http://www.ucsusa.org/assets/documents/nwgs/slr_in_china.pdf

Satellite Laser Ranging in China
Yousaf Butt
Union of Concerned Scientists, Cambridge, MA, USA
January 8, 2007
ABSTRACT

Satellite Laser Ranging (SLR) is a widely used technique for determining the orbits of objects in space with high accuracy. There are seven known SLR stations in China, two of which are mobile. These stations are part of a scientific collaboration called the International Laser Ranging Service (ILRS) based at the Goddard Space Flight Center in Greenbelt, Maryland. The typical average laser power used in the Chinese SLR stations is below about 1 Watt (W), although experimental systems of roughly 40W have also been used to characterize objects such as space debris. Most of the ranging takes place at night although some capability for more technically challenging daytime SLR reportedly exists at two of the fixed stations. In this paper, we consider laser ranging to an earth-observing imaging satellite and what effect that might have on the satellite. We show that under a broad set of conditions such ranging would not adversely affect the satellite’s sensitive detector, but that cases exist in which the effects can be significant, although the probability of damaging the detector is extremely low. We find that SLR cannot be considered an anti-satellite (ASAT) weapon and, in fact, would be ineffective in this role. Nonetheless, the possibility of laser ranging to ground-imaging satellites without authorization, resulting in unexpected detector performance, is motivation for converging on a set of international rules governing it use.

Yousaf Butt is a postdoctoral science fellow in the Union of Concerned Scientists’ Global Security Program. He is also on staff at the Harvard Smithsonian Center for Astrophysics, where he worked on the Chandra X-ray Observatory from 1999-2004. He holds a PhD in experimental nuclear astrophysics from Yale University.