking. How does IFF work, and is it really hackable.

huh... never really thought about it past premise 3

1) Wouldn't pirates hack the transponders to change the ship ID?

I think that ship ID's could be like 700 digit prime numbers, or something very unique

they dont even need to be that...

see... this is the thing, in OP...IFF is there to
a. let you know immediatly who is going to attack you and whats what.
b. use friend or foe missles and,
c. designate ships only... your computer decides who is hostile and can decide in a moments notice to change its mind if the environment changes... furthermore, you can lock onto and destroy anybody... your compy does not block you from shooting your guns or any other missle at a friendly.

if pirates make themselves milita, they couldnt use FF missles against milita. furthermore, if they changed the apperance of their fighters and everything to mimic milita, soon as the get near the pirate base, boom! still furthermore, the merchant who gets attacked's compy will designate them as hostiles the minute they open fire, no matter how badly they say theyre milita....

but wait, couldnt they still use it to smuggle?
A. how many times do you get scanned everywhere you go?
the penalty for smuggling is death in the game universe.... dont matter who you are....

but wait, couldnt they just turn off iff to evade your missles?
A. no, because whether its off or on makes no difference if youre hostile. the IFF beacon is there to prevent FRIENDLY fire... meaning... that missile goes to any ship that the compy desingnates NOT friendly... not NOT enemy... and if YOUR beacon is destroyed, and you launch two FF's, they might just turn around and nail you. also, the feds might just think youre flying a stolen ship if it has no IFF code... (hey look... they ground off the serial number)

i brought up IFF because it HAS to be off if youre in silent mode... to be in silent mode, you have to be an RF black hole. zero transmissions... submarines can sit at the bottom of the sea for quite some time listening and crusing in slo-mo... the minute they kick up their props tho, they might as well be using active radar....

thats the neat thing about passive mode, you know that there is something there... but nothing else... you might have some really good optics that can focus on it, (and you do... target camera anyone?) so you know the ship type, but you have no idea just who's in that talon...

a loophole i thought of for engines and inbound jumps.... there is RF noise coming from it... but its too low frequency for your antenna to pick up.

... and you could say that afterburners ruin the engine harmonics, and AB's paint you just as well as if you were in active mode....

thereby, in gameplay the rules for passive mode are this:
1.you can pick up and ID anyone who is active
2.you dont exist till the active ship gets close enough
3.you have to trip over other passive ships to know theyre there. (see them with your own 2 eyes)
4.absolutly no one knows your intent and who you are till you go into active mode. even if theyre in active and have you in target lock, they still only know what your ship looks like... nothing more.
5.passive mode coms have to be optical
6.you can jump and hide... but you cannot run... your speed is limited to X amount in passive and absolutly NO afterburners. (radiation threshold and engine harmonics)
7.the moment youre in active, the jig is up... everyone knows everything about you, and if theres some ships that have been looking for you... they'll come out of hiding right about now... (hope you didnt tick anybody off )

the more i think about this... the more it seems that OP's universe is like this.... the drone in the opening movie gets blasted because he doenst have iff... ships dont actually spawn, they just become active... *ie: come out of nowhere*

also, the shortest distance between 2 points is a straight line: (unless you use jump drives ) there actually ARE trade lanes... and pirates scan them with their LR optics.... thats why, you go into auto (youre flying straight) then you drop out of it when hostiles or 'roids appear... the compy tells you to get your butt out of bed, we've got problems.

[chuck_starchaser]

1) Wouldn't pirates hack the transponders to change the ship ID?

I think that ship ID's could be like 700 digit prime numbers, or something very unique

they dont even need to be that...

see... this is the thing, in OP...IFF is there to
a. let you know immediatly who is going to attack you and whats what.
b. use friend or foe missles and,
c. designate ships only... your computer decides who is hostile and can decide in a moments notice to change its mind if the environment changes... furthermore, you can lock onto and destroy anybody... your compy does not block you from shooting your guns or any other missle at a friendly.

if pirates make themselves milita, they couldnt use FF missles against milita. furthermore, if they changed the apperance of their fighters and everything to mimic milita, soon as the get near the pirate base, boom! still furthermore, the merchant who gets attacked's compy will designate them as hostiles the minute they open fire, no matter how badly they say theyre milita....

