# Lesson 12 Flashcards

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<summary><strong>1. How do ES and ELINT differ in purpose and data depth?</strong></summary>
<div class="card-answer"><p>ES collects just enough to answer <em>what radar, what mode, right now</em>, fast enough for the aircrew. ELINT collects full parametric depth on every emitter — including future threats — to build a library. ES fights the fight; ELINT studies the fight.</p></div>
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<summary><strong>2. What bounds the bandwidth ES versus ELINT must cover?</strong></summary>
<div class="card-answer"><p>ES is bounded by <em>known</em> threats — it only recognizes catalogued emitters. ELINT is bounded by <em>any possible</em> threat, since its job is to find the ones not yet catalogued. ELINT's product becomes the threat library the RWR classifies against.</p></div>
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<summary><strong>3. Name the four functions of every threat-warning system and their OODA phases.</strong></summary>
<div class="card-answer"><p>Observe (monitor the bands → Observe), Detect (recognize a threat signal → Orient), Classify (determine type and mode → Decide), Alert (warn aircrew and cue defenses → Act). Same four in any system, RF or IR.</p></div>
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<summary><strong>4. Which of the four functions holds the hard engineering, and why?</strong></summary>
<div class="card-answer"><p>Classify. Observe, Detect, and Alert are plumbing and ergonomics — wide antennas, a threshold, a display. Resolving a merged pulse stream into named emitters with current modes is where the real difficulty lives.</p></div>
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<summary><strong>5. Walk the RWR block diagram from antenna to display.</strong></summary>
<div class="card-answer"><p>Antennas (≈four, one per quadrant; small, broadband, low-gain) → Receiver (measures each pulse's parameters) → Processor (sorts, classifies, decides) → Display + cueing (aircrew scope plus chaff/jammer/decoy cues).</p></div>
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<summary><strong>6. Why does an RWR use four small, low-gain antennas instead of one big one?</strong></summary>
<div class="card-answer"><p>One per quadrant gives all-aspect coverage and a coarse bearing from the start. A warning receiver trades antenna gain for the ability to hear across the whole spectrum and all directions at once.</p></div>
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<summary><strong>7. State the RWR's minimum-detectable-signal contract and the term that hurts it.</strong></summary>
<div class="card-answer"><p><span class="math notranslate nohighlight">\(S_{\min} = kTB \cdot \text{NF} \cdot \text{SNR}_{\text{req}}\)</span>. Same form as a radar, but the bandwidth <span class="math notranslate nohighlight">\(B\)</span> now spans tens of GHz, so the noise floor is far higher.</p></div>
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<summary><strong>8. The RWR's noise floor is much worse than a radar's — how does it still work?</strong></summary>
<div class="card-answer"><p>Every decade of bandwidth costs about 10 dB of sensitivity, so a tens-of-GHz RWR is deaf-ish by comparison. But it detects <em>transmitters</em>, and radar main lobes arrive one-way and loud. For warning, wide-open beats narrow and sharp.</p></div>
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<summary><strong>9. Name the five receiver types and their defining trait.</strong></summary>
<div class="card-answer"><p>Crystal video (wide, fast, one signal); IFM (frequency only, ~octave); superheterodyne (selective, recovers any modulation, one at a time); channelized (many simultaneous signals); digital (wide, fast, flexible — the modern default).</p></div>
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<summary><strong>10. What is a PDW, and what can you measure from one, two, and many pulses?</strong></summary>
<div class="card-answer"><p>A pulse descriptor word — the measured record of an intercepted pulse. One pulse: frequency, PW, TOA, AoA, power, polarization, modulation. Two pulses: PRI (most diagnostic). Many pulses: staggered PRI, carrier modulation, antenna scan rate.</p></div>
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<summary><strong>11. Why is scan rate measured last in the classification sequence?</strong></summary>
<div class="card-answer"><p>The cheap, fast measurements run first and the processor stops once the ID resolves. Scan rate can't be hurried — you must wait for the threat's beam to sweep back across you to time how fast it rotates.</p></div>
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<summary><strong>12. List the processor's deinterleave-to-classify sequence.</strong></summary>
<div class="card-answer"><p>(1) Deinterleave — cluster PDWs by frequency, AoA, and PW into per-emitter buckets; (2) estimate PRI by differencing TOAs in each bucket; (3) classify against the threat library; (4) determine mode — search/track/launch, with PRF jumps betraying the handoff. Sorting comes before classifying.</p></div>
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<summary><strong>13. When is the RWR blind, and what's the doctrinal lesson?</strong></summary>
<div class="card-answer"><p>Against anything that doesn't radiate RF: LPI radars (below the detection floor), EMCON (no transmission until late), passive IR/EO seekers (no launch warning), and silent terminal phases (GPS/inertial/home-on-jam). Survivability never rides on one sensor — a quiet scope is not a safe sky (B3 covers IR).</p></div>
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