Geodesy of the Terrestrial Planets

Flashcards about Geodesy of the Terrestrial Planets

What type of rotation does the Earth have?

Prograde rotation, from West to East.

In what direction do the Sun, Moon, and stars rise and set due to Earth's rotation?

Rise in the East, set in the West.

How many degrees does the Earth rotate per hour?

15° / hour

If a satellite in Low-Earth Orbit (LEO) has an orbital period of 90 minutes, how many degrees does the Earth rotate in that time?

22.5°

In what direction do Earth satellites in prograde LEO orbits rise and set when observed from the ground?

Rise in the West, set in the East

What is the length of a sidereal day?

23h 56m 4.1s (stellar day)

What is the length of a synodic day?

24h 00m (solar day)

What is the sidereal period?

The time required for a planet or a satellite to return to the same state (rotation or position) relative to the stellar reference frame.

What is the synodic period?

The time required for a planet or a satellite to return to the same state (rotation or position) relative to some observer.

What is the synodic rotational period of a planet?

The time between successive recurrences of the same phase with respect to the Sun.

What is the relationship between sidereal and synodic periods for prograde orbits?

Synodic periods are longer than sidereal periods.

What is the relationship between sidereal and synodic periods for retrograde orbits?

Synodic periods are shorter than sidereal periods.

What is the formula to compute the synodic rotation period from the sidereal period for prograde rotation?

𝑇syn = 𝑇sid * 𝑇orb / (𝑇sid − 𝑇orb)

What is the formula to compute the synodic rotation period from the sidereal period for retrograde rotation?

𝑇syn = 𝑇sid * 𝑇orb / (𝑇sid + 𝑇orb)

What is the approximate value of the Earth's orbital period (Torb) used for calculating the synodic rotational period?

365.2563604167 days

What is the synodic period?

The time between successive recurrences of the same phase with respect to the Sun.

How is the synodic period of Earth and Mars with respect to each other defined?

The time required for Mars to be overtaken by the Earth as both planets go around the Sun.

What causes the seasons on Earth?

The tilt of the Earth's rotational axis.

What is the tilt of the Earth's equator with respect to the ecliptic?

23.4°

What characterizes the Northern Solstice around June 21/22?

Long daylight hours in the north, short daylight hours in the south. Areas beyond the Arctic circle in permanent daylight and areas beyond the Antarctic Circle in permanent darkness. Sub-solar point moves along the Northern Tropic.

What characterizes the Equinoxes around March 20/21 and September 22/23?

Equally long (12) daylight hours everywhere, north and south. Sub-solar point moves along the Equator.

What characterizes the Southern Solstice around December 21/22?

Long daylight hours in the south, short daylight hours in the north. Areas beyond the Arctic circle in permanent darkness and areas beyond the Antarctic Circle in permanent daylight. Sub-solar point moves along the Southern Tropic.

How are the beginnings and endings of the seasons defined?

By equinoxes and solstices

Why are the seasons not equally long?

Because of the eccentricity of Earth's orbit and varying Earth's orbital speed.