Astrogator in STK
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Astrodynamics (AERO0024) TP1: Introduction Teaching Assistant ⎯ Amandine Denis Contact details Space Structures and Systems Lab (S3L) Structural Dynamics Research Group Aerospace and Mechanical Engineering Department Room: +2/516 (B52 building) [email protected] 04 3669535 2 Today’s program Objectives Presentation of STK Exercise 1: « What does STK do, anyway? » Exercise 2: Do It Yourself! 3 Objectives of this session Discover STK and its possibilities Discover STK interface Discover basic functions and options Illustrate the first lesson 4 Objectives of this session At the end of this session, you should be able to: Create a new scenario Handle graphics windows (2D and 3D, view from/to, …) Use common options of the Properties Browser Insert a satellite in three different ways (database, Orbit Wizard, manually) Insert a facility Calculate a simple access Generate simple reports 5 Presentation of STK Design, analyze, visualize, and optimize land, sea, air, and space systems. 6 Presentation of STK – interface 7 8 9 Presentation of STK 10 11 Presentation of STK – basic elements New scenario - Model the World! Insert object - Populate the World! Properties browser - Decide everything! Animation Reports Tabs 12 Exercise 1 First contact: « What does STK do, anyway? » AGI tutorial Illustration of a Molniya orbit Notion of scenario Rules of thumb Orbit Wizard Insertion of a facility Graphics windows Calculation of a simple access 13 Exercise 1: what does STK do, anyway? Î Are Molniya orbits really a great way to spy on the USA? How many periods of access? When does the first access occur? What is the duration of the first access? Remarks/questions ? 14 Exercise 2 Do It Yourself! : Application to the satellites of the first lesson Insertion of satellites and definition of orbits: • Using Orbit Wizard • Importing from Data Base • Manually Illustration of differents satellites and orbits Options of visualization 15 Exercise 2: application to the 1st lesson >> Represent in STK all the satellites named during the first lesson. To create a satellite: ⇒ Insert >>New… >> Satellite Orbit wizard : cfr ex1 From Database Define properties Visualization: ⇒ Day/night limit ( 2D graphics Properties Browser >> Lighting) 16 Exercise 2: application to the 1st lesson Debriefing: 17 Astrodynamics (AERO0024) TP2: Introduction (2) Today’s program Objectives Exercise 1: A concrete problem Exercise 2: Use in celestial mechanics Exercise 3: Delfi-C3 operation 2 Objectives of this session At the end of this session, you should be able to: Use STK autonomously to solve simple problems Define and use constraints Calculate access Import and visualize planets 3 Exercise 1 A concrete problem: « When could I see the ISS ? » AGI tutorial Outline to build a scenario Constraints 4 Exercise 2 Use in celestial mechanics: The Venus Transit of 2004 AGI tutorial Planets and orbits Insertion of sensors Access calculation (Deck Access) 5 6 7 Exercise 3 Delfi-C3 operations When does the Delfi-C3 team have access to their satellite? When can they operate it? How much does it help if the OUFTI-1 ground station is also used? How long can the two teams communicate through Delfi-C3 transponder ? 8 Astrodynamics (AERO0024) TP3: Orbital elements Today’s program Objectives Exercises 1 & 2: SSO satellites Exercise 3: XMM - RKF7 algorithm 2 Objectives of this session At the end of this session, you should be able to: Calculate orbital elements Check your results with STK Create customized reports Export reports and use data in Matlab 3 Exercise 1 & 2: SSO satellites Ex. 1: Determine the altitude and the inclination of a sun- synchronous satellite for which T=100 min (circular orbit). Use STK to check your results. 4 Exercise 1 & 2: SSO satellites Ex. 2: Determine the perigee and apogee for the following satellite: -SSO - Constant argument of perigee -T = 3h Use STK to check your results. 5 Exercise 3 : XMM - RKF7 algorithm Reproduce graph from Lecture 4, showing time-step of the RKF7(8) algorithm vs true anomaly for XMM satellite. XMM data: Perigee = 7000 km Apogee = 114000 km i = 40° 6 Astrodynamics (AERO0024) TP4: Astrogator Today’s program Objectives Introduction to Astrogator Exercise 1: OUFTI-1 Exercise 2: Hohmann transfer 2 Today’s objectives After this exercise session, you should be able to: design missions involving orbital, impulsive maneuvers This imply that you will be able to: • Use Astrogator when appropriate • Create a simple mission control sequence (MCS) • Use the following segments: ‘initial state’, ‘propagate’, ‘impulsive maneuver’ • Create summaries 3 Today’s program Introduction to Astrogator ⇒ What is it ? ⇒ Components of Astrogator: • Mission Control Sequence • Segments • Stopping conditions Ex.1: OUFTI-1 Ex.2: Hohmann transfer 4 What’s Astrogator? Astrogator is STK’s mission planning module Used for: ⇒ Trajectory design ⇒ Maneuver planning ⇒ Station keeping ⇒ Launch window analysis ⇒ Fuel use studies Derived from code used by NASA contractors Embedded into STK 5 Astrogator in STK Astrogator is one of 11 satellite propagators Propagator generates ephemeris Astrogator satellite acts like other STK satellites ⇒ Can run STK reports (including Access) ⇒ Can animate in 3D and 2D windows Generates ephemeris by running Mission Control Sequence (MCS) Components used in MCS configured in Astrogator Browser 6 Astrogator MissionMission Control Control Sequence Sequence ConfigurationConfiguration Astrogator EphemerisEphemeris Runs Mission Control Sequence OtherOther Mission Mission DataData The Mission Control Sequence A series of segments that define the problem A graphical programming language Two types of segments ⇒ Segments that produce ephemeris ⇒ Segments that change the run flow of the MCS Segments pass their final state as the initial state to the next segment ⇒ Some segments create their own initial state 8 The Mission Control Sequence State Segment 1 Ephemeris State Segment 2 Ephemeris State 9 10 MCS tree 11 MCS toolbar 12 13 14 15 Parameters of the segment currently selected 16 Segments Two types: That produce ephemeris That change the run flow 17 Segments that produce ephemeris Initial State – specifies initial conditions Launch – simulates launching Propagate – integrate numerically until some event Maneuver – impulsive or finite Follow – follows leader vehicle until some event Update – updates spacecraft parameters 18 Initial state segment Specify spacecraft state at some epoch Choose any coordinate system Enter in Cartesian, Keplerian, etc. Enter spacecraft properties: mass, fuel, etc. 19 Launch segment Specify launch and burnout location Specify time of flight Use any central body Connects launch and burnout points with an ellipse Creates its own initial state 20 Propagate segment Numerically integrates using chosen propagator Propagator can be configured in Astrogator browser Propagation continues until stopping conditions are met 21 Stopping conditions Define events on which to stop a segment Stop when some “calc object” reaches a desired value ⇒ A calc object is any calculated value, such as an orbital element ⇒ Calc objects can be user-defined 22 Stopping conditions Can also specify constraints: ⇒ Only stop if another calc object is =, <, >, some value ⇒ Determines if exact point stopping condition is met, then checks if constraints are satisfied ⇒ Multiple constraints behave as logical “And” Segments can have multiple stopping conditions ⇒ Stops when the first one is met ⇒ Behaves as a logical “Or” 23 Stopping conditions Multiple conditions : «OR» Constraints : « AND » 24 Maneuver segment Maneuver segment owns two distinct segments: ⇒ Finite maneuver ⇒ Impulsive maneuver Combo box controls which one is run Finite maneuver created from impulsive maneuver with “Seed” button 25 Impulsive maneuver Adds delta-V to the current state Can specify magnitude and direction of delta-V Computes estimated burn duration and fuel usage, based on chosen engine Can configure engine model in Astrogator browser 26 Impulsive maneuver State Impulsive Maneuver Add delta-V to state State 27 Finite maneuver Works like propagate segment, thrust added to force model Can specify the direction of the thrust vector ⇒ Can be specified in plug-in Magnitude of thrust comes from engine model 28 Follow segment Choose leader to follow Specify offset from the leader Follow leader between “joining conditions” and “separation conditions” ⇒ Behave just like stopping conditions Creates its own initial state 29 Update segment Used to update spacecraft properties Useful to simulate stage separation, docking, etc Set properties to a new value, or add or subtract from their current value 30 Update segment State Update Update state parameters State 31 Segments that change run flow Auto-Sequences – called by propagate segments Target Sequence – loops over segments, changing values until goals are met Backwards Sequence – changes direction of propagation Return – exits a sequence Stop – stops computation 32 Auto-sequences Automatic sequence browser Instead of stopping a segment, stopping conditions can trigger an auto-sequence An auto-sequence is another sequence of segments ⇒ Behaves like a subroutine After the auto-sequence is finished, control returns to the calling segment Auto-sequences can inherit stopping conditions from the calling segment 33 Auto-sequences example Initial State Propagate Apoapsis Duration = 1 day Periapsis Burn In Plane Burn Out Of Plane Sequence Sequence