										Rev 1 (11-14-97)
				VISUAL / IR / RADAR / ESM /  SONAR
  				   FORMULA SPREADSHEET NOTES


	H2 Sensor calculations - What went wrong:  Radar, ESM, Visual, and IR Calculations in H2 are not based on any sort of normal electromagnetic (i.e. 1/R^2) phenomena.  Instead, the inverse log of the sensors search input plus the targets cross section is used, with a few modifiers.  While this gives OK ranges for cross sections in the middle area, low and high cross sections would be detected at wildly inaccurate ranges.  Low cross section ranges would be way too low, while ranges for targets with high cross sections would be outrageously high.  The good folks at 360 Inc. "fixed" this problem by bumping all sensor input sensitivities way, way up, thus giving sensors good performance against low cross section targets.  Unfortunately,  both the mid and high cross section targets would now be picked up at extremely high ranges.  This was "corrected" by adding a Maximum range value, which in effect "cuts off" the sensor from seeing any further than it should.  The end result is that most sensors will automatically detect all but the smallest targets as soon as they cross that sensor's maximum range, provided that target is above the horizon.  

	Proposed fixes:  Two fixes are needed to bring the H2 sensor system back near reality.  First of all, Sensor Input Values must be reduced.  Second, high and low Cross Sections need to be "scrunched" more towards the center.  Both fixes are done using the accompanying spreadsheet by modifying the formulas used to come up with these values.  Both fixes must be used simultaneously.  

Cross Section Calculation Notes:
Overview:   Cross sections were not always based on the proper factors.  In most cases, they were determined as if the ship/aircraft were a rectangular slab of metal with the length/width of the entire ship or aircraft, all of it pointing at a nice, 90 degree angle from the sensor.  They did not take into account the fact that, for example, most ships have nothing above the main deck for roughly half of their length, or that aircraft tails do not run the entire length of the aircraft.   For the accompanying spreadsheet, the first set of columns are for the dimensions of the platform.  All dimensions are in meters.  The second set of columns are used for inserting modifiers as listed below (Page 3).  Modifiers are not to be added together- use the single one which most fits and place it in the "Modifiers" column.  If the modifier states "-# from result" then do not use this in the Modifiers column.  Instead, subtract the number from the result the spreadsheet gives you.  

Aircraft:  All aircraft cross sections needed some modifications.  Visual Cross Sections especially needed some serious reductions. In H2 with the old numbers, an F-18 can be seen almost 20 miles away with the naked eye.  Anyone who has ever been to an airshow knows that, without the smoke machine on, most fighter aircraft are impossible to see more than a few miles away.  Air-to-air visual sighting can be even more difficult.  For swing-wing aircraft, use span at minimum sweep.  Examples of  Radar Stealth Modifiers:  F-117: 5, B-2: 6, F-18E: 0.1, Grippen: 0.5. 

Helicopters:  Comments under Aircraft apply here as well.  Width and length of the fuselage are rarely given in references.  Use rotor diameter = length and (height/2) = width.  For coaxial rotors use length = (1.5*rotor diameter), for attack helicopters use width = (height/3).  Examples of Radar Stealth Mod:  RAH-66 Comanche:  0.9.  

Missiles: Comments under Aircraft apply here as well.  Examples of  Radar Stealth Mods:  RAM application (late modal Tomahawks): 0.75.  Missile shape and RAM application (JSOW, SLAM-ER): 0.95.

Torpedoes:  Torpedoes can be picked up by radar, IR and visual sighting when on the surface (i.e. attacking surface ships).  All values need to be adjusted (not just passive and active sonar). Use the following values depending on Torpedo Type:

324mm Electric (Most small ASW torps): 	V -150/-100/-150  IR -300/-300/-300  R -900/-900/-900                                            PS 60/62/64  AS 1/5/1
324mm Turbine (Mk.46, Mk.50):		V -100/-50/-100  IR -200/-200/-200  R -900/-900/-900                                             PS 70/72/74  AS 1/5/1
533mm Electric (Tigerfish):		V -50/-25/-50  IR -200/-200/-200  R -900/-900/-900                                               PS 65/67/69  AS 5/10/5
533mm Turbine (Mk.48):			V -5/5/-5  IR -175/-175/-175  R -900/-900/-900                                                   PS 77/79/81  AS 5/10/5
650mm Turbine (Type 65):		V 5/10/5  IR -150/-150/-150  R -900/-900/-900                                                    PS 82/84/86  AS 10/15/10

