Systems Engineering Glossary
Key terms across all 20 industry packs — aerospace SMAD, defense DoD 5000, medical device IEC 62304, energy NERC, banking SR 11-7, automotive ISO 26262, rail CENELEC, nuclear 10 CFR 50, pharma 21 CFR 211, oil & gas API + IEC 61511, maritime IMO, water EPA SDWA, telecom FCC + 3GPP, construction OSHA + IBC, chemical TSCA + REACH, semiconductor SEMI + JEDEC, insurance NAIC + Solvency II, mining MSHA, agtech USDA + FSMA, govtech FedRAMP — plus requirements engineering, risk management, and phase-gate review vocabulary.
10 CFR 50 / 52
NRC regulations covering domestic licensing of production and utilization facilities (10 CFR 50) and early site permits, standard design certifications, and combined licenses (10 CFR 52).
21 CFR 211
FDA Current Good Manufacturing Practice (cGMP) regulations for finished pharmaceuticals. Covers organization and personnel, buildings and facilities, equipment, components and containers, production and process controls, and records and reports.
21 CFR Part 11
FDA regulation for electronic records and electronic signatures. Requires validated systems, audit trails, access controls, and signature non-repudiation for records submitted to FDA.
3GPP
3rd Generation Partnership Project. Global standards body developing specifications for 3G, 4G LTE, 5G NR, and future 6G mobile telecommunications.
510(k)
An FDA premarket submission demonstrating that a device to be marketed is substantially equivalent to a legally marketed predicate device. The most common clearance pathway for Class II medical devices.
Attitude Control System
ACSThe subsystem responsible for maintaining and changing the orientation of a spacecraft. Includes sensors (star trackers, sun sensors, gyroscopes) and actuators (reaction wheels, thrusters, magnetic torquers).
Apogee
The point in an orbit farthest from the central body. For Earth orbits, the highest altitude above Earth's surface.
Argument of Periapsis
The angle from the ascending node to the periapsis of the orbit, measured in the orbital plane in the direction of motion. One of the six Keplerian elements.
Atomic Oxygen
AOHighly reactive oxygen atoms present in the upper atmosphere that erode polymer surfaces on LEO spacecraft. Drives material selection for thermal blankets and solar array substrates.
AS9100
A widely adopted aerospace quality management system standard, building on ISO 9001 with aerospace-specific requirements for risk management, configuration control, and product safety.
Automotive SPICE
ASPICEProcess assessment framework specific to automotive software development (derived from ISO/IEC 15504). Defines SWE.1 through SWE.6 processes for software requirements, design, construction, unit verification, integration, and qualification.
ALKS R157
UNECE Regulation 157 for Automated Lane Keeping Systems — the first binding international regulation for a Level 3 autonomous driving function.
API 510 / 570 / 653
American Petroleum Institute inspection codes: 510 (pressure vessels), 570 (piping systems), 653 (aboveground storage tanks). Required inspection intervals driven by corrosion rate, criticality, and service.
API 754
American Petroleum Institute Recommended Practice 754: Process Safety Performance Indicators for the Refining and Petrochemical Industries. Tier 1-4 leading and lagging indicators.
AWIA §2013
America's Water Infrastructure Act Section 2013 (2018) requires community water systems serving >3,300 people to conduct a Risk and Resilience Assessment (RRA) and develop an Emergency Response Plan (ERP).
AWWA G-Series
American Water Works Association G-Series management standards: G100 Water Treatment Plant Operation, G200 Distribution Systems, G400 Utility Management, G500 Security Practices.
ACI 318
American Concrete Institute Building Code Requirements for Structural Concrete. Governs design, detailing, and construction of reinforced concrete buildings in the US.
AISC 360
American Institute of Steel Construction Specification for Structural Steel Buildings. The primary US standard for the design of structural steel.
ASCE 7
American Society of Civil Engineers Minimum Design Loads and Associated Criteria for Buildings and Other Structures. Governs wind, seismic, snow, rain, ice, flood, and tsunami loads for US construction.
ANSI/ESD S20.20
ANSI/ESD Association standard for ElectroStatic Discharge Control Program. Requirements for training, compliance verification, grounding, footwear and wrist straps, packaging, and personnel / equipment.
AEC-Q100
Automotive Electronics Council Failure Mechanism Based Stress Test Qualification for Integrated Circuits. Defines grades 0-3 based on temperature range and stress test methods.
ASOP
Actuarial Standard of Practice. ASB-promulgated standards that US actuaries must follow. Covers opinions, reserving, pricing, data quality, experience studies, and disclosures.
Bus
The structural and functional core of a spacecraft that houses and supports the payload and all subsystems. Includes power, thermal, communications, propulsion, and attitude control.
Budget (Mass/Power/Link)
An accounting of resource allocation across spacecraft subsystems with margins. Mass budgets track weight, power budgets track electrical consumption, and link budgets track signal strength through the communications chain.
See budget tools in Features →Ballistic Coefficient
A measure of how an object's mass and shape resist atmospheric drag, calculated as mass divided by (drag coefficient times area). Higher values mean lower drag deceleration.
Beta Angle
The angle between the orbital plane and the Sun vector. Determines the fraction of an orbit spent in eclipse and drives thermal hot-case and cold-case analysis.
Beta angle calculator →Bipropellant
A propulsion system using separate fuel and oxidizer combined in a combustion chamber. Higher Isp than monopropellants but more complex plumbing and mass.
Bit Error Rate
BERThe fraction of received bits that differ from the transmitted bits. Common targets are 10⁻⁵ for telemetry and 10⁻⁹ for data, achieved by combining link margin with error-correcting codes.
