Hunting for Asteroids. Roy A. Tucker Goodricke - Pigott Observatory. Canary Islands January 2013

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1 Hunting for Asteroids Roy A. Tucker Goodricke - Pigott Observatory Canary Islands January 2013

2 Asteroids The first, Ceres, discovered January 1, 1801 in Palermo Sicily by Giuseppe Piazzi The Bode-Titius Rule predicted an object at about 2.8 AU Star-like objects detected by their motion 10,000 numbered by 2005 Over 310,000 numbered now About as many known, unnumbered objects

3 Asteroid Nomenclature When first reported, a designation is assigned by the discoverer The Minor Planet Center assigns a provisional designation consisting of the year of discovery, a letter indicating the halfmonth of discovery, and a letter indicating the order of discovery (the letter I is not used). If there are more than 25, a number is attached at the end, for example 1997 MW1. An asteroid is numbered when its orbit is known so well that it will never be lost again Upon being numbered, the discoverer may suggest a name

4 Near-Earth Asteroids Amor asteroids approach the Sun closer than 1.3 AU Apollo asteroids have average distances from the sun greater than 1.0 AU but closest distance to the Sun inside the orbit of the Earth (the orbits cross) Aten asteroids have an average distance from the Sun of less than 1.0 AU but greatest distance outside the orbit of the Earth (the orbits cross) There are asteroids with orbits entirely inside that of the Earth but the class is not officially named

5 Search Methodology? Look for something moving First searches were visual, using field sketches and, later, careful timing Photography began to be used in late 1800 s CCD imaging began in 1980 s, pioneered by Dr. Tom Gehrels

6 The Modern Era of Asteroid Searching CCD imaging camera with high QE and precisely defined X-Y array of pixels Powerful, inexpensive computers Massive, precise star catalogs on easily distributed media

7 Stare-mode Imaging Point the telescope to an area of sky Accurately track the moving sky Open the camera shutter to collect the light Close the shutter and read out the CCD Repeat a minimum of three times

8 Disadvantages of Stare-mode Imaging Requires an accurately pointing and tracking mounting, very expensive and collects no photons No photons are collected when the shutter is closed

9 Scan-mode Imaging The CCD is oriented with the parallel registers oriented in the motion direction Parallel registers clocked at a rate that will transport the accumulating charge at the same rate that the image drifts across the imager surface Continuous readout of the image data as a long strip of sky like a fax machine

10 Advantages of Scan-mode Imaging Continuous imaging process, no wasted photons, high instrument productivity Simultaneous integration, read out, and movement to the next field Low cost telescope mounting Reduction of CCD cosmetics due to averaging effect of the imaging process Simplified and improved image calibration

11 Disadvantages of Scan-mode Imaging Limited control of imaging parameters such as integration time Not suitable for high declinations (clocking shear, drift curvature) Need to frequently explain how it works Large data volume results in loss of sleep and fewer recreational opportunities

12 Example System Images 1024^2 pixels 14 aperture 48 arcmin 191 sec int

13 120 square degrees average nightly coverage per telescope

14 Searching From The Ground Easiest to look at the opposition region because it is visible most of the night and asteroids become brighter near opposition because of retro-reflection and no shadows NEOs do not necessarily favor the opposition region Desirable to look at small solar elongations but time is limited Magnitude penetration limited by skyglow Sky coverage limited by geographical location

15 Searching From Space Eliminates skyglow Can point anywhere except at the Sun or Earth (or other nearby planet) At least 10,000 times as expensive Detections limited by Zodiacal Light Possible to use thermal infrared detectors

16 Show and Tell Time! What do asteroids actually look like in images?

17 Thank you! My thanks to The Planetary Society for their past support of my efforts by a Eugene Shoemaker Grant Any questions?