but wait, couldnt they still use it to smuggle?
A. how many times do you get scanned everywhere you go?
the penalty for smuggling is death in the game universe.... dont matter who you are....

but wait, couldnt they just turn off iff to evade your missles?
A. no, because whether its off or on makes no difference if youre hostile. the IFF beacon is there to prevent FRIENDLY fire... meaning... that missile goes to any ship that the compy desingnates NOT friendly... not NOT enemy... and if YOUR beacon is destroyed, and you launch two FF's, they might just turn around and nail you. also, the feds might just think youre flying a stolen ship if it has no IFF code... (hey look... they ground off the serial number)

Interesting; so there's actually no advantage to hacking the IFF. Perhaps having complete control of IFF might be a holly grail, like being able to look like a friendly the moment you launch an FF missile at them, then switch back once the missile is gone; but very hard to implement. I think transponders would still use highly secure protocols and tamper-proof packaging, but given your analysis, they look a lot more secure now.

i brought up IFF because it HAS to be off if youre in silent mode... to be in silent mode, you have to be an RF black hole. zero transmissions... submarines can sit at the bottom of the sea for quite some time listening and crusing in slo-mo... the minute they kick up their props tho, they might as well be using active radar....

Good point; transponders should, and would, have a "silent" mode; otherwise there'd be such a big market for transponder-free ships the enumeration authority would lose control. And come to think of it, a ship running in active mode but with no transponder would probably be ID'd as "kilrathi" by your nav computer. Unless kilrathis have their own transponder standard, which can be distinguished from confed.

thats the neat thing about passive mode, you know that there is something there... but nothing else... you might have some really good optics that can focus on it, (and you do... target camera anyone?) so you know the ship type, but you have no idea just who's in that talon...

And you don't know the range, either. Yeah, this is going to take some time to program, I think; lots of details...

a loophole i thought of for engines and inbound jumps.... there is RF noise coming from it... but its too low frequency for your antenna to pick up.

... and you could say that afterburners ruin the engine harmonics, and AB's paint you just as well as if you were in active mode....

Right. For a very simple implementation, we could have several emission ranges, say,
Active radar emission range 1000 klicks
Afterburner emmission range 500 klicks
Engines at max emission range 200 klicks
Engines at half range 100 klicks
(or better yet, make the range variable with engine throttle)
Then, active radar bounce back about 50 klicks
and lock range about 10 klicks
Or something along the lines.

thereby, in gameplay the rules for passive mode are this:
1.you can pick up and ID anyone who is active
2.you dont exist till the active ship gets close enough

Except for engines emissions, as you pointed out.

3.you have to trip over other passive ships to know theyre there. (see them with your own 2 eyes)

Ditto.

4.absolutly no one knows your intent and who you are till you go into active mode. even if theyre in active and have you in target lock, they still only know what your ship looks like... nothing more.

Good point. Come to think of it, your passive mode radar should provide a rough estimation of signal strength so you know whether the bounce of active radar off your ship is likely to be detected. And/or some "Lock" indicator...

5.passive mode coms have to be optical

You mean to be able to com with friendlies in passive mode within your flightgroup? Good point, and in WC there's optical link between fighters in a squadron.

6.you can jump and hide... but you cannot run... your speed is limited to X amount in passive and absolutly NO afterburners. (radiation threshold and engine harmonics)

Ideally we'd model a radiation pattern around the ship, with a stronger heat signature from the back, stronger active radar signature from the front, or depending on sweep mode. No big deal programming this, but plugging it into the engine may be a huge challenge.

7.the moment youre in active, the jig is up... everyone knows everything about you, and if theres some ships that have been looking for you... they'll come out of hiding right about now... (hope you didnt tick anybody off )

On the other hand, if you've managed to skirt around enemies in an AF for the first half of your trip to another jump point, they might not be able to catch up with you.

the more i think about this... the more it seems that OP's universe is like this.... the drone in the opening movie gets blasted because he doenst have iff... ships dont actually spawn, they just become active... *ie: come out of nowhere*

Two damn good points!

also, the shortest distance between 2 points is a straight line: (unless you use jump drives ) there actually ARE trade lanes... and pirates scan them with their LR optics.... thats why, you go into auto (youre flying straight) then you drop out of it when hostiles or 'roids appear... the compy tells you to get your butt out of bed, we've got problems.

