Introduction to Astrodynamics and the Air Force Maui Optical and Supercomputing Site (AMOS)

Transcription

1 Introduction to Astrodynamics and the Air Force Maui Optical and Supercomputing Site (AMOS) Dr. Moriba K. Jah Director, Advanced Sciences & Technology Research Institute for Astrodynamics (ASTRIA) Air Force Research Laboratory PA 377ABW Approved for public release; distribution is unlimited.

2 Agenda Brief historical background of Astrodynamics General principles of Astrodynamics What we do at AMOS Questions and Answers 2

3 Historical Background (1 of 2) Nicholas Copernicus ( ) De Revolutionibus Orbium Coelestium (1543) Heliocentric (circular) Galileo Galilei ( ) Agreed with Copernicus Performed gravity experiments at the tower of Pisa Tycho Brahe ( ) Detailed observations used by Kepler 3

4 Our Solar System Photo courtesy of JPL: Basics of Space Flight 4

5 Our Solar System Photo courtesy of JPL: Basics of Space Flight 5

6 Our Solar System Photo courtesy of JPL: Basics of Space Flight 6

7 Historical Background (2 of 2) Johannes Kepler ( ) Harmonices Mundi Libri V (1619) Kepler s 3 observations (kinematic) Planet orbits are ellipses with Sun at one focus Planet-Sun line sweeps equal areas in equal times Square of the period is proportional to cube of its mean distance to the sun (semi-major axis) Isaac Newton ( ) Philosophiae Naturalis Principia Matematica (1687) Newton s 3 laws (kinetic) Every body continues in its state of rest, or of uniform motion in a right (straight) line, unless it is compelled to change that state by forces impressed upon it. The change of motion is proportional to the motive force impressed and is made in the direction of the right line in which that force is impressed. To every action there is always opposed an equal reaction: or, the mutual actions of two bodies upon each other are always equal and directed to contrary parts. 7

8 What is an Orbit? 8

9 Orbital Path 9

10 Planetary Orbits Are Ellipses P a 3 10

11 Planetary Orbits Are Ellipses Kepler: Equal Areas In Equal Times 11

12 Conic Sections and Orbits 2 v e 2 r 2a 12

13 Satellite Orbit 6 independent parameters completely describe an orbit R and V COE Ra, Dec, Range, Ra-rate, Dec-rate, Range-rate (can substitute Ra and Dec with Az and El Photo courtesy of Dr. Steve Nerem: Satellite Geodesy at CU 13

14 Orbit Determination Deterministic Uses observations and analytical expressions to determine the satellite orbit Gauss and Laplace Methods Statistical Uses observations and some differential correction method (or estimation theory) to improve upon a priori information (reference orbit). 14

15 Orbit Determination We have a reference orbit or best guess as to where the spacecraft was/will be and a probability of it being there (knowledge) Our spacecraft predictions are based on our mathematical/physical models and are only as good as our knowledge of the spacecraft s location and errors in our models Our observations are taken of a spacecraft on its true (actual) trajectory, however we will NEVER recover the true trajectory (observations aren t perfect [i.e. corrupted by noise and error sources]) Can we improve our knowledge of where the spacecraft was/will be based on our observations? The observations are telling us something about the true trajectory and about the forces and parameters affecting it Can we reduce errors in our dynamic and non-dynamic models? Orbit determination seeks to minimize the differences between what we actually observe and what we think we should observe. If our models were perfect, this difference would be a zero mean white noise. The Kalman filter attempts to estimate (or adjust) model parameters in order to achieve this (depending on how strong or sensitive the data are in recovering these parameters). 15

16 Orbit Determination Knowledge Ellipse Observed Orbit True Orbit Reference Orbit Atmospheric Interface 16

17 Purpose of Orbit Determination Trajectory Reconstruction Where was the spacecraft? Best estimated flight path How well do we know where it was? Associated error of the estimated flight path What information did we recover from this? Do we know something more about our models (dynamic and/or measurement) Trajectory Prediction Where will the spacecraft be? How well do we know where it will be? Do we have refined models (dynamic and/or measurement)? 17

18 What affects our dynamics? The trajectory is determined by a number of forces acting on the spacecraft: Gravitational forces Dominant body force (dominant body is treated as spherically symmetric; produces pure Keplerian motion) Non-dominant body forces (third body forces) Dominant body gravity field asymmetries General relativistic effects Non-gravitational forces Thruster activity Trajectory Correction Maneuvers or Orbit Trim Manuevers Attitude Control System Angular Momentum Desaturations (AMDs) Solar radiation pressure and Earth Albedo Thermal radiation Aerodynamic effects (Drag) Gas leaks (real or compensative) Propulsion system Outgassing Unknown/unmodeled accelerations 18

19 Modeling Earth Photo courtesy of Dr. Steve Nerem: Satellite Geodesy at CU 19

20 Earth Gravity GRIM5-1C Combined Solution Photo courtesy of Dr. Steve Nerem: Satellite Geodesy at CU 20

21 Solar Radiation Pressure/ Earth Albedo Photo courtesy of David Vallado (1997) 21

22 Thermal Radiation/Energy Balance 22

23 Acceleration Due To Outgassing km/s 2 23

24 AMOS Resources State-of-the-Art Systems, Facilities & People Maui High Performance Computing Center (MHPCC) Maui Space Surveillance System (MSSS) 1.2m Beam Director Raven 1.6m Tracker DoD Computational Capability (7.6 TFLOPS) Laser Beam Director 3.67m GEODSS 3 Mounts at Sea-Level Baker-Nunn 2 Raven (testbed, HANDS) 24/7 Optical Capabilities (weather dependent) 24

25 AMOS Environment State-of-the-Art Systems, Personnel, & Facilities Maui Space Surveillance System (MSSS) Remote Maui Experiment (RME) Premier Place MSSS Engineering/Admin Offices Maui High Performance Computing Center (MHPCC) 25

26 Astrodynamics Current Capabilities Extremely accurate deep space metrics Autonomous operations Photometric observations Rapidly deployable and upgradeable systems Future Capabilities Even better metric accuracy Daylight LEO tracking Detect fainter objects Improved SOI signature data WFOV sensors to search for lost/new objects Transportable system HANDS world-wide network Employed Techniques Autonomous deep space sensors Low O&M cost Low acquisition cost Astrometry Photometry Narrow and wide field-of-view telescopes Raven Telescope 26

27 Resolved Imaging Nighttime Imaging (Infrared Image) Daytime Imaging (Post- Processing) Terminator Imaging (AEOS adaptive optics) Ops: Day, Night, Terminator Sensors: Visible to LWIR, Radiometers Image Enhancement Options - Adaptive Optics systems - Post Processing via MHPCC 27

28 Non-Imaging SOI 28

29 Non-Imaging SOI 29

30 Non-Imaging SOI 30

31 Questions?? 31