The Stealth Concept as explained by Low Probability of Intercept and Low Observability
Dr Theodoros G. Kostis CEng MIEE Radar Concepts – Stealth Concepts
HELLENIC MILITARY ACADEMY, GREECE 3rd CryCybIW, Vari, 27th MAY 2016.
Kallima Inachis
Definition of Stealth General Definition the act of movement in a furtive, concealed, clandestine, unobtrusive or imperceptible manner that provides as low probability of intercept (LPI) as possible by an adversary by incorporating Low Observability qualities
Stealth Airplane Specific Definition the special design of an aircraft in geometry, emissions, modulations, coating, fuel and ordnance storage that contributes to low observability (LPI) by an adversary through weak overall signature composition (radar, IR, acoustic, optical for both tx & rx functions)
Therefore stealth includes movement & wake! It is different from hiding (ie. no wake)!
Stealth in High Entropy The outer colours and form or geometry of the asset are changed in an abstract form in order to blend with the environment
Ghillie Suit
Stealth in Medium Entropy Only the outer colours of the asset are changed in order to blend with the environment No form or geometry of asset is changed
Stealth in Low Entropy The outer colours, form or geometry of the asset are changed into a specific object usually in rich natural abundance in order to blend with the environment. Also the behaviour of the copied object is imitated.
Stealth Aircraft RCS = Small Bird RCS
Radar Stealth Concept
Radar Basic Points Radar Primary Early Warning Detection Technology for Aircraft Radar Detection: Threshold Logic Radar Detection Problems: Noise and Clutter Clutter: Unwanted Radar Returns hide Targets
Non-Cooperative Target No identification collaboration from the target therefore Identification Friend or Foe (IFF) decision is difficult.
Conventional Radar Basics Detection - Tracking - Recognition Threshold Logic
http://www.radartutorial.eu/18.explanations/ex10.en.html
Detected targets cross the threshold
Detection Probability Detection in Noise radar correclty sees a real target
Error Type Ι (False Alarm) radar displays a nonexistent target
prediction
real target
no target
positive
real positive
false positive
negative
false negative
real negative
Error Type ΙΙ radar does not display a real target
radar correctly does not display any targets
Radar Stealth Concept
Battlespace Dominance DENY SITUATIONAL AWARENESS TO ADVERSARY FORCES FOR CRUCIAL AMOUNTS OF TIME LEADING TO BATTLESPACE DOMINANCE
Stealth Supercruise Altitude Maneuverability See First – Shoot First – Kill First
Radar MASINT MASINT - Measurement & Signature Intelligence Other important Intelligence Gathering Methods applicable to aircrafts are: • • • • •
HUMINT ACOUSTINT RF/EMPINT IRINT VISINT
(Human Intelligence) (Acoustic Intelligence) (RF/Electromagnetic Pulse Intelligence) (Infrared/Heat Intelligence) (Visual Intelligence)
But Radar MASINT is first line of defence!
Military Radar Types Force Multiplier LPI (Stealth) Radar: The need to reveal(detect), track, classify or identify a non-cooperative target without being counterdetected by the non coop target
ISAR • Use the movement of the target to synthesize a larger virtual antenna than the physical • Obtain target imaging
• • • •
ω-k (range migration) Polar Format Range Doppler Chirp Scaling
Low Probability of Intercept
Pi - Probability of intercept Pd tOT Pi tSCAN Pi
probability of intercept
Pd
probability of detection
tOT
time on target
tSCAN
overall scan time
LPI Characteristics Low Sidelobe Antenna Irregular Antenna Scan Pattern High Duty Cycle – Wideband Good Power Management = Average Power Carrier Frequency – Correct Use of Radar Band Very High Sensitivity High Processing Gain Coherent Detection Monostatic-Bistatic Configurations
Increasing Pd •Bistatic/Multistatic Radar
•Optical Detection
•Wavelength Match
•ISAR & Stealthy Hotspots
•Infrared (heat) Detection
•Over-the-horizon Radar
Bistatic/Multistatic Radar RCS reduction techniques aimed principally at minimising monostatic RCS; bistatic geometry can intercept energy scattered in other directions
Forward scatter radars
Forward scatter geometry can give high RCS, even withtruly stealthy target Passive receiver, immune to interception Can utilise “illuminators of opportunity� (TV Stations, Number Stations)
Space-based Bistatic
Griffiths, H.D., Baker, C.J., 2007, Signal and interference environment in Passive Bistatic Radar, Information, Decision and Control Symposium, Adelaide.