Exactly. This never made any sense to me, but with the player having the ability to run in silent mode, this whole enigma suddenly makes sense.

[micheal_andreas_stahl]

if your on passive mode and someone comes up behind you and locks on to you, would it show up in your cab that someone has locked onto you, does it tell you that they have locked onto you.

[chuck_starchaser]

Technically, "locking" means that the radar dish stops performing a sweep, and instead focuses on a single object; so, whether the mode is active or passive is orthogonal to the issue of locking. However, the normal use of the term locking means that you're in active mode and bouncing radar signals off your target that can guide a missile to it. So, I would say yes: Let lock imply active mode, and if someonelocks you you'll know it immediately. Though someone could sneak behind you and use the guns instead.

And, come to think of it, using guns should be roughly equivalent to putting on afterburner, in terms of emmissions.

[Zool]

I think I understood more when Dilloh and Rlaan were posting in german.......

[chuck_starchaser]

Hahaha, sorry; I don't know a word of German; I could translate to Spanish if that helps

Well, if it's about the last post, what I mean is that, okay: At the nose of fighter aircraft there's usually a radar. Think of it like a little satellite dish. It has motors so that it can be oriented up and down and to the sides. In a typical sweep mode it moves very fast from right to left, but slowly up and down, so as to cover a rectangular angle area in front of you. When you lock a bogie, it means that it stops moving like that, and instead it follows the target you locked. And what I was saying is that, technically, you could do that without sending a signal. I.e.: locking onto the electromagnetic emissions of the target, in passive mode. But the common use of the term "lock" is to lock a target in active mode, that being, when your dish is sending bleeps that hit the target and are reflected back, which is essential for guiding most radar seeking missiles; or at least essential for them to acquire the target.
Depends on the type of missile. Some missiles require that you "illumine" the target continuously, as they only have a passive radar receiver. Some missiles have active radar. Then again, others don't use radar at all, and instead lock onto the heat signature. And the most modern missiles have image recognition. Actually, I'm not sure whether they are in service yet, but I used to see job ads by Northrop and other companies describing image recognition projects for advanced missiles, years ago.

[Sunfire]

I think I understood more when Dilloh and Rlaan were posting in german.......

let me say a few things about radar and Radio Frequency(RF) waves

you can think of RF waves in kind of the same way as light waves

a comparison then can be made about an isometric antenna and a directional antenna...

a naked light bulb can be thought of as an isometric antenna, a flashlight would then be a directional antenna. if you take the reflector away from the flashlight, then you have a weak amount of light in all directions(isometric radiator)... put the reflector back on, you still have the exact same amount of light, but it all goes in one direction... (directional beam)

you can think of radar like this.... say youre in a really big room with no windows, the lights are out, and the only thing you have to find your way to the lightswitch is one of those mini flashlights. you know that somewhere on the 20'x20' wall in front of you is the lightswitch (it could be anywhere bc its not in the normal place for lightswitches) so you have to search the whole wall with your mini flashlight... the best way to do this would be to use a grid like pattern to make sure you leave no areas behind. (you couldnt take the reflector off and use it like a candle, because theres far too much area, and your eyes arent that good...) this is what is meant by 'illuminating' the target. once youve found the switch, you keep pointing the light at the switch (this would be radar lock) so you can then hit it with your 20' long stick to turn on the lights

any questions?

[Sunfire]

Interesting; so there's actually no advantage to hacking the IFF. Perhaps having complete control of IFF might be a holly grail,

again, IFF is like a serial number or licence plate... the compy on your own ship decides its relationship value to you...

a ship running in active mode but with no transponder would probably be ID'd as "kilrathi" by your nav computer. Unless kilrathis have their own transponder standard, which can be distinguished from confed.

the Kats probably would... they have FF missles too... ships with no IFF would probably read 'unknown'

Right. For a very simple implementation, we could have several emission ranges, say,
Active radar emission range 1000 klicks
Afterburner emmission range 500 klicks
Engines at max emission range 200 klicks
Engines at half range 100 klicks
(or better yet, make the range variable with engine throttle)
Then, active radar bounce back about 50 klicks
and lock range about 10 klicks
Or something along the lines.

i know this is kind of a rough sketch... but heres some ideas...

active radar and AB emission would be about the same range (really sloppy harmonics)
engine range i would cut substatially... or better yet, make logarithmic... PLEASE dont limit me to 1 kps in AFs.... say.. 10 kicks for half throttle and 200 klicks for full throttle
active radar illumination would be roughly a quarter of the length that it can be 'heard' (using the same antennas)

And/or some "Lock" indicator...

definately...

