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Lowell Observatory Near-Earth-Object Search (LONEOS) was a project designed to discover asteroids and comets that orbit near the Earth. The project, funded by NASA, was directed by astronomer Ted Bowell of Lowell Observatory in Flagstaff, Arizona. The LONEOS project began in 1993 and ran until the end of February 2008.
LONEOS, in its final configuration, used a 0.6-meter f/1.8 Schmidt telescope, acquired from Ohio Wesleyan University in 1990, and a Lowell-built 16 megapixel CCD detector. This combination of instruments provided a field of view of 2.88 by 2.88 degrees (8.3 square degrees). It had a maximum nightly scan area of about 1,000 square degrees (covered four times). The instrument could cover the entire accessible dark sky in about a month. The CCD has detected asteroids as faint as visual magnitude 19.8 but its typical limiting visual magnitude was 19.3. The instrument is located at Lowell Observatory's dark sky site, Anderson Mesa Station, near Flagstaff, Arizona, US.
Four computers were used. Two were used for frame reductions, one for telescope pointing control and one for camera control. The camera control software had scripting capability and could control all the other computers.
Asteroids were found by obtaining four pictures (frames) of the same region of sky, each frame temporally separated by 15 to 30 minutes. The set of four frames were then submitted to reduction software which located all star-like sources on the frame and identified sources that moved with asteroid-like motion. The observer visually examined all asteroid detections that had motion different from a typical main-belt asteroid. Human examination was required because most putative NEO detections were not real but some kind of imaging artifact.
All asteroid positions were converted to equatorial coordinates. Various USNO star catalogs[1] were used for this conversion until 2007. Then the Sloan Digital Sky Survey catalog was used, along with supplemental information from the Carlsberg Catalog[2] and the 2MASS catalog. Asteroid brightness was converted to standard visual magnitude. These data, along with the time of the observations, were sent to the Minor Planet Center (MPC) from which they were distributed to the scientific community. Potential near-Earth objects were handled expeditiously so that other observers could locate the asteroid on the same night and make further observations.
Telescope operation was automated to the extent that the survey could be run all night without observer intervention. However, the telescope was seldom operated in the automatic mode because an observer was required to reduce data promptly and to correct any malfunctions that might have occurred.
As of 2017, LONEOS is credited by the Minor Planet Center with the discovery of 22,077 minor planets between 1998 and 2008. The discoveries include main-belt asteroids, near-Earth Objects (NEO) and Mars-crossers. During the period of LONEOS operation, several other NASA funded NEO searches were underway (number of discoveries in parentheses):
Amateur observers made a significant contribution during this time with independent NEO discoveries and by performing follow-up observations of recent discoveries made by the NASA sponsored surveys.[3]
The table below lists the number of discoveries made by LONEOS each year of operation. Asteroids thought to be larger than one kilometer in diameter were used as benchmarks in assessing survey completeness. Hence, some table elements have two numbers separated by a slash. The second number represents the number of discoveries larger than one kilometer. The column labeled "Asteroid Observations" is the number of observations sent to the Minor Planet Center. Each asteroid was typically observed four times (once per frame) each night.[4]
| width=50 | Year | Asteroid Observations | width=50 | NEAs | width=45 | PHAs | width=50 | Atens | width=50 | Apollos | width=50 | Amors | Comets |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1998 | 122,550 | 7/4 | 0 | 0/0 | 3/2 | 4/2 | align=center | 1 | |||||
| 1999 | 128,220 | 14/7 | 5 | 2/2 | 6/3 | 6/2 | align=center | 6 | |||||
| 2000 | 271,237 | 38/10 | 4 | 3/0 | 18/5 | 17/5 | align=center | 6 | |||||
| 2001 | 626,976 | 42/11 | 9 | 4/0 | 17/4 | 21/7 | align=center | 7 | |||||
| 2002 | 407,064 | 21/4 | 3 | 3/1 | 9/0 | 9/3 | align=center | 3 | |||||
| 2003 | 720,528 | 54/10 | 17 | 5/1 | 26/3 | 23/6 | align=center | 2 | |||||
| 2004 | 716,152 | 39/4 | 9 | 5/0 | 22/4 | 12/0 | align=center | 4 | |||||
| 2005 | 820,609 | 42/4 | 8 | 6/0 | 15/1 | 21/3 | align=center | 8 | |||||
| 2006 | 679,927 | 19/1 | 2 | 0/0 | 11/1 | 8/0 | align=center | 2 | |||||
| 2007 | 630,469 | 12/0 | 2 | 2/0 | 4/0 | 6/0 | align=center | 3 | |||||
| 2008 | 88,953 | 1/0 | 0 | 0/0 | 1/0 | 0/0 | align=center | 0 | |||||
| Total | 5,212,685 | 289/55 | 59 | 30/4 | 131/23 | 127/28 | align=center | 42 | |||||
A complete list of LONEOS NEO observations can be found at the NeoDys[5] web site.
The LONEOS frame archive provides a data set with wide spatial and temporal sky coverage. Other investigators have used these characteristics to produce the following research papers and presentations.
Lowell staff:
Collaborators: