After the James Webb Space Telescope took off from the UK, engineers conducted a "reception check" on the mid-infrared instruments of the James Webb Space Telescope at NASA's Goddard Space Flight Center.

JPL flight technicians Johnny Melendez (right) and Joe Mora inspect the MIRI cryogenic cooler before shipping it to Northrop Grumman in Redondo Beach, California. There, the cooler is connected to the main body of the Webb telescope.

This part of the MIRI instrument seen at the Appleton Laboratory in Rutherford, UK contains infrared detectors. The cryocooler is located far away from the detector because it operates at a higher temperature. A tube with cold helium gas connects the two parts.

MIRI (left) is sitting on the balance beam of Northrop Grumman in Redondo Beach. Engineers prepare to connect it to the Integrated Scientific Instrument Module (ISIM) using an overhead crane. ISIM is the heart of Weber and has four scientific instruments with telescopes.

Before the MIRI instrument-one of the four scientific instruments on the observatory-can operate, it must be cooled to almost the lowest temperature that the substance can reach.

NASA’s James Webb Space Telescope will be launched on December 22. It is the largest space observatory in history. It has an equally difficult task: collecting infrared light from far corners of the universe, allowing scientists to detect the structure and origin of the universe. . Our universe and our place in it.

Many cosmic objects—including stars and planets, as well as the gas and dust where they are formed—produce infrared light, sometimes called thermal radiation. But the same is true for most other warm objects, such as toasters, humans, and electronics. This means that Weber's four infrared instruments can detect their own infrared light. To reduce these emissions, the instrument must be very cold-about 40 Kelvin, or minus 388 degrees Fahrenheit (minus 233 degrees Celsius). But to function properly, the mid-infrared instrument or the detector in the MIRI must become colder: below 7 Kelvin (minus 448 degrees Fahrenheit, or minus 266 degrees Celsius).

This is only a few degrees higher than absolute zero (0 Kelvin)—the coldest temperature theoretically possible, although it can never be physically reached, because it means that there is no heat at all. (However, MIRI is not the coldest imaging instrument ever operating in space.)

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Temperature is essentially a measurement of the moving speed of atoms. In addition to detecting its own infrared light, the Weber detector can also be triggered by its own thermal vibration. The energy range of light detected by MIRI is lower than that of the other three instruments. Therefore, its detector is more sensitive to thermal vibration. These unwanted signals are what astronomers call "noise", and they can drown out the weak signals that Weber is trying to detect.

After launch, Weber will unfold a sun visor the size of a tennis court, which can block MIRI and other instruments from the effects of solar heat and allow them to passively cool down. Starting approximately 77 days after launch, MIRI's cryogenic cooler will take 19 days to reduce the temperature of the instrument's detector to less than 7 Kelvin.

"It is relatively easy to cool an object to that temperature on Earth, and it is usually used for scientific or industrial applications," said Constantine Penanen, a freezer expert at NASA’s Southern California Jet Propulsion Laboratory, a laboratory for NASA Manage MIRI instruments. "But those earth-based systems are very large and energy inefficient. For the space observatory, we need a physically compact, energy-efficient cooler, and it must be very reliable because we can’t go out and repair it. So these are what we face. Challenges. In this regard, I would like to say that MIRI cryogenic coolers are definitely at the forefront."

One of Weber's scientific goals was to study the properties of the first generation of stars formed in the universe. Weber's near-infrared camera or NIRCam instrument will be able to detect these extremely distant objects, and MIRI will help scientists confirm that these faint light sources are clusters of first-generation stars, rather than the evolution of the second-generation stars that formed later.

By observing dust clouds that are thicker than near-infrared instruments, MIRI will reveal the birthplace of stars. It will also detect common molecules on Earth, such as water, carbon dioxide, and methane, as well as rock minerals (such as silicates) in the cool surroundings of nearby stars that may form planets. Near-infrared instruments are better at detecting these molecules as vapor in hotter environments, while MIRI can treat them as ice.

"By combining expertise from the United States and Europe, we have developed MIRI as a powerful feature of Webb, which will enable astronomers from all over the world to answer major questions about how stars, planets and galaxies form and evolve," Gillian It is said that Wright is the co-head of the MIRI scientific team and the lead European researcher of the instrument at the UK Astronomical Technology Centre (UK ATC).

The MIRI cryocooler uses helium gas - enough to fill about nine party balloons - to take the heat away from the instrument's detectors. Two electric compressors pump helium through a tube that extends to the location of the detector. The tube passes through a metal block, which is also connected to the detector; the cooled helium absorbs excess heat from the metal block, thereby keeping the detector's operating temperature below 7 Kelvin. The warm (but still cold) gas then returns to the compressor, where the excess heat is discharged, and the cycle begins again. Fundamentally, the system is similar to that used in household refrigerators and air conditioners.

The helium-carrying pipe is made of gold-plated stainless steel and is less than one-tenth of an inch (2.5 mm) in diameter. It extends approximately 30 feet (10 meters) from the compressor located in the spacecraft bus area to the MIRI detector located in the optical telescope element, behind the main honeycomb mirror of the observatory. Hardware called deployable tower components or DTA connect these two areas. When packaged and launched, the DTA is compressed, a bit like a piston, to help install the stowed observatory into a protective device on the top of the rocket. Once in space, the tower will extend to separate the room temperature spacecraft bus from the cooler optical telescope instruments and allow the sun visor and telescope to be fully deployed.

This animation shows the ideal deployment performance of the James Webb Space Telescope within hours and days after launch. The expansion of the central deployable tower assembly will increase the distance between the two parts of MIRI. They are connected by coils with cooled helium gas.

However, the elongation process requires the helium tube to be extended together with the expandable tower assembly. So the tube is coiled like a spring, which is why MIRI engineers nicknamed this part of the tube "Slinky".

"There are some challenges when working on a system that spans multiple areas of the observatory," said Analysyn Schneider, MIRI project manager at the Jet Propulsion Laboratory. “These different areas are led by different organizations or centers, including Northrop Grumman and NASA’s Goddard Space Flight Center. We have to interact with everyone. No other hardware on the telescope needs to do this. So this is a unique challenge for MIRI. For MIRI cryogenic coolers, this is definitely a long road, and we are ready to see how it performs in space."

The James Webb Space Telescope will be launched in 2021 and will become the world's premier space science observatory. inside. Webb is an international project led by NASA, its partners ESA (European Space Agency) and the Canadian Space Agency.

MIRI was developed through a 50-50 partnership between NASA and ESA (European Space Agency). JPL leads the United States' efforts for MIRI, and the multinational consortium of European Astronomical Institutions contributes to ESA. George Rieke of the University of Arizona is the head of MIRI's American Science Team. Gillian Wright is the head of MIRI's European scientific team.

Alistair Glasse of ATC in the UK is an instrument scientist at MIRI, and Michael Ressler is an American project scientist at JPL. Laszlo Tamas manages the European consortium together with the British ATC. The development of the MIRI cryogenic cooler is led and managed by Jet Propulsion Laboratory in collaboration with NASA Goddard Space Flight Center in Greenbelt, Maryland, and Northrop Grumman in Redondo Beach, California.

For more information about Weber’s mission, please visit:

https://www.nasa.gov/webb

Jet Propulsion Laboratory, Pasadena, California

calla.e.cofield@jpl.nasa.gov

Goddard Space Flight Center, Greenbelt, Maryland

laura.e.betz@nasa.gov

alise.m.fisher@nasa.gov

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