Organization that was formed in the early 1980s to coordinate what is probably the least practised aspect of amateur astronomy - radio observations of Solar System and cosmic radio sources. SARA encourages the continual surveillance of wide areas of the sky in search of new or unusual radio emissions. It publishes a monthly Journal; the membership also includes professional radio astronomers.
SOFIA Abbreviation of stratospheric observatory for infrared astronomy software, astronomical Modern professional astronomy relies extensively on software - the programmed sequences of instructions that control modern digital computers. Astronomers use computers networked through the Internet and World Wide Web to plan observations. Some observatories use intelligent scheduling programs to determine when observations will be made. During an observation, a telescope is controlled by programs that correct for telescope deformation and keep the telescope tracking the target object (see active optics, adaptive optics). The instrumentation generates electronic data (perhaps passing it first through a processing sequence that removes any instrument-specific effects) in a standard format that can be handled by one of the standard astronomical data reduction systems. If the observation forms part of a large-scale survey, the data may be automatically processed to determine basic characteristics such as object type and redshift, and stored in an Internet-accessible database.
The astronomer may wish to examine the data in detail, displaying it in different ways, experimenting with image processing techniques, probing for the secrets it contains. The Flexible Image Transport System (FITS), developed by astronomers to encode definitions of image data and the data themselves, is a platform-independent system now widely used for interchanging data between observatories that has also become widely used outside astronomy.
Astronomical data reduction is a specialist process requiring specialist software, usually written by programmers employed at observatories or other astronomical institutions such as universities. Telescope and instrument control software is generally even more specialized, since each instrument has its own particular characteristics, so the software is usually written by those building the instrument or telescope. The software required for a new instrument now often represents a significant fraction of the total cost.
The main astronomical data reduction systems are NOAO's Image Reduction and Analysis Facility (IRAF) and ESO's Munich Image Data Analysis System (MIDAS) in the optical region, and NRAO's Astronomical Image Processing System (AIPS, and its successor, AIPS++) in the radio region. These can be seen as software component frameworks, with a structure that allows new components to be added easily and provides most of the basic services (for example data file access, user interaction) that the new component needs. Data acquisition systems can be structured in the same way, although, being real-time systems, they are significantly more complex. Most major observatories have developed their own data acquisition frameworks, but there are only a few such systems, notably the royal greenwich observatory's ADAM (Astronomical Data Acquisition Monitor) and its descendant, DRAMA, developed at the Anglo-Australian Observatory and first used on the Two-degree Field (2dF) project (see anglo-australian telescope).
Astronomical software is not restricted to large research institutions. Commercial packages are available for amateur telescope control (see drive; go to telescope). Image-processing techniques previously used only by professionals are now available to amateur observers wishing to use their personal computers to enhance images obtained with CCD cameras or to eliminate the effects of light pollution. 'Virtual planetarium' programs can bring the Universe to one's home.
SOHO Abbreviation of solar and heliospheric observatory
SOHO, Comets Numerous comets, making close perihelion approaches to the Sun, discovered by the LASCO C2 and C3 coronagraphs aboard the SOHO spacecraft. As of late 2001, almost 380 had been found, most of them very small objects on kreutz sungrazer orbits. Nearly all of these comets were tiny, with nuclei perhaps only a few tens of metres in diameter. Very few SOHO comets have been observed to survive perihelion passage. One notable exception was C/1998 J1 (SOHO), discovered on 1998 May 3 as a magnitude 0 object in the coronagraphs' field of view. The comet, which was not a Kreutz sungrazer, faded rapidly after perihelion, but was reasonably well seen in small telescopes from southern hemisphere locations.
C/1996 B2 hyakutake was visible in the SOHO coronagraph field at its 1996 May 1 perihelion, and 2P/encke has also been observed close to the Sun using this spacecraft. The SOHO comet discoveries follow on from several made using the SOLWIND coronagraph aboard the US military P78-1 satellite in the late 1970s and early 1980s.
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