Systems Flashcards

Question

What drives payload selection?

Answer 1

Mission objective

Answer 2

Measurement of object properties on Earths surface using data acquired from aircraft and satellites Measurement at a distance, not in-situ

Answer 3

Spatial resolution - spacing between ideal samples on Earth Spectral resolution - ability to resolve spectral features Radiometric resolution - number of bits per pixel Temporal resolution - revisit/re-imaging time

Answer 4

Visible - solar Near InfraRed - solar Shortwave IR - solar Mid wave IR - solar and thermal Thermal or long wave IR - thermal Microwave, radar - thermal (passive), artificial (active)

Answer 5

IR/visible (passive) - radiometers, spectrometers, LiDAR Microwave (active) - radar (altimeter, scatterometer, SAR), radiometers

Answer 6

Line scanner - 1 sensor Whisk broom - a couple, still moves Pushbroom - a line of sensors

Answer 7

Ground-projected Sample Interval (GSI) Ground-projected Instantaneous Field of View (GIFOV) Number of bits used to code signal Q

Answer 8

- the exploration and use of space shall be carried out for the benefit and in the interest of all countries and shall be the province of all mankind - space shall be free for exploration and uses by all states - space is not subject to national appropriation by claim of sovereignty - states shall not place nuclear weapons or other weapons of mass destruction in orbit or on celestial bodies or station them in space - the moon and other celestial bodies are for peaceful purposes - astronauts regarded as envoys of mankind - states are responsible for national space activities whether governmental or not - states are liable for damage cause by their space objects - states shall avoid harmful contamination of space and celestial bodies

Answer 9

Prevents a human colony on mars - contamination Prevents space mining - can’t make a profit

Answer 10

International liability - Skylab debris landed in Australia - $400 littering fine Operation Morning Light - clean up of radioactive debris in Canada from Kosmos 954. Cost Soviet Union C$3 million

Answer 11

All man made objects including fragments, in earth orbit or re-entering the atmosphere, that are non functional Eg. adaptor rings, paint flakes, upper stages Even the smallest pieces can cause hyper velocity impacts - risk to spacecraft

Answer 12

Using outer space in a way future generations can also use. No but it’s making progress to being more sustainable

Answer 13

Limit debris released in normal operations - limits stage release, and other parts ie tethers, lens caps, fairings and adaptors Designed to prevent accidental explosions and ruptures at end of life Additional lifetime stage planned for disposal

Answer 14

Batteries - interrupt power supply and limit battery recharging Electro-explosive devices, pyrotechnic devices, actuators - deactivate/remove electrical power Reaction wheels and gyros - remove electrical energy inputs Propellant tank (propellant and pressurant), propulsion lines - depressurise tank, empty tank and lines Heat piper - demonstrate low probability of rupture

Answer 15

S/c should be manoeuvred far enough away from GEO to not cause interference with other orbiting craft in GEO. The s/c should remain in orbit above GEO protected region Minimum increase in rp of 235 km + (1000*Cr*A/m) and eccentricity <0.003 Disposal from LEO - re entry but more expensive than just increasing orbit

Answer 16

LEO - spherical region extending from earths surface to Z = 2000km Geosynchronous - segment of spherical shell between Z=Zgeo -200 km and Z=Zgeo+200km and +/-15 deg latitude where Zgeo is 35786km

Answer 17

DV for disposal = 11m/s but 1.5km/s for reentry Equivalent to 1/4 yearly station keeping budget therefore more expensive

Answer 18

A design that performance is insensitive to variations Equivalent to quality. Reduce variability, increase quality, reduce cost

Answer 19

High cost and can have a high variation

Answer 20

Any deviation in target value will result in a loss of quality

Answer 21

Design parameter - variables under the control of the designer Noise factor - variables that cannot or are too expensive to be controlled

Answer 22

Testing all possible combinations of DP and NF to select best design parameters is expensive and time consuming. DoE is a structured method of determining relationship between process inputs and outputs to choose what info to gather to determine relationship with minimal effort

Answer 23

Molniya orbit - perigee fixed in Southern Hemisphere, apogee in northern. Critical inclination combined with high eccentricity means good coverage for high latitude ground stations. Used for high latitude telecoms in Russia Don’t have an eclipse in commas operations, allows for targeting specific latitudes if stable orbit is designed