Beginning of Life
BOLThe performance state of a system at the start of its operational lifetime, before any degradation. BOL solar array power is typically 15-30% higher than EOL.
Bulk Electric System
BESPer NERC, transmission elements operating at 100 kV or higher plus real and reactive power resources connected to them. NERC CIP reliability standards apply to BES Cyber Assets that could affect the reliable operation of the BES.
Battery Energy Storage System
BESSA grid-connected electrochemical storage asset (commonly lithium-ion) used for frequency regulation, peak shaving, renewable firming, or arbitrage. Subject to IEEE 1547, UL 9540, and local AHJ fire-code requirements.
Basel III
International regulatory framework (BIS) for banks covering minimum capital ratios, leverage ratio, liquidity coverage ratio (LCR), and net stable funding ratio (NSFR). Extensively implemented in US regulation (12 CFR Part 217).
BSA / AML
Bank Secrecy Act and Anti-Money Laundering requirements. US banks must maintain CTR / SAR filings, customer due diligence (KYC), sanctions screening (OFAC), and transaction monitoring programs.
Concept of Operations
ConOpsA document describing how a system will be used from the user's perspective. Covers operational scenarios, mission timeline, ground segment operations, and contingency procedures.
Controlled Unclassified Information
CUIInformation that requires safeguarding or dissemination controls per law, regulation, or government-wide policy, but is not classified. Common in defense and government space programs.
Critical Design Review
CDRA phase gate review that evaluates the detailed design to ensure it satisfies the requirements and can proceed to fabrication, manufacturing, or coding. Typically occurs at the end of Phase C.
See phase gate use case →C3 Energy
The characteristic energy of an interplanetary trajectory, equal to the square of the hyperbolic excess velocity. C3 quantifies how much energy a launch vehicle must impart for a given destination.
C3 energy calculator →Cold Gas Thruster
A simple propulsion device that releases compressed inert gas through a nozzle for thrust. Low Isp but very reliable, often used on CubeSats and human spaceflight maneuvering.
Control Moment Gyroscope
CMGAn attitude actuator consisting of a constant-speed rotor on a gimbal. Tilting the gimbal produces a much larger torque than a reaction wheel of equivalent mass, useful for large agile spacecraft.
CubeSat
A class of small satellite built in standardized 10 cm cube units (1U, 3U, 6U, 12U). Originally designed for educational missions, now widely used for commercial Earth observation and technology demonstration.
Capability Development Document
CDDA JCIDS document defining the operational performance attributes (Key Performance Parameters, Key System Attributes) required for a system at Milestone B. Signed by the sponsor Service.
Contract Data Requirements List
CDRLA list of data items a contractor must deliver under a DoD contract, each referencing a Data Item Description (DID) that specifies format and content. Standard deliverable mechanism in defense programs.
Cybersecurity Maturity Model Certification
CMMCA DoD certification framework assessing cybersecurity practices of contractors handling CUI and FCI. CMMC 2.0 has three levels; required for most DoD prime and subcontract awards.
Commercial Operation Date
CODThe date on which an energy project has completed commissioning and achieved the performance and reliability milestones required by its Power Purchase Agreement or Interconnection Agreement, enabling revenue service.
CENELEC EN 50126
European standard for railway applications specifying RAMS (Reliability, Availability, Maintainability, Safety). The governing framework for railway safety case preparation.
CENELEC EN 50128
European standard for software for railway control and protection. Defines SIL (Safety Integrity Level) 0-4 software development techniques, verification, and validation.
CENELEC EN 50129
European standard for safety-related electronic systems for signalling. Defines the Safety Case structure: Generic Application Safety Case (GASC) + Specific Application Safety Case (SASC).
Clean Water Act
CWAUS federal law governing water pollution. Establishes the NPDES permit program for point-source discharges and the §404 permit program for dredge-and-fill activities.
CBRS
Citizens Broadband Radio Service — FCC shared 3.5 GHz spectrum with a three-tier access framework (Incumbent Access, Priority Access, General Authorized Access) managed by SAS and certified by CPI.
CCPS RBPS
Center for Chemical Process Safety Risk-Based Process Safety framework. 20 management-system elements organized under four pillars: commit to process safety, understand hazards and risk, manage risk, learn from experience.
CHIPS Act
CHIPS and Science Act of 2022 — US law providing ~$52B for domestic semiconductor manufacturing, R&D, and workforce development, with export control provisions restricting sales to entities of concern.
CMMC
Cybersecurity Maturity Model Certification. DoD framework for supply chain cybersecurity with three levels: L1 Foundational (self-assessment), L2 Advanced (C3PAO certification), L3 Expert (DIBCAC assessment).
CISA BOD
CISA Binding Operational Directive. Compulsory direction to federal executive-branch agencies. Examples: BOD 18-02 (web/email security), BOD 20-01 (VDP), BOD 22-01 (KEV patching), BOD 23-01 (asset visibility).
Delta-V
ΔVThe change in velocity required for an orbital maneuver. A fundamental measure of the propulsive effort needed to transfer between orbits, maintain station, or deorbit.
Downlink
Data transmission from a spacecraft to a ground station. Downlink budget analysis determines if the signal is strong enough to be received with acceptable bit error rate.
Doppler Shift
The change in observed frequency due to relative motion between transmitter and receiver. Critical for LEO ground station tracking, where shifts can exceed ±50 kHz at S-band.
Doppler shift calculator →Depth of Discharge
DODThe percentage of a battery's capacity that has been discharged. Lower DOD per cycle means longer battery life. LEO designs often limit DOD to 25-30% to achieve thousands of cycles.
