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A Low Earth Orbit (LEO) is strictly defined by an orbital period of exactly 128 minutes and an eccentricity of 0.25.
Answer: False
Explanation: The definition of Low Earth Orbit (LEO) specifies an orbital period of 128 minutes or less, not exactly 128 minutes. Similarly, the eccentricity must be less than 0.25.
The region generally considered Low Earth Orbit (LEO) extends up to an altitude of approximately 2,000 kilometers above the Earth's surface.
Answer: True
Explanation: The Low Earth Orbit (LEO) region is generally defined as extending up to an altitude of approximately 2,000 kilometers above the Earth's surface.
The Kármán line, often considered the boundary between Earth and space, is located well below the typical altitude range of LEO.
Answer: False
Explanation: The Kármán line, at approximately 100 kilometers altitude, is considered the boundary between Earth and space and lies within the lower reaches of the Low Earth Orbit (LEO) region.
An orbital period of 128 minutes corresponds to a semi-major axis of approximately 8,413 kilometers, according to Kepler's third law.
Answer: True
Explanation: According to Kepler's third law, an orbital period of 128 minutes corresponds to a semi-major axis of approximately 8,413 kilometers.
The LEO region is defined as an object's specific path around the Earth meeting certain orbital parameters.
Answer: False
Explanation: The LEO region refers to a zone in space up to 2,000 km altitude, whereas a LEO orbit describes an object's specific path meeting orbital criteria. Objects not in a LEO orbit can still enter the LEO region.
Which of the following best defines the orbital period criterion for Low Earth Orbit (LEO)?
Answer: An orbital period of 128 minutes or less.
Explanation: A low Earth orbit (LEO) is characterized by an orbital period of 128 minutes or less.
What is the typical upper altitude limit defining the Low Earth Orbit (LEO) region?
Answer: 2,000 kilometers
Explanation: The LEO region is generally considered to extend up to an altitude of approximately 2,000 kilometers above the Earth's surface.
The Kármán line, often considered the boundary between Earth and space, is situated at approximately what altitude?
Answer: 100 kilometers
Explanation: The Kármán line, widely recognized as the boundary between Earth's atmosphere and outer space, is situated at an approximate altitude of 100 kilometers.
Objects in LEO experience significantly less gravitational pull than objects on Earth's surface, which is the primary reason they remain in orbit.
Answer: False
Explanation: The gravitational pull in LEO is only slightly diminished compared to Earth's surface. Objects remain in orbit due to a continuous state of free fall, balancing gravitational force with their orbital velocity, not solely due to reduced gravity.
Weightlessness experienced by astronauts in LEO is caused by the complete absence of gravitational force at that altitude.
Answer: False
Explanation: Weightlessness in LEO is a result of continuous free fall, where the spacecraft and its occupants are constantly falling around the Earth. Gravitational force is still present and is essential for maintaining the orbit.
Satellites orbiting below approximately 300 km in LEO are unlikely to be significantly affected by atmospheric drag.
Answer: False
Explanation: Satellites orbiting below approximately 300 kilometers in LEO are subject to significant atmospheric drag from the thermosphere and exosphere, which can lead to rapid orbital decay.
Orbits higher than LEO generally expose electronic components to less intense radiation compared to LEO.
Answer: False
Explanation: Orbits situated higher than Low Earth Orbit can expose electronic components to more intense radiation, potentially leading to component failure and charge accumulation issues.
The oblateness of Earth's shape is one factor that can cause variations in an object's altitude, even in seemingly circular orbits.
Answer: True
Explanation: The oblateness of Earth's shape, along with other factors like local topography, can cause variations in an object's altitude even in orbits that appear circular.
The mean orbital velocity required for a stable LEO is approximately 7.8 kilometers per hour.
Answer: False
Explanation: The mean orbital velocity required for a stable LEO is approximately 7.8 kilometers per second, not per hour. This equates to roughly 28,000 kilometers per hour.
Orbital velocity increases as altitude increases within LEO.
Answer: False
Explanation: Orbital velocity decreases as altitude increases within LEO. Satellites at lower altitudes require higher velocities to maintain orbit.
Objects in LEO are in a continuous state of free fall, which is why they remain in orbit.
Answer: True
Explanation: Objects in LEO remain in orbit because they are in a continuous state of free fall, where their sideways velocity balances the gravitational pull, preventing them from falling to Earth.