Answer 24

Advantages - satellite at high elevation at high latitude ground sites - no eclipse during commas operations - flexibility of design allows targeting specific latitudes if stable orbit designed - high eccentricities allows for a longer time spent in apogee region hence offer enhanced coverage for regions at apogee point Disadvantages - ground station must track s/c - satellite switching protocol required - more than 1 s/c needed for 24h regional coverage - variation in satellite range and range rate - impacts commas payload design - variation in time of signal propagation, frequency variation due to Doppler, variation in received signal power, change in ground coverage pattern during each orbit

Answer 25

A collection of satellites of usually similar design, performing similar functions simultaneously in similar orbits Global coverage and temporal coverage High spatial resolution, low latency, user experience But high cost and complexity in no of sats/ground stations/launchers

Answer 26

Walker-Delta Walker Star Total of t satellites, with s satellites evenly distributed on p orbit planes. All orbits are circular, at same height, inclination and the ascending nodes of p orbit planes are evenly distributed around equator at intervals of 360/p for WD and 180/p for WS

Answer 27

Payload, latency, coverage, cost

Answer 28

A system is a set of interrelated subsystems and components which interact with one another towards a common purpose

Answer 29

Systems engineering is an interdisciplinary approach and is the means to enable the production of robust systems, on-time and on-budget Plans and integrates technical solutions within schedule and budget

Answer 30

European Cooperation for Space Standardisation- sets out formal processes and standards by which systems engineering is achieved in a European space context Defines procedures and standards - expresses what to do but not how Aims to lower life costs whilst improving quality, functional integrity and compatibility of all project elements by applying common standards for hardware, software, operations, info and activities in projects

Answer 31

Large complex teams Cost plus funding Performance requirements frozen from onset Only space qualified tech can be tolerated Complex system - checklist approach to analysis and testing

Answer 32

Plans and integrates technical solutions within a schedule and budget

Answer 33

Phase 0 - mission analysis - support customer in identifying their needs, propose possible systems concepts Phase A - feasibility - finalise expression of needs, propose solutions to meet perceived needs Phase B - preliminary definition - establish prelim definition of selected option, demonstrate solution meets technical requirements to schedule, cost and organisation requirements Phase C - detailed definition - establish system detailed definition, demonstrate capability to meet tech requirements Phase D - qualification and production- finalise development by qualification and acceptance. Finalise prep or operations and utilisation Phase E - operations/use - support launch campaign, support entities in charge of operation and exploitation, support anomaly investigation Phase F - disposal - support entity in charge of disposal

Answer 34

CUSTOMER is a consumer in a BUSINESS AGREEMENT which is provided by a SUPPLIER which provides the PRODUCT which is received by a CUSTOMER CUSTOMER specifies needs through PRD which is read and accepted by a SUPPLIER who responds with an ID which is reviewed and accepted by a CUSTOMER

Answer 35

Due to the combined effect of earth gravity, luni-solar and solar radiation pressure perturbations

Answer 36

A low eccentricity reduces change in de/dt due to luni-solar perturbations Increases change in de/dt due to SRP Reduces volume of space the spacecraft will occupy **But ensures s/c will always remain above GEO protected region if altitude guideline is followed

Answer 37

Choosing values of w and omega such that: w + omega = lambda_sun (In de/dt equation, sin term must equal 0)

Answer 38

Requirements can be quantitative or qualitative contractual obligation to which hardware or software must comply to achieve full mission success criteria Specifications are derived from mission objectives and passed down assembly chain in requirement subsets. They must dictate the requirement, traceability, at what stage verified, at what architectural level and the method

Answer 39

- limit debris released during normal operations - minimise potential for post-mission break-ups resulting from stored energy - prevention of on-orbit collisions - minimise potential for break ups during operational phases - avoidance of intentional destruction and other harmful activities - post mission disposal - geosynchronous region - post mission disposal - objects passing through LEO region

Answer 40

LiDAR is affected by poor weather conditions due to its short wavelength and losing energy over distance whereas radar is not affected due to its larger wavelength and lower attenuation. Radar is also cheaper as tech has been around longer More complicated power and attitude subsystems needed to keep attitude precise

Answer 41

Fast moving targets appear in different positions due to the individual lines in a CCD for RGB

Answer 42

Get a higher sample density with overlap that increases data quality and correlation

Answer 43

New Frontiers focuses on targeted solar system exploration with the aim to improve understanding of the solar systems origin. Juno's mission is to visit jupiter and the kupier belt to understand the origin and evolution of jupiter. This is done by looking for a solid planetary core, mapping the magnetic field, measuring water and ammonia in the atmosphere and observe the auroras.