DoD 5000.02
DoD Instruction 5000.02 — the Adaptive Acquisition Framework governing US defense programs. Defines six acquisition pathways (Major Capability, Middle Tier, Urgent, Software, Services, Business Systems) with milestone reviews (MDD, Milestone A/B/C, FRP, IOC, FOC).
DoDAF
Department of Defense Architecture Framework — a standard for describing the enterprise architecture of defense systems through operational, system, services, data, and capability viewpoints. Used across DoD programs for acquisition and interoperability.
Design History File
DHFPer 21 CFR 820.30(j), the compilation of records describing the design history of a finished medical device. Contains design inputs, outputs, reviews, verification, validation, and transfer documentation. Required for FDA inspections.
Device Master Record
DMRPer 21 CFR 820.181, the compilation of records containing the procedures and specifications for a finished medical device. Covers product specs, production procedures, QA specs, packaging, and labeling.
Digital Operational Resilience Act
DORAEU regulation (Regulation 2022/2554) effective January 2025 requiring financial entities to manage ICT risk, conduct threat-led penetration testing (TLPT), and oversee critical third-party ICT providers.
DFARS 252.204-7012
Defense FAR Supplement clause requiring adequate security for covered defense information (CDI) and rapid reporting (within 72 hours) of cyber incidents.
Eclipse
The period during an orbit when the spacecraft is in the shadow of the central body and cannot generate solar power. Eclipse duration drives battery sizing and thermal design.
End of Life
EOLThe planned end of a spacecraft's operational mission. EOL power and thermal analysis accounts for degradation of solar panels, batteries, and thermal coatings over the mission lifetime.
Eccentricity
A dimensionless orbital element describing how much an orbit deviates from a perfect circle. Values range from 0 (circular) to 1 (parabolic escape). Most LEO missions fly e < 0.01.
Escape Velocity
The minimum speed needed for an object to break free of a gravitational body's influence without further propulsion. From Earth's surface, ~11.2 km/s.
Escape velocity calculator →Electric Propulsion
EPPropulsion technologies that accelerate propellant using electric or electromagnetic fields. Includes ion thrusters, Hall effect thrusters, and pulsed plasma thrusters. Very high Isp but low thrust.
EIRP
Effective Isotropic Radiated Power — the apparent power radiated in the peak antenna direction relative to a perfect isotropic radiator. Combines transmit power with antenna gain.
Engineering Change Proposal
ECPA formal request to modify a baselined design or specification. ECPs go through review boards to assess cost, schedule, and technical impact before approval.
ECSS
European Cooperation for Space Standardization — a body publishing standards used by ESA and European space industry, covering project management, engineering, product assurance, and sustainability.
ERTMS / ETCS
European Rail Traffic Management System and European Train Control System. Unified train control across European railways with Levels 1 (beacons), 2 (continuous radio), and 3 (moving block).
EU GMP Annex 1
EU Good Manufacturing Practice Annex 1 (effective Aug 2023) for sterile medicinal products. Introduces the Contamination Control Strategy (CCS) as a mandatory framework.
EPA RMP
EPA Risk Management Program (40 CFR 68) for facilities handling listed regulated substances above threshold quantities. Programs 1, 2, and 3 with progressively more stringent requirements.
EEXI / CII
Energy Efficiency Existing Ship Index (EEXI) and Carbon Intensity Indicator (CII) — IMO regulations under MARPOL Annex VI requiring ships to calculate attained-vs-required energy efficiency and annual operational carbon intensity.
Forward Error Correction
FECCoding schemes that add redundancy to a data stream so errors can be detected and corrected at the receiver without retransmission. Convolutional, Reed-Solomon, LDPC, and Turbo are common.
Free Space Path Loss
FSPLThe signal attenuation between an isotropic transmitter and isotropic receiver in free space, dependent on distance and frequency. The dominant loss term in most space-to-ground link budgets.
FSPL calculator →Factor of Safety
FoSA multiplier applied to expected loads when sizing structures, accounting for uncertainties. Typical aerospace values are 1.4 for ultimate and 1.25 for yield, per NASA-STD-5001.
Failure Modes and Effects Analysis
FMEAA systematic technique for identifying potential failures of a system and assessing their effects on mission objectives. Each failure mode is rated by severity, occurrence, and detection.
Failure Modes, Effects, and Criticality Analysis
FMECAAn extension of FMEA that adds quantitative criticality analysis, ranking failure modes by likelihood-weighted severity to prioritize mitigation efforts.
Full Operational Capability
FOCFull fielding of a system to all planned units with required sustainment capabilities. Follows IOC and signals production ramp-up and transition to sustainment.
FFIEC
Federal Financial Institutions Examination Council. Interagency body that prescribes uniform examination principles and procedures for US banks. Publishes the FFIEC IT Examination Handbook.
FCC Part 15
47 CFR Part 15 Radio Frequency Devices. Governs unintentional and intentional radiators, including unlicensed transmitters, WiFi, Bluetooth, and Part 15 devices.
FSMA
Food Safety Modernization Act of 2011 — the most comprehensive reform of US food safety laws in 70+ years. Implemented through rules including PCHF (21 CFR 117), Produce Safety (21 CFR 112), FSVP (21 CFR 1 Subpart L), Sanitary Transport, Intentional Adulteration, and Sec 204 Traceability (21 CFR 1 Subpart S).
FSMA Sec 204
FDA Food Traceability Rule requiring additional recordkeeping for foods on the Food Traceability List (FTL). Compliance deadline: January 20, 2026. Key Data Elements (KDEs) captured at Critical Tracking Events (CTEs) with 24-hour FDA response.
