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Precovery (pre-recovery) is a term used in astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 that describes the process of finding the image
Image

An image is an artifact, usually two-dimensional , that has a similar appearance to some subject —usually a physical object or a person....
 of an object (usually a minor planet
Minor planet

An asteroid group or minor planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid....
, but sometimes a comet
Comet

A comet is a Small Solar System body that orbits the Sun and, when close enough to the Sun, exhibits a visible coma or a tail?both primarily from the effects of solar radiation upon the Comet nucleus....
 or even a natural satellite
Natural satellite

A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. Technically, the term natural satellite could refer to a planet orbiting a star, or a dwarf galaxy orbiting a major galaxy, but it is normally synonymous with moon and used to identify non-artificial satellites...
) in old archived images or photograph
Photograph

A photograph is an created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a Charge-coupled device or a Complementary metal?oxide?semiconductor chip....
ic plates, for the purpose of calculating a more accurate orbit
ORBit

ORBit is a Common Object Request Broker Architecture 2.4 compliant Object Request Broker . It features mature C , C++ and Python bindings, and less developed bindings for Perl, Lisp , Pascal , Ruby , and Tcl....
. The name is based on pre-recovery; recovery being the process of making new observations of a previously-observed object after a period of non-observation.

To accurately calculate an orbit for any solar system
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
 object, it is necessary to measure its angular position on multiple occasions.






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Precovery (pre-recovery) is a term used in astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 that describes the process of finding the image
Image

An image is an artifact, usually two-dimensional , that has a similar appearance to some subject —usually a physical object or a person....
 of an object (usually a minor planet
Minor planet

An asteroid group or minor planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break-up of a single asteroid....
, but sometimes a comet
Comet

A comet is a Small Solar System body that orbits the Sun and, when close enough to the Sun, exhibits a visible coma or a tail?both primarily from the effects of solar radiation upon the Comet nucleus....
 or even a natural satellite
Natural satellite

A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. Technically, the term natural satellite could refer to a planet orbiting a star, or a dwarf galaxy orbiting a major galaxy, but it is normally synonymous with moon and used to identify non-artificial satellites...
) in old archived images or photograph
Photograph

A photograph is an created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a Charge-coupled device or a Complementary metal?oxide?semiconductor chip....
ic plates, for the purpose of calculating a more accurate orbit
ORBit

ORBit is a Common Object Request Broker Architecture 2.4 compliant Object Request Broker . It features mature C , C++ and Python bindings, and less developed bindings for Perl, Lisp , Pascal , Ruby , and Tcl....
. The name is based on pre-recovery; recovery being the process of making new observations of a previously-observed object after a period of non-observation.

To accurately calculate an orbit for any solar system
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
 object, it is necessary to measure its angular position on multiple occasions. The more widely separated these are in time, the more accurately the orbit can be calculated. However, for a newly discovered object, only a few day
Day

A day is a units of measurement of time equivalent to approximately 24 hours. It is not an International System of Units unit but it is accepted for use with SI....
s or week
Week

A week is a grouping of days or a division of a larger grouping such as a lunar month, year, etc. The week allows for shorter routine than a month and benefits groups of people with organising market days, worship, taxes, etc....
s worth of measured positions are available, which is only sufficient for a preliminary (not very precise) orbit calculation.

When an object is of particular interest, for instance a near-Earth asteroid with a chance of impacting the Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
, a precovery effort is made. Using the preliminary orbit calculation to predict where the object might appear on old archival images (sometimes from decades ago), those images are searched to see if it had been in fact photographed at the time. If so, a far more precise orbital calculation can then be made.

Before modern inexpensive and fast computer
Computer

A computer is a machine that manipulates Data according to a list of Code .The first devices that resemble modern computers date to the mid-20th century , although the computer concept and various machines similar to computers existed earlier....
s, it was impractical to analyze and measure images for possible minor planet discoveries because this involved a considerable amount of manual labor. Usually such images were made years or decades ago for other purposes (studies of galaxies
Galaxy

A galaxy is a massive, gravitation system that consists of stars and stellar remnants, an interstellar medium of gas and cosmic dust, and an important but poorly-understood component tentatively dubbed dark matter....
, etc.) and it was not worth anyone's while to look for run-of-the-mill minor planets. Today, computers can easily analyze digital astronomical images and compare them to online star catalogue
Star catalogue

A star catalogue, or star catalog, is an astronomical catalogue that lists stars. In astronomy, many stars are referred to simply by catalogue numbers....
s containing up to a billion
1000000000 (number)

1,000,000,000 is the natural number following 999,999,999 and preceding 1,000,000,001.In scientific notation, it is written as 109....
 or so star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
 positions, and the identification of minor planet candidates is automated to a much greater extent. Such modern techniques (since about the mid 1990s) have enormously increased the rate of minor planet discoveries.

Examples


An extreme case of precovery is the following. On December 31, 2000, a discovery was made, designated 2000 YK66, and a near-Earth orbit was calculated. Precovery revealed that it had previously been discovered on February 23, 1950 and given the provisional designation 1950 DA, and then been lost for half a century. The exceptionally long observation period allowed an unusually precise orbit calculation, and the asteroid was determined to have a small chance of colliding with the Earth. After an asteroid's orbit is calculated with sufficient precision, it can be assigned a number (in this case, (29075) 1950 DA
(29075) 1950 DA

1950 DA is a near Earth asteroid. It is notable for having the highest known probability of Impact event Earth, according to the Palermo Technical Impact Hazard Scale ....
).

The asteroid 69230 Hermes
69230 Hermes

69230 Hermes is an Apollo asteroid, Mars-crosser asteroid and Venus-crosser asteroid that passed Earth at about twice the distance of the Moon on October 30, 1937....
 was found in 2003 and numbered, but was found to be a discovery from 1937 which had even been named, but subsequently lost. Consequently, its old name "Hermes" has been applied to it.

Another extreme case of precovery concerned Neptune. Galileo
Galileo Galilei

Galileo Galilei was a Grand Duchy of Tuscany physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution....
 observed Neptune on both December 28, 1612 and January 27, 1613, when it was in a portion of its orbit where it was nearly directly behind Jupiter as seen from Earth. Because Neptune moves very slowly and is very faint, Galileo mistook Neptune for a fixed star, leaving Neptune undiscovered until 1846. He did note that the "star" Neptune did seem to move, noting that between his two observations its apparent distance from another star had changed. However, unlike photographic images, drawings such as those Galileo made are usually not precise enough to be of use in refining an object's orbit.

See also

  • DANEOPS
    DANEOPS

    DANEOPS, the DLR-Archenhold Near Earth Objects Precovery Survey, has been initiated to systematically search existing photographic plate archives for precovery images of known Near-Earth Objects....