60 – Vol. 97 Register online at www.ATIcourses.com or call ATI at 888.501.2100 or 410.956.8805

Space Systems Fundamentals

May 18-21, 2009Albuquerque, New Mexico

June 22-25, 2009Beltsville, Maryland

$1590 (9:00am - 4:30pm)

"Register 3 or More & Receive $10000 eachOff The Course Tuition."Summary

This four-day course provides an overview of thefundamentals of concepts and technologies of modernspacecraft systems design. Satellite system andmission design is an essentially interdisciplinary sportthat combines engineering, science, and externalphenomena. We will concentrate on scientific andengineering foundations of spacecraft systems andinteractions among various subsystems. Examplesshow how to quantitatively estimate various missionelements (such as velocity increments) and conditions(equilibrium temperature) and how to size majorspacecraft subsystems (propellant, antennas,transmitters, solar arrays, batteries). Real examplesare used to permit an understanding of the systemsselection and trade-off issues in the design process.The fundamentals of subsystem technologies providean indispensable basis for system engineering. Thebasic nomenclature, vocabulary, and concepts willmake it possible to converse with understanding withsubsystem specialists.

The course is designed for engineers and managerswho are involved in planning, designing, building,launching, and operating space systems andspacecraft subsystems and components. Theextensive set of course notes provide a concisereference for understanding, designing, and operatingmodern spacecraft. The course will appeal to engineersand managers of diverse background and varyinglevels of experience.

InstructorDr. Mike Gruntman is Professor of Astronautics at

the University of Southern California. He is a specialistin astronautics, space technology, sensors, and spacephysics. Gruntman participates in several theoreticaland experimental programs in space science andspace technology, including space missions. Heauthored and co-authored more 200 publications invarious areas of astronautics, space physics, andinstrumentation.

Course Outline1. Space Missions And Applications. Science,

exploration, commercial, national security. Customers.2. Space Environment And Spacecraft

Interaction. Universe, galaxy, solar system.Coordinate systems. Time. Solar cycle. Plasma.Geomagnetic field. Atmosphere, ionosphere,magnetosphere. Atmospheric drag. Atomic oxygen.Radiation belts and shielding.

3. Orbital Mechanics And Mission Design. Motionin gravitational field. Elliptic orbit. Classical orbitelements. Two-line element format. Hohmann transfer.Delta-V requirements. Launch sites. Launch togeostationary orbit. Orbit perturbations. Key orbits:geostationary, sun-synchronous, Molniya.

4. Space Mission Geometry. Satellite horizon,ground track, swath. Repeating orbits.

5. Spacecraft And Mission Design Overview.Mission design basics. Life cycle of the mission.Reviews. Requirements. Technology readiness levels.Systems engineering.

6. Mission Support. Ground stations. DeepSpace Network (DSN). STDN. SGLS. Space LaserRanging (SLR). TDRSS.

7. Attitude Determination And Control.Spacecraft attitude. Angular momentum. Environmentaldisturbance torques. Attitude sensors. Attitude controltechniques (configurations). Spin axis precession.Reaction wheel analysis.

8. Spacecraft Propulsion. Propulsionrequirements. Fundamentals of propulsion: thrust,specific impulse, total impulse. Rocket dynamics:rocket equation. Staging. Nozzles. Liquid propulsionsystems. Solid propulsion systems. Thrust vectorcontrol. Electric propulsion.

9. Launch Systems. Launch issues. Atlas andDelta launch families. Acoustic environment. Launchsystem example: Delta II.

10. Space Communications. Communicationsbasics. Electromagnetic waves. Decibel language.Antennas. Antenna gain. TWTA and SSA. Noise. Bitrate. Communication link design. Modulationtechniques. Bit error rate.

11. Spacecraft Power Systems. Spacecraft powersystem elements. Orbital effects. Photovoltaic systems(solar cells and arrays). Radioisotope thermalgenerators (RTG). Batteries. Sizing power systems.

12. Thermal Control. Environmental loads.Blackbody concept. Planck and Stefan-Boltzmannlaws. Passive thermal control. Coatings. Active thermalcontrol. Heat pipes.

What You Will Learn• Common space mission and spacecraft bus

configurations, requirements, and constraints.• Common orbits.• Fundamentals of spacecraft subsystems and their

interactions.• How to calculate velocity increments for typical

orbital maneuvers.• How to calculate required amount of propellant.• How to design communications link..• How to size solar arrays and batteries.• How to determine spacecraft temperature.

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Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

Space Systems Fundamentals Part 02

Universe. Galaxy.Solar system.

Coordinate systems.

Mike Gruntman

XX-XX Xxxx 2006Applied Technology Institute

2006 by Mike Gruntman 2006_06_MG_SSF_Part_02 13/20

Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

Coordinate Systems

Coordinate systems play an exceptionally important role in exploration of space. They provide the means to describe complicated motions of celestial bodies and spacecraft.