Answer 44

The assessment group consists of independent experts from fields relevant to the programme. Their role is to assess the quality of mission proposals in terms of the scientific objectives, mission requirements and the scientific support activities from studies of the proposed missions. The group propose a short list of candidate missions

Answer 45

Earth Explorer focuses on science and research specific to the Earth system and processes, specifically towards climate change. Missions collect long term climate relative datasets and also test innovative remote sensing technologies. Missions are typically limited on a set of science challenges and may use new technologies (not so robust). Earth Watch focuses on operational services for weather and natural hazards etc. Instruments provide continuous data that is compatible with older data sets and likely will not use new technology to ensure robustness of service

Answer 46

Radar, altimeter, radiometer, scatterometer, SAR. All are active (bar radiometers) and hence, have large power requirements. These instruments have high spatial resolution and require fine pointing control such as reaction wheels Radiometers are passive and detect microwave radiation - relatively low power but also low spatial resolution.

Answer 47

- radar pulses at 50 micro secs - sat moves 250 m in this time (image swath) - successive image strips are superimposed and averaged in SAR mode - star trackers measure the orientation - two antennas receive radar echo simultaneously - difference in path length of radar wave is measured and used to provide echo direction S/c needs accurate knowledge of position. Uses DORIS to measure the doppler shift of signals broadcast from ground based radio beacons and short laser pulses fired at ground are reflected to retro reflector system to measure time interval and hence position. DORIS and retro-reflector on the Earth facing side. Star trackers look in cross track direction to measure baseline. Both position and baseline orientation are needed to determine altitude above earth surface

Answer 48

Dawn dusk would be suitable for a payload not concerned with the sun illumination angle i.e. microwave payload. Microwave payloads can observe the earth at all times and are unaffected by cloud. Payload could be active or passive. SAR would provide high resolution imagery to map extent of ice. An altimeter would be able to map extent of ice if similar to cryosat but would require additional instrumentation to track orbit accurately which a sun synchronous orbit is not ideal for. A passive microwave radiometer woud be able to measure the ice characteristics through scattering

Answer 49

UN Space Debris Mitigation Guidelines - high level, non quantitative representation of IDAC guidelines. The first 5 are short term whilst the last 2 aim to prevent the generation of debris after the mission 1. Limit debris released during normal operations 2. Minimise the potential for break-ups in operational phases 3. limit the probability of accidental collision in orbit 4. avoid intentional destruction and other harmful activities 5. minimise the potential for post mission break-ups resulting from stored energy 6. Limit long term presence of s/c and LV stages in LEO post mission 7. Limit long term interference of s/c and LV stages in GEO post mission IADC also recommends s/c with a high risk of on-ground casualty to perform a controlled de-orbit (typically s/c with a large mass). These guidelines affect the mission design by: 1. reducing mission debris - ie., lens caps must be tethered and avoid use of explosive bolts 2. shielding and protection for debris impact 3. use of collision avoidance manoeuvre - needs a propulsion system 4. dont plan an anti-satellite test 5. requires a reliable passivation of s/c at EOL - vent excess propellant (or use for mission disposal), drain batteries and short circuit them etc. 6. needs a way to de-orbit or move through propellant or deployable structures (sails)

Answer 50

Mostly the payload specification which is driven by the mission objective. The payload also affects the orbit and launch vehicle requirements which also affect the s/c design

Answer 51

1. GEO 2. LEO 3. HEO

Answer 52

the transmission time delay introduced by the finite speed of electromagnetic waves

Answer 53

LEO 1 hop is 0.003s, 4 is 0.013s MEO 1 hop 0.053s, 4 is 0.213s GEO 1 hop 0.12s, 4 is 0.48s

Answer 54

low latitudes - almost no coverage at the poles and high lats

Answer 55

minimum 3 for coverage over +/-70 deg lat

Answer 56

reducing E, increases coverage angle but then signal is likely to be blocked by trees, mountains etc

