Breaking Through the Atmosphere: Humanity's Journey to Unveil the Invisible Universe with Infrared Space Telescopes
When we gaze at the starry sky, the brilliant Milky Way visible to the naked eye is merely the tip of the iceberg within the visible light spectrum of the cosmos. Shrouded by Earth's atmosphere, the vast majority of the electromagnetic spectrum—including infrared and ultraviolet waves—is filtered out layer by layer, leaving humanity's understanding of the universe in a prolonged state of "viewing flowers through a fog."
However, astronomers have never ceased their exploration. From instruments carried by balloons to the sophisticated optical systems of the James Webb Space Telescope, from ground-based observatories to deep-space orbits at Lagrange Point L2, the development of infrared space telescopes is a magnificent epic of humanity breaking through physical limits and decoding the universe's mysteries.
01
Breaking Through the Atmosphere: Early Explorations from Balloons to Aircraft
Water vapor, carbon dioxide, and ozone in Earth's atmosphere act like an invisible barrier, blocking starlight in the mid- and far-infrared wavelengths from ground-based observers. To breach this barrier, astronomers began experimenting with balloon-borne detectors in the mid-20th century. Although this method could briefly reach altitudes of 15-20 km, its shortcomings—short observation times and poor stability—made it difficult to meet scientific needs.
In 1974, NASA modified a Lockheed C-141 transport aircraft into the Kuiper Airborne Observatory (KAO). Cruising in the stratosphere at 14 km, its 0.915-meter aperture telescope could observe 85% of infrared wavelengths for over 7.5 hours continuously. This "flying observatory" not only discovered the rings of Uranus and the atmosphere of Pluto but also detected water molecules and organic molecules in interstellar space for the first time, providing key evidence for star formation theories.
The success of the KAO laid the foundation for subsequent developments. In 2010, the upgraded Stratospheric Observatory for Infrared Astronomy (SOFIA), carrying a 2.5-meter aperture telescope, took to the skies. Its Boeing 747SP platform could fly continuously for 10 hours at night, observing wavelengths from 1 to 1600 micrometers. As the only mobile observatory currently capable of working in the terahertz band, SOFIA studied comet structures and planetary atmospheres, and even discovered molecular jets around the supermassive black hole at the center of our galaxy, providing new perspectives for understanding galactic evolution.
02
The Journey to Space: The "Ice-Breaking" Mission of Infrared Satellites
The launch of the Infrared Astronomical Satellite (IRAS) in 1983 marked humanity's formal entry into the era of space-based infrared observation. Weighing 1.08 tons and equipped with a 0.57-meter primary mirror, this satellite in a 900 km sun-synchronous orbit completed the first all-sky infrared survey, discovering 350,000 infrared sources and 10 new celestial bodies. Its 73 kg liquid helium cooling system cooled the telescope to -271°C, pioneering ultra-cryogenic observation. Although its liquid helium depleted after 9 months, IRAS's data directly advanced the study of protoplanetary disks and cosmic dust distribution, providing an important reference for subsequent missions.
The Infrared Space Observatory (ISO), launched in 1995, further improved observational accuracy. Its 0.6-meter primary mirror and 283 kg liquid helium supply allowed it to operate in the 2.5-240 micrometer band for nearly three years, with a sensitivity a thousand times greater than IRAS. ISO discovered young planets around dying stars,颠覆了行星形成理论; detected water molecules in the Orion Nebula, providing clues for research into the origins of interstellar life; and for the first time detected hydrogen fluoride molecules in interstellar gas clouds, revealing the complexity of cosmic chemistry.
The Spitzer Space Telescope, launched in 2003, extended its operational life through innovative design. Its 0.85-meter beryllium primary mirror and 50.4 kg liquid helium allowed it to operate in the near-infrared for nearly 17 years. It not only directly captured infrared radiation from exoplanets but also discovered the double-helix nebula near the galactic center, providing visual evidence for the existence of black holes. Even after its helium was depleted, Spitzer, in its "warm mission" phase, discovered hundreds of exoplanets and brown dwarfs, becoming a "long-lived legend" of infrared astronomy.
