A balloon-borne telescope is a type of airborne telescope, a sub-orbital astronomical telescope that is suspended below one or more stratospheric balloons, allowing it to be lifted above the lower, dense part of the Earth's atmosphere. This has the advantage of improving the resolution limit of the telescope at a much lower cost than for a space telescope. It also allows observation of frequency bands that are blocked by the atmosphere. [1]
Balloon-borne telescopes have been used for observation from the stratosphere since the Stratoscope I was launched in 1957. [2] A number of different instruments have since been carried aloft by balloons for observation in the infrared, microwave, X-ray and gamma ray bands. The BOOMERanG experiment, flown between 1997–2003, [3] and the MAXIMA, which made flights in 1998 and 1999, [4] were used to map the Cosmic Microwave Background Radiation.
Balloon-borne telescopes have the disadvantage of relatively low altitude and a flight time of only a few days. However, their maximum altitude of about 50 km is much higher than the limiting altitude of aircraft-borne telescopes such as the Kuiper Airborne Observatory and Stratospheric Observatory for Infrared Astronomy, which have a limiting altitude of 15 km. [1] [5] A few balloon-borne telescopes have crash landed, resulting in damage to, or destruction of the telescope.
The balloon obscures the zenith from the telescope, but a very long suspension can reduce this to a range of 2°. The telescope must be isolated from the induced motion of the stratospheric winds as well as the slow rotation and pendulum motion of the balloon. The azimuth stability can be maintained by a magnetometer, plus a gyroscope or star tracker for shorter term corrections. A three axis mount gives the best control over the tube motion, consisting of an azimuth, elevation and cross-elevation axis. [5]
| Name | Active | Description and purpose |
|---|---|---|
| Stratoscope I | 1957–59 | 12-inch telescope attached to a polyethylene balloon. [2] This was the first balloon-borne astronomical telescope. [6] It took photographic images of the sun, showing granulation features. In 1959 it was flown again, this time with a television transmitter. [2] |
| Stratoscope II | 1963–71 | 36-inch telescope with a tandem balloon system. [2] |
| THISBE | 1973–76 | Infrared telescope used for observations of extended sources, including OH airglow, the zodiacal light, and the central galaxy region. [7] |
| HIREGS | 1991–98 | High-resolution spectrometer for examining gamma ray and hard X-ray emissions from solar flares and galactic sources. It used an array of liquid nitrogen-cooled germanium detectors. [8] |
| BOOMERanG experiment | 1997–2003 | Microwave telescope with cryogenic detectors that was carried on long-duration flights over the antarctic. It was used to map the cosmic microwave background radiation (CMBR). [3] |
| MAXIMA | 1998–99 | Microwave telescope with a cryogenic receiver that was used to measure the CMBR. [4] |
| HERO | 2001–10 | Hard X-ray telescope that flew successfully beginning in 2001 but crashed in 2010, destroying the telescope. [9] |
| BLAST | 2003– | Submillimetre telescope with a 2 m aperture. It was destroyed during the third flight, but was rebuilt and completed a fourth flight in 2010. [10] |
| InFOCμS | 2004– | Hard X-ray telescope with a 49 cm2 collecting area. [11] |
| HEFT | 2005 | Hard X-ray telescope that uses grazing-incidence optics. [12] |
| Sunrise | 2009– | 1 m ultraviolet telescope with image stabilization and adaptive optics for observing the Sun. [13] |
| PoGOLite | 2011– | Telescope for polarised hard X-rays and soft gamma-rays. [14] |
| Spider | 2015– | Submillimeter telescope searching for primordial gravitational waves. [15] |
| SuperBIT | 2015– | Near-IR to Near-UV, wide-field, optically diffraction-limited telescope mapping out dark matter distribution in galaxy clusters through weak lensing. [16] |
NASA is planning to launch the largest ever balloon observatory on December 1, 2024 with a 400 foot balloon and 2.5 metre far-infrared telescope. [17] ASTHROS (Astrophysics Stratospheric Telescope for High Spectral Resolution Observations at Submillimeter-wavelengths) will launch from the Antarctic and is envisioned to last for four weeks. Its primary mirror consists of nine panels and is 8.2-foot (2.5-meter) in diameter. Optics is produced by Italian manufacturer Media Lario. The balloon may reach an altitude of 130,000 feet (40 kilometers). [18]
When fully inflated, the 40-million-cubic-feet helium balloon will be about 400 feet (150 meters) wide. The current best estimate for the weight of the observatory, including the gondola, solar panels, antenna, scientific instrument and communication systems, is about 5,500 pounds (2,500 kilograms). The telescope's detectors must be cooled down to 4 Kelvin using a cryocooler powered by electricity from its solar panels. One of ASTHROS' main science goals is to provide new information about stellar feedback in the Milky Way and other galaxies, a process in which stars either accelerate or decelerate the formation of new stars in their galaxy. ASTHROS will be the first mission to conduct high spectral resolution spectrometry in a few specific wavelengths of light, and identify two specific nitrogen ions that are formed by the processes that drive stellar feedback. As a target of opportunity, ASTHROS will observe TW Hydrae. [19]
Infrared astronomy is a sub-discipline of astronomy which specializes in the observation and analysis of astronomical objects using infrared (IR) radiation. The wavelength of infrared light ranges from 0.75 to 300 micrometers, and falls in between visible radiation, which ranges from 380 to 750 nanometers, and submillimeter waves.