Answer 57

Hohmann transfer (high thrust) Low thrust chemical Electric propulsion (low thrust high isp) Decreasing the amount of prop needed but increasing transfer time

Answer 58

- high latency - large power consumption - need large solar array - large antenna needed - expensive to get to GEO

Answer 59

highly elliptical 12 hr (1/2 sidereal day) with inclination at critical value 63.4 deg to obtain a frozen orbit, eccentricity 0.72 and perigee in southern hemisphere. Good coverage for high latitudes - spends 90% of period in northern hemisphere, complement s GEO missions

Answer 60

Adv - sats at high elevation and high latitude ground stations - allows for comms at poles - no eclipse in operation - ability to target specific areas with the flexibility in orbit design - higher eccentricity - longer time in apogee region for enhanced coverage Dis - tracking needed - distance to ground station constantly changing - satellite switching protocol needed - more than 1 sat needed for 24 hr regional coverage - variation in sat range and range rate - varies time of sig propagation - freq variation - doppler - signal power varies - changes in ground coverage pattern in each orbit

Answer 61

WS - Polar WD - mid lats

Answer 62

4 2 intra-orbital - adjacent sat in same plane, ahead and behind, no need to adjust antenna 2 inter-orbital - adjacent in neighbouring plane No sat links across orbital seam - relative speeds are too high

Answer 63

10 launches every 5 years Hence need disposal or many sats getting in the way

Answer 64

system - set of interrelated subsystems & components which interact with one another toward a common purpose system engineering - interdisciplinary approach and means to enable production of robust systems, on time and on budget European Cooperation for Space Standards - sets out formal processes and standards by which is achieved in an European Space context

Answer 65

For the spacecraft - demanding performance requirements - highly complex systems - many interfacing systems/parties - multidisciplinary - severe reliability/safety requirement - logistical complexity For the environment - hot and cold extremes - ultra high vacuum - outgassing and cleanliness - atomic oxygen - UV/high energy EM radiation - particle radiation - plasma, cosmic rays, Van Allen belts - debris risk - micrometeoroids - mechanical environment - vibration, shock, acceleration - microgravity - weightlessness

Answer 66

Payload - interacts with electrical power and dry mass Spacecraft bus - all health systems (thermal, data handling, TT&C) add dry mass Launcher -affects wet mass for propellant Orbital trajectory - transfers add propellant mass and hence wet mass, also affects ADCS and station keeping which all add wet mass Ground station - interacts with software, TT&C but doesn't add mass to system directly.

Answer 67

Design to cost - design to meet objectives, avoid nice to have features - understand the space environment and design to meet it realistically Innovative engineering - failure resilience by use of 'layered' system architecture - employ high performance components in non critical areas Reasonable PA/QA - avoid 'over insurance' - use volume components and burn in Effective Project management - small dedicated teams - short lines of communication - minimum bureaucracy - concise but necessary Planning team to plan the timeline and events that follow

Answer 68

'platform' or housekeeping systems - all the key subsystems needed to support the payload and mission

Answer 69

space, ground and launcher

Answer 70

Set of unrelated subsystems and components which interact with each other toward a common purpose

Answer 71

interdisciplinary approach and its means to enable production of robust systems, on time and on budget identification and quantification of system goals creation of alternative system design concepts performance of design trades selection and implementation of the best design verification that the design is properly built and implemented post implementation assessment of how well the system met goals

Answer 72

European Cooperation for Space Standardisation Sets out formal processes and standards to be achieved in an European Space Context

Answer 73

objectives to be fulfilled within constraints of budget and time must be well defined and concise make up a mission

Answer 74

mission, its operations, system configuration, subsystem specification, quality assurance and reliability

Answer 75

Programs -> missions -> elements -> subsystems -> units with increasing level of detail

Answer 76

key devices/controls that support critical element operations

Answer 77

primary functional and physical mission components

Answer 78

long term 'big picture' plan/strategies for sustainable progress

Answer 79

1. define mission statement with mission objectives, mission users and operations concept 2. identify subject 3. select payload 4. select orbit 5. size s/c 6. identify space transportation 7. identify communication network

Answer 80

space vehicle control -> environmental control and life support -> structure -> space transportation -> electrical power -> comms & data handling -> space vehicle control

