Recently, Ph. D candidate ZHANG Yigong, Prof. WANG Jiancheng, from Yunnan Observatories of the Chinese Academy of Sciences, and their cooperators, propose a new method to improve the precision of astrometric observation for near-Earth objects. Their research is published online on November 19 in The Astronomical Journal.

The precise astrometric observation of small near-Earth objects (NEOs) is an important observational research topic in the astrometric discipline, which greatly promotes multidisciplinary research, such as the origin and evolution of the solar system, the detection and early warning of small NEOs, and deep-space navigation.

Incidents of small NEOs hitting the earth have occurred frequently, such as the “Tunguska Event” occurred on 1908 June 30 in the Tunguska region of Siberia, the meteorite impact event occurred in Chelyabinsk, Russia, on 2013 February 15, and the bolide event occurred in Diqing, Yunnan Province, on 2017 October 4. These collision incidents have aroused widespread concern in the international community. In recent years, the international community has paid more attention to the monitoring and early warning of small near-Earth objects, and China is also actively developing a near-Earth object defense system. Long-period and multi-epoch astrometric observations of small near-Earth objects are helpful to monitor the orbit of these targets, so that humans can have sufficient response time to deal with potential risks.

The characteristics of small NEOs, such as faintness and fast moving speed, restrict the accuracy and precision of their astrometric observations. In order to reduce the impact of the above reasons, the researchers propose a new method. The images of background stars and moving objects in the obtained observation data set are segmented into two independent data sets, and then for the background stars and moving objects using the “shift-and-stack” method, respectively. The researchers perform image fusion for the superimposed image sets according to the observation time. A high-quality image set can be obtained, which contains many background stars and moving objects with high signal-to-noise ratios (S/Ns). Meanwhile, the saturation of brighter background stars can be avoided.

Using this new method, the researchers performed astrometric reduction on the image data of small near-Earth object observed by 1 m optical telescope in Yunnan Observatory. The results show that this new method can significantly improve the accuracy and precision of astrometry.

The researchers also propose a method for establishing observable limiting apparent magnitude (OLAM) of moving objects based on the measured data at the observation station, and further propose an observational strategy for the moving targets.

Contact:

ZHANG Yigong, Yunnan Observatories, CAS

zhyg@ynao.ac.cn