- Q-ROUTE — Q-Route (Cleared Route)
- A pre-surveyed, mine-swept shipping route kept clear for the safe transit of vessels.
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- Q/V-band
- Radio frequency bands at 40-75 GHz being explored for satellite feeder links. Very large bandwidth but require adaptive fade mitigation due to atmospheric attenuation.
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- 2D animationTry it: Space Fundamentals GuideTry it: Constellation Guide
- QAM — Quadrature Amplitude Modulation
- A modulation scheme that encodes data by varying both amplitude and phase of the carrier. Higher-order QAM (16, 64, 256) increases data rate but requires higher SNR.
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- QE — Quantum Efficiency
- The fraction of incident photons a detector converts into measurable charge carriers.
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- QFE — Query Field Elevation
- The altimeter setting that causes the instrument to read height above a specific airfield reference point.
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- QKD — Quantum Key Distribution
- Cryptographic key establishment using quantum states (typically photon polarisation) over a dedicated channel. Any eavesdropper perturbs the state, revealing interception. BB84 and E91 are foundational protocols; operational deployments remain short-range (<100 km fibre, sat-ground demonstrated).
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- DiagramTry it: Defense Breakthrough Guide
- QNH — Query Nautical Height
- The altimeter setting that causes the instrument to read altitude above mean sea level.
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- QoS — Quality of Service
- Network mechanisms (DSCP marking, queuing, shaping, policing) that prioritise specific traffic classes so latency-sensitive flows (voice, video, tactical comms) survive congestion at the expense of best-effort traffic. Essential in DiffServ networks and MPLS backbones.
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- DiagramTry it: Constellation Guide
- QPSK — Quadrature Phase Shift Keying
- A digital modulation scheme encoding two bits per symbol using four phase states separated by 90 degrees. Doubles spectral efficiency compared to BPSK with ~3 dB SNR penalty.
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- QRF — Quick Reaction Force
- A military unit positioned to respond rapidly to emerging situations, typically within 15-60 minutes. Provides reserve capability for immediate crisis response.
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- Qualification Testing
- Formal testing against specification to demonstrate a design meets requirements across the full operational envelope. Typically performed on dedicated qualification units with margins beyond flight conditions.
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- DiagramTry it: Software Testing GuideTry it: Ethics Standards GuideTry it: Space Program Lifecycle+1 more
- Quantum Sensing
- Precision measurement using quantum properties (superposition, entanglement, squeezing). Applications in defense: chip-scale atomic clocks for A-PNT, quantum gravimeters for underground detection, and quantum magnetometers for submarine localisation.
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- DiagramTry it: Ssa Guide
- Quaternion
- A four-component mathematical representation of 3D rotation that avoids gimbal lock. Standard for spacecraft attitude representation and control algorithms.
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- QUEST — Quaternion Estimator
- A closed-form algorithm solving Wahba's problem to compute attitude from paired vector observations.
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- QUIC — Quick UDP Internet Connections
- A UDP-based transport protocol providing multiplexed, encrypted, low-latency connections.
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- QWIP — Quantum Well Infrared Photodetector
- An infrared detector using intersubband transitions in semiconductor quantum wells, typically for the long-wave band.
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- QZSS — Quasi-Zenith Satellite System
- Japan's regional GNSS augmentation — 4 satellites in inclined geosynchronous orbit, optimised for high-elevation visibility over Japan. Augments GPS; future independent capability.
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- 3D modelTry it: Space Fundamentals GuideTry it: Pnt GuideTry it: Constellation Guide+1 more
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