Answer 81

end product of mission design process consists of overall system design. Covers all elements of with necessary specifications to meet mission objectives in optimum way Doesn't do anything to individual elements then to establish functional, cost and schedule feasibility wuth assumptions in system plan Establishes mutual dependence of various system elements to provide complete and structured framework of formulas for req and characteristics of elements

Answer 82

- identification and quantification of system goals - creation of alternative system design concepts - performance of design trades - selection and implementation of best design - verification that design is properly built and integrated - post implementation assessment of how well system met goals

Answer 83

Phase 0 - mission design - Mission Design Review (MDR) Phase A - Feasibility - Preliminary Requirement Review (PRR) Phase B - Mission Architecture - System Requirement Review (SRR), Preliminary Design Review (PDR) Phase C - Detailed Design - Critical Design Review (CDR) Phase D - Testing, manufacture - Qualification review, Far Acceptance Review (FAR) Phase E - operational in orbit Phase F - Disposal

Answer 84

Independent critical assessment and forum for comms. Should be clear and concise

Answer 85

Mission management - tracking & controlling project cost, schedule and performance - juggling money, time, facilities, people and other resources Planning & analysis - plan mission timelines and events after - analyse trade-off between tech options Systems engineering - define and validate system and subsystem level requirement - apply analysis and design tools to define system architecture System assembly - screening components for form fit and function - assembling components to build subsystems and integrate - testing to ensure performance under flight conditions

Answer 86

Simultaneous & training - develop computer software to simulate major mission events - practice operational procedures using simulations Flight control - monitoring and interpret telemetry - tracking s/c or LV position and velocity - sending commands to s/c to change operating conditions and fix System maintenance and support - perform routine maintenance to clean rooms, thermal/vacuum chambers and other operating systems - updating ground software to improve performance or correct issues Data processing & handling - distribute mission data to users - analyse and archive s/c engineering data

Answer 87

Big space - large complex teams - cost plus funding - performance requirements frozen from outset - only space qualified tech tolerated - complex system -> checklist approach to analysis - long schedules - risk averse - high cost Small space - small empowered team - collocation - fixed cost/secure funding - performance as dependent variable - unproven/advanced variable - prudent analysis and testing - low cost - short schedule - acceptable risk

Answer 88

The purpose of ECSS is to express what to do (not how) in the form of regulatory provisions such as requirements, recommendations and permissions. The documentation structure is: System - defines system of standardisation documents and how to us wrt space projects Management - responsible for completing project objectives, quality organisation with timely and cost effective execution Product assurance - quality, dependability, safety, parts, material and processes, software and audits Engineering - defines end goal and verifies clients technical requirements are met and in conformance with regulation and company constraints Sustainability - ensures appropriate use of space for present and future space activities

Answer 89

top level customer - specifies the need/problem prime contractor - takes needs and supplies a PRD, organises manufaacture of product and project management tier 1 subcontractors - take on sections of manufacture (maybe 4 different ones etc), still managementy tier2 subcontractors - lower level do the physical manufacture directed by tier 1 lower level suppliers - provide materials

Answer 90

In phase 0, requirements have the highest RE, manufacturing does very little as the problem is being specified At the end of phase A, the design sector increases relative effort as the solution is defined By the end of B, requirements provide little effort but manufacturing kicks in whilst design starts to plateau off. At the end of C, requiremtns have no involvement (expensive to make changes at this point). The product is realise and both design and manufacture taper off ufor operation at E

Answer 91

Hierarchy Programs - Agency Missions - prime contractor Elements - tier 1 subcontractors Subsystems - tier 2 subcontractors Units - low level suppliers

Answer 92

competitiveness - standards have important economic and social role for enabling industry to stay competitive and conquer new markets Efficiency - standards make development, manufacturing and supply of products and services more efficient, reliable, safer and cleaner Trading facilitation - allow for trading between organisations to progress easier and fairer Knowledge transfer - aid in transferring knowledge and enhancing engineering capabilities to smaller or developing organisations Education - educate todays and future engineers - avoids designers reinventing the wheel

Answer 93

Express what to do (but not how to do it) in terms of regulatory provisions (requirements, recommendations or permissions). These provisions focus on a contractual relationship

