Space News' Chinese satellite in near miss with Russian ASAT test debris links to the announcement below, and quotes "satellite tracker Jonathan McDowell" poo-pooing the claimed closest approach of 14.5 meters as unfounded, as China's capabilities could not possibly know it to this level of accuracy.
The notice stated that the closest approach was to a distance of 14.5 meters, but there is likely much more uncertainty regarding the distances involved, satellite tracker Jonathan McDowell, of the Harvard-Smithsonian Center for Astrophysics, told SpaceNews via email.
“While publicly available U.S. tracking data confirm that debris object 49863 did pass very close to the Tsinghua Science Satellite on January 18, the claim that the distance was only 14.5 meters is meaningless since they don’t quote any error bar, or the level of uncertainty,” McDowell stated.
“It is very unlikely China’s tracking can determine this distance to an accuracy of better than 100 meters or more, so “within a few hundred meters” is probably all they can reliably say.”
The Chinese announcement is internally inconsistent; a probability of 3.71×10-4 is 0.0371%, not the 0.000371% that the announcement also states. This corresponds to a factor of 10 in the distance of closest approach, and might be some hint as to what's going on.
But here I'd like to ask:
Question: How does Jonathan McDowell know that Chinese Tracking could not possibly have determined a closest approach of 14.5 meters between two space objects?
I'm assuming they use their latest sophisticated technology rather than just download TLEs from celestrak, though I'm not sure they have their interferometric radar up and running yet. But I want to know how one can be so certain.
- Does transmitting from a few dishes significantly improve the performance of radar surveillance from Earth at GEO and beyond? If so, how exactly?
- this answer to Is radar interferometry used, or feasible, for ground based astronomy?
- this answer to How can we install a radar on radio telescopes like FAST or GMRT?
Google translate of 22-1-19 16:37 来自 新版微博 weibo.com https://weibo.com/7558137714/LbuA4hZNx:
#Space Fragment# [Good risk! Russian anti-satellite debris passed by our satellite! 】 On January 18, early warning calculations of the Space Debris Monitoring and Application Center of the National Space Administration found that my country's Tsinghua Science Satellite (No. 46026) will have an extremely dangerous rendezvous with Russia's Cosmic 1408 Debris (No. 49863), with a collision probability of 3.71×10-4 (0.000371%), the closest distance is 14.5 meters.
The Tsinghua Science Satellite was launched from the Jiuquan Satellite Launch Center on August 6, 2020 by the Long March 2D carrier rocket. It is currently operating in a low-earth orbit with a perigee of 478 kilometers and an apogee of 499 kilometers. It is a gravity and atmospheric science satellite, responsible for Scientific exploration and technical verification are two important tasks.
Fragment number 49863 is the disintegration debris generated by the Russian anti-satellite test on November 15, 2021. This incident is no accident. On November 15 last year, a Russian anti-satellite test produced an estimated 1,600 disintegration debris larger than 10 centimeters in size, most of which were distributed in the orbital altitude range of 400 to 1,100 kilometers.
In recent years, the number of space debris has increased due to collision and disintegration events, and the collision risk of #over 170 million tiny space debris surrounding the Earth# satellites has increased.
Source: Public Account of the Space Debris Center of the National Space Administration
Original Chinese from 22-1-19 16:37 来自 新版微博 weibo.com https://weibo.com/7558137714/LbuA4hZNx
#空间碎片# 【好险！俄反卫碎片与我国卫星擦肩而过！】 1月18日，国家航天局空间碎片监测与应用中心预警计算发现，我国清华科学卫星（编号46026）将与俄罗斯的宇宙1408碎片（编号49863）发生一次极危险交会，碰撞概率为3.71×10-4（0.000371%），最近距离14.5米。