Far-infrared astronomy is the branch of astronomy and astrophysics that deals with objects visible in far-infrared radiation.
The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), is an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, following IRAS (1983) and ISO (1995–1998). It was the first spacecraft to use an Earth-trailing orbit, later used by the Kepler planet-finder.
Observational cosmology is the study of the structure, the evolution and the origin of the universe through observation, using instruments such as telescopes and cosmic ray detectors.
The Stratospheric Observatory For Infrared Astronomy (SOFIA) was an 80/20 joint project of NASA and the German Aerospace Center (DLR) to construct and maintain an airborne observatory. NASA awarded the contract for the development of the aircraft, operation of the observatory and management of the American part of the project to the Universities Space Research Association (USRA) in 1996. The DSI managed the German parts of the project which were primarily science- and telescope-related. SOFIA's telescope saw first light on May 26, 2010. SOFIA was the successor to the Kuiper Airborne Observatory. During 10-hour, overnight flights, it observed celestial magnetic fields, star-forming regions, comets, nebulae, and the Galactic Center.
BOOMERanG experiment was an experiment that flew a telescope on a (high-altitude) balloon and measured the cosmic microwave background radiation of a part of the sky during three sub-orbital flights. It was the first experiment to make large, high-fidelity images of the CMB temperature anisotropies, and is best known for the discovery in 2000 that the geometry of the universe is close to flat, with similar results from the competing MAXIMA experiment.
The Calar Alto Observatory is an astronomical observatory located in Almería province in Spain on Calar Alto, a 2,168-meter-high (7,113 ft) mountain in the Sierra de Los Filabres range.
Llano de Chajnantor Observatory is the name for a group of astronomical observatories located at an altitude of over 4,800 m (15,700 ft) in the Atacama Desert of northern Chile. The site is in the Antofagasta Region approximately 50 kilometres (31 mi) east of the town of San Pedro de Atacama. The exceptionally arid climate of the area is inhospitable to humans, but creates an excellent location for millimeter, submillimeter, and mid-infrared astronomy. This is because water vapour absorbs and attenuates submillimetre radiation. Llano de Chajnantor is home to the largest and most expensive astronomical telescope project in the world, the Atacama Large Millimeter Array (ALMA). Llano de Chajnantor and the surrounding area has been designated as the Chajnantor Science Reserve by the government of Chile.
HD 80606 and HD 80607 are two stars comprising a binary star system. They are approximately 217 light-years away in the constellation of Ursa Major. Both stars orbit each other at an average distance of 1,200 astronomical units. The binary system is listed as Struve 1341 in the Struve Catalogue of Double Stars; however, this designation is not in wide use and the system is usually referred to by the HD designations of its constituent stars. An extrasolar planet has been confirmed to orbit HD 80606 in a highly elliptical orbit.
Spider is a balloon-borne experiment designed to search for primordial gravitational waves imprinted on the cosmic microwave background (CMB). Measuring the strength of this signal puts limits on inflationary theory.