Blog: FSMA Sec 204 go-live →FIFRA
Federal Insecticide, Fungicide, and Rodenticide Act. EPA administration of pesticide registration, label approval, Restricted Use Pesticide designation, REI / PHI compliance, and Worker Protection Standard.
FedRAMP
Federal Risk and Authorization Management Program. Government-wide program providing standardized approach to security assessment, authorization, and continuous monitoring for cloud products used by federal agencies. Moderate and High baselines align to NIST 800-53.
Blog: FedRAMP JAB P-ATO →FISMA
Federal Information Security Modernization Act. Requires federal agencies and contractors to implement an information security program aligned with NIST Risk Management Framework (RMF) 6-step process.
Geostationary Orbit
GEOA circular orbit at approximately 35,786 km altitude with zero inclination and an orbital period matching Earth's rotation. Spacecraft in GEO appear stationary relative to a ground observer.
Ground Segment
The collection of ground-based systems that support a space mission, including ground stations, mission control centers, data processing facilities, and communication networks.
G/T
A receive system figure of merit equal to antenna gain divided by system noise temperature. Larger G/T means better receive sensitivity, dominated by ground station design at most frequencies.
Galactic Cosmic Rays
GCRHigh-energy charged particles originating from outside the solar system. The dominant contributor to deep-space radiation dose for crewed missions, and a significant SEU source for all space hardware.
GEVS
NASA's General Environmental Verification Standard (GSFC-STD-7000) defining environmental test levels and procedures for spacecraft hardware. Widely used as a default baseline.
GHS
Globally Harmonized System of Classification and Labelling of Chemicals. UN-developed framework adopted in the US by OSHA 1910.1200 HazCom 2012.
GISTM
Global Industry Standard on Tailings Management (2020). ICMM / UNEP / PRI framework covering 15 principles for tailings storage facility (TSF) safety, including consequence classification, Engineer of Record, and Responsible Tailings Facility Engineer.
GFSI
Global Food Safety Initiative. CGF-owned scheme that benchmarks and recognizes food safety certification programs. Recognized schemes include SQF, BRC, FSSC 22000, IFS, and GlobalGAP.
Highly Elliptical Orbit
HEOAn orbit with high eccentricity, providing long dwell times over specific regions at apogee. Molniya and Tundra orbits are common HEO types for high-latitude coverage.
Hohmann Transfer
A two-burn elliptical transfer between two coplanar circular orbits. The most propellant-efficient way to move between two altitudes when transfer time is unconstrained.
Hohmann transfer calculator →Hall Effect Thruster
HETAn electric propulsion device that uses crossed electric and magnetic fields to ionize and accelerate a noble gas (typically xenon or krypton). Common on commercial GEO satellites and constellations.
Hosted Payload
A payload that flies on a spacecraft owned by another organization, sharing power, thermal, and downlink resources. Lower cost than a dedicated bus but with constraints from the host mission.
HACCP
Hazard Analysis and Critical Control Points. 7-principle food safety methodology mandated by 9 CFR 417 (FSIS meat/poultry), 21 CFR 120 (juice), 21 CFR 123 (seafood), and incorporated into FSMA PCHF.
Inclination
The angle between the orbital plane and the equatorial plane. Determines the range of latitudes the spacecraft ground track covers. A 90-degree inclination is a polar orbit.
International Traffic in Arms Regulations
ITARUS regulations controlling the export and import of defense-related articles, services, and technical data. Most spacecraft and satellite technologies are ITAR-controlled.
ITAR compliance details →Inertial Measurement Unit
IMUA package of gyroscopes and accelerometers that measures angular rates and linear accelerations. Used for short-term attitude propagation between absolute fixes from star trackers.
Interface Control Document
ICDA document defining the interfaces between two or more subsystems or organizations, including mechanical, electrical, data, and operational interfaces. Critical for distributed development.
In-Orbit Test
IOTA formal performance verification campaign conducted on-orbit after LEOP, confirming that the spacecraft and payload meet specifications before commercial service or science operations begin.
Initial Operational Capability
IOCThe first attainment of the capability to employ effectively a system, unit, or weapon system by operators. Formally declared by the using Service.
IEC 62304
International standard specifying lifecycle requirements for medical device software. Defines safety classes (A/B/C), required documentation, and processes for development, maintenance, risk management, and configuration management.
ISO 14971
International standard for the application of risk management to medical devices. Defines the process for identifying hazards, estimating and evaluating risks, controlling risks, and monitoring effectiveness throughout the device lifecycle.
ISO 13485
International standard specifying requirements for a Quality Management System (QMS) for organizations designing, producing, installing, and servicing medical devices. Required for CE marking and broadly accepted by regulators worldwide.
IEEE 1547
IEEE standard for interconnection and interoperability of distributed energy resources (DER) with associated electric power systems. Defines voltage/frequency ride-through, reactive power support, and islanding protection for solar, wind, and BESS interconnections.
INCOSE V-Model
The systems engineering process diagram endorsed by INCOSE, showing decomposition of needs into requirements and design on the left side and integration/verification/validation on the right side, meeting at implementation. Widely used for generic SE programs.
ISO/IEC/IEEE 15288
ISO 15288International standard defining the processes and lifecycle stages for systems engineering. Covers agreement, organizational, technical, and technical management processes from concept through retirement. The normative reference behind INCOSE practice.
Integrated Verification and Validation
IV&VIndependent Verification and Validation — technical assessments performed by an organization technically, managerially, and financially independent of the development organization. Common in NASA, DoD, and FDA-regulated programs.