You mean to be able to com with friendlies in passive mode within your flightgroup? Good point, and in WC there's optical link between fighters in a squadron.

yes, but this doesnt really have to be modeled, just needs to be an explanation for secure TX... and ANY TX in passive...

Ideally we'd model a radiation pattern around the ship, with a stronger heat signature from the back, stronger active radar signature from the front, or depending on sweep mode. No big deal programming this, but plugging it into the engine may be a huge challenge.

Ack! i didnt even THINK about IR.... DOH
Obviously its ingame... (HS missles) ok, so your sensor array would pick up RF, IR and optical wavelengths, then the compy would put the 3 together to tell you all sorts of stuff about the ship (but still no range or positive ID) (doppler should tell you its speed and direction tho)

the thing about the other ship in active is, it tells you where to point your sensors...

you could also think of active radar as a game of 'marco polo' where passive would be just listening for someone to say 'marco'

something about IR... youre not in an atmosphere, but you ARE in (nearly) absolute zero. we dont know much about engines and exhaust, but we do know that the exhaust ports would get hot. IR rad would be zero from the front, and quite high near the back as long as you can 'see' the exhaust ports. so someone coming straight at you at full burn would still have an IR profile of zero (RF transmissions would be another matter... lol engine harmonics again )

from a modeling perspective, you could merge RF & IR into one sphere and just arbitrarily say anyone in passive is passive, anyone breaking the speed limit or using comms or guns or any other rule is 'active'

a point about missles, missles have a pretty short range as it is, and by the time they get close enough, their engine signature would show up on sensors... plus the direction they came from would be extrapolated thereby rendering the attacker 'active'

On the other hand, if you've managed to skirt around enemies in an AF for the first half of your trip to another jump point, they might not be able to catch up with you.

yup... as long as you dont dally too long... this is kind of the point of running in passive mode in the first place... well... that and piracy

[chuck_starchaser]

Interesting; so there's actually no advantage to hacking the IFF. Perhaps having complete control of IFF might be a holly grail,

again, IFF is like a serial number or licence plate... the compy on your own ship decides its relationship value to you...

LOL, you grasp my own theory easier than I do.

Okay, so how's this:
(I've no idea about actual absolute figures, so I'm just normalizing to 1000 klicks)
Active radar detection 1000 klicks
Afterburner detection 1000 klicks
Gun firing detection 1000 klicks
Active radar bounce 250 klicks
Engines detection 100 klicks * throttle %^2 (squared)

Indeed, there should be stuff from the megahertz band, through VHF, UHF, microwave, IR, visual, UV and X-ray, to make this complete; and the radiation pattern for each band subdivided isospherically; but such code was promised a million times and never delivered... I'd rather simplify and get at least a monobandic, isometric model that at least has active and passive modes and works. TFX's model was amazing. I remember one of the missions with an F117, had to bomb a site twice, and there were 2 fighter planes flying around the site. So I would try to present my profile to their backs all the time, getting away in like a slowly growing spiral, so as to never pass in front of their eyes, much less show them my engines. But had to do two passes, and they were two planes, so when I couldn't be on the back of both, I'd turn my engines off and glide... Pretty hard mission.

[Sunfire]

LOL, you grasp my own theory easier than I do.

hehe...

Okay, so how's this:
(I've no idea about actual absolute figures, so I'm just normalizing to 1000 klicks)
Active radar detection 1000 klicks
Afterburner detection 1000 klicks
Gun firing detection 1000 klicks
Active radar bounce 250 klicks
Engines detection 100 klicks * throttle %^2 (squared)

making half throttle be detectable at 25k, 10% at 1k (unless i left my math brain in the sink again... ) i like that... very nice...
but it leads me to this... im no good with the absolute figures either... and am perfectly willing to fudge them somewhat for gameplay as long as its reasonable... you could even reduce it by a factor of 10... but i would say keep the relationships pretty much there... why? because then it makes no sense to go active... if active radar bounce is only good for 25k while it broadcasts you 1000k... thats a really hefty penalty... (and physically not rational) but again... gameplay takes precidence. (tho i suppose the engine relationship could be a little fudged too..)

