In all uses, please courtesy "Video courtesy of Analytical Graphics, Inc. (www.agi.com)."
In all uses, please courtesy "Video courtesy of Analytical Graphics, Inc. (www.agi.com)."
Ephemeris
USAF Space Command (AFSPC) published two-line element (TLE) set.
Time Frame
BX-1 deployment and close approach on Sept. 27, 2008
Orbit Coordinate Frame
The BX-1 orbit is drawn with two different reference frames - a traditional
inertial frame (ECI) in one window and relative to the Shenzhou VII in another.
Sensor
The sensor model is purely notional.
Attitude
The attitude of the spacecraft and BX-1 is notional.
Implementation of data
The source data used comes from the space object catalog. Several sequential TLEs
are used for each of the objects, covering the analysis time span. Given the uncertainty
associated with TLEs, there are discontinuities. For example, at the time the BX-1
separated form the Shenzhou, the best available TLE shows the two objects approximately
1.8 km apart. This gap most likely carries through most of the subsequent orbit path,
such that the geometry and the distance of the close approach were probably slightly
different (and closer) than this data suggests. In addition, the SGP4 propagator is not
usually the most accurate method for high-precision orbit propagation. Collectively,
the posted VDF should not be used to quote exact distances but rather to understand the
nature of the close approach.