The James Webb Space Telescope is now 90 percent off the road to its destination, Lagrangian point 2 (L2), where it will begin its 10-plus-year mission by looking into the distant depths of the cosmos.
JWST's expected arrival at L2 on 23 January will not be the last step for the telescope to complete before embarking on its scientific mission - with months of instrument calibration and testing left - but it will mark the successful end of a long physical journey. , which started with a secret trip down the Panama Canal in October.
But JWST's journey in time will continue. It began as a mere concept in the late 1980s, slowly took physical shape and was refined over more than 20 years and will soon begin to function in the years to come - all to look billions of years into the past for to witness the birth of the very first galaxies in our universe. JWST is the largest space telescope ever launched, and is designed to help us cross space and time and measure things that previously existed only in our imagination and our mathematics.
Where is JWST now?
According to NASA Goddard Space Flight Center "Where's Webb?" website, the space agency's flagship observatory had reached more than 835,000 miles from Earth the following Tuesday, and there was a little more than 63,000 miles left before it went into orbit around L2. L2 is a point about 1 million miles from Earth where the Earth's gravity and the Sun's gravity equalize, allowing the JWST to maintain a constant position relative to the Earth as they both orbit the Sun.
What's next for JWST?
While NASA considers the telescope to be "completely unrolled" after the successful deployment of its primary mirror on January 8, JWST still has tasks to perform in this final stretch to reach orbits around L2.
First, ground operators are in the midst of a 10-day implementation of each of the 18 beryllium mirror segments that make up JWST's primary mirror. Each segment can and must be focused individually in order for the mirror to function as a single mirror with a diameter of 6.5 meters as intended, but first they must be moved out of the positions they were locked in for JWST's launch back on 25 December. Each segment has approx. 12.5 millimeters to move, and it takes about a day to move all 18 segments by one millimeter, a pace NASA compares to watching grass grow.
Next, JWST must complete its third and final course correction firing, which will insert it into orbits around L2. There is little chance of failure here - an efficient launch and orbit have so far saved JWST enough fuel for NASA to believe it will work for longer than expected in 10 years - but efforts are high. If JWST could not achieve orbit around L2, it could continue to sail into deep space, irrevocably.
Once JWST is safe in orbit around L2, JWST needs to relax: From Tuesday afternoon, the business side of JWST, shielded from the sun's heat by a five-layer sunshade, sat between minus 330 and minus 340 Fahrenheit (the "heat"). side facing the Earth and the Sun was between 50 and 133 degrees Fahrenheit) .But as an exquisitely sensitive infrared telescope, the JWST must cool down to minus 388 degrees Fahrenheit to ensure that its instruments are not dazzled by "glare".
Once the JWST has cooled down, it still has months of calibration and testing to perform. When fully extended from their firing positions, the slow-moving mirror segments will be focused so that they can create a precise, in-focus image of JWST's scientific goals.
Once the optics are focused, NASA will calibrate each of the JWST's four scientific instruments and test them individually, then calibrate and test them together.
All in all, it is a process that is expected to last well into the summer, and only then can scientists finally breathe a sigh of relief that everything has worked and start making groundbreaking science.
What will JWST do when it is operational?
As a high-aperture infrared telescope, the JWST is perfectly suited for looking further into the universe, and therefore further back in time, than any telescope ever built. It should be able to image some of the first stars and galaxies so astronomers can see the universe as it was less than 200 million years after the big bang, the terrible twos in our now 13.8 billion year old universe.
Being set to look across the infrared part of the spectrum and carry a spectrometer also means that JWST will be able to study distant exoplanets in completely new details, decompose the components of these world atmospheres and search for organic compounds that could be signs of life, and help answer the question of whether we are alone.
JWST will also turn on the objects in our solar system by using its powerful infrared instruments to help planetary scientists better understand the atmosphere of the outer planets, map organic matter on the surface of Mars and once again search for signs of life in water jets seen erupt from icy moons like Jupiter's Europe and Saturn's Enceladus.