Satellites in lower LEO altitudes require less frequent re-boosting due to reduced atmospheric drag.
Answer: False
Explanation: Satellites in lower LEO altitudes experience greater atmospheric drag, leading to more rapid orbital decay and thus requiring *more* frequent re-boosting, not less.
What is the approximate mean orbital velocity required to maintain a stable Low Earth Orbit?
Answer: 7.8 kilometers per second
Explanation: The mean orbital velocity needed to maintain a stable Low Earth Orbit is approximately 7.8 kilometers per second.
Why do objects remain in orbit around the Earth in LEO, despite the presence of gravity?
Answer: Objects are in a continuous state of free fall, balancing gravitational pull with their sideways velocity.
Explanation: Objects remain in orbit because they are in a continuous state of free fall, where their sideways velocity perfectly balances the gravitational pull, preventing them from falling to Earth.
What atmospheric layer do satellites in LEO, particularly those below 600 km, interact with, causing atmospheric drag?
Answer: The Thermosphere or Exosphere
Explanation: Satellites in LEO, especially below 600 km, encounter atmospheric drag from gases in the thermosphere or the exosphere.
What significant challenge do satellites in lower LEO altitudes face?
Answer: Rapid orbital decay due to significant atmospheric drag.
Explanation: Satellites in lower LEO altitudes face rapid orbital decay due to significant atmospheric drag.
Which of the following is NOT a factor mentioned that can cause the altitude of an object in orbit to vary?
Answer: The gravitational pull of the Moon
Explanation: Factors mentioned that can cause altitude variation include Earth's oblateness, local topography, and altitude variation above ground for polar orbits. The gravitational pull of the Moon is not listed as a cause in the provided data.
How does the orbital velocity of a satellite change as its altitude increases within LEO?
Answer: It decreases.
Explanation: Orbital velocity decreases as altitude increases within LEO. Satellites at lower altitudes require higher velocities to maintain orbit.
All space stations launched and operated to date have been located within Medium Earth Orbit (MEO).
Answer: False
Explanation: All space stations that have been launched and operated thus far have been situated within Low Earth Orbit (LEO), not Medium Earth Orbit (MEO).
A significant disadvantage of LEO satellites for global coverage is their wide field of view, allowing a single satellite to see most of the Earth.
Answer: False
Explanation: A significant disadvantage of LEO satellites for global coverage is their relatively small field of view, necessitating a constellation of many satellites for continuous coverage.
The International Space Station (ISS) orbits at an altitude of roughly 400 kilometers and requires periodic re-boosting due to orbital decay.
Answer: True
Explanation: The International Space Station (ISS) orbits at an altitude of approximately 400 to 420 kilometers and requires periodic re-boosting maneuvers to counteract orbital decay.
Earth observation satellites are often placed in LEO because their higher altitude provides better resolution for imaging.
Answer: False
Explanation: Earth observation satellites are often placed in LEO because their proximity to Earth allows for clearer images and data capture, not because a higher altitude provides better resolution.
The Hubble Space Telescope orbits at an altitude significantly higher than the International Space Station.
Answer: True
Explanation: The Hubble Space Telescope orbits at an altitude of approximately 540 kilometers, which is higher than the International Space Station's orbital altitude of roughly 400-420 kilometers.
The Chinese Tiangong space station orbits at altitudes between 340 and 450 kilometers.
Answer: True
Explanation: The Chinese Tiangong space station maintains an orbit at altitudes ranging between 340 and 450 kilometers.
The Japanese satellite Tsubame holds the record for the lowest altitude achieved by an Earth observation satellite, orbiting at approximately 167.4 kilometers.
Answer: True
Explanation: The Japanese satellite Tsubame achieved a record for the lowest altitude for an Earth observation satellite, orbiting at approximately 167.4 kilometers.
The European Space Agency's (ESA) GOCE mission orbited at a very low altitude of approximately 255 kilometers.
Answer: True
Explanation: The European Space Agency's (ESA) gravimetry mission GOCE operated at a very low altitude of approximately 255 kilometers.
In the film *2001: A Space Odyssey*, the fictional Earth transit station 'Space Station V' was depicted orbiting at approximately 300 kilometers above Earth.
Answer: True
Explanation: The fictional 'Space Station V' in the film *2001: A Space Odyssey* was depicted orbiting at approximately 300 kilometers above Earth.
What is a primary advantage of using Low Earth Orbit (LEO) for communication satellites?
