- O3b mPOWER
- SES's MEO data constellation at ~8,000 km. Steerable spot beams, ~10× capacity of legacy O3b. 11 satellites, dedicated to enterprise + government high-throughput links.
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- OAKOC — Obstacles, Avenues, Key Terrain, Observation, Cover
- A framework for the military analysis of terrain and its effects on operations.
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- OBC — On-Board Computer
- The spacecraft's main processing unit responsible for autonomous operations, command execution, housekeeping, fault detection, and payload data management.
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- Oberth Effect
- The increase in kinetic energy per unit propellant when a propulsive burn is performed at high speed (deep in a gravity well). Fundamental to efficient interplanetary trajectories and capture manoeuvres.
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- Diagram
- OBJ — Objective
- Physical area, feature, or installation to be seized or secured by friendly forces. Always named (e.g., OBJ TARAWA) for command-and-control clarity.
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- OBSINTEL — Obstacle Intelligence
- Information about enemy obstacles: location, composition, depth, presence of lanes or bypasses, and covering fires. Drives whether to breach, bypass, or mark-and-report.
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- OCA — Offensive Counter-Air
- Operations to destroy, disrupt, or degrade enemy air and missile capabilities as close to their source as possible. Includes attacks on airfields, SAM sites, and C2 nodes.
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- OCO — Offensive Cyber Operations
- Operations through cyberspace to project power, create effects in, and deny use of adversary networks and systems.
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- OCOKA — Observation, Cover, Obstacles, Key Terrain, Avenues
- A legacy mnemonic for the military aspects of terrain analysis.
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- OD — Orbit Determination
- The process of estimating an object's orbit from tracking observations and a dynamics model.
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- ODA — Operational Detachment Alpha
- The twelve-man Army Special Forces team that is the basic operational unit for unconventional warfare.
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- OEE — Overall Equipment Effectiveness
- A metric combining availability, performance, and quality to measure manufacturing productivity.
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- OEM — Orbit Ephemeris Message
- A CCSDS-standard format for exchanging time-tagged spacecraft position and velocity data.
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- OEW — Operating Empty Weight
- Aircraft weight without payload or usable fuel.
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- OFDM — Orthogonal Frequency Division Multiplexing
- A modulation scheme that transmits data over many closely spaced orthogonal subcarriers to resist multipath.
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- OFDMA — Orthogonal Frequency Division Multiple Access
- A multi-user version of OFDM that assigns subsets of subcarriers to different users.
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- OGS — Optical Ground Station
- A ground terminal with a telescope and detectors for free-space optical (laser) satellite communication.
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- OIC — Officer in Charge
- The officer responsible for the conduct and supervision of a specific activity or function.
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- OIE — Operations in the Information Environment
- Military actions to generate effects and operational outcomes within the information environment.
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- OISL — Optical Inter-Satellite Link
- A laser-based communication link between satellites offering very high data rates, narrow beamwidths, and no requirement for radio spectrum licensing.
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- OISL Topology
- How optical inter-satellite links interconnect a constellation — ring (intra-plane), grid (intra + inter-plane), mesh (any-to-any). Determines latency, resilience, routing complexity. Starlink uses 4-link grid (2 intra + 2 inter-plane).
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- OMM — Orbit Mean-elements Message
- A CCSDS-standard format expressing mean orbital elements, a modern XML/KVN alternative to the TLE.
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- OMS — Orbital Maneuvering System
- A propulsion system providing the larger burns for orbit insertion and change, distinct from small RCS thrusters.
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- OMUX — Output Multiplexer
- A filter bank on a satellite that combines amplified channel signals onto the downlink antenna.
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- On-Orbit
- The phase of a space mission after launch and orbit insertion, covering nominal operations through end-of-life. Distinguishes from pre-launch (AIT), launch, LEOP, and disposal phases. Drives the sustainment cost share of mission lifecycle budgets.
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- OneWeb
- Eutelsat-OneWeb global broadband LEO constellation, ~650 satellites at ~1,200 km in 12 polar planes. Targets enterprise, government, maritime, aviation. Lower satellite count than Starlink, higher altitude, no ISLs in current generation.
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- OOD — Officer of the Deck
- The officer in charge of the ship’s watch, responsible for its safe navigation and operation.
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- OODA — Observe-Orient-Decide-Act
- Boyd's decision cycle model. Compressing your OODA loop relative to the adversary — making faster, better-informed decisions — confers decisive tactical and operational advantage.
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- OOTW — Operations Other Than War
- Military activities below the threshold of declared conflict including peacekeeping, humanitarian assistance, counter-terrorism, NEO, sanctions enforcement, FONOPS, FID, and HADR. Governed by JP 3-07 with 13 recognized categories.
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- OP — Observation Post
- A position from which military observations are made or fire directed and adjusted.
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- OPCON — Operational Control
- Authority to perform functions of command over subordinate forces: organising, employing commands, assigning tasks, and designating objectives.
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- Operational Art
- The cognitive approach by which commanders translate strategy into tactical action — sequencing operations, arranging time and resources, and selecting decisive points. Bridges strategy (the why) and tactics (the how-to-fight).
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- Operator Training
- The structured preparation of operators (pilots, controllers, technicians, watchstanders) to operate a system safely and effectively. Drives the Training System (curriculum, simulators, instructors, evaluation) for any major acquisition.