Submillimeter Wave Astronomy Satellite is a NASA submillimetre astronomy satellite, and is the fourth spacecraft in the Small Explorer program (SMEX). It was launched on 6 December 1998, at 00:57:54 UTC, from Vandenberg Air Force Base aboard a Pegasus XL launch vehicle. The telescope was designed by the Smithsonian Astrophysical Observatory (SAO) and integrated by Ball Aerospace, while the spacecraft was built by NASA's Goddard Space Flight Center (GSFC). The mission's principal investigator is Gary J. Melnick.
Archeops was a balloon-borne instrument dedicated to measuring the Cosmic microwave background (CMB) temperature anisotropies. The study of this radiation is essential to obtain precise information on the evolution of the Universe: density, Hubble constant, age of the Universe, etc. To achieve this goal, measurements were done with devices cooled down at 100mK temperature placed at the focus of a warm telescope. To avoid atmospheric disturbance the whole apparatus is placed on a gondola below a helium balloon that reaches 40 km altitude.
TopHat was a scientific experiment launched from McMurdo Station in January 2001 to measure the cosmic microwave background radiation produced 300,000 years after the Big Bang. The balloon was launched on January 2, 2001 and proceeded to fly for 644 hours over the continent of Antarctica before landing on January 31, 2001. The balloon flew over the continent 38 kilometers (125,000 ft) above the ground. The working payload was shut down on January 10, 2001 after the liquid cryogens cooling the detectors were exhausted, and the balloon simply circled the continent until it was safe to land. The vorticial winds that typically carry balloons around the continent dissipated part of the way through the flight, and the balloon had to be terminated in a suboptimal location. The landing missed the targeted ice shelf by around one half mile, and while the discs containing the information were recovered safely using a Twin Otter, the gondola itself had not been recovered by August 2001.
BICEP and the Keck Array are a series of cosmic microwave background (CMB) experiments. They aim to measure the polarization of the CMB; in particular, measuring the B-mode of the CMB. The experiments have had five generations of instrumentation, consisting of BICEP1, BICEP2, the Keck Array, BICEP3, and the BICEP Array. The Keck Array started observations in 2012 and BICEP3 has been fully operational since May 2016, with the BICEP Array beginning installation in 2017/18.
The kinetic inductance detector (KID) — also known as a microwave kinetic inductance detector (MKID) — is a type of superconducting photon detector first developed by scientists at the California Institute of Technology and the Jet Propulsion Laboratory in 2003. These devices operate at cryogenic temperatures, typically below 1 kelvin. They are being developed for high-sensitivity astronomical detection for frequencies ranging from the far-infrared to X-rays.
Calvin Barth Netterfield, known as Barth Netterfield, is a Canadian astrophysicist, and a Professor in the Department of Astronomy and the Department of Physics at the University of Toronto. He is a leading expert in the development of balloon-borne telescopes. These are astrophysical experiments that are lifted into the stratosphere by high-altitude balloons where they conduct observations that would be hindered by atmospheric interference if done on the ground. Netterfield is primarily known for his work in observational cosmology, specifically in developing instrumentation to observe the cosmic microwave background (CMB) radiation. Most notably, he was a key member of the instrument team for BOOMERANG, the experiment that made one of the first accurate determinations of the age, geometry, and mass-energy content of the universe. More recently, he has delved into the field of submillimetre astronomy and the physics of star formation, through his involvement with the BLAST telescope. Netterfield was featured prominently in BLAST!, a documentary film about the 2005 and 2006 flights of BLAST from Sweden and Antarctica.
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The Super-pressure Balloon-borne Imaging Telescope (SuperBIT) is a highly stabilized, high-resolution telescope that operates in the stratosphere via NASA's superpressure balloon (SPB) system. At 40 km altitude above sea level, the football-stadium-sized balloon carries SuperBIT to a suborbital environment above 99.2% of the Earth's atmosphere in order to obtain space-quality imaging. As a research instrument, SuperBIT's primary science goal is to provide insight into the distribution of dark matter in galaxy clusters and throughout the large-scale structure of the universe. As demonstrated by numerous test flights, the survey data generated by SuperBIT is expected to have similar quality and data collection efficiency as the Hubble Space Telescope while complementing surveys from other up-and-coming observatories such as the James Webb Space Telescope (JWST), the Vera C. Rubin Observatory, and the Nancy Grace Roman Space Telescope.
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