Answer: Offers high bandwidth with low communication latency.
Explanation: LEO offers high bandwidth with low communication latency, making it advantageous for many communication applications.
The International Space Station (ISS) orbits at an altitude of approximately 400-420 km and experiences orbital decay of about how much per month?
Answer: 2 kilometers
Explanation: The International Space Station (ISS) experiences orbital decay of about 2 kilometers per month.
Why are Earth observation and remote sensing satellites frequently placed in LEO?
Answer: Because their proximity allows for clearer images and data capture.
Explanation: Earth observation and remote sensing satellites are frequently placed in LEO because their proximity to the Earth's surface allows for clearer images and data capture.
What is the approximate altitude of the Hubble Space Telescope?
Answer: 540 kilometers
Explanation: The Hubble Space Telescope orbits the Earth at an altitude of approximately 540 kilometers.
Which of the following is an example of a satellite internet constellation utilizing Low Earth Orbit?
Answer: Iridium
Explanation: The Iridium satellite constellation operates in Low Earth Orbit, fitting the criteria for a satellite internet constellation.
What is the approximate altitude of the Chinese Tiangong space station?
Answer: Between 340 and 450 km
Explanation: The Chinese Tiangong space station orbits the Earth at altitudes between 340 and 450 kilometers.
What is the primary reason that providing continuous global coverage requires a large constellation of satellites in LEO?
Answer: LEO satellites have a relatively small field of view.
Explanation: LEO satellites have a relatively small field of view, meaning a large constellation is required to achieve continuous global coverage.
Kessler syndrome describes a scenario where space debris in LEO is easily cleared by atmospheric drag.
Answer: False
Explanation: Kessler syndrome describes a scenario where cascading collisions in LEO generate debris, increasing the probability of further collisions and potentially rendering the orbit unusable, rather than being easily cleared by atmospheric drag.
NASA's Orbital Debris Program tracks over 25,000 objects larger than 10 cm in Low Earth Orbit.
Answer: True
Explanation: According to NASA's Orbital Debris Program, over 25,000 objects larger than 10 centimeters are actively tracked in Low Earth Orbit.
Even small particles of space debris are not dangerous in LEO due to the low orbital velocities.
Answer: False
Explanation: Even small particles of space debris are highly dangerous in LEO due to the extremely high orbital velocities, which impart significant kinetic energy upon impact.
Where is the highest concentration of artificial objects in space typically found within the LEO region?
Answer: Around 800 kilometers (500 miles).
Explanation: The majority of artificial objects in space are found in LEO, with the highest concentration typically occurring around an altitude of 800 kilometers (500 miles).
What theoretical scenario describes cascading collisions in LEO due to high object density, potentially rendering the orbit unusable?
Answer: The Kessler Syndrome
Explanation: The Kessler Syndrome is a theoretical scenario where the density of objects in LEO leads to cascading collisions, generating debris that increases the probability of further collisions and potentially renders the orbit unusable.
Why are collisions involving space debris in LEO particularly dangerous?
Answer: Debris travels at extremely high speeds, possessing significant kinetic energy.
Explanation: Collisions involving space debris in LEO are particularly dangerous because the debris travels at extremely high speeds, possessing significant kinetic energy that can cause severe damage.
According to NASA's Orbital Debris Program, how many objects larger than 10 cm are tracked in LEO?
Answer: Over 25,000
Explanation: NASA's Orbital Debris Program tracks over 25,000 objects larger than 10 centimeters in diameter within Low Earth Orbit.
What is the estimated number of space debris particles in LEO between 1 and 10 cm in size?
Answer: Approximately 500,000
Explanation: It is estimated that there are approximately 500,000 particles of space debris in LEO between 1 and 10 cm in size.
The delta-v requirement for launching into LEO is typically around 9.4 kilometers per second.
Answer: True
Explanation: The delta-v, representing the change in velocity a rocket must achieve, needed to reach Low Earth Orbit typically starts around 9.4 kilometers per second.
What does delta-v represent in the context of rocket launches to LEO?
Answer: The change in velocity a rocket must achieve.
Explanation: Delta-v represents the change in velocity a rocket must achieve to reach its target orbit, such as Low Earth Orbit.
Which historical human spaceflight program is mentioned as having ventured beyond Low Earth Orbit?
Answer: The Apollo program
Explanation: Historically, only the lunar missions of the Apollo program have traveled beyond Low Earth Orbit.