Ships/Subs:  Radar cross sections needed reduction, especially for larger targets such as carriers.  In addition, sea clutter does not seem to have been modeled and should be factored in as well (to a limited extent).  Height is not a dimension readily available in most references.  Since draft generally provides a good ratio to freeboard and is readily available, it is used instead.  Use Length overall (not length at waterline).  Use Draft not including sonar dome (or draft including sonar dome - 3 meters).  For catamarans or SWATH ships, multiply (draft * 1.5).  Examples of IR Suppression Mods:  Arleigh Burke: 0.8, SAAR V: 0.95.  Examples of Radar Stealth Mods:  Arleigh Burke: 0.7, Lafayette: 0.85, add RAM to any ship: 0.4.  Active and Passive Sonar changes are based on the work of Oliver Einhaeuser and are still considered experimental - although they already work much better than the values 360 originally had.  Unlike what the 360 manual states, passive sonar cross section does not directly depend on ship/sub size.  Use the following table and extrapolate:

TYPE				X-Section Range	        Example                                  Surface Vessels
                    
Nuclear Supercarrier		115-125		        Nimitz
Nuclear Cruiser/Supertanker	100-106		        Virginia, Kirov
Average Cruiser		        90 - 98			Leahy, Slava
Average Destroyer/Frigate	82 - 88			Sovremney, Tourville
Quiet Destroyer/Frigate	        74 - 80			OH Perry, Type 23, Spruance/Ticonderoga
Small Combatant		        70 - 80			Any PGM.

Submarines

Noisy nuclear sub		80 - 90			Echo II, Alpha
Average nuke / Older diesel	65 - 75			Victor III, Sturgeon, Tango
Quiet nuke / Later diesel	55 - 65			Los Angeles, Akula, Kilo, Type 209
Super quiet nuke/diesel	        50 - 55		        Ohio, Collins, Seawolf.

		

Facilities:  All facility cross sections needed massive changes.  The good (?) folks at 360 do not seem to have taken the time to be even remotely accurate with facility numbers.  Using current numbers, a Stinger Team can be detected by an AWACS at over 200 miles!!  In reality, ground clutter will make it impossible for most radars to detect all but the largest ground structures.  Most tactical units such as SAM batteries will be camouflaged and/or dug in, making visual sighting extremely difficult as well.  Only IR sensors really have a decent chance of detecting tactical ground units at any significant distance.   Modifiers:  Most tactical units (SAM or SSM batteries, HQs, AAA Guns) should use 0.5 modifiers for both visual and radar.  Man portable SAMs should use the 0.9 modifier for both visual and radar.  Most tactical units (except man portable SAMs and non-self propelled AAA) should use the 1 modifier for IR.







Sensor Input and Output Value Calculation Notes:

Overview:  Ranges used should be the maximum range against a very large (B-52 or CVN) target.  Use this same range figure for the sensors "Maximum Range" figure in PFEdit or the H2 Platform Editor.  For FC radars, use max range vs. a 1 meter^2 target multiplied by 3.2, or max Range * 2.

Radar/ESM:  The Radar Output value is needed for ESM counter-detection.  For Low Probability of Intercept Radars (i.e the ones on the B-2 or F-22), multiply this figure by 0.6 - 0.5, depending on how advanced the technology is (0.5 for the most advanced).  For determining ESM Passive Input Values, use the following information and extrapolate:
			Type					Passive Input	     Max Range
	Early ESM systems					-640 to -660		350
	Current low-end systems  				-670 to -700		700
	Current high-end systems				-710 to -740+		1050


Sonar:  Active and Passive Sonar Input and Output parameters are based on the work of Oliver Einhaeuser and are still considered experimental.  