03
Masterpieces: The "Eyes on the Cosmos" - Herschel and James Webb
The Herschel Space Observatory, launched in 2009, pushed infrared observation to new heights. Its 3.5-meter silicon carbide primary mirror was the largest space optical system at the time, capable of covering the 55-672 micrometer band and peering through interstellar dust clouds to observe early galaxies. During its 4-year mission, Herschel discovered interstellar oxygen molecules, confirmed that Earth's water might have come from comet impacts, and detected water vapor eruptions on the dwarf planet Ceres, redefining the classification of solar system bodies. Its data processing continued until 2017, making it an observatory that "kept working after retirement."
The James Webb Space Telescope (JWST), launched in 2021, represents the current pinnacle of technology. Its 6.5-meter gold-coated beryllium mirror, composed of 18 hexagonal segments, is 100 times more sensitive than Hubble, capable of capturing the infrared afterglow of the first stars and galaxies just 138 million years after the Big Bang. Webb has not only revealed the complex structures of early galaxies but also detected carbon dioxide and methane in exoplanet atmospheres, providing key clues in the search for habitable planets. Its iconic images, like the "Cosmic Cliffs," have viscerally conveyed the power of infrared observation to the public.
04
Chinese Contribution: From Follower to Leader
For a long time, China's infrared telescope technology was constrained by reliance on imports for high-performance detectors and precision optical systems. But in recent years, Chinese research teams have made breakthroughs in several key areas: domestically developed infrared detector chips have increased sensitivity tenfold, enabling domestic telescopes to capture fainter infrared signals; intelligent tracking systems can lock onto transient events like supernova explosions within 1 minute, such as the observation of SN2024xal in 2024, providing valuable data for astrophysical research; multi-wavelength collaborative observation networks link infrared, X-ray, and radio telescopes, enabling multi-dimensional observations of celestial bodies. For example, in the study of the Crab Nebula, data from different bands corroborated each other, revealing complex activities in the neutron star's magnetosphere.
The "Tianxunzhe" (Sky Surveyor) infrared telescope, commissioned in 2023, is equipped with a 1.2-meter primary mirror and achieves internationally advanced accuracy in near-infrared observations. Its participation in the "Milky Way Panorama Project" has already mapped the infrared spectra of 100,000 stars, providing massive datasets for studying the structure and evolution of our galaxy. The planned "Qiyuan" (Origins) infrared space telescope, scheduled for launch around 2030, will carry a 4-meter primary mirror focused on galaxy formation during the Cosmic Dawn, expecting to make major breakthroughs in dark energy detection and exoplanet atmosphere analysis.
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Future Prospects: The Leap from "Seeing" to "Understanding"
With advancing technology, infrared space telescopes are moving from "discovery" to "analysis." The US-planned Nancy Grace Roman Space Telescope, slated for launch in 2027, will feature a 2.4-meter wide-field primary mirror and, through the "Legacy Survey of Space and Time," will map the distribution of 300 million galaxies to reveal dark energy's influence on cosmic expansion. The Origins Space Telescope, planned for around 2035, with its potential 8-15 meter primary mirror and 10,000 times the angular resolution of Herschel in the far-infrared, will enable detailed spectroscopic analysis of exoplanet atmospheres, searching for chemical evidence of life.
China is advancing the "Tiangong-IR" infrared observatory plan, whose 2-meter primary mirror will operate in a co-orbital configuration with the space station, enabling long-term, continuous observations of celestial targets. Simultaneously, the application of quantum technology could bring revolutionary breakthroughs – quantum entanglement imaging technology could surpass the traditional diffraction limit, increasing the resolution of infrared telescopes by tens of times, potentially even allowing us to "see" surface features of exoplanets.
From the simple instruments of the Kuiper Airborne Observatory to the sophisticated systems of the James Webb Telescope, from IRAS's first sky survey to the grand vision of the Origins Telescope, the development of infrared space telescopes is a crystallization of human curiosity and technological creativity. They are not just cold combinations of metal and glass; they are the "Eyes of Time and Space" connecting Earth to the cosmos, allowing us to pierce through dust and fog, tracing the birth of stars, the evolution of galaxies, and even the origins of life.
When China's "Tianxunzhe" telescope captures the infrared afterglow of a supernova, and when James Webb reveals the galactic network of the early universe, we are weaving the ultimate answers of the cosmos with photons. And all of this begins with that simple yet profound belief: guided by light, humanity will ultimately reach the depths of the starry sea.