IFRS 17
International Financial Reporting Standard for insurance contracts (effective Jan 2023). Measures contracts using GMM (General Measurement Model), VFA (Variable Fee Approach), or PAA (Premium Allocation Approach), with CSM, LRC, and LIC components.
ISO 26262
International standard for functional safety of electrical and electronic systems in production automobiles. Defines ASIL (Automotive Safety Integrity Level) classifications A–D based on severity, exposure, and controllability.
ISO/SAE 21434
International standard for road vehicle cybersecurity engineering covering risk management, product development, production, operations, maintenance, and decommissioning. Required input to UN R155 CSMS.
ISO 21448 SOTIF
Safety Of The Intended Functionality — standard addressing hazards from insufficient functionality (as opposed to component failure). Critical for ADAS and autonomous systems where hazardous behavior can occur without any component failure.
IATF 16949
International Automotive Task Force quality management standard for automotive production parts and service parts organizations. Built on top of ISO 9001 with automotive-specific requirements.
IEEE 603
IEEE Standard Criteria for Safety Systems for Nuclear Power Generating Stations. Defines requirements for safety system design, independence, qualification, and Class 1E electrical equipment.
ICH Q7-Q12
International Council for Harmonisation quality guidelines: Q7 (GMP for APIs), Q8 (pharmaceutical development), Q9 (quality risk management), Q10 (pharmaceutical quality system), Q11 (development and manufacture of APIs), Q12 (post-approval changes).
ICH E6(R3) GCP
International Council for Harmonisation Good Clinical Practice guideline for clinical trials. R3 revision (effective 2025) modernizes the framework for diverse trial designs including decentralized and adaptive trials.
IEC 61511
International standard for Safety Instrumented Systems (SIS) in the process industry. Defines Safety Integrity Level (SIL) targets based on risk reduction requirements and proof-test intervals for Safety Instrumented Functions (SIF).
IMO SOLAS
International Maritime Organization Safety of Life at Sea convention. The primary international treaty on safety of merchant ships, covering construction, equipment, operation, and radio communications.
IMO MARPOL
International Maritime Organization Marine Pollution convention. Six annexes covering oil, chemicals, harmful substances in packages, sewage, garbage, and air pollution.
IACS URs
International Association of Classification Societies Unified Requirements. Technical standards adopted in common by member class societies (ABS, DNV, LR, BV, RINA, NK, KR, CCS, RS, PRS, CRS, IRS).
International Building Code
IBCModel building code developed by the International Code Council. Adopted (often with amendments) by US states and municipalities as the baseline for commercial and residential building regulation.
ISO 14644
International standard for cleanrooms and associated controlled environments. Defines Class 1-9 airborne particulate cleanliness and requirements for design, construction, start-up, and monitoring.
ICMM
International Council on Mining and Metals. 10 principles and 39 performance expectations for member mining companies covering ethics, human rights, health and safety, environment, biodiversity, and reporting.
J2 Perturbation
The dominant orbital perturbation caused by Earth's equatorial bulge (oblateness). Causes secular drift in RAAN and argument of periapsis, and is exploited to design sun-synchronous orbits.
JEDEC JESD22
JEDEC test methods for reliability characterization of microelectronics. Standards cover HTOL, temperature cycle, humidity, moisture, mechanical, ESD, and package-level stresses.
Ka-band
A radio frequency band from 26.5 to 40 GHz, increasingly used for high-bandwidth satellite downlinks. Higher gain than X-band but more vulnerable to rain attenuation.
Key Performance Parameter
KPPPer JCIDS, a performance attribute so significant that failure to meet the threshold can be cause for program reassessment or termination. KPPs are documented in the ICD/CDD/CPD.
Link Budget
A detailed accounting of all gains and losses in a communications link from transmitter to receiver. Includes transmit power, antenna gains, path loss, atmospheric losses, and receiver sensitivity.
Low Earth Orbit
LEOAn orbit with an altitude between roughly 200 km and 2,000 km. LEO offers lower latency, higher resolution imaging, and lower launch costs, but requires more satellites for continuous coverage.
Lambert's Problem
The orbital mechanics problem of finding the trajectory between two specified position vectors in a specified time of flight. Foundation of rendezvous and interplanetary trajectory design.
Lagrange Point
L-pointOne of five positions in a two-body system where a small object can maintain its position relative to the two larger bodies. L1, L2, and L3 are unstable; L4 and L5 are stable.
Launch Window
The time interval during which a launch can occur to achieve a target orbit or interplanetary trajectory. May be constrained by orbital geometry, ground station coverage, or sun angle.
Launch and Early Orbit Phase
LEOPThe intense operational phase immediately after launch where the spacecraft is checked out, deployed, and brought to its operational orbit. Typically lasts days to weeks.
LCRR
Lead and Copper Rule Revisions. EPA revision requiring public water systems to develop a lead service line inventory, conduct classification, and plan replacement. Compliance required by Oct 2024.
LEED
Leadership in Energy and Environmental Design — US Green Building Council's green building certification program. Ratings: Certified, Silver, Gold, Platinum based on points across Location, Sustainable Sites, Water, Energy, Materials, Indoor Environmental Quality, Innovation.
Margin
The difference between a resource allocation and the current best estimate. Positive margin means the design has room. Margin policies typically require 20-30% margin at PDR and 10-15% at CDR.
Mass Budget
A comprehensive accounting of the mass of every component, subsystem, and the total spacecraft. Includes dry mass, wet mass (with propellant), and contingency margins at each level.
