The longevity of the James Webb Space Telescope is limited by the amount of fuel it carries. However, it also contains solar panels. Why not put them to work instead to keep JWST orbiting?
James Webb Telescope You may be able to work for more than a decade. Its launch was so perfect that JWST It can have enough fuel to operate for 20 years. Hence, this would be up to four times its initial life: the observatory’s mission is set to last at least 5 years (not counting The first months of operation).
But why is James Webb so limited in his fuel? After all, it has solar panels on board. One can imagine that he uses it to produce all the energy he needs, as Hubble does. However, the two devices do not work the same way. JWST, which depends on its fuel, will not operate in low Earth orbit like Hubble. You will be 1.5 million kilometers from our region planetrevolve around the sun.
In fact, Hubble does not need fuel
« The Hubble Space Telescope’s orbit is not controlled, explains to Numerama Olivier La Marle, Coordinator of Astronomy Programs at Cnes. It descends very slowly. In every “mission serve” [ndlr : mission de maintenance] With the space shuttle, NASA took the opportunity to return to orbit. So this is no longer the case since the last time in 2009, but it has some margin, at an altitude of about 547 kilometers. »
JWST is currently on its way to its final location. By the end of January 2022, it should reach the L2 Lagrange point, which aligns with the Earth and the Sun. James Webb will not be placed exactly at point L2, but in orbit around it (he will complete an orbit around this point every 6 months). In this way, the observatory will always be outside the shadow of the Earth and on the moon Unlike Hubble, which enters and exits the Earth’s shadow every 1.5 hours.
But it is impossible to do without fuel for JWST
to James Webb, so no maintenance job possible. « JWST needs fuel, Emphasizes Olivier Lamarle, As is the case with almost all other satellites other than Hubble. Irreplaceable: To produce acceleration in space without any external force, any machine must expel matter in the opposite direction. This way James Webb will be able to stay in orbit around the L2 Lagrangian point.
As a result of, ” Life is limited by the amount of fuel used to maintain orbit “,” Abstract NASA Q&A, since the observatory can’t carry an unlimited amount of fuel – it’s filled 168 kg of hydrazine and 133 kg of nitrous oxide, which will be used together.
As for the solar panels, which are installed on the side of the observatory platform, they effectively ensure the production of electrical energy for James Webb. In this way, all systems are always up and running. The role of solar panels is to power scientific instruments and enable communications.
Olivier de la Marly asserts that they could not have played the same role as fuel. ” Sometimes used to make satellites run on themselves (they act as windmills facing the pressure of solar radiation), but rarely (they have a very weak effect) Expert details.
Why not use the principle of solar sail?
Like solar panels, they are not suitable for James Webb. this binoculars It basically needs “brakes” when hitting L2, which the sail won’t be able to provide, and any chemical thrust will save relatively little cost and fuel. In addition, the sail represents a large excess mass Olivier La Marle concludes.
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