![]() We are currently doing the analysis to determine just how much more correction of Webb’s trajectory will be needed, and how much fuel will be left, but we already know that the Ariane 5’s placement of Webb was better than requirements. There was also time to do a test firing of the required thruster before executing the actual burn. Ground stations in Malindi Kenya, Canberra Australia, and Madrid Spain provided the necessary ranging data. The burn wasn’t scheduled immediately after launch to give time for the flight dynamics team to receive tracking data from three ground stations, widely separated over the surface of the Earth, thus providing high accuracy for their determination of Webb’s position and velocity, necessary to determine the precise parameters for the correction burn. This leaves as much remaining fuel as possible for Webb’s ordinary operations over its lifetime: station-keeping (small adjustments to keep Webb in its desired orbit) and momentum unloading (to counteract the effects of solar radiation pressure on the huge sunshield). This time was chosen because the earlier the course correction is made, the less propellant it requires. The largest and most important mid-course correction (MCC), designated MCC-1a, has already been successfully executed as planned, beginning 12.5 hours after launch. Instead, as the diagram indicates, Webb operates in a very loose orbit (many hundreds of thousands of km in diameter) around L2, in constant sunlight and with clean communications with the ground stations. In addition, when Webb’s communication antennas point at Earth to receive commands, they would be blinded by the huge radio emission of the Sun in the same direction. Right at that point, Earth’s shadowing of the Sun would be large enough to greatly reduce the amount of power available for Webb’s solar arrays, without greatly simplifying the cooling challenges. Webb’s orbit is around L2-a point of gravitational balance on the other side of Earth from the Sun-but it does not reside exactly at the L2 point. After release of the observatory from the rocket, several small tweaks to the trajectory are planned, to ease the observatory into its operating orbit about one month after launch. ![]() In sending the Webb Observatory into its orbit around the Sun-Earth L2 point, the vast majority of the energy required was provided by the Ariane 5 rocket. To hear more about these important maneuvers, here is Randy Kimble, the Webb Integration, Test, and Commissioning Project Scientist, at NASA Goddard: 25, the Webb team successfully executed the first of three planned orbit corrections to get Webb into its halo orbit around the second Lagrange point, L2.
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