Active Sonar:
Unlike radar, active sonar range determination is based on a number of factors, including input and output values, own ship noise and speed, and frequency of the sonar itself.  To determine an active sonars search input and output parameters, determine the maximum range of the sonar from published sources and extrapolate using the tables below.  The tables are based on the maximum range against a very large sonar target (i.e. an Oscar II side view).  The detecting sonar is considered to be on a quiet destroyer at 5 kts in sea state 0, in other words near optimum conditions.  For Torpedo sonar, find the values as above using the high frequency chart, but add -10 to the input value.  

LF Active Sonar:
			Output Value
Input Value	220	200	180	160
30	         23nm	 9nm	 4nm	 2nm
35	         13nm	 6nm	 2nm	 1nm
40	          9nm	 4nm	 1nm	 0nm
 

MF Active Sonar
			Output Value
Input Value	200	180	160	140
10	         18nm	 11nm	 6nm	 2nm
15	         14nm	 8nm	 4nm	 1nm
20	         11nm    6nm	 2nm	 0nm


HF Active Sonar
			Output Value
Input Value	160	140	120	100
-15	         7nm	 5nm	 3nm	 2nm
-10	         6nm	 4nm	 2nm	 1nm
-5	         5nm	 3nm	 1nm	 0nm


Passive Sonar:  Like Active sonar, H2 Passive sonar range determination is based on numerous factors, and is still in the experimental stage.  Submarine based hull sonars should have lower values than contemporary ship-based hull sonars (wave action against the hull), while western systems should have lower values than contemporary Russian or Chinese systems (better Signal Processing), up until the late 1980s at least.  Use the following table and extrapolate:

TYPE									Passive Input Value		.
Ultra-long range LF Towed Array  (SURTASS)					-120
Modern long range LF Towed Array (TB-16)					-68
Early LF Towed Array (SQR-18, Horse Tail)					-58
Modern LF Hull Sonar (SQS-53 w/SSQ-89)						-50
Early LF Hull Sonar (SQS-26, Horse Jaw) 					-44
Modern MF Hull Sonar								-36
Early MF Hull Sonar								-20
Modern Torpedo/Sonobouy								-25
Early Torpedo/Sonobouy								-15



Worksheet Notes:  

Overview:  Simply plug in any input value and cross section to find out what the maximum detection range for that sensor/target combination would be.  Examples of input values:  Visual (naked eye): -668, E-3 AWACS Radar (APY-2): -2130, average fighter radar:  -1865 to -2010.  

ESM:  Use the IR worksheet for ESM, substituting the target radars Output Value for Cross Section.  
 
Modifiers:


SHIP/SUB:

Visual:    none

IR:          Nuclear         		1
             IR Suppression    	.7-1 (1 being greatest)

 Radar:   Percentage of Cross Section Reduction as a decimal (ie 75% reduction = .75)


AIRCRAFT:

Visual:    none

IR:	Subsonic low-power jet		 5		(i.e. S-3 Viking, E-3 Sentry)
	Subsonic high-power jet   	10 		(i.e. AV-8 Harrier, A-6E Intruder)
	Supersonic jet			15
	IR Suppression 		       -30               from result

Radar:	Amount of Cross Section Reduction as a factor of 10 (ie 1,000x = 3, 10,000x = 4).


HELO

Visual:	 none

IR: 	IR Suppression   	-30 from result.

Radar:	Percentage of Cross Section Reduction as a decimal (ie 75% reduction = .75)


MISSILE:

Visual:	Rocket Powered		3

IR:	Subsonic      		1
	Supersonic   		2

Radar:    Percentage of  Stealth Cross Section Reduction as a decimal (ie 75% reduction = .75)
	Sea Clutter Mod:  Weapon flies at:	10m	-40 from result
					        20m	-30 from result
					        30m	-20 from result
					        40m	-10 from result


FACILITY:

Visual:	Unit likely dug in or camouflaged		.5
	Unit made up of humans only		        .9

IR:	Unit is likely dug in			-25 from result.
	Unit is a vehicle or uses a generator	 1
	Unit made up of humans only		-100 from result.

Radar:	Unit likely dug in or masked by terrain	.5
	Unit made up of humans only		.9