The most commonly used coordinate system in science and engineering is the Cartesiancoordinate system formed by three orthogonal (perpendicularto each other) vectors x,y,z. The coordinate system that is used most often in space (and in astronomy as well) is the spherical coordinate system.

In the spherical coordinate system, one describes a position of a point by a distance from the center of coordinates and two angles between the direction to the point and two coordinate-system-specific reference vectors.

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Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

Coordinate Systems• Reference vectors

reference vector selection determines the reference plane (normal to the vector)associated with natural phenomena (provided by nature)

• rotation of the earth about its axisdefines the equatorial plane

• motion of the earth around the sundefines the ecliptic plane

assumed fixed in inertial space• in reality, precession

reference vectors are preferred to be perpendicular to each other

• how do we define the second vector?

• CenterDepending on application, the center of the coordinate system is selected in such a way as to simplify the description of particle (spacecraft) motion:

geocentricheliocentricplanetocentriccenter of galaxy….

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Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

Eclipticand

EquatorialPlanes

• The plane, which contains the earth’s orbit around the sun, is called the ecliptic plane.Obviously, the sun is in this plane. The axis of the earth’s rotation around the sun (and correspondingly the ecliptic plane) is fixed in inertial space (except for small precession).

• An angle between the orbital plane of a planet and the ecliptic plane is called the inclination of the orbital plane. The orbits of the planets are close to the ecliptic plane, except those of Mercury and especially Pluto.

• The Earth rotates about its axis (which defines the South-North direction). This axis of rotation is fixed in inertial space (except for small precession) and its direction does not change as earth moves around the sun.

• The axis of rotation is not perpendicular (normal) to the ecliptic plane; the angle between the axis of earth’s rotation and direction perpendicular to the ecliptic plane is 23.5 . This inclination of the axis is the most important factor “responsible” for the seasons.

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Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

Vernal Equinox Vector

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Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

VernalEquinoxVector

• The vernal equinox is a reference vector to establish longitude in both celestial and heliocentric systems of coordinates.

• There are two equinoxes each year, in the spring and in the fall. At equinox, earth is located at the intersection line of the equatorial and ecliptic planes. The equinox in the spring (around March 21) is called the vernal equinox; the equinox in the fall – the autumnal equinox.

• The direction from the center of mass of the Earth to the center of the sun at the vernal equinox is the reference vector (the vernal equinox vector) to determine longitude.

• The vernal equinox was first established thousands of years ago. At that time the vernal equinox vector passed through constellation of Aries (The Ram). The astronomical sign of the Ram, , is still used for the vernal equinox vector although over the years the vector moved to Pisces (The Fishes).

• The equinox vector precession rate is 0.014 degrees per year …. Why does it happen?

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Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

Coordinate Systems

• Geocentric CelestialFor a spacecraft orbiting the Earth, it would be convenient to use the system of coordinate with the center at the Earth’s center and using the Earth’s equator as a reference plane. Such a coordinate system is called the geocentric system of coordinates (see figure). The equatorial plane is the reference plane and the X-axis is the vernal equinox vector.

• HeliocentricFor a spacecraft traveling from one planet to another, say from Earth to Jupiter, it would be convenient to place the center of the coordinate system at the Sun and use the ecliptic plane as a reference plane. Such a coordinate system is called the heliocentric system of coordinates. The equatorial plane is inclined at an angle 23.5 with respect to the ecliptic.

• GalacticFor determining position of stars belonging to our galaxy, it would be convenient to use the galactic plane as a reference plane. Such a coordinate system is called the galactic system of coordinates.

• Space missions typically require use of various systems of coordinates

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Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

TimeApparent Solar Time• One day is determined as an

interval between two successive high noons (two successive solar transits across a local meridian).The problem is that all days are slightly different because

Earth’s orbit is not exactly circularEarth rotates around the SunEarth rotates about its axisthe spin axis is not normal to the ecliptic planeEarth’s axis slightly wobbles

• All these effects are small and predictable. So it is possible to build a time scale based on the mean motion of the Earth relative the Sun, mean solar time.

Mean solar time• This is the time that you have on your

watch.• It assumes a circular orbit of the Earth,

the spin axis normal to the ecliptic plane, no axis-wobbling, etc.

• A mean solar day is equal to exactly24 hours or 1440 minutes or86,400 seconds

Universal Time• The mean solar time at Greenwich

(England) is called the Universal Time (UT).

• Scientific data obtained from spacecraft are very often time-tagged using the UT system.

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Mike Gruntman Space Systems Fundamentals – Part 02. Universe. … Coordinate systems

• In this time scale, the motion of the Earth relative to the stars determines the time. A sidereal day is slightly different from the mean solar day.

This difference is illustrated in figure.

• A mean solar day = 1.0027379 mean sidereal day.• 1 sidereal day = 23 hr 56 min 4.09 sec • Spacecraft in geostationary orbit (GEO)

Sidereal Time