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- OPFOR — Opposing Force
- Dedicated units trained to replicate adversary tactics and equipment during exercises. Provides realistic threat representation for training evaluation.
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- OPIR — Overhead Persistent Infrared
- Space-based infrared sensor systems (e.g., SBIRS) that detect and track missile launches and other thermal events from GEO and HEO orbits.
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- OPLAN — Operation Plan
- A complete plan for conducting a military operation, developed for possible future execution.
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- OPORD — Operations Order
- A formal 5-paragraph military order: Situation, Mission, Execution, Sustainment, and Command & Signal.
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- OPSEC — Operations Security
- A process to identify, control, and protect critical information about friendly operations. Denies adversaries the indicators they need to anticipate friendly actions. Part of information protection doctrine.
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- OPSUM — Operations Summary
- A periodic report summarizing the operational situation and significant activities over a reporting period.
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- OPTEMPO — Operating Tempo
- The rate of military operations and activity of a unit, often measured by equipment usage and deployments.
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- ORBAT — Order of Battle
- The hierarchical organization, composition, strength, and disposition of military forces for a specific operation or theater. Includes unit identification, command relationships, equipment tables, and personnel strength.
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- Orbit Determination
- The process of estimating a satellite's orbital state from observations (range, range-rate, angles). Techniques include batch least-squares, extended Kalman filter, and the classical Gauss and Laplace methods.
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- Orbital Conjunction Assessment
- The end-to-end process of screening tracked objects against a protected spacecraft, propagating covariance to TCA, computing Pc, and issuing CDMs. Run continuously by CARA (NASA), JSpOC (US), EU SST, and commercial analytics.
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- Orbital Period
- The time for one complete revolution of a satellite around its primary body. For circular orbits: T = 2pi * sqrt(a^3/mu). LEO ~90 min, GEO = 23h 56m 4s.
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- Orbital Regime
- A categorization of orbits by altitude range: LEO (200-2,000 km), MEO (2,000-35,786 km), GEO (35,786 km), and HEO (highly elliptical with apogee beyond GEO). Each regime has distinct applications and environmental characteristics.
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- Orbital Slot
- A designated position in geostationary orbit assigned by the ITU for satellite operations. Slots are separated by 2-3 degrees longitude to prevent RF interference between adjacent satellites.
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- ORDEM — Orbital Debris Engineering Model
- NASA's engineering model for the orbital debris environment characterising the flux, size distribution, velocity, and direction of debris particles from 10 µm to 1 m at altitudes up to 2000 km. Used for spacecraft shielding design and risk assessment.
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- DiagramTry it: Space Environment Effects GuideTry it: Space Fundamentals Guide
- ORM — Operational Risk Management
- A decision-making process to identify, assess and mitigate risk in naval operations.
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- ORP — Objective Rally Point
- A location near an objective where a unit makes final preparations and reassembles after actions on the objective.
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- ORSE — Operational Reactor Safeguards Examination
- An examination assessing the safe operation of a naval nuclear-propulsion plant and its crew.
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- ORTHO — Orthorectified Imagery
- Imagery geometrically corrected so that scale is uniform and features are in true map positions.
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- OS-CFAR — Ordered-Statistic Constant False Alarm Rate
- A CFAR detector that estimates the noise level from a ranked reference cell, robust to interfering targets.
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- OSAM — On-orbit Servicing, Assembly and Manufacturing
- Capabilities to inspect, repair, refuel, assemble, or build structures in space.
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- OSHA — Occupational Safety and Health Administration
- The U.S. agency that sets and enforces workplace safety and health standards.
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- OSINT — Open Source Intelligence
- Intelligence from publicly available sources: news, academic publications, social media, commercial satellite imagery, and government reports.
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- OSPF — Open Shortest Path First
- A link-state interior gateway routing protocol that computes shortest paths within a domain.
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- OSR — Optical Solar Reflector
- Radiator surface treatment using back-silvered quartz tiles that reflect ~90% of solar input while emitting ~80% in thermal IR. Used on GEO comsat radiator panels to reject payload waste heat.
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- OST — Outer Space Treaty
- The 1967 treaty forming the foundation of international space law. Prohibits national appropriation of celestial bodies and placement of nuclear weapons in orbit.
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- OT&E — Operational Test and Evaluation
- Testing under realistic operational conditions by independent organisations to determine if a system is operationally effective and suitable for fielding.
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- OTA — Other Transaction Authority
- A flexible acquisition instrument outside FAR/DFARS enabling faster prototyping agreements with non-traditional defense companies and commercial firms.
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- OTC — Officer in Tactical Command
- The officer holding tactical command of a force and responsible for its coordinated actions.
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- OTH — Over-The-Horizon
- Detection or engagement beyond the radar horizon.
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- OTP — One-Time Pad
- The only encryption scheme proven mathematically unbreakable (Shannon, 1949). Requires a truly random key at least as long as the message, used exactly once. Impractical for most applications due to key distribution challenges.
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- Outgassing
- Release of volatile species (water, solvents, plasticisers) from materials exposed to vacuum. Deposits on cold surfaces contaminate optics, solar cells, and sensitive instruments. Managed by material screening (NASA ASTM E595), bake-out, and venting paths.
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- DiagramTry it: Space Fundamentals GuideTry it: Waterfall Test GuideTry it: Space Standards Guide
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