Eight years ago, on September 27, 2008, the Shenzhou-7 carying three taikonauts deployed the microsatellite Banxing-1 for testing maneuvers and external imaging. A few hours later at 15:07 UTC the pair passed the ISS with only about 45 kilometers between Shenzhou-7 and the ISS. Banxing-1 is described in detail here.
On September 27 at 3:07 p.m. Greenwich Mean Time, the Shenzhou-7 ship passed within 45 kilometers of the International Space Station, according to the U.S. Strategic Command...
No one has offered a full explanation for why Beijing would do this. But China's track record of using all of its Shenzhou missions since 1999 for dual military-civil missions justifies speculation that it might have been part of a test of a new antisatellite missile technology. About four hours before Shenzhou's point of closest approach to the space station, Shenzhou-7 started one of its main missions: the launching of a 40-kilogram maneuvering microsatellite called BanXing-1 or BX-1...
It seems that after it was deployed, Banxing-1 was out of control during this close pass. The intended purpose was to remain and maneuver close to Shenzhou-7 and photograph it. Luckily it was drifting on the opposite side from the ISS.
Chinese state television reported on October 2 that "after the satellite was released by the Shenzhou-7 last weekend, it quickly started drifting away from its intended trajectory." NASA has not responded to questions about the BX-1 ventured closer to the space station than the Shenzhou incident. Neither has Washington.
Is that unusually close to the ISS to deploy and test a new satellite's propulsion and maneuvering without warning? The relative velocity seems to be about 3 kilometers per second!
Below are plots made from the TLEs. I've rotated the data into the frame of the ISS (black dot at the origin) with the thin black line pointing Earthwards (Nadir). Distances in kilometers. Blue/solid = Shenzhou-7, red/dashed = Banxing-1.