Follow-up and recovery
of Near Earth Asteroids (NEAs)
Near Earth Asteroids (NEAs) are asteroids with an orbit which can bring them close to the Earth's orbit, and then potentially to the Earth itself. Some of them are listed as Potentially Hazardous Asteroids (PHAs). This denomination, clearly subjective, will depend on how close they could be to the Earth.... The present limit for that list is 0.05 astronomical units (AU), and the closest approach to the Earth of a known object for the next 100 years is 0.0026 AU, i.e. little more than the distance to the Moon. Have a look at the MPC web page on NEAs and PHAs. NEAs are discovered generally when close to the Earth, where they are bright and have an apparent fast motion. They are then easy to detect among the other more classical asteroids. Dedicated observing programs on a few telescopes around the world make most of the discoveries of the NEAs. As soon as they are detected, predictions for the following nights are made available to all the observers who will try to follow them for getting enough positions to build a preliminary orbit which will confirm whether or not they are real NEAs. Very quickly they become difficult to observe, as their distance from the Earth is rapidly increasing, making them too faint for most of the instruments used in the asteroid observation community. If their orbit based on an arc of 10 days (a very short one for long term predictions) suggests that they could come close to the Earth, we need to have more observations for improving the orbital elements and the quality of the predictions. This is where a larger telescope, with the possibility of tracking a moving object, is needed. What you need is to be able to give a good astrometric position of a 21 to 23 mg object moving at 3 '/hr, or around 8 pixels/mn with STIS2 on MOS. CFHT is excellent for that kind of tracking, able to guide on a star and moving the guide probe according to the motion of the asteroid with a good accuracy. The follow-up of NEAs started with a 3 nights run on MOS in May
1998 as a collobaration between UVic, DAO and CFHT, and has received two
more nights in October 1998. Since that, a very few observations have been
made on Discretionnary Time and on a small fraction of aobserving time
allocated partially for that purpose.
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1998 HH49
1998 FG2
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1991 VB
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1998 HH49
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1998 FG02
1998 FH12 The observations (here) allowed to extend the orbital arc from 26 to 66 days. Closest predicted approach to Earth before 2100 is 0.0397 AU in 2047. 1998 FL03 The observations (here) allowed to extend the orbital arc from 7 to 69 days. Closest predicted approach to Earth before 2100 is 0.045AU in 2090. 1998 FL05 The observations (here) allowed to extend the orbital arc from 24 to 70 days. It's not classified as a PHA... 1998 FW04
1998 HH49
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