Lecture

Nodal Regression and Sun-synchronous Orbits

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Description

This lecture covers the progression of nodes in space mission design, focusing on nodal regression and Sun-synchronous orbits. It explains the effects of Earth's equatorial bulge on orbital dynamics, the forces and torques involved in nodal regression for Low Earth Orbit (LEO), and the calculation of nodal regression rate. Additionally, it discusses how the nodal regression rate varies with orbital inclination and altitude, highlighting the drift of the line of nodes for different types of orbits. The lecture also delves into the requirements and specific inclinations and altitudes for achieving a Sun-synchronous orbit.

In MOOC

Space Mission Design and Operations

Space exploration is a very exciting subject. Consider the achievements of Sputnik 1, Yuri Gagarin's first flight in space, the Apollo missions to the Moon, followed by the Shuttle program, the Hubble Space Telescope launch and maintenance on orbit, and finally the assembly and exploitation of the International Space Station. These were challenging undertakings involving space agencies and industrial teams of several nations, and private companies as well. Space telescopes are in service, and several compon

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Related concepts (32)

Orbital station-keeping

In astrodynamics, orbital station-keeping is keeping a spacecraft at a fixed distance from another spacecraft or celestial body. It requires a series of orbital maneuvers made with thruster burns to keep the active craft in the same orbit as its target. For many low Earth orbit satellites, the effects of non-Keplerian forces, i.e. the deviations of the gravitational force of the Earth from that of a homogeneous sphere, gravitational forces from Sun/Moon, solar radiation pressure and air drag, must be counteracted.

Geocentric orbit

A geocentric orbit, Earth-centered orbit, or Earth orbit involves any object orbiting Earth, such as the Moon or artificial satellites. In 1997, NASA estimated there were approximately 2,465 artificial satellite payloads orbiting Earth and 6,216 pieces of space debris as tracked by the Goddard Space Flight Center. More than 16,291 objects previously launched have undergone orbital decay and entered Earth's atmosphere. A spacecraft enters orbit when its centripetal acceleration due to gravity is less than or equal to the centrifugal acceleration due to the horizontal component of its velocity.

Orbital maneuver

In spaceflight, an orbital maneuver (otherwise known as a burn) is the use of propulsion systems to change the orbit of a spacecraft. For spacecraft far from Earth (for example those in orbits around the Sun) an orbital maneuver is called a deep-space maneuver (DSM). The rest of the flight, especially in a transfer orbit, is called coasting.

Equatorial bulge

An equatorial bulge is a difference between the equatorial and polar diameters of a planet, due to the centrifugal force exerted by the rotation about the body's axis. A rotating body tends to form an oblate spheroid rather than a sphere. Earth ellipsoid The planet Earth has a rather slight equatorial bulge; its equatorial diameter is about greater than its polar diameter, with a difference of about of the equatorial diameter. If Earth were scaled down to a globe with an equatorial diameter of , that difference would be only .

Orbital plane

The orbital plane of a revolving body is the geometric plane in which its orbit lies. Three non-collinear points in space suffice to determine an orbital plane. A common example would be the positions of the centers of a massive body (host) and of an orbiting celestial body at two different times/points of its orbit. The orbital plane is defined in relation to a reference plane by two parameters: inclination (i) and longitude of the ascending node (Ω).

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