Answer 94

System - define system of standardisation documents and specifies how to use it in space projects Management - project manager is responsible for the achievement of the complete of mission objectives and for the quality organisation and its timely, cost effective execution Product assurance - responsible for implementing quality assurance elements of project and other activities such as dependability, safety, parts, materials and processes, software and audits Engineering - defines end product, verification that customers technical requirements are achieved and its conformance with regulation and company constraints Sustainability - requirements and principles for continuous sustainability of space environment for appropriate and safe present and future of space activities

Answer 95

CUSTOMER is a consumer in a BUSINESS AGREEMENT which specifies the need/problem. The SUPPLIER provides a BUSINESS AGREEMENT The CUSTOMER specifies needs through a PRD which is reviewed and accepted by the SUPPLIER who responds with the ID which the CUSTOMER reviews and accepts The SUPPLIER provides a product which is received by the CUSTOMER after the solution has been developed

Answer 96

Top level customer (agency) Prime contractor (large system integrator) Tier 1 subcontractors Tier 2 subcontractors Lower level suppliers

Answer 97

0 and A focus on elaboration of system function and technical requirements. Identify system concepts to comply with mission statement accounting for technical and programmatic constraints identified by project initiator and top level customer. 6-12 months 0 - mission analysis/needs identification A - feasibility (identification, characterisation and feasibility of mission. System trade off and baseline mission selection. Assessment of launcher, orbit and operational constraints. Evaluation of system concepts, payload, instruments and platform. Identification of critical development activities. Preliminary functional specifications and development plan B - preliminary definition of product and project Further assessment of technical and programmatic risk, initiation of pre development activities. Identification of all activities and resources used in development (Define a complete and coherent mission architecture and system design. Finalise SRP, flow down and define the product tree and specifications. Detailed definition of programmatic (schedule, cost and risk), industrial structure and development/verification planning. Supplier selection. PDR to provide coherent system. 12-18 months) C/D - detailed definition, production and verification All activities needed to develop and qualify the space and ground segments and their products (Finalise detailed definition of products and interfaces. Define detailed qualification and verification activities. Complete all equipment reviews and confirm manufacturability . Integrate, test. 24 -36 months) E - utlisation all activities to launch, commision, utilise and maintain ground segment (ready to lauch and operate, FRF, operations, in orbit performance assessment) (5-20 yrs) F - disposal LEO within 25 years

Answer 98

Idea section MDR - mission definition review PRR - preliminary requirements review SRR - systems requirement review PDR - preliminary design review Build CDR - critical design review QR - qualification review AR - acceptance review Launch ORR - operational readiness review FRR - flight readiness review LRR - launch readiness review CRR - commissioning result review ELR - end of life review disposal MCR - mission close-out review only when the outcome determines readiness of the project does the project move forward

Answer 99

Mission Development Review - MDR - phase 0/A - definition of mission baseline and assessment of feasibility of user requirements. Allows solid start of preliminary design System Requirements Review - SRR - B - freeze of highest level requirements Preliminary Design Review - PDR - B - freeze of mission baseline and requirements down to subsystem level. Confirmation of design at system level. Confirmation of AIV plan. Forms the basis for industrial phase c/d/e Critical Design Review - CDR - C - confirmation of detailed design at unit level. Authorisation to complete qualification/build flight units Qualification Review - QR - D - confirmation of system qualification Acceptance Review - AR - D - Confirmation of readiness to fly

Answer 100

0 - mission analysis - support customer in identifying their needs, propose possible system concepts A - feasibility - finalise the expression of needs, propose solutions to meet the perceived needs B - Preliminary Definition - establish system preliminary definition for selected option, demonstrate the solution meets the technical requirements to schedule, cost and organisation requirements C - Detailed definition - establish system detailed definition, demonstrate capability to meet the technical requirements D - Qualification and production - finalise development of the system by qualification and acceptance, finalise preparation for operations and utilisation E - operations/utilisation - support launch campaign, support entities in charge of operations and exploitation, support anomaly investigation F - disposal - support entity in charge of disposal

Answer 101

ESA is a contractor agency that arranges the work. It communicates between the industry building the satellites and academia Invitations to Tender (IITs) are issued through ESA and the industry/academia respond to these with various bids. Based on the bids, ESA selects 1+ to go forward. ESA makes the rules, arranges competition and builds the European space infrastructure All work, processes, documents must be ECSS compliant

Answer 102

ESA applies competition based approach by releasing an announcement of opportunities to seek new ideas, which is responded to by industry and academia by bids. One or more winning teams go through and undertake a feasibility study and then preliminary definition and adaptation before the mission is realised

