Terahertz technology has been driven largely by applications in astronomy and space science. For more than three decades cosmochemists, molecular spectroscopists, astrophysicists, and Earth and planetary scientists have used submillimeter-wave or terahertz sensors to identify, catalog and map lightweight gases, atoms and molecules in Earth and planetary atmospheres, in regions of interstellar dust and star formation, and in new and old galaxies, back to the earliest days of the universe, from both ground based and more recently, orbital platforms. The past ten years have witnessed the launch and successful deployment of three satellite instruments with spectral line heterodyne receivers above 300 GHz (SWAS, Odin, and MIRO) and a fourth platform, Aura MLS, that reaches to 2520 GHz, crossing the terahertz threshold from the microwave side for the first time. The former Soviet Union launched the first bolometric detectors for the submillimeter way back in 1974 and operated the first space based submillimeter wave telescope on the Salyut 6 station for four months in 1978. In addition, continuum, Fourier transform and spectrophotometer instruments on IRAS, ISO, COBE, the recent Spitzer Space Telescope and Japan's Akari satellite have all encroached into the submillimeter from the infrared using direct detection bolometers or photoconductors. At least two more major satellites carrying submillimeter wave instruments are nearing completion, Herschel and Planck, and many more are on the drawing boards in international and national space organizations such as NASA, ESA, DLR, CNES, and JAXA. This paper reviews some of the programs that have been proposed, completed and are still envisioned for space applications in the submillimeter and terahertz spectral range.

THz Instruments for Space

The Infrared Space Observatory (ISO) mission

The origin of water vapor and carbon dioxide in Jupiter's stratosphere

The enigmatic object η Carinae is believed to represent an important, but short-lived, unstable phase in the life of the most massive stars, occurring shortly before they explode as supernovae or collapse directly to black holes. The putative binary1,2 system believed to constitute η Carinae survived an outburst in the previous century that lasted 20 years; and which created a nebula with pronounced bipolar lobes that together contain about 2.5 solar masses of material. The nebula also exhibits an equatorial ‘waist’ containing about 0.5 solar masses3. The physical mechanisms responsible for the outburst and the bipolar geometry are not understood. Here we report infrared observations (spectroscopy and imaging) that reveal the presence of about 15 solar masses of material, located in an equatorial torus. The massive torus may have been created through highly non-conservative mass transfer, which removed the entire envelope of one of the stars, leaving an unstable core that erupted in the nineteenth century. The collision of the erupted material with the pre-existing torus provides a natural explanation for the bipolar shape of the nebula.

Discovery of a massive equatorial torus in the η Carinae stellar system

Far-infrared astronomy has advanced rapidly since its inception in the late 1950's, driven by a maturing technology base and an expanding community of researchers. This advancement has shown that observations at far-infrared wavelengths are important in nearly all areas of astrophysics, from the search for habitable planets and the origin of life, to the earliest stages of galaxy assembly in the first few hundred million years of cosmic history. The combination of a still developing portfolio of technologies, particularly in the field of detectors, and a widening ensemble of platforms within which these technologies can be deployed, means that far-infrared astronomy holds the potential for paradigm-shifting advances over the next decade. In this review, we examine current and future far-infrared observing platforms, including ground-based, sub-orbital, and space-based facilities, and discuss the technology development pathways that will enable and enhance these platforms to best address the challenges facing far-infrared astronomy in the 21st century.

Review: Far-Infrared Instrumentation and Technology Development for the Next Decade

The Long-Wavelength Spectrometer (LWS) is one of two complementary spectrometers aboard the European Space Agency's Infrared Space Observatory (ISO) (Kessler et al., 1996AA a companion paper (Swinyard et al, 1996) describes its performance and calibration.

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J. A. Long

Papers

The ISO Long-Wavelength Spectrometer