Chopping is a technique used with infrared telescopes to minimize interference from external or internal heat. [1] The chopper is the mechanism that rocks a mirror (typically a secondary mirror) inside a telescope back and forth in rapid succession because background radiation would change too quickly to measure otherwise. [2]
There are two major drawbacks to using the method of chopping. First is the variance of the background radiation. This can change when the telescope is shifting between the beams making thing appear strange. Secondly, this method can only be used when the object in question is not too far away, because otherwise it would be out of the telescope's range. [3]
Main: Infrared telescope
With Infrared Telescopes, chopping is used to eliminate the background radiation by taking pictures at slightly different angles. By comparing separate images, it becomes much easier to tell what the background heat is and what is coming from the object in question. This allows it to be used to gain information about the object that a visible light telescope or a UV telescope can't see. [4]
Main: Gemini Observatory
The Gemini Observatory is a set of two telescopes with one in Hawaii and the other in Chile. Both of these telescopes are infrared and both use chopping to eliminate background radiation. The telescopes chop their secondary mirrors at a rate of 3-5 Hz. Both observatories utilize tilt-tip correction to ensure that the image quality remains crisp. The observatories also received help from the University of Florida to improve its chopping mechanism. [5]
Main: SOFIA Telescope
The SOFIA Telescope was an infrared telescope integrated into a Boeing 747. This telescope utilized its Second Mirror Assembly (SMA) primarily for chopping and also partially for small corrections. The signals that the SOFIA Telescope would be searching for could be tens of thousands of times less significant than the background emission, so the telescope has an average chopping frequency of 2-5 Hz, but can reach rates of 20 Hz. The chopping action follows a square wave pattern. [6]
Main: James Webb Space Telescope
Although the James Webb Space Telescope is an Infrared Telescope, it doesn't use chopping action to prevent interference. Instead, it uses gold-coated mirrors to reflect almost all heat. [7] Additionally, it doesn't use chopping because it is meant to bore into deep space, and the angle would have to be refocused depending on how far away the object is.
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.
Subaru Telescope is the 8.2-metre (320 in) telescope of the National Astronomical Observatory of Japan, located at the Mauna Kea Observatory on Hawaii. It is named after the open star cluster known in English as the Pleiades. It had the largest monolithic primary mirror in the world from its commissioning until the Large Binocular Telescope opened in 2005.
The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have 10 m (33 ft) aperture primary mirrors, and, when completed in 1993 and 1996, they were the largest optical reflecting telescopes in the world. They are currently the third and fourth largest.
The James Webb Space Telescope (JWST) is a space telescope designed to conduct infrared astronomy. As the largest telescope in space, it is equipped with high-resolution and high-sensitivity instruments, allowing it to view objects too old, distant, or faint for the Hubble Space Telescope. This enables investigations across many fields of astronomy and cosmology, such as observation of the first stars and the formation of the first galaxies, and detailed atmospheric characterization of potentially habitable exoplanets.
Observational astronomy is a division of astronomy that is concerned with recording data about the observable universe, in contrast with theoretical astronomy, which is mainly concerned with calculating the measurable implications of physical models. It is the practice and study of observing celestial objects with the use of telescopes and other astronomical instruments.
The Gemini Observatory comprises two 8.1-metre (26.6 ft) telescopes, Gemini North and Gemini South, situated in Hawaii and Chile, respectively. These twin telescopes offer extensive coverage of the northern and southern skies and rank among the most advanced optical/infrared telescopes available to astronomers. (See List of largest optical reflecting telescopes).
NASA's series of Great Observatories satellites are four large, powerful space-based astronomical telescopes launched between 1990 and 2003. They were built with different technology to examine specific wavelength/energy regions of the electromagnetic spectrum: gamma rays, X-rays, visible and ultraviolet light, and infrared light.
The Stratospheric Observatory For Infrared Astronomy (SOFIA) was a 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.
The Hale Telescope is a 200-inch (5.1 m), f/3.3 reflecting telescope at the Palomar Observatory in San Diego County, California, US, named after astronomer George Ellery Hale. With funding from the Rockefeller Foundation in 1928, he orchestrated the planning, design, and construction of the observatory, but with the project ending up taking 20 years he did not live to see its commissioning. The Hale was groundbreaking for its time, with double the diameter of the second-largest telescope, and pioneered many new technologies in telescope mount design and in the design and fabrication of its large aluminum coated "honeycomb" low thermal expansion Pyrex mirror. It was completed in 1949 and is still in active use.
The Near Infrared Camera and Multi-Object Spectrometer (NICMOS) is a scientific instrument for infrared astronomy, installed on the Hubble Space Telescope (HST), operating from 1997 to 1999, and from 2002 to 2008. Images produced by NICMOS contain data from the near-infrared part of the light spectrum.
A coronagraph is a telescopic attachment designed to block out the direct light from a star or other bright object so that nearby objects – which otherwise would be hidden in the object's bright glare – can be resolved. Most coronagraphs are intended to view the corona of the Sun, but a new class of conceptually similar instruments are being used to find extrasolar planets and circumstellar disks around nearby stars as well as host galaxies in quasars and other similar objects with active galactic nuclei (AGN).
The NASA Infrared Telescope Facility is a 3-meter (9.8 ft) telescope optimized for use in infrared astronomy and located at the Mauna Kea Observatory in Hawaii. It was first built to support the Voyager missions and is now the US national facility for infrared astronomy, providing continued support to planetary, solar neighborhood, and deep space applications. The IRTF is operated by the University of Hawaii under a cooperative agreement with NASA. According to the IRTF's time allocation rules, at least 50% of the observing time is devoted to planetary science.
Submillimetre astronomy or submillimeter astronomy is the branch of observational astronomy that is conducted at submillimetre wavelengths of the electromagnetic spectrum. Astronomers place the submillimetre waveband between the far-infrared and microwave wavebands, typically taken to be between a few hundred micrometres and a millimetre. It is still common in submillimetre astronomy to quote wavelengths in 'microns', the old name for micrometre.
A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally, it was an optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects – an optical telescope. Nowadays, the word "telescope" is defined as a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.
Frank James Low was an American solid state physicist who became a leader in the new field of infrared astronomy, after inventing the gallium doped germanium bolometer in 1961. This detector extended the range of the observable spectrum to much longer wavelengths.
An infrared telescope is a telescope that uses infrared light to detect celestial bodies. Infrared light is one of several types of radiation present in the electromagnetic spectrum.
The Great Observatories Origins Deep Survey, or GOODS, is an astronomical survey combining deep observations from three of NASA's Great Observatories: the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory, along with data from other space-based telescopes, such as XMM Newton, and some of the world's most powerful ground-based telescopes.
SAFIR is a proposed NASA space observatory for far-infrared light. The plan calls for a single large mirror 5–10 meters (16–33 ft) in diameter, cryogenically cooled to 5 kelvins. This would feed detector arrays sensitive from 5 to 1000 μm. The possibility of servicing such a telescope in space has been evaluated.