Indeed, there should be stuff from the megahertz band, through VHF, UHF, microwave, IR, visual, UV and X-ray, to make this complete; and the radiation pattern for each band subdivided isospherically;

well.. Mhz, vhf, and low uhf probably not... you need some pretty big antennas to get any kind of decent range... lol and theyd rapidly get unwieldy if youre using them for radar and this was kind of the basis for my loophole... low frequency stuff wouldnt be heard too well... (ie: jumping, engine harmonics)but also of course, low amplitude of any frequency (ie engine noise at half throttle)

anyways... youre right... and really... why stop there? why not do the Whole shebang?

I'd rather simplify and get at least a monobandic, isometric model that at least has active and passive modes and works.

definatly... single band isometric works for me! (because really... once you pick up something on ANY band... youd turn your sensor suite to the bogey anyways)and it follows a golden rule... the simpler implementation, the better...

TFX's model was amazing. I remember one of the missions with an F117, had to bomb a site twice, and there were 2 fighter planes flying around the site. So I would try to present my profile to their backs all the time, getting away in like a slowly growing spiral, so as to never pass in front of their eyes, much less show them my engines. But had to do two passes, and they were two planes, so when I couldn't be on the back of both, I'd turn my engines off and glide... Pretty hard mission.

[/quote]
wow... sounds alot like a nightmare...

[z30]

Different radar sweeps would be quite a challenge to model. We can postpone that to "some day", but active/passive modes should be quite doable. Currently I'm looking at armor code, but later I'll take a look at radar code, see if I can figure it out.

Thank you - this was one of my great frustrations when this project started. While PR is very, very configurable there really are some things that need a change in the code base for them to work.

[micheal_andreas_stahl]

If you sit on AB would you be able to be easier to be found as your putting more heat out your backside?

[Zool]

something about IR... youre not in an atmosphere, but you ARE in (nearly) absolute zero. we dont know much about engines and exhaust, but we do know that the exhaust ports would get hot. IR rad would be zero from the front, and quite high near the back as long as you can 'see' the exhaust ports. so someone coming straight at you at full burn would still have an IR profile of zero (RF transmissions would be another matter... lol engine harmonics again).

Unless being in space (nearly absolute zero) means INSTANT cooling, then if you're looking at a target front on and said target is on AB's then the heat flare would still be visible, as it would radiate outwards in a semi spherical pattern towards the rear, and even if not on AB's wouldn't there be some residual "heat flare"behind the ship radiating around the rear of the ship thus giving it an IR profile from the front?

[z30]

If you sit on AB would you be able to be easier to be found as your putting more heat out your backside?

Assuming infrared sensors are being used - just like the heatseekers.

[Sunfire]

Unless being in space (nearly absolute zero) means INSTANT cooling,

hahaha... good point...

then if you're looking at a target front on and said target is on AB's then the heat flare would still be visible, as it would radiate outwards in a semi spherical pattern towards the rear, and even if not on AB's wouldn't there be some residual "heat flare"behind the ship radiating around the rear of the ship thus giving it an IR profile from the front?

well... my point here is that we (well.. I) have no idea just exactly HOW the engines get thier power nor what their emissions patterns are likely to be... we know that they do have emissions bc we have exhaust ports... furthermore, there is no atmosphere to absorb the heat thereby causing a heat flare in the surrounding medium... also, the exhaust pattern is likely to be very focused and conal rather than spherical for efficency... (hmmm.... this has suddenly become very interesting to me... imagine an experiment where you fire a torch in a complete vacuum, then look for IR patterns from the exact front...) again... exhaust being very focused, your ship would probably block the IR signature... one last thing... the WC game cannon says HS missles wont work from the front, only from the rear.

[chuck_starchaser]

Officially, intra-system engines are ion engines. Yeah, I know they produce milligrams of thrust, but Origin doesn't know it. Anyhow, assuming the are producing oodles of ions to get the kinds of thrust they get, I imagine the grids would get pretty toasty. No heat trails in vacuum, but definitely hot parts for IR targetting to play with, no problemo. Additionally, ion engines produce a bluish "plume" due to the de-ionizing injectors at the exhaust, which look pretty much like the engine exhaust from Vegastrike; --not the "supernova" but the other; the longish one.

