PC 1 Study Guide Flashcards
Assignment 1 + Study Guide: Physics Intro, Two Body Problem, Kepler's Laws, Reference Frames, Classic Orbital Elements, Kepler's Problems, Orbit Types
How long is the Period of a satellite in Low Earth Orbit (LEO)?
90-120 minutes
What is the inclination and eccentricity of Geo-stationary GEO orbit?
𝑖 = 0 and 𝑒 = 0
The same sun angle or shadow every orbit is a characteristic of what orbit?
Sun-Synchronous Orbit
(SSO)
What orbit creates long dwell times, normally over the northern latitudes, for mission requirements?
Highly-Elliptical Orbit
(HEO)
What operational consideration describes the portion of Earth’s surface that is geometrically visible from the satellite’s position in space?
Field of regard
What operational consideration describes the instantaneous coverage area capable of being seen by the payload?
Field of view
What operational consideration describes the length of time a satellite has line of sight to a point on Earth?
Dwell time
Principal Direction of:
Earth Centered Inertial
(ECI)
Vernal Equinox
Principal Direction of:
Earth Centered Earth Fixed
(ECEF)
0° Latitude, 0° Longitude
Principal Direction of:
Perifocal
Eccentricity Vector
Principal Direction of:
Radial In-track Cross-track
(RIC)
Radial
Use case of:
Earth Centered Inertial
(ECI)
A non-rotating view
Use case of:
Earth Centered Earth Fixed
(ECEF)
Show a satellite’s ground track
Use case of:
Perifocal
A frame centered at the focus of the orbit
Use case of:
Radial In-track Cross-track
(RIC)
Relative motion and maneuvers
What orbital element is used to find size of orbit?
Semi major axis, 𝑎
What orbital element is used to find shape of orbit?
Eccentricity, 𝑒
What orbital element is used to find tilt of orbit?
Inclination, 𝑖
What orbital element is used to find twist of orbit?
Right Ascension of the Ascending Node
(RAAN), Ω
What orbital element is used to find orbit rotation/orientation?
Argument of Perigee, 𝜔
What orbital element is used to find satellite location?
True Anomaly, 𝜈
What 3 orbital elements have a range of 0 to 360°?
- RAAN, Ω
- Argument of Perigee, 𝜔
- True Anomaly, 𝜈
What is the range of the Semi Major Axis, 𝑎?
0 to ∞
What is range of Eccentricity, 𝑒?
0 to 1+
The chart in the packet says 0 to 1 but remember that an eccentricity of over 1 is hyperbolic.
What is the range of Inclination, 𝑖?
0 to 180°
The ECI and ECEF reference frames utilize what as their fundamental plane?
Equatorial Plane
Which reference frame uses a satellite as its origin?
Radial In-track Cross-track (RIC)
Newton’s 3rd Law
To every action there is always an opposed and equal reaction
Define:
Newton’s 1st Law
An object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force
Define:
Universal Gravitation
Any two bodies attract one another with a force proportional to the product of their masses and inversely proportional to the square of the distance between them
Define:
Newton’s 2nd Law
The rate of change of momentum is proportional to the force impressed and is in the same direction as that force
Define:
Kepler’s 2nd Law
The orbiting body must be moving faster when it is closer and slower when it is farther away
Kepler’s 2nd Law is also known as what?
Law of Equal Areas
Kepler’s 1st Law
The planets orbit the sun in elliptical orbits, with the Sun at one focus of the ellipse
Kepler’s 1st Law is also known as what?
Law of Ellipses
Kepler’s 3rd Law
The period of the orbit squared is proportional to the semi-major axis cubed
Kepler’s 3rd Law is also known as what?
Law of Harmonies
How long is a sidereal day?
23H 56M 04.09S
Low Earth Orbit (LEO) has a period of?
90 to 120 minutes
Low Earth Orbit (LEO) has an altitude of?
2000 km or less
Medium Earth Orbit (MEO) has a period of?
Greater than 120 minutes and less than 24 hours
Medium Earth Orbit (MEO) supports what mission(s)?
- Position, Navigation, & Timing (PNT)
- SATCOM
- Persistent Earth Observation
MEO Semi-Synchronous Orbit is a MEO orbit with a period of?
~12 hours
Geo-Synchronous Orbit (GEO) orbits have a period of?
~24 hours
Geo-Synchronous Orbit (GEO) orbits have an altitude of?
35,786 km
How can you get global coverage with the exception of the polar regions?
Three satellites in Geo-Synchronous Orbit (GEO)
Define:
Geo-Stationary Orbit
A GEO orbit where inclination and eccentricity both equal 0
Define:
Sun-Synchronous Orbit (SSO)
Special, near-polar inclination, LEO orbit with a retrograde motion
Highly Elliptical Orbit (HEO) orbits allow max coverage at higher latitudes. Why is this needed?
There are gaps left by GEO orbits
Geo-Synchronous Orbit (GEO) supports what mission(s)?
- SATCOM
- Missile Warning
Define:
Field of Regard
The portion of Earth’s surface that is geometrically visible from the satellite’s position in space
Define:
Field of View
The instantaneous coverage area capable of being seen by the payload
Define:
Dwell Time
The length of time a satellite has line of sight to a point on the Earth
What is the semi-major axis of Geo-Synchronous Orbit (GEO)?
42,164 km
ECI reference frame is used to do what?
- Describe orbits
- Define classical orbital elements
What is a non-rotating reference frame?
Earth Centered Inertial
(ECI)
What reference frame is “rotating” with the Earth?
Earth Centered Earth Fixed
(ECEF)
The ECEF reference frame used to do what?
Describe ground tracks and the path a satellite travels relative to the Earth’s surface
What reference frame is best used to describe motion from an individual satellite’s perspective?
Radial In-track Cross-track (RIC)
What is the shape of 𝑒 = 0?
Eccentricity
Circular
What is the shape of 0 < 𝑒 < 1?
Eccentricity
Elliptical
What is the shape of 𝑒 = 1?
Eccentricity
Parabolic
What is the shape of 𝑒 > 1?
Eccentricity
Hyperbolic
What type of orbit is 𝑖 = 0°, 180°?
Equatorial
What type of orbit is 𝑖 = 90°?
Polar Orbit
What type of orbit is 0° > 𝑖 > 90°?
Prograde Orbit
What type of orbit is 90° < 𝑖 < 180°?
Retrograde Orbit
How is Right Ascension of the Ascending Node (RAAN)(Ω) measured?
From Vernal Equinox (First Point of Aries) to Ascending Node
How is Argument of Perigee (𝜔) measured?
From Ascending Node to Perigee
How is True Anomaly (𝜈) measured?
From perigee to the satellite location
What do Sidereal Angles determine?
Determine when to do a launch, in order to launch at a specific RAAN, Ω
What is the most commonly used orbital regime?
Low Earth Orbit (LEO)
What is the inclination of a satellite orbiting Earth measured off of?
Equatorial Plane
The greater the energy of an orbit, the larger the what?
Orbit/Size
