How Webb's Course Corrections Changed Everything

 

NASA's 29 days on the edge is in full swing and the James Webb space telescope has undergone two of its three course corrections

 on the way to its orbiting point

 if the corrections failed the possibility is strong that the 10 billion three decade project would fly right past its target and into deep space it would then become what one observer called the most expensive space junk in history welcome to Science Reads in today's article we dig deep into the course corrections that mean the difference between unprecedented success for humanity's most ambitious observatory project and a study in useless technology course corrections are more than critical for Webb's mission to succeed they are life and death reaching destination l2 or the sun earth second lagrange point is vital for the project to gather the unprecedented data it's designed for while most of the energy necessary to propel the telescope to its final destination was provided by the rn5 rocket reaching the proper orbiting point requires more trajectory changes along the way the most important mid-course correction mcc dubbed by nasa as mcc-1a began 12.5 hours after the rocket left the spaceport in kuru French Guyana on December 25th besides the obvious challenge of making sure JWST reached its destination nasa also determined this time for course correction based on fuel consumption propellant took 10 days to load due to how toxic and dangerous it is specifically 159 liters or 43 gallons of hydrazine fuel and 79.5 liters or 21 gallons of dinitrogen tetroxide oxidizer this amount of fuel is the main factor in how long the spacecraft's life span extends the correction time was chosen for 12.5 hours after launch to be early enough that less fuel will be consumed by the correction meaning more remains for regular operations and extending Webb's lifetime more on that later the correction wasn't scheduled sooner to allow the flight dynamics team to get tracking data from widely dispersed ground stations in Kenya, Australia and Spain this gave them critically accurate details on Webb's journey thus far so the correction burn would be exactly what was needed to reach the right point at l2 and while the team worked to analyze exactly how much of a correction was needed it was apparent quickly that Ariane 5's positioning of web was better than the mission required now it's time to correct course and if it's done incorrectly mission aborted imagine being in a vehicle with only an

 accelerator you will eventually slow down and hopefully at the right point but if

 at any moment you accelerate too much you overshoot your destination with no possibility of turning back and getting there for the james webb space telescope it is a similar challenge it was always intended for the rn5 to deliver a slight underburn when launched because there is no course correction possible for overthrust it is critical that webb maintains its sun-facing side pointed back and away from the telescope's cold optics there cannot be heat to condense on the observatory's coal side or mission over thus the thrusters can only push JWST away from the sun so overshooting l2 leaves no way to return likewise this led to mcc-1a also being designed to slightly under burn just as any overthrust by aureon5 dooms the mission it's the same results from any subsequent course correction that goes too far at the same time much like any spacecraft Webb needed to perform this trajectory maneuver to atone for slight differences in where the Ariane 5 placed it so far so good at 8 55 pm eastern time on December 25th after 65 nail-biting minutes of course correction burn JWST was successfully pointed toward its destination mission control was elated by this 65-minute burn which may seem like a long time but could easily have lasted as long as three hours not only did it require less fuel but it was also accurate and added 72 kilometers per hour or 45 miles per hour to web speed however two more crucial course corrections are coming one only two days later the second course correction was completed by nasa two days after the James Webb space telescope launched and it was also critical that the spacecraft be properly aligned on course to its l2 destination and especially that the level of thrust provided did not cause it to fly right past its target and into infamy nasa reported the second course correction dubbed mcc-1b began at 7:20 pm eastern time on Monday December 27th 60 hours after liftoff it was a shorter process lasting only 9 minutes and 27 seconds and was successful as well not only did the course correction nerve-wracking though it was go off without a hitch just minutes later Webb crossed the moon's orbit nasa officials tweeted it's been a busy evening not only did we just complete our second burn but hashtag nasa web also passed the altitude of the moon as it keeps cruising on to the second lagrange point to hashtag unfold the universe by at nasa moon perhaps it should be noted that by moon did not mean that Webb came anywhere near earth's satellite just that it crossed the average distance of the moon's orbit from earth 240 000 miles or 384 000 kilometers it was observed by astronomer Jonathan McDowell that the closest web came to the moon was when it sat on the launch pad in kuru so do we want the good news or the better news first from the beginning the saga of the James Webb space telescope is one of missed targets cost overruns and shall we say engineering challenges the first launch date of 2007 whiz by just like the next one and the next one and so on but why dwell on the past when the present is going so well first the good news all is well thus far both course corrections work as planned deployments have gone smoothly and what project engineers practice repeatedly has worked like a charm and now the better news there was never

 going to be a Hubble type lifespan for Webb the Hubble space telescope was deployed in 1990 and is coming up on its 32nd year of operation not so for web the rocket propellant on board is a critical factor in the observatory's lifespan and web launched with a minimum baseline of a five year mission besides mid-course corrections and insertion into orbit around l2 the fuel must be available for other necessary functions such as small thruster burns to adjust Webb's orbit to maintain proper orientation in space now it's time to tip our hats to the aryan space aryan 5 launch it was obvious to mission engineers early on that the rocket outperformed expectations in putting Webb on the correct trajectory then there's the first mid-course correction maneuver which as we already noted took only 65 minutes when planners foresaw up to three hours of burn needed now add to that the extra 72 kilometers per hour that's 45 miles per hour to its velocity due to the precision of the correction maneuver plus the second correction maneuver on day three put another 6.3 miles per hour or 10.1 kilometers per hour on the spacecraft speedometer meaning even less fuel needed to retail too add all this together and you get the news that nasa posted on day five december 29th the web team has analyzed its initial trajectory and determined the observatory should have enough propellant to allow support of science operations in orbit for significantly more than a 10-year science lifetime nasa further says the analysis shows that less propellant than originally planned for is needed to correct Webb's trajectory toward its final orbit around l2 a point of gravitational balance on the far side of earth away from the sun consequently Webb will have much more than the baseline estimate of propellant though many factors could ultimately determine Webb's duration of operation so before the entire James Webb space telescope is completely unfurled we have the expectation of double or more of the science anticipated at launch as critical as this seems it's even more critical in that web will be virtually impossible to be serviced or refueled as it might be in an earth orbit and

 there's still one more correction to come remember nasa's 29 days on the edge day 29 will see the third mid-course correction for Webb and this time if all goes well it will be to insert the observatory into the optimal orbit around l2 as mike menzel webb mission lead system engineer said there are no second chances we have 300 single point failure items and they will all have to work right when you are a million miles away from earth you cannot send someone to fix it with so many potential obstacles ahead uncorking champagne must wait until mid-summer at the earliest there's much nail-biting and hand-wringing left to be done by nasa and all of us who want a closer look at our universe but it is understandable that after so many years of rolling the rock up the hill only to see it come tumbling back down nasa maybe just maybe is on the verge of seeing its historic mission to explore the beginnings of the universe come to fruition so what do you think about the progress thus far of the James Webb space telescope are you sharing in nasa's 29 days on the edge checking for updates on humanity's latest and greatest mission to peer into our universe's past tell us in the comments and as always

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