Solar System, Planets, and Orbits

Kepler’s First Law

All planets move in elliptical orbits with the sun at one focus and the other focus empty

Kepler’s Second Law

Law of Areas; Line joining planet to sun sweeps over equal areas in equal time intervals

Kepler’s Third Law

Law of Periods; For any planet, the square of the period is directly proportional to the cube of the mean distance from the sun

perigee

pt closest to the earth/sun

apogee

pt farthest from Earth/sun

where is a satellite the fastest?

perigee

Where is a satellite the slowest?

apogee

Law of Universal Gravitation

Any 2 objects in the Universe attract each other w/ a force directly proportional to the product of the masses/distance between squared

Newton’s First Law

Objects in motion stay in motion and objects at rest stay at rest unless acted upon by an external net force

Newton’s Second Law

F=ma

Newton’s Third Law

Every action has an equal and opposite reaction

escape velocity for earth

7 miles/sec

orbital elements

length of semi major axis, eccentricity, inclination, right ascension of the ascending node, argument of perigee, and time of perigee passage

major axis

line joining perigee and apogee

semi-major axis (a)

one half of the major axis (or the radius of a circular orbit)

eccentricity (e)

defines the shape of an orbit, is between 0 and 1 for ellipses, the greater the eccentricity the more elliptical an orbit is

if eccentricity > 1…

the satellite will escape Earth’s gravitational field

inclination (i)

the angle between the equatorial plane and orbital plane

right ascension of the ascending node

the angle between the x-axis and ascending node (measure East)

argument of perigee

angle between ascending node and the point of perigee (measure in direction of motion)

ascending node

pt at which satellite crosses equator, going South to North

descending node

pt at which satellite cross the equator, going from North to South

prograde

satellite moves eat at ascending node, inclination<90

polar orbit

inclination=90

retrograde

satellite moves west at ascending node; 90<inclination<180

groundtrack

projection of spacecraft on Earth’s surface

groundtrack shifts ____ as satellite orbits

west

precession

rotation of the orbital plane around the earth’s polar axis

which direction is precession for prograde orbits?

west

which direction is precession for retrograde orbits?

east

orbital inclination

equal to latitude of launch site

geostationary orbit

stays at same point on earth

polar orbit

used for military satellite, cross poles

low earth orbit (LEO)

158-2000km above earth, most satellite are here

elliptical orbit (ell)

orbit in shape of ellipse

circular orbit ( c)

orbit in shape of a circle

transfer orbit

way to move from 1 orbit to another

Hohmann Transfer

type of transfer from one circular orbit to another

other types of transfer orbits

spiral, direct

SOI

Sphere of influence when talking about gravity

g assist

spacecraft uses gravitational pull of a planet to alter speed/trajectory, sort of like a slingshot

graveyard orbit

orbit for decommissioned spacecraft

terrestrial plants

mercury, Venus, earth, mars

gas giants

jupiter, saturn

ice giants

uranus, neptune

TNO

trans-neptunian objects, located in Kuiper Belt

period of mars

687 days

distance from sun to mars

1.6 au

distance from sun to mercury

0.4 au

distance from sun to neptune

29 au

dennsity of earth

5.5 g/cm³

densest planet

earth

density of saturn

0.7 gm/cm³

least dense planet

saturn

which planets have no moons?

mercury and venus

1 au

93 million miles

Europa clipper

flagship mission to Europa (moon of Jupiter)

New Horizons

flagship mission to pluto

Cassini

flagship mission to Titan (moon of Saturn)

purpose of Molniya orbit

communication satellites

mercury orbital period

88 days

neptune orbital period

164 years