Wavelength Match LOW FREQUENCY RADAR Advantages • Transmitted wavelength may match aircrafts physical dimensions Disadvantages • Issues with resolution, both in azimuth (antenna size) and range (bandwidth) • Also with interference with and from other users of these frequencies
Air Combat & Infrared Detection Infrared Search & Track Systems - IRST See First Shoot First http://www.ausairpower.net/APAFlanker-Radars.html
• OLS (Mig-35) Optical Locator System
Optical & Acoustical Detection Dazzle Camouglage Scheme
Since the F-22 is 25-30 percent larger than the F-15 and 40 percent larger than the F-18, it might be visually detected from ranges on the order of 10 miles. Brinkley, R., 1991, Future US Fighters Are at a Cost/Technology Crossroad," Armed Forces Journal International, p.49.
Sound, especially at low altitude may be a giveaway!
ISAR & Stealthy Hotspots Measuring a Stealth Airplane’s robustness
Stimson G. W., 1998, introduction to Airborne Radar, Scitech Publishing, http://www.amazon.com/IntroductionAirborne-Edition-Aerospace-Systems/dp/1891121014
Over-the-Horizon Radar (OTH) Weather Radar Jindalee Operational Radar Network The JORN is so sensitive it is able to track planes as small as a Cessna 172 taking off and landing in East Timor 2600 km away. It is also reportedly able to detect stealth aircraft Most stealthy aircraft are optimized for defeating much higher frequency radars from front-on rather than low-frequency radars from above JORN is reputedly able to detect aircraft wake turbulence. http://www.dsto.defence.gov.au/page/3984/ http://web.archive.org/web/20071116065249/http://defence-data.com/features/fpage37.htm http://www.drtomorrow.com/lessons/lessons6/26.html
Decreasing Pd Stealth Tactic 1 - Threading the Needle
Countermeasure Home-on Jam Mode
Decreasing Pd Stealth Tactic 2 - Pecking the Lobe
Stealth Entropy Levels & Speed
As Stealth Entropy increases so does Speed with Low Probability of Intercept by an adversary
SEAD with Stealth Electronic Warfare Important!
http://www.ausairpower.net/API-VLO-Strike.html
Low Observability
Stealth Basics Low Observability (angled external geometry designed to deflect radar waves making aircraft virtually undetectable to threshold logic)
cone of silence
{http://www.f-16.net/f-16_forum_viewtopic-t-5525-start-510.html}
stealth vs legacy fighter aircraft rcs estimates
Minimize PRX, don’t cross the threshold means survivability, surprise, more room to operate
Low Observability A stealth design must be ideally able to provide an rcs which is 1% airframe and 99% on-board electronics and ordnance dependent
{http://gentleseas.blogspot.com/2010/01/russian-indian-pak-fa-t-50-first-test.html}
A stealthy airframe must be able to accommodate the required hidden electronics, fuel and ordnance.
Low Observability Stealth Airplane Security (amount of time taken to achieve detection of the stealth airplane’s radar signature by adversary radar stations)
http://mariettascientific.com/understanding/under.htm
Low Observability Have Glass Code name for Radar Cross Section reduction measures for the F-16 fighter.
Addition of an indium-tin-oxide layer to the gold tinted cockpit canopy reflective to radar frequencies. Adding such a radar reflective coating actually reduces the plane's visibility to radar by diffusion. An ordinary canopy would let radar signals straight through where they would strike the many edges and corners inside and bounce back strongly to the source. The reflective layer diffuses these signals instead. Have Glass reduces an F-16's RCS by some 15 percent. Applied with the CASPER (Computer Aided Spray Paint Expelling Robot) system.
Low Observability Inside Structure
Low Observability Metamaterials Materials engineered to have properties that have not yet been found in nature. Metamaterial units are arranged in repeating patterns at scales that are smaller than the wavelengths of the phenomena they attempt to influence. Metamaterials derive their properties not from the properties of the base materials but from their newly designed structures. Metamaterial cloaking (Redirecting e/m waves) The purpose of a cloaking device is to hide something, so that a defined region of space is invisibly isolated from passing electromagnetic fields or sound waves.
How is overall LO achieved? Low Probability of Intercept Radar
PAK-FA AESA MAKS
Conclusions
Stealth Stealth is a factor of visual, infrared, acoustic and electromagnetic signature reductions in active (emissions) and passive (scattering) modes Stealth means reaction time reduction to the adversary air defence resources Low Probability of Intercept means less reaction time to opponents
Pd ďƒ— tOT Pi  tSCAN Low Observability lowers the probability of detection thus lowers the probability of intercept
Mathematical Representation
PRX SNR ( Pd , Pfa ) N PRX (radar cross section)
Pd tOT Pi tSCAN
Stealth via LPI & LO
Thank you! Questions? Further Questions: Theodoros G. Kostis https://www.facebook.com/theodoros.kostis