A paper describes a new technique designed to increase significantly the sensitivity for finding and tracking small, dim, and fast-moving near Earth asteroids (NEAs). The technique relies on a combined use of a novel data processing approach and a new generation of high-speed CCD cameras. These new cameras have very low readout noise (≈le–) and allow taking short exposures of moving objects at high frame rates, effectively “freezing” their motion on the CCD. A long-exposure image is synthetically created as if the telescope were tracking the object with a significantly higher SNR — an approach called “synthetic tracking.” By changing the shift/add vector, multiple dim objects moving in different directions can be detected in the same data set.
Synthetic tracking was applied to observations of two known asteroids conducted on the Palomar 200-inch telescope and a tenfold improvement of astrometric precision over the traditional long exposure approach was demonstrated.
This work was done by Michael Shao, Bijan Nemati, Chengxing Zhai, Jagmit S. Sandhu, and Slava G. Turyshev of NASA’s Jet Propulsion Laboratory at Caltech. NPO-47342
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Preparation, Planning, and Concept Demo of a Technique to Find =7-to-10-m Near Earth Asteroids
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Overview
The document outlines a project led by NASA's Jet Propulsion Laboratory (JPL) focused on developing a new technique for detecting small, fast-moving near-Earth asteroids (NEAs) measuring approximately 7 to 10 meters in size. The primary objective is to enhance the capabilities of existing telescopes, particularly the Palomar 200-inch telescope, by utilizing a method called "synthetic tracking." This innovative approach allows for the integration of moving NEAs over extended periods, significantly improving the signal-to-noise ratio (SNR) and enabling the detection of objects that are up to 10 times fainter than current methods.
The synthetic tracking technique involves shifting and co-adding successive frames of data in post-processing, effectively creating a long-exposure image that simulates the telescope tracking the object. This method not only increases the chances of finding dim targets by a factor of approximately 10 but also enhances astrometric precision. Traditional optical astrometry has achieved an accuracy of around 0.2 arcseconds, while synthetic tracking can reduce this error to less than 7 milliarcseconds (mas), greatly improving orbit determination for detected asteroids.
The project also emphasizes the importance of high-speed, low-noise CCD cameras, which are crucial for capturing short exposures of moving objects at high frame rates. These cameras, originally designed for medical imaging, can take up to 100 frames per second with minimal read-out noise, making them ideal for detecting faint NEAs. The document discusses the potential for a third-generation camera that could further increase the solid angle coverage, allowing for the discovery of up to 30 times more small objects per night compared to existing facilities.
In summary, the document presents a comprehensive overview of the efforts to refine asteroid detection techniques through synthetic tracking and advanced imaging technology. The anticipated outcomes include improved detection rates of small NEAs, enhanced astrometric accuracy, and a greater understanding of potential targets for NASA's Asteroid Retrieval Mission (ARM). The project aims to significantly expand the volume of space that can be searched for these objects, ultimately contributing to planetary defense and scientific knowledge of near-Earth objects.
