• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer
  • Advertise
  • Subscribe

Test & Measurement Tips

Oscilloscopes, electronics engineering industry news, how-to EE articles and electronics resources

  • Oscilloscopes
    • Analog Oscilloscope
    • Digital Oscilloscope
    • Handheld Oscilloscope
    • Mixed-signal Oscilloscope
    • PC-based Oscilloscopes – PCO
  • Design
  • Calibration
  • Meters & Testers
  • Test Equipment
  • Learn
    • eBooks/Tech Tips
    • FAQs
    • EE Training Days
    • Learning Center
    • Tech Toolboxes
    • Webinars & Digital Events
  • Video
    • EE Videos
    • Teardown Videos
  • Resources
    • Design Guide Library
    • Digital Issues
    • Engineering Diversity & Inclusion
    • Leap Awards
    • White Papers
  • Subscribe
You are here: Home / Test and Measurement News / Another Covid casualty: The James Webb telescope

Another Covid casualty: The James Webb telescope

March 26, 2020 By David Herres Leave a Comment

NASA has announced it will pause work on the James Webb Space Telescope because of the ongoing COVID-19 pandemic. The launch is still currently on the books for 2021, but there are questions about whether that date will hold.

Webb
A robotic arm installs the last of the telescope’s 18 mirror segments onto the telescope structure.

The James Webb Space Telescope, successor to the Hubble and Spitzer instruments, was originally scheduled to launch on an Ariadne 5 rocket from French Guiana in October, 2018. It has been subject to repeated cost overruns a rescheduling since its inception in 1996.

Once it is finally in orbit, the telescope will see farther back in time than its predecessors, imaging faint entities whose light has been in transit almost the entire 13.82 billion-year age of the universe.

The Webb Space Telescope will have far greater resolution that even the amazing Hubble Space Telescope. Having almost three times Hubble’s aperture, 6.5 m (21 ft), it will see from long-wavelength visible light through near-infrared to mid-infrared. A unique feature of the Webb instrument is its large sun shield, which will keep the mirror and associated instrumentation at a uniform 50°K. The effect of all this hardware will be to enable the instrument to process light from extremely faint objects and from the epoch of re-ionization. It is anticipated that exoplanets will be directly imaged, as opposed to being inferred by their effects on the host stars.

To do so, Webb’s mirrors collect light from the sky and direct it to instruments which filter the light, or spectroscopically disperse it, before finally focusing it onto the detectors. NASA says Webb has extended the state-of-the-art for infrared detectors by producing arrays that are lower noise, larger format, and longer lasting than their predecessors.

detector
A James Webb Space Telescope Near Infrared Camera (NIRCam) detector. Light collects in the purple mercury-cadmium-telluride film. Not shown is a black optical baffle that admits light onto the detectors while blocking it from hitting any surfaces that might reflect, such as the edges of a detector.

Webb uses two different types of detectors: mercury-cadmium-telluride (HgCdTe) “H2RG” detectors for the 0.6-5-μm near-infrared spectrum and arsenic-doped silicon (Si:As) detectors for the 5-28-μm mid-infrared range. (H2RG is the name of the Teledyne product line. Raytheon Vision Systems made the mid-infrared detectors.) Each Webb H2RG detector has about 4 million pixels. The mid-infrared detectors have about 1 million pixels each.

By varying the ratio of mercury-to-cadmium in the HgCdTe detectors, it is possible to tune the material to sense light of longer or shorter wavelengths. Webb takes advantage of this by using two compositions of HgCdTe: one with proportionally less mercury for 0.6 – 2.5 μm, and another with more for 0.6 – 5 μm. This has a number of advantages, including the possibility of tailoring each detector for peak performance over the specific wavelengths for which it will be used.

The telescope may read the pixels in its detectors more than once before resetting them. This provides several benefits. For example, it is possible to average multiple non-destructive reads to reduce the noise. Another advantage is that using multiple samples of the same pixel makes it possible to see the “jumps” in signal level that are the tell-tale sign that a cosmic ray has disturbed the pixel. Then ground-based processing can apply a correction to recover much of the scientific value of the affected pixel.

You may also like:

  • radio telescopes
    Will 5G make earth-bound radio telescopes impractical?

  • Working with optical fiber

  • Using a scope to read signals obscured by noise
  • telescope axes
    Basics of telescope optics and mounting

Filed Under: FAQ, Featured, Test and Measurement News Tagged With: FAQ

Reader Interactions

Leave a Reply Cancel reply

You must be logged in to post a comment.

Primary Sidebar

Featured Contributions

Why engineers need IC ESD and TLP data

Verify, test, and troubleshoot 5G Wi-Fi FWA gateways

How to build and manage a top-notch test team

How to use remote sensing for DC programmable power supplies

The factors of accurate measurements

More Featured Contributions

EE TECH TOOLBOX

“ee
Tech Toolbox: Internet of Things
Explore practical strategies for minimizing attack surfaces, managing memory efficiently, and securing firmware. Download now to ensure your IoT implementations remain secure, efficient, and future-ready.

EE TRAINING CENTER

EE Learning Center

EE ENGINEERING TRAINING DAYS

engineering
“test
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, tools and strategies for EE professionals.
“bills

RSS Current EDABoard.com discussions

  • ISL8117 buck converter blowing up
  • need of carrier supression when locking to cavity resonator
  • Wireless microphone reviews
  • audio transformers impedance
  • Help Creating .lib File for SCR in LTspice

RSS Current Electro-Tech-Online.com Discussions

  • RS485 bus: common ground wire needed or not?
  • Kawai KDP 80 Electronic Piano Dead
  • Good Eats
  • What part is this marked .AC ?
  • Photo interrupter Connections
Search Millions of Parts from Thousands of Suppliers.

Search Now!
design fast globle

Footer

EE World Online Network

  • 5G Technology World
  • EE World Online
  • Engineers Garage
  • Analog IC Tips
  • Battery Power Tips
  • Connector Tips
  • DesignFast
  • EDA Board Forums
  • Electro Tech Online Forums
  • EV Engineering
  • Microcontroller Tips
  • Power Electronic Tips
  • Sensor Tips

Test & Measurement Tips

  • Subscribe to our newsletter
  • Advertise with us
  • Contact us
  • About us

Copyright © 2025 · WTWH Media LLC and its licensors. All rights reserved.
The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media.

Privacy Policy