[Zool]

... furthermore, there is no atmosphere to absorb the heat thereby causing a heat flare in the surrounding medium...

But the heat from the exhaust just doesn't simply and instantly vanish.

Anyhow, assuming the are producing oodles of ions to get the kinds of thrust they get, I imagine the grids would get pretty toasty. No heat trails in vacuum, but definitely hot parts for IR targetting to play with, no problemo.

Yes, that's it exactly.

[Melonhead]

One more thought to add to our long list of things to do...

If someone else is in active, but you're in passive, you get an azimuth and elevation cut on them right away, but no range--as already discussed. However, as you and they continue to fly along, you will start to get an idea how far away they are based on how much change there is in the direction to the other ship. Closer means the angles will change more rapidly; farther away, they'll change more slowly. Since both objects are moving in 3D, it won't be a simple direction-finding exercise, but this is 2669...perhaps in X seconds, you get a readout of close-midrange-far.

Also, since it's 2669, multiple antennas on your ship might be able to figure out a rough approximation of range, basically using parallax (to oversimplify quite a bit). This could be something else to buy; perhaps it gives you a more precise range readout in Y seconds.

And, just for fun...if you point a passive antenna at someone radiating (in an attempt to get that range info about them), they will likely get a HUGE radar return off your antenna, which will let them see you far beyond normal range--this is the principle that fiberglass sailboats use when they hang a radar reflector up in the rigging, so big ships will see them on radar.

[chuck_starchaser]

One more thought to add to our long list of things to do...

If someone else is in active, but you're in passive, you get an azimuth and elevation cut on them right away, but no range--as already discussed.

No accurate range in RL (judged by signal strength); no range at all perhaps in game. Though perhaps you can passively lock the radar on the target, then use a telescope to resolve an image, and if the craft type is recognized, and its size is known, then the optical system can give you a pretty good idea of its distance.

However, as you and they continue to fly along, you will start to get an idea how far away they are based on how much change there is in the direction to the other ship. Closer means the angles will change more rapidly; farther away, they'll change more slowly. Since both objects are moving in 3D, it won't be a simple direction-finding exercise,

Good point, but that'd be rather complex to compute, depends on "relative speed" (i.e.: The other ship may be moving too) as well as on distance; so we'd perhaps get a range of possible distance; which complicates representation. But I also like the gameplay aspect of the player, rather than the computer, having to rely on "gut feeling" to estimate distance.
Anyways, I haven't done almost any engine work, so my goals are very modest: First to get the most basic passive mode working. IF I succeed, then maybe refine it a bit to add asymmetric emission patterns. I think this would be easier to do and much more valuable to gameplay. Third highest priority would be asteroid field obscuring. Fourth: sweep modes.

but this is 2669...perhaps in X seconds, you get a readout of close-midrange-far.

I'm fond of saying that the speed of technology advancements is a bit overrated. Most of the gadgetry we have today was invented in the first half of last century, like radio, telephones, planes, rockets, computers, cars, television... up to the moon landings. Ever since then there's been improvements and refinements and miniaturization and recombinations of those inventions; but nothing much *really* new has been invented. Fuel cells and a few other things. One more generation and I think science fiction will lose its prophetic reputation and mystique.

Also, since it's 2669, multiple antennas on your ship might be able to figure out a rough approximation of range, basically using parallax (to oversimplify quite a bit). This could be something else to buy; perhaps it gives you a more precise range readout in Y seconds.

I really doubt this one, from a required accuracy point of view.

[micheal_andreas_stahl]

No accurate range in RL (judged by signal strength); no range at all perhaps in game.

Huh? What's RL again? No range in the whole game? HUH!?

I'm fond of saying that the speed of technology advancements is a bit overrated. Most of the gadgetry we have today was invented in the first half of last century, like radio, telephones, planes, rockets, computers, cars, television... up to the moon landings. Ever since then there's been improvements and refinements and miniaturization and recombinations of those inventions; but nothing much *really* new has been invented. Fuel cells and a few other things. One more generation and I think science fiction will lose its prophetic reputation and mystique.

Amen. I'm with you mate. I was waiting for some one to that pointout.