Answer 103

examinations of technical status of project and associated issues at a point in time and against pre-defined set of objectives. Reviews run by mixed group of insiders and outsiders to project. Assesses results from ESA project, industrial contractors, any external partners. Can provide recommendations on recovery and redirection but these are advisory. Number and objectives are project dependent

Answer 104

requirement engineering - elicit, write, organise, flow down and maintain requirements. Validate top-level requirements with users Systems analysis - define functions, justify physical architecture, derive end-to-end performance, analyse impacts on cost and schedule, establish all relevant environments, perform trade-offs, define analysis methods, tools and models Design and configuration - elaborate system design and configurations, define and manage interfaces Verification - define and perform product verification, ensure verification is successfully closed out at each stage Integration and control - define, plan and manage integrated technical effort amongst all disciplines, define and maintain system budgets as well as margin policy, ensure availability and exchange engineering data, identify and manage candidate technologies, support risk, change, non conformances control

Answer 105

establishes the intended purpose of a product, its associated constraints and environment, the operational and performance features for each relevant situation of its life profile and the permissible boundaries in terms of technical requirements

Answer 106

functional - what it must do - mission, system functions, programming configurational - the parts its composed of interfaces - between parts and external world - i.e., launcher physical - characteristics - size, mass, volume, shape, materials environment - conditions in which functions are performed - acceleration, altitude, humidity, meteoroids, pressure, radiation etc. quality factors - how well it performs function - workmanship, system safety, reliability, efficiency operation - how must it be operable - autonomy, control, failure and failure management support - support needed to do functions - maintenance, facility training, personnel verification - methods to verify requirements - inspection, review of design, test

Answer 107

These arise when a requirement is not met which raises a Non Compliance Review. A RFD requests for a change in requirements with some relaxation of requirement A RFW requests an omission of the requirement with due justification

Answer 108

Requirements are traceable from systems requirements document SRD Specification dictates requirement, traceability and the stages at which verification is needed at what architectural method and level Shall - requirement should -goals

Answer 109

derived from mission objectives and flown down assembly chain in subsets of requirements tree: level 1 - system: system specification -> support spec and Interface Requirement documents (IRD) level 2 - subsystem: subsystem 1, 2.. n spec level 3 - set: set A, B C.. spec level 4- equipment: equip A1, A2, B1, B2 spec 5 - assembly: assy K1 K2.. spec part number

Answer 110

User requirements/mission objectives - user - non-technical, high level, general. Gives rationale for project. Contains mission need statement mission requirements - ESA - functional, technical, overall performance. Applies to mission system requirements - ESA - functional, technical, overall performance, applies to system system requirements - mission prime - detailed, technical, reflects the architectural design. Represents interpretation of customer requirements from developer lower level req - lower tier supplier - very specific and detailed. flow down of system requirements interface requirements - ESA/Prime - allows connecting the system with other systems operations req - operator - technical, includes constraints, for operation

Answer 111

testing mostly occurs in C/D major objectives come from reviews where if progress cannot continue until verification and review is complete

Answer 112

provides definitions and general requirements on: verification process verification planning " execution " close-out proposes list of verification documents deliverable per review. Completed with a verification guidelines handbook that has explanations, advices and examples for preparation and execution of verification programme

Answer 113

IN C/D where the testing, hardware production, programmatic risk and manpower utilisation is

Answer 114

Technical difficulties, waiting for verification or failing verification - lots of relying on other parts to be done before moving on

Answer 115

Verification: process which demonstrates through the provision of objective evidence that the product is designed and produced according to specifications and the agreed deviations and waivers and is free of defects. Building the system right Validation : is the proess which demonstrates that the product is able to accomplish its intended use in the intended operational environment. Building the right system - fulfils mission req Can pass verification but not validation when a product is built as per specification but the specifications do not meet the users needs

Answer 116

Test - verification method by measurement of product performance and functions under representative simulated environments - preferred method Analysis - method by theoretical or empirical evaluation with techniques agreed with customer - can be analysis by similarity Review of design - using approved records or evidence that unambiguously shows that the requirement is met Inspection - visual determination of physical characteristics

Answer 117

Demonstrates that a unit built to certain design is able to withstand a defined environmental stress. Test level will exceed expected environmental stress by a margin. Done on a Qualification Model (QM)