Medium Earth Orbit
MEOAn orbit with altitude between LEO and GEO, typically 2,000 to 35,786 km. GPS and navigation constellations operate in MEO, balancing coverage area against signal latency.
Mission Assurance
Systematic activities ensuring a mission meets its requirements with acceptable risk. Covers reliability engineering, quality assurance, parts screening, and failure analysis.
Mission Lifetime
The planned operational duration of a space mission. Drives design choices for component reliability, radiation hardening, propellant budget, solar panel degradation, and battery cycle life.
Mean Anomaly
A linear-in-time angle that increases uniformly as the spacecraft traverses its orbit. Used as an input to Kepler's equation for computing true and eccentric anomaly.
Monopropellant
A single-component propellant that releases energy through catalytic decomposition. Hydrazine is the canonical example, used widely in satellite attitude control thrusters.
Maximum Power Point Tracking
MPPTA power conditioning technique that continuously adjusts solar array operating voltage to extract maximum available power as conditions change. Common in modern LEO and GEO designs.
Magnetorquer
An attitude actuator that produces torque by running current through a coil in the presence of Earth's magnetic field. Common on small satellites for momentum dumping and slow maneuvers.
Manufacturing Readiness Level
MRLA 1-10 scale that measures the maturity of a manufacturing process, complementary to TRL. MRL drives schedule and cost risk during production transition.
Model-Based Systems Engineering
MBSEA systems engineering approach that uses formal models (often in SysML) as the primary artifacts of design and analysis, rather than text documents. Reduces ambiguity and enables automated traceability.
Milestone Decision Authority
MDAThe DoD executive authorized to approve a program to proceed through each acquisition milestone. Typically the DAE, SAE, or PEO depending on Acquisition Category (ACAT level).
Materiel Development Decision
MDDThe formal DoD entry point into the acquisition process, granting authorization to conduct an Analysis of Alternatives and enter the Materiel Solution Analysis phase. Precedes Milestone A.
Milestone B
The DoD 5000 decision point authorizing entry into Engineering and Manufacturing Development (EMD). Requires an approved Capability Development Document (CDD), TEMP, and acquisition strategy.
Milestone C
The DoD 5000 decision point authorizing entry into Production and Deployment, including Low-Rate Initial Production (LRIP). Requires successful developmental test, operational assessment, and an approved Capability Production Document (CPD).
Measure of Effectiveness
MOEA mission-level metric expressing how well a system meets stakeholder needs under operational conditions. MOEs are stakeholder-facing and typically translate into multiple Measures of Performance (MOPs).
Measure of Performance
MOPA system-level metric quantifying a specific performance attribute under defined conditions. MOPs flow down from MOEs and become measurable requirements in the technical baseline.
MSHA 30 CFR
Mine Safety and Health Administration regulations at 30 CFR. Parts 46 (surface miner training), 48 (underground / coal training), 56 (surface M/NM), 57 (underground M/NM), 70 (respirable dust), 75 (UG coal), 77 (surface coal).
Non-Conformance Report
NCRA document recording a deviation from specification or process during fabrication, integration, or test. Each NCR triggers a disposition decision: use as-is, rework, repair, or scrap.
NASA Procedural Requirements
NPRNASA's formal procedural documents covering everything from project management (NPR 7120.5) to engineering (NPR 7123.1) to safety. Required for NASA-funded programs.
NERC CIP
North American Electric Reliability Corporation Critical Infrastructure Protection standards. Mandatory cybersecurity requirements for owners/operators of the Bulk Electric System (BES). Series covers asset identification, security management, personnel, access, training, incident response, and supply chain.
NQA-1
ASME Quality Assurance Requirements for Nuclear Facility Applications. The baseline QA standard for work supporting NRC-licensed facilities. 18 required program criteria.
NENA i3
National Emergency Number Association i3 standard for Next Generation 9-1-1 (NG9-1-1). IP-based ESInet delivering calls + data from PSAPs across jurisdictional boundaries.
NAIC MCAS
NAIC Market Conduct Annual Statement. Standardized data call collecting transactional market-conduct data by line of business to support risk-focused market examinations.
NIST 800-53
NIST SP 800-53 Security and Privacy Controls for Information Systems and Organizations. Rev 5 is the current version with ~1,000 controls organized into 20 families (AC, AT, AU, CA, CM, CP, IA, IR, MA, MP, PE, PL, PM, PS, PT, RA, SA, SC, SI, SR).
NIST 800-171
NIST SP 800-171 Protecting Controlled Unclassified Information in Nonfederal Systems and Organizations. 110 requirements organized into 14 families. Required for DoD contractors handling CUI under DFARS 252.204-7012.
Orbit Determination
ODThe process of estimating a spacecraft's orbit from tracking observations. Uses ground-based radar, GPS, or optical measurements to compute position and velocity.
Orbital Decay
The gradual reduction of orbital altitude due to atmospheric drag. Severity depends on solar activity, ballistic coefficient, and altitude. LEO satellites below 600 km experience significant decay.
Orbital decay calculator →Own Risk and Solvency Assessment
ORSAA self-assessment of current and future risk and solvency position performed by insurance carriers. Required by NAIC Risk Management and ORSA Model Act in the US, and by Solvency II in the EU.
OSHA PSM
OSHA Process Safety Management standard (29 CFR 1910.119). 14-element program covering employee participation, process safety information, PHA, operating procedures, training, contractors, mechanical integrity, MOC, incident investigation, emergency response, compliance audits.
