| Image in infrared light by NASA’s new James Webb Space Telescope, revealing previously invisible areas of star birth. On July 13, NASA published its official review of the performance of its new James Webb Space Telescope (JWST) after 6 months of commissioning: positioning, alignment, calibration, and testing. Conclusion: JWST exceeds every significant design goal. JWST has demonstrated the sensitivity, stability, image quality, and spectral range (span of light wavelengths) to achieve its design goals of enabling “fundamental breakthroughs in our understanding of the formation and evolution of galaxies, stars, and planetary systems”. JWST’s demonstrated performance exceeds expectations in: · precise alignment of its 18 main-mirror segments, · image resolution (seeing fine detail), stability over time · and pointing accuracy (keeping targets centered during long exposures). Precisely executed launch and navigation to its destination, orbiting L2, saved enough fuel to extend JWST’s useful life to 20 years, twice its design goal. L2 is the second Lagrange point of Earth’s orbit around the Sun. A satellite at L2 orbits the Sun in lockstep with Earth, maintaining a constant distance of about 1 million miles. The Sun, Earth, and L2 always lie on a straight line. JWST excels at imaging infrared light, and can therefore see “deeper” (farther away and closer to the beginning of time) than can visible light telescopes like Hubble. Infrared light has much longer wavelength and much lower energy than visible light, so JWST must operate at very low temperatures. This is extremely challenging in outer space, where it’s almost impossible to dissipate heat. JWST’s elaborate 5-layer sunshield meets that challenge. The primary mirror operates at 45K (45 Kelvin or –380ºF). The secondary mirror is at 29K (–407ºF), and the infrared imager (MIRI) is at 6.4K (–448ºF). JWST’s temperature stability is outstanding — the telescope varies only ±0.04K, and the imaging instruments vary only ±0.01K. These infrared images of part of a nearby galaxy compare the JWST (right) to NASA’s previously best infrared space telescope, Spitzer at its prime (left). At launch, JWST had 344 single-point failure risks — if any one of 344 components failed, the whole mission was doomed, no “plan B”. Now, 295 of these critical components have performed properly and are no longer needed. This leaves 49 critical components that are still needed, and must continue to work properly; the radio antenna that transmits image data back to Earth is one example. It has no backup, but its risk of failure is deemed very low. One unpleasant reality of all space telescopes is being hit by micrometeriods that are ubiquitous in the Solar System, with numerous small ones and a few large ones. NASA estimated the primary mirror would suffer 1 hit per month, and indeed, after 6 months in space, it has been hit 6 times. Unfortunately, one micrometeriod caused about 10 times more damage than the expected average. NASA hopes that was a fluke and won’t recur often. The telescope remains within its design criterion, even after that damage. Mirror quality is quantified by Wave Front Error (WFE), the average (“rms”) mirror surface deviation from the perfect shape. The micrometeriod impact raised JWST’s WFE from 52 to 59 nm (1 nm = 1 billionth of a meter; 59 nm ~ 2 millionth of an inch) The design calls for WFE less than 70 to 130 nm, depending on the wavelength of light being imaged. With great results from over 100 commissioning tests, JWST has begun Cycle 1, its first sequence of scientific observations. Here is JWST’s first “deep” image, presented on behalf of a proud nation by President Biden. Hubble revolutionized our understanding of the universe and our place in the cosmos. James Webb is its worthy successor, promising new breakthroughs that will further astonish and amaze. Best Wishes, Robert July, 2022 Note: Previous newsletters can be found on my website. | 