What is a LEO satellite?
The correct answer is D: A satellite in low earth orbit. A LEO satellite is a satellite in low earth orbit. Low Earth Orbit is typically between 160-2000 km altitude, where most amateur satellites operate. LEO satellites orbit relatively close to Earth, completing orbits in about 90-120 minutes. For amateur radio operators, LEO satellites are the most common type of amateur satellite, including popular satellites like AO-91, SO-50, and the ISS. Understanding LEO characteristics helps explain why these satellites have short pass times (10-20 minutes) and significant Doppler shift.
Exam Tip
LEO = Low Earth Orbit. Think 'L'EO = 'L'ow 'E'arth 'O'rbit. Satellites at 160-2000 km altitude, completing orbits in 90-120 minutes. Most amateur satellites are LEO. Not about sun-sync, elliptical orbits, or power modes.
Memory Aid
"LEO = Low Earth Orbit. Think 'L'EO = 'L'ow 'E'arth 'O'rbit (160-2000 km). Most amateur satellites are LEO. Fast-moving, short passes, significant Doppler shift."
Real-World Application
AO-91 is a LEO satellite orbiting at about 400 km altitude. It completes an orbit every 90 minutes, giving you 10-15 minute passes as it travels overhead. Because it's in low orbit, it moves quickly relative to your station, causing significant Doppler shift. Most amateur satellites are LEO because they're easier and cheaper to launch to low altitude.
Key Concepts
Why Other Options Are Wrong
Option A: Incorrect. Sun synchronous refers to a specific orbital inclination that keeps the satellite in constant sunlight, not the orbit altitude. LEO satellites can be sun-synchronous, but it's not what LEO means.
Option B: Incorrect. Highly elliptical orbit (HEO) satellites have very elongated orbits with high apogee and low perigee. LEO satellites have relatively circular orbits at low altitude.
Option C: Incorrect. Low energy operation mode refers to a power-saving mode, not an orbit type. LEO is about orbit altitude, not power mode.
题目解析
The correct answer is D: A satellite in low earth orbit. A LEO satellite is a satellite in low earth orbit. Low Earth Orbit is typically between 160-2000 km altitude, where most amateur satellites operate. LEO satellites orbit relatively close to Earth, completing orbits in about 90-120 minutes. For amateur radio operators, LEO satellites are the most common type of amateur satellite, including popular satellites like AO-91, SO-50, and the ISS. Understanding LEO characteristics helps explain why these satellites have short pass times (10-20 minutes) and significant Doppler shift.
考试技巧
LEO = Low Earth Orbit. Think 'L'EO = 'L'ow 'E'arth 'O'rbit. Satellites at 160-2000 km altitude, completing orbits in 90-120 minutes. Most amateur satellites are LEO. Not about sun-sync, elliptical orbits, or power modes.
记忆口诀
LEO = Low Earth Orbit. Think 'L'EO = 'L'ow 'E'arth 'O'rbit (160-2000 km). Most amateur satellites are LEO. Fast-moving, short passes, significant Doppler shift.
实际应用示例
AO-91 is a LEO satellite orbiting at about 400 km altitude. It completes an orbit every 90 minutes, giving you 10-15 minute passes as it travels overhead. Because it's in low orbit, it moves quickly relative to your station, causing significant Doppler shift. Most amateur satellites are LEO because they're easier and cheaper to launch to low altitude.
错误选项分析
Option A: Incorrect. Sun synchronous refers to a specific orbital inclination that keeps the satellite in constant sunlight, not the orbit altitude. LEO satellites can be sun-synchronous, but it's not what LEO means. Option B: Incorrect. Highly elliptical orbit (HEO) satellites have very elongated orbits with high apogee and low perigee. LEO satellites have relatively circular orbits at low altitude. Option C: Incorrect. Low energy operation mode refers to a power-saving mode, not an orbit type. LEO is about orbit altitude, not power mode.
知识点
LEO satellites, Low earth orbit, Satellite orbits, Amateur satellites
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.