The JWST will be located near the second Lagrange point (L₂) of the Earth-Sun system, which is 1,500,000 kilometres (930,000 mi) from Earth, directly opposite to the Sun.
Normally an object circling the Sun farther out than Earth would take longer than one year to complete its orbit, but near the L₂ point the combined gravitational pull of the Earth and the Sun allow a spacecraft to orbit the Sun in the same time it takes the Earth.
The telescope will circle about the L₂ point in a halo orbit, which will be inclined with respect to the ecliptic, have a radius of approximately 800,000 kilometres (500,000 mi), and take about half a year to complete.
Since L₂ is just an equilibrium point with no gravitational pull, a halo orbit is not an orbit in the usual sense: the spacecraft is actually in orbit around the Sun, and the halo orbit can be thought of as controlled drifting to remain in the vicinity of the L₂ point.
This requires some station-keeping: around 2–4 m/s per year from the total budget of 150 m/s.
Two sets of thrusters constitute the observatory's propulsion system.
The JWST will be located near the second Lagrange point (L₂) of the Earth-Sun system, which is 1,500,000 kilometres (930,000 mi) from Earth, directly opposite to the Sun. Normally an object circling the Sun farther out than Earth would take longer than one year to complete its orbit, but near the L₂ point the combined gravitational pull of the Earth and the Sun allow a spacecraft to orbit the Sun in the same time it takes the Earth. The telescope will circle about the L₂ point in a halo orbit, which will be inclined with respect to the ecliptic, have a radius of approximately 800,000 kilometres (500,000 mi), and take about half a year to complete. Since L₂ is just an equilibrium point with no gravitational pull, a halo orbit is not an orbit in the usual sense: the spacecraft is actually in orbit around the Sun, and the halo orbit can be thought of as controlled drifting to remain in the vicinity of the L₂ point. This requires some station-keeping: around 2–4 m/s per year from the total budget of 150 m/s. Two sets of thrusters constitute the observatory's propulsion system.
James Webb Space Telescope