O-RAN
Open Radio Access Network. O-RAN ALLIANCE specifications defining open, virtualized, AI-enabled RAN architectures with disaggregated RU/DU/CU, open fronthaul (O-FH), and RIC.
OSHA 1926
29 CFR 1926 Safety and Health Regulations for Construction. Covers general safety, fall protection, scaffolding, electrical, excavation, cranes, PPE, and ~20 subparts.
Payload
The instrument or system that performs the mission's primary function. For Earth observation: cameras or sensors. For communications: transponders. For science: spectrometers, magnetometers, etc.
Perigee
The point in an orbit closest to the central body. For Earth orbits, the lowest altitude above Earth's surface.
Phase Gate
A review milestone where a program's readiness to proceed to the next development phase is evaluated. Standard gates include SRR, PDR, CDR, and TRR.
Phase gate review use case →Power Budget
An accounting of electrical power generation (solar panels, batteries) and consumption (subsystems, payload, heaters) across all mission modes including eclipse and contingency.
Preliminary Design Review
PDRA phase gate review that evaluates the preliminary design to confirm it meets requirements and the design approach is feasible. Typically occurs at the end of Phase B.
Plane Change Maneuver
An orbital maneuver that changes the inclination or RAAN of an orbit. Inclination changes are extremely propellant-expensive at high velocities, so they are typically performed at apoapsis.
Plane change calculator →Power Purchase Agreement
PPAA long-term contract between a power generator and an offtaker (utility, corporate, or ISO) specifying price, delivery point, operating requirements, and performance guarantees. Primary financing instrument for renewable energy projects.
Point of Interconnection
POIThe location where a generator, storage, or load interconnects with the transmission or distribution grid. Defines the boundary for metering, protection, and compliance with interconnection standards.
Positive Train Control
PTCUS rail safety system mandated by the Rail Safety Improvement Act of 2008. Prevents train-to-train collisions, derailments from excessive speed, and incursions into work zones.
Probabilistic Risk Assessment
PRASystematic methodology for evaluating nuclear plant risk. Level 1 (core damage frequency), Level 2 (containment performance + source term), Level 3 (offsite consequences).
Requirements Traceability Matrix
RTMA document or tool that maps each requirement to its source (upstream traceability) and its verification method (downstream traceability). Ensures every requirement is tested and every test has a purpose.
RTM in Features →Revisit Time
The time interval between consecutive opportunities for a satellite to observe the same ground location. Key performance parameter for Earth observation constellations.
Risk Matrix
A grid plotting risk likelihood against consequence severity. Used to categorize and prioritize program risks. Typically 5x5 with color coding (green, yellow, red) for risk levels.
Risk Register
A structured list of identified program risks with likelihood scores, consequence scores, mitigation plans, owners, and status. Central artifact for program risk management.
Risk management features →Right Ascension of the Ascending Node
RAANThe angle from the vernal equinox to the ascending node of an orbit, measured eastward in the equatorial plane. One of the six classical Keplerian orbital elements.
Reaction Wheel
An attitude control actuator consisting of a flywheel spun by an electric motor. Conservation of angular momentum rotates the spacecraft when the wheel speed changes. Three-axis control needs at least three wheels.
Random Vibration
A vibration test environment used to qualify hardware against launch-induced loads, characterized by a power spectral density curve. GEVS and launch-vehicle-specific specs define the levels.
Rideshare
A launch service business model where multiple payloads share a single launch vehicle to reduce per-customer cost. Common rideshare brokers include SpaceX Transporter, ESPA Grande, and ISILaunch.
Risk-Based Capital
RBCThe NAIC framework for setting minimum capital thresholds for insurance companies based on asset, credit, insurance, and business risk components (R0 through R5). Action levels escalate from Company Action to Mandatory Control.
REACH
EU Regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals (1907/2006). Registration required for manufacturers/importers of substances >1 tonne/year. SVHC list governs authorization.
Space Mission Analysis and Design
SMADThe standard methodology for spacecraft mission engineering, covering the full lifecycle from concept studies through operations. Defined in the textbook series by Wertz, Everett, and Puschell.
Sun-Synchronous Orbit
SSOA near-polar LEO orbit where the orbital plane precesses at the same rate as Earth's revolution around the Sun. Provides consistent lighting conditions for Earth observation.
Suspect Link
A traceability link flagged for review because the source or destination requirement has been modified. Suspect links indicate that downstream requirements may need updating.
Read: Why traceability breaks →System Requirements Review
SRRA phase gate review that evaluates whether the system requirements are complete, consistent, and testable before proceeding to preliminary design. Typically occurs at the end of Phase A.
Semi-Major Axis
Half the longest diameter of an elliptical orbit. Defines the orbit's size and, via Kepler's third law, its period. Together with eccentricity, fully determines orbit energy.
Specific Impulse
IspA measure of propulsion system efficiency, equal to thrust divided by propellant mass flow rate (in seconds). Higher Isp means more delta-V per kilogram of propellant.
Star Tracker
An attitude sensor that captures images of the star field and matches them against an onboard catalog to determine three-axis orientation with arcsecond accuracy.
Sine Sweep
A vibration test where input frequency varies linearly or logarithmically through a range while maintaining a defined amplitude. Used to find resonances and verify low-frequency response.
Single Event Upset
SEUA bit flip in a memory cell or register caused by a single ionizing particle striking sensitive circuit nodes. Mitigated through EDAC, hardware redundancy, or rad-hard parts.
South Atlantic Anomaly
SAAA region over the South Atlantic where the inner Van Allen radiation belt dips closest to Earth. LEO spacecraft experience significantly elevated radiation flux when crossing the SAA.
SysML
A general-purpose modeling language for systems engineering, derived from UML. Used in MBSE to capture requirements, structure, behavior, and parametric constraints in formal diagrams.
Safe Mode
A spacecraft operational state designed to preserve health and power when an anomaly is detected. The spacecraft sun-points solar arrays, drops to minimal power, and waits for ground intervention.
State of Health
SOHThe set of telemetry parameters that characterize whether a spacecraft is operating within nominal limits. Continuously monitored by mission operations and trended for early warning.
Software Safety Class
Per IEC 62304, a classification (A, B, or C) based on the worst-case hazard from software failure. Class A: no injury possible. Class B: non-serious injury possible. Class C: death or serious injury possible. Determines depth of documentation required.
Software of Unknown Provenance
SOUPIn IEC 62304, any software component already developed and generally available that has not been developed for the purpose of being incorporated into the medical device. Must be assessed for applicability and risks before reuse.
SR 11-7
Federal Reserve and OCC supervisory guidance on model risk management issued in 2011. Defines the three-pillar framework (development, validation, ongoing monitoring) with required independence between validators and developers.
Banking Pack →Solvency II SCR / MCR
Solvency Capital Requirement and Minimum Capital Requirement under the EU Solvency II directive. SCR covers a 1-in-200-year loss event across market, default, life, health, non-life, intangible, and operational risk modules.
STCW
International Convention on Standards of Training, Certification and Watchkeeping for Seafarers. Sets minimum standards for crew competency, medical fitness, and rest hours.
SDWA
Safe Drinking Water Act. US federal law protecting public drinking water supplies. EPA-administered National Primary Drinking Water Regulations set MCLs for 90+ contaminants.
SEMI S2
SEMI standard for Environmental, Health, and Safety Guidelines for Semiconductor Manufacturing Equipment. Covers electrical, fire, chemical, mechanical, radiation, and ergonomic hazards.
SERFF
System for Electronic Rate and Form Filing. NAIC-operated system through which insurers submit rate, rule, and form filings to state insurance departments. 50-state coverage.
SMCRA
Surface Mining Control and Reclamation Act of 1977. OSMRE oversight of coal mining permits, reclamation bonds, and abandoned mine land reclamation. Administered through state regulatory authorities with OSMRE federal oversight.
StateRAMP
State Risk and Authorization Management Program. 501(c)(6) nonprofit providing a standardized approach for states, local governments, and higher-ed to verify security posture of cloud service providers. Modeled after FedRAMP.
Section 508
Section 508 of the Rehabilitation Act (29 USC 794d). Requires federal agencies to ensure electronic and information technology is accessible to people with disabilities. Enforced via 36 CFR 1194 with WCAG 2.1 AA as the baseline.
Test Readiness Review
TRRA phase gate review confirming that the test program, test procedures, test facilities, and test articles are ready for formal testing. Occurs before environmental and acceptance testing.
Thermal Control System
TCSThe subsystem that maintains spacecraft temperatures within acceptable ranges. Uses passive methods (coatings, MLI, radiators) and active methods (heaters, heat pipes, louvers).
Two-Line Element Set
TLEA standardized 70-character text format for representing the orbital elements of an Earth-orbiting object at a specific epoch. Published by NORAD and used by SGP4 propagators worldwide.
True Anomaly
The angle from periapsis to the spacecraft's current position, measured at the focus of the orbital ellipse. Tracks where in its orbit the spacecraft currently is.
Tsiolkovsky Rocket Equation
The fundamental equation of rocket propulsion: ΔV = Isp · g₀ · ln(m₀/m_f). Relates achievable delta-V to specific impulse and mass ratio.
Rocket equation calculator →TT&C
Telemetry, Tracking, and Command — the spacecraft subsystem and ground operations responsible for sending commands, receiving health data, and tracking position.
Total Ionizing Dose
TIDThe cumulative absorbed radiation dose over a mission lifetime, measured in rads or grays. Drives selection of radiation-hardened parts and shielding mass for long-life missions.
Technology Readiness Level
TRLA 1-9 scale defined by NASA and DoD for measuring the maturity of a technology, from basic principles observed (TRL 1) through flight-proven (TRL 9). Used to assess program risk.
Test and Evaluation Master Plan
TEMPThe authoritative DoD planning document for developmental, operational, and live-fire test and evaluation activities over a program’s lifecycle. Required at Milestones B and C.
Technical Performance Measure
TPMA key technical parameter tracked across the lifecycle against a defined threshold and objective, with planned values at each review gate. Common TPMs: mass, power, availability, range, latency.
TSCA
Toxic Substances Control Act. EPA administration of chemical inventory, PMN (Pre-Manufacture Notice) for new chemicals, and risk evaluation under Section 6. Amended by the Frank R. Lautenberg Chemical Safety Act of 2016.
Uplink
Data or command transmission from a ground station to a spacecraft. Uplink budget analysis ensures commands are received reliably.
UN R155 / R156
UNECE regulations for vehicle cybersecurity management systems (R155) and software update management systems (R156). Mandatory for new vehicle type approvals in UN 1958 Agreement countries.
USDA Organic
National Organic Program under 7 CFR 205. USDA certification for crops, livestock, wild crops, handlers, and processors through accredited certifiers.
Verification
The process of confirming a requirement has been met. Methods include test (T), analysis (A), inspection (I), and demonstration (D). Each requirement should have an assigned verification method.
X-band
A radio frequency band from 8 to 12 GHz used heavily for deep space and high-rate Earth observation downlinks. Offers good antenna gain per area and moderate atmospheric attenuation.
See these concepts in action
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