Answer 118

demonstrates unit is built acceptable for flight. Has a smaller margin over environmental stress level and testis done on Flight Model (FM)

Answer 119

Manufacture and assembly: - handling fixture or container reactions - stresses induced by manufacturing processes (welding) Transport and handling: - crane or dolly reactions - land, air, sea environments Testing: - environments from vibration or acoustic tests - test fixture reaction loads Prelaunch: - handling during stacking sequence and pre-flight tests Launch and ascent: - steady stae boosters accelerations - vibro-acoustic noise in launch and transonic phase -propulsion system engine vibrations - transient loads in booster ignition and burn out, stage separation, vehicle manoeuvres, prop slosh and payload fairing separation - pyrotechnic shock from separation events Misiion operations: - steady state thruster accelerations - transient loads during pointing manoeuvres and AC burns or docking - pyrotechnic shock from separation events and deployment - thermal events Reentry and landing (if applicable): - aerodynamic heating - transient wind and landing loads

Answer 120

structure must withstand the proof loads and any other effects such as vibration and heating without excessive elastic/plastic deformation. The structure must withstand ultimate loads and accompanying effects without failure

Answer 121

fundamental stowed frequencies of a s/c must be above defined minimum values to avoid excessive vibrations and accelerations. Frequencies must be acceptable based on s/c attitude and orbit control requirements Small stiff structures will have high natural frequencies and Q factors (very little damping) - an react excessively to random vibration spectrum of LV resulting in 100's of g's

Answer 122

maximum loads to be expected in each critical period with an allowance for statistical variation

Answer 123

numerical multiplying factor to account for variations in material properties, fabrication quality and service degradation

Answer 124

limit load * yield factor of safety structure must not sustain any significant deformation under this load

Answer 125

limit load * ultimate factor of safety structure must not rupture or collapse or undergo gross deformation under this level of yield

Answer 126

maximum operating pressure of a system

Answer 127

pressure applied to vessels to demonstrate their structural integrity prior to use. Must not cause excessive deformation

Answer 128

test performed to demonstrate the behaviour of a structure under ultimate load - performed on Structural Qualification Model

Answer 129

test performed to demonstrate behaviour of as structure under proof load - performed on Flight Model (FM)

Answer 130

predict overall natural frequencies predict structural response to low-frequency vibration determine static and dynamic load distributions and load paths predict mission specific max loads, deflections and accelerations ability to optimally apportion material to meet the strength and stiffness req of mission must carefully choose elements to minimise computing time and maximise fidelity

Answer 131

design ultimately needs to be physically tested s/c is tested under static load to acceptance and qualification levels and tested dynamically on a vibration facility Exs of tests - low and high level sinusoidal sweep for frequency response ad prove static strength Shaped random vibrations for LV vibration spectrum

Answer 132

s/c put into vacuum and heated or called to cause temp of s/c to cycle between testing limits. Performance is monitored as well as temp/performance telemetry

Answer 133

illuminates the s/c under vacuum with powerful light source (xenon arc lamp) to replicate the solar spectrum and high light flux levels

Answer 134

Remediation (removal), collision avoidance, net based retrieval, robotic arm, harpoon

Answer 135

The conventional view is that if design parameters are maintained within a certain tolerance then the quality of the product is maintained. However, usually there is some loss of quality as the parameters move away from their nominal values. Therefore, we want a product that maintains a level of quality even when parameters are not nominal. In the diagram, we can choose a value of x (DP) so that we maximise the quality but would be sensitive to noise and hence quality can be very low either side of nominal value. Alternatively, for the same drift from x, we can have a product where the quality changes only slightly. Graph of Q against x with a sharp peak and a more U peak with a flatter top

Answer 136

SMA = 42164 km INC = 0 deg ECC = 0

Answer 137

LEO or Molniya (GEO not applicable for polar) minimal change in sig power vs signal varying with altitude varying simple ground station vs complex GS to track sat eclipse in operation vs no eclipse many sats needed for 24hr cover vs 3 needed smaller sats vs larger sats

Answer 138

GEO will have les satellites and hence less cost to produce satellites. Tracking fewer GEO sats is easier to many LEO. But latency is higher as well as the power requirement

Systems Flashcards

(162 cards)