Orbits — Set 4

Correct Answer: B. Geosynchronous (inclined)

An inclined geosynchronous orbit has the same period as Earth's rotation but is tilted. From the ground, it appears to oscillate north and south over a fixed longitude. This creates a characteristic ground track resembling the number eight.

Correct Answer: A. Orbital Velocity

Orbital velocity is the specific speed needed to keep an object in orbit. For LEO, it is approximately 7.8 km/s (28,000 km/h). If the speed is lower, the object falls; if higher, the orbit becomes elliptical or escapes.

Correct Answer: C. Rotational Assist

Launching towards the east from near the equator adds the Earth's rotational speed to the rocket. This saves a significant amount of fuel and allows for heavier payloads. This is why many launch sites, like Sriharikota, are on east coasts near the equator.

Correct Answer: B. Semi-Synchronous Orbit

A semi-synchronous orbit has a period of half a sidereal day. This is the specific orbit used by GPS satellites at about 20,200 km altitude. It allows the satellite to pass over the same two points on the equator every day.

Correct Answer: B. Ascending Node

The ascending node is one of the two orbital nodes where the orbit intersects a reference plane. Tracking these nodes is essential for calculating a satellite's exact position in space. The opposite point is called the descending node.

Correct Answer: B. Sun-Synchronous

Sun-synchronous orbits take advantage of the Earth's non-spherical shape (oblateness) to precess at the same rate the Earth orbits the Sun. This allows the satellite to always have the same lighting for its photography. It is a favorite for environmental monitoring.

Correct Answer: A. Parking Orbit

A parking orbit is a temporary LEO used by spacecraft before they are injected into a higher orbit or deep space. It allows mission control to verify the health of the spacecraft. It also provides flexibility in timing the final burn for the destination.

Correct Answer: B. Van Allen Radiation Belts

The Van Allen belts are two layers of energetic charged particles held in place by Earth's magnetosphere. Satellites must be shielded to pass through these belts safely. Most orbits are chosen to either stay below or sit between these radiation zones.

Correct Answer: B. Kepler's Third Law

Kepler's Third Law allows scientists to calculate the exact distance of an orbit if they know the required period. This is how the altitude of the Geostationary orbit was determined. It applies to all orbiting bodies in the solar system.

Correct Answer: B. Line of Apsides

The line of apsides is the major axis of an elliptical orbit. It passes through the center of the Earth and both the closest and farthest points of the orbit. Its orientation in space is one of the orbital elements used to define a mission.