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posted by Fnord666 on Monday October 02 2017, @02:05AM   Printer-friendly
from the testing-integration dept.

The launch of the James Webb Space Telescope has been delayed yet again:

The launch of NASA's James Webb Space Telescope (JWST) has been rescheduled to occur sometime between March and June 2019 from French Guiana. The delay follows a schedule assessment of the remaining integration and test activities that need to occur prior to launch. The JWST was previously scheduled to launch in October 2018. "The change in launch timing is not indicative of hardware or technical performance concerns," Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate at Headquarters in Washington, said in a NASA press release. "Rather, the integration of the various spacecraft elements is taking longer than expected."

The change in launch window request has been coordinated with the European Space Agency (ESA), which is providing the Ariane 5 launch vehicle for the JWST. As part of an agreement with ESA, NASA recently conducted a routine schedule assessment to ensure launch preparedness and determined that a reschedule was necessary.

While testing of the telescope and science instruments at NASA's Johnson Space Center (JSC) in Houston, Texas, continues to go well and remain on schedule, the spacecraft itself, made up of the spacecraft bus and sunshield, has experienced delays during its integration and testing at Northrop Grumman in Redondo Beach, California. "Webb's spacecraft and sunshield are larger and more complex than most spacecraft," said Eric Smith, program director for the James Webb Space Telescope at NASA Headquarters in Washington. "The combination of some integration activities taking longer than initially planned, such as the installation of more than 100 sunshield membrane release devices, factoring in lessons learned from earlier testing, like longer time spans for vibration testing, has meant the integration and testing process is just taking longer. Considering the investment NASA has made, and the good performance to date, we want to proceed very systematically through these tests to be ready for a Spring 2019 launch."

An upside? A better chance of being prepared to image Planet Nine during the 5-10 year operating life of JWST.

Also at NASA.

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  • (Score: 2) by takyon on Monday October 02 2017, @07:37PM

    by takyon (881) <{takyon} {at} {}> on Monday October 02 2017, @07:37PM (#576128) Journal

    Unclear (to me):

    • While JWST was not designed to be easily serviced by astronauts or robotic craft, and is much further away than Hubble, could it still be serviced by either method if we chose to do so?
    • Will JWST be permanently damaged once coolant runs out? ie. If we refill the coolant, propellant, and replace batteries in 20 years, will it still be unusable?
    • Would the JWST's eventual drift from the L2 point once it runs out of propellant permanently prevent the craft from being useful or reachable?
    • Can JWST operate in the near-infrared even after coolant runs out?
    • Is the 5-10 year lifetime estimate yet another conservative NASA estimate? Example: the Opportunity rover has lasted over 13 years instead of 90 days. []

    However, infrared telescopes have an Achilles heel—they need to stay extremely cold, and the longer the wavelength of infrared, the colder they need to be.[45] If not, the background heat of the device itself overwhelms the detectors, making it effectively blind.[45] This can be overcome by careful spacecraft design, in particular by placing the telescope in dewar with an extremely cold substance, such as liquid helium.[45] This has meant most infrared telescopes have a lifespan limited by their coolant, as short as a few months, maybe a few years at most.[45] It has been possible to maintain a temperature low enough through the design of the spacecraft to enable near-infrared observations without a supply of coolant, such as the extended missions of Spitzer or NEOWISE. Another example is Hubble's NICMOS instrument, which started out using a block of nitrogen ice that depleted after a couple years, but was then converted to a cryocooler that worked continuously. The James Webb Space Telescope is designed to cool itself without a dewar, using a combination of sun-shield and radiators with the mid-infrared instrument